Update dependencies

12 files changed, 4618 insertions, 14 deletions

diff --git a/vendor/gopkg.in/mgo.v2/internal/json/LICENSE b/vendor/gopkg.in/mgo.v2/internal/json/LICENSE
new file mode 100644
index 0000000..7448756
--- /dev/null
+++ b/vendor/gopkg.in/mgo.v2/internal/json/LICENSE
@@ -0,0 +1,27 @@
+Copyright (c) 2012 The Go Authors. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+   * Redistributions of source code must retain the above copyright
+notice, this list of conditions and the following disclaimer.
+   * Redistributions in binary form must reproduce the above
+copyright notice, this list of conditions and the following disclaimer
+in the documentation and/or other materials provided with the
+distribution.
+   * Neither the name of Google Inc. nor the names of its
+contributors may be used to endorse or promote products derived from
+this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
diff --git a/vendor/gopkg.in/mgo.v2/internal/json/decode.go b/vendor/gopkg.in/mgo.v2/internal/json/decode.go
new file mode 100644
index 0000000..ce7c7d2
--- /dev/null
+++ b/vendor/gopkg.in/mgo.v2/internal/json/decode.go
@@ -0,0 +1,1685 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Represents JSON data structure using native Go types: booleans, floats,
+// strings, arrays, and maps.
+
+package json
+
+import (
+	"bytes"
+	"encoding"
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"reflect"
+	"runtime"
+	"strconv"
+	"unicode"
+	"unicode/utf16"
+	"unicode/utf8"
+)
+
+// Unmarshal parses the JSON-encoded data and stores the result
+// in the value pointed to by v.
+//
+// Unmarshal uses the inverse of the encodings that
+// Marshal uses, allocating maps, slices, and pointers as necessary,
+// with the following additional rules:
+//
+// To unmarshal JSON into a pointer, Unmarshal first handles the case of
+// the JSON being the JSON literal null. In that case, Unmarshal sets
+// the pointer to nil. Otherwise, Unmarshal unmarshals the JSON into
+// the value pointed at by the pointer. If the pointer is nil, Unmarshal
+// allocates a new value for it to point to.
+//
+// To unmarshal JSON into a struct, Unmarshal matches incoming object
+// keys to the keys used by Marshal (either the struct field name or its tag),
+// preferring an exact match but also accepting a case-insensitive match.
+// Unmarshal will only set exported fields of the struct.
+//
+// To unmarshal JSON into an interface value,
+// Unmarshal stores one of these in the interface value:
+//
+//	bool, for JSON booleans
+//	float64, for JSON numbers
+//	string, for JSON strings
+//	[]interface{}, for JSON arrays
+//	map[string]interface{}, for JSON objects
+//	nil for JSON null
+//
+// To unmarshal a JSON array into a slice, Unmarshal resets the slice length
+// to zero and then appends each element to the slice.
+// As a special case, to unmarshal an empty JSON array into a slice,
+// Unmarshal replaces the slice with a new empty slice.
+//
+// To unmarshal a JSON array into a Go array, Unmarshal decodes
+// JSON array elements into corresponding Go array elements.
+// If the Go array is smaller than the JSON array,
+// the additional JSON array elements are discarded.
+// If the JSON array is smaller than the Go array,
+// the additional Go array elements are set to zero values.
+//
+// To unmarshal a JSON object into a map, Unmarshal first establishes a map to
+// use, If the map is nil, Unmarshal allocates a new map. Otherwise Unmarshal
+// reuses the existing map, keeping existing entries. Unmarshal then stores key-
+// value pairs from the JSON object into the map.  The map's key type must
+// either be a string or implement encoding.TextUnmarshaler.
+//
+// If a JSON value is not appropriate for a given target type,
+// or if a JSON number overflows the target type, Unmarshal
+// skips that field and completes the unmarshaling as best it can.
+// If no more serious errors are encountered, Unmarshal returns
+// an UnmarshalTypeError describing the earliest such error.
+//
+// The JSON null value unmarshals into an interface, map, pointer, or slice
+// by setting that Go value to nil. Because null is often used in JSON to mean
+// ``not present,'' unmarshaling a JSON null into any other Go type has no effect
+// on the value and produces no error.
+//
+// When unmarshaling quoted strings, invalid UTF-8 or
+// invalid UTF-16 surrogate pairs are not treated as an error.
+// Instead, they are replaced by the Unicode replacement
+// character U+FFFD.
+//
+func Unmarshal(data []byte, v interface{}) error {
+	// Check for well-formedness.
+	// Avoids filling out half a data structure
+	// before discovering a JSON syntax error.
+	var d decodeState
+	err := checkValid(data, &d.scan)
+	if err != nil {
+		return err
+	}
+
+	d.init(data)
+	return d.unmarshal(v)
+}
+
+// Unmarshaler is the interface implemented by types
+// that can unmarshal a JSON description of themselves.
+// The input can be assumed to be a valid encoding of
+// a JSON value. UnmarshalJSON must copy the JSON data
+// if it wishes to retain the data after returning.
+type Unmarshaler interface {
+	UnmarshalJSON([]byte) error
+}
+
+// An UnmarshalTypeError describes a JSON value that was
+// not appropriate for a value of a specific Go type.
+type UnmarshalTypeError struct {
+	Value  string       // description of JSON value - "bool", "array", "number -5"
+	Type   reflect.Type // type of Go value it could not be assigned to
+	Offset int64        // error occurred after reading Offset bytes
+}
+
+func (e *UnmarshalTypeError) Error() string {
+	return "json: cannot unmarshal " + e.Value + " into Go value of type " + e.Type.String()
+}
+
+// An UnmarshalFieldError describes a JSON object key that
+// led to an unexported (and therefore unwritable) struct field.
+// (No longer used; kept for compatibility.)
+type UnmarshalFieldError struct {
+	Key   string
+	Type  reflect.Type
+	Field reflect.StructField
+}
+
+func (e *UnmarshalFieldError) Error() string {
+	return "json: cannot unmarshal object key " + strconv.Quote(e.Key) + " into unexported field " + e.Field.Name + " of type " + e.Type.String()
+}
+
+// An InvalidUnmarshalError describes an invalid argument passed to Unmarshal.
+// (The argument to Unmarshal must be a non-nil pointer.)
+type InvalidUnmarshalError struct {
+	Type reflect.Type
+}
+
+func (e *InvalidUnmarshalError) Error() string {
+	if e.Type == nil {
+		return "json: Unmarshal(nil)"
+	}
+
+	if e.Type.Kind() != reflect.Ptr {
+		return "json: Unmarshal(non-pointer " + e.Type.String() + ")"
+	}
+	return "json: Unmarshal(nil " + e.Type.String() + ")"
+}
+
+func (d *decodeState) unmarshal(v interface{}) (err error) {
+	defer func() {
+		if r := recover(); r != nil {
+			if _, ok := r.(runtime.Error); ok {
+				panic(r)
+			}
+			err = r.(error)
+		}
+	}()
+
+	rv := reflect.ValueOf(v)
+	if rv.Kind() != reflect.Ptr || rv.IsNil() {
+		return &InvalidUnmarshalError{reflect.TypeOf(v)}
+	}
+
+	d.scan.reset()
+	// We decode rv not rv.Elem because the Unmarshaler interface
+	// test must be applied at the top level of the value.
+	d.value(rv)
+	return d.savedError
+}
+
+// A Number represents a JSON number literal.
+type Number string
+
+// String returns the literal text of the number.
+func (n Number) String() string { return string(n) }
+
+// Float64 returns the number as a float64.
+func (n Number) Float64() (float64, error) {
+	return strconv.ParseFloat(string(n), 64)
+}
+
+// Int64 returns the number as an int64.
+func (n Number) Int64() (int64, error) {
+	return strconv.ParseInt(string(n), 10, 64)
+}
+
+// isValidNumber reports whether s is a valid JSON number literal.
+func isValidNumber(s string) bool {
+	// This function implements the JSON numbers grammar.
+	// See https://tools.ietf.org/html/rfc7159#section-6
+	// and http://json.org/number.gif
+
+	if s == "" {
+		return false
+	}
+
+	// Optional -
+	if s[0] == '-' {
+		s = s[1:]
+		if s == "" {
+			return false
+		}
+	}
+
+	// Digits
+	switch {
+	default:
+		return false
+
+	case s[0] == '0':
+		s = s[1:]
+
+	case '1' <= s[0] && s[0] <= '9':
+		s = s[1:]
+		for len(s) > 0 && '0' <= s[0] && s[0] <= '9' {
+			s = s[1:]
+		}
+	}
+
+	// . followed by 1 or more digits.
+	if len(s) >= 2 && s[0] == '.' && '0' <= s[1] && s[1] <= '9' {
+		s = s[2:]
+		for len(s) > 0 && '0' <= s[0] && s[0] <= '9' {
+			s = s[1:]
+		}
+	}
+
+	// e or E followed by an optional - or + and
+	// 1 or more digits.
+	if len(s) >= 2 && (s[0] == 'e' || s[0] == 'E') {
+		s = s[1:]
+		if s[0] == '+' || s[0] == '-' {
+			s = s[1:]
+			if s == "" {
+				return false
+			}
+		}
+		for len(s) > 0 && '0' <= s[0] && s[0] <= '9' {
+			s = s[1:]
+		}
+	}
+
+	// Make sure we are at the end.
+	return s == ""
+}
+
+// decodeState represents the state while decoding a JSON value.
+type decodeState struct {
+	data       []byte
+	off        int // read offset in data
+	scan       scanner
+	nextscan   scanner // for calls to nextValue
+	savedError error
+	useNumber  bool
+	ext        Extension
+}
+
+// errPhase is used for errors that should not happen unless
+// there is a bug in the JSON decoder or something is editing
+// the data slice while the decoder executes.
+var errPhase = errors.New("JSON decoder out of sync - data changing underfoot?")
+
+func (d *decodeState) init(data []byte) *decodeState {
+	d.data = data
+	d.off = 0
+	d.savedError = nil
+	return d
+}
+
+// error aborts the decoding by panicking with err.
+func (d *decodeState) error(err error) {
+	panic(err)
+}
+
+// saveError saves the first err it is called with,
+// for reporting at the end of the unmarshal.
+func (d *decodeState) saveError(err error) {
+	if d.savedError == nil {
+		d.savedError = err
+	}
+}
+
+// next cuts off and returns the next full JSON value in d.data[d.off:].
+// The next value is known to be an object or array, not a literal.
+func (d *decodeState) next() []byte {
+	c := d.data[d.off]
+	item, rest, err := nextValue(d.data[d.off:], &d.nextscan)
+	if err != nil {
+		d.error(err)
+	}
+	d.off = len(d.data) - len(rest)
+
+	// Our scanner has seen the opening brace/bracket
+	// and thinks we're still in the middle of the object.
+	// invent a closing brace/bracket to get it out.
+	if c == '{' {
+		d.scan.step(&d.scan, '}')
+	} else if c == '[' {
+		d.scan.step(&d.scan, ']')
+	} else {
+		// Was inside a function name. Get out of it.
+		d.scan.step(&d.scan, '(')
+		d.scan.step(&d.scan, ')')
+	}
+
+	return item
+}
+
+// scanWhile processes bytes in d.data[d.off:] until it
+// receives a scan code not equal to op.
+// It updates d.off and returns the new scan code.
+func (d *decodeState) scanWhile(op int) int {
+	var newOp int
+	for {
+		if d.off >= len(d.data) {
+			newOp = d.scan.eof()
+			d.off = len(d.data) + 1 // mark processed EOF with len+1
+		} else {
+			c := d.data[d.off]
+			d.off++
+			newOp = d.scan.step(&d.scan, c)
+		}
+		if newOp != op {
+			break
+		}
+	}
+	return newOp
+}
+
+// value decodes a JSON value from d.data[d.off:] into the value.
+// it updates d.off to point past the decoded value.
+func (d *decodeState) value(v reflect.Value) {
+	if !v.IsValid() {
+		_, rest, err := nextValue(d.data[d.off:], &d.nextscan)
+		if err != nil {
+			d.error(err)
+		}
+		d.off = len(d.data) - len(rest)
+
+		// d.scan thinks we're still at the beginning of the item.
+		// Feed in an empty string - the shortest, simplest value -
+		// so that it knows we got to the end of the value.
+		if d.scan.redo {
+			// rewind.
+			d.scan.redo = false
+			d.scan.step = stateBeginValue
+		}
+		d.scan.step(&d.scan, '"')
+		d.scan.step(&d.scan, '"')
+
+		n := len(d.scan.parseState)
+		if n > 0 && d.scan.parseState[n-1] == parseObjectKey {
+			// d.scan thinks we just read an object key; finish the object
+			d.scan.step(&d.scan, ':')
+			d.scan.step(&d.scan, '"')
+			d.scan.step(&d.scan, '"')
+			d.scan.step(&d.scan, '}')
+		}
+
+		return
+	}
+
+	switch op := d.scanWhile(scanSkipSpace); op {
+	default:
+		d.error(errPhase)
+
+	case scanBeginArray:
+		d.array(v)
+
+	case scanBeginObject:
+		d.object(v)
+
+	case scanBeginLiteral:
+		d.literal(v)
+
+	case scanBeginName:
+		d.name(v)
+	}
+}
+
+type unquotedValue struct{}
+
+// valueQuoted is like value but decodes a
+// quoted string literal or literal null into an interface value.
+// If it finds anything other than a quoted string literal or null,
+// valueQuoted returns unquotedValue{}.
+func (d *decodeState) valueQuoted() interface{} {
+	switch op := d.scanWhile(scanSkipSpace); op {
+	default:
+		d.error(errPhase)
+
+	case scanBeginArray:
+		d.array(reflect.Value{})
+
+	case scanBeginObject:
+		d.object(reflect.Value{})
+
+	case scanBeginName:
+		switch v := d.nameInterface().(type) {
+		case nil, string:
+			return v
+		}
+
+	case scanBeginLiteral:
+		switch v := d.literalInterface().(type) {
+		case nil, string:
+			return v
+		}
+	}
+	return unquotedValue{}
+}
+
+// indirect walks down v allocating pointers as needed,
+// until it gets to a non-pointer.
+// if it encounters an Unmarshaler, indirect stops and returns that.
+// if decodingNull is true, indirect stops at the last pointer so it can be set to nil.
+func (d *decodeState) indirect(v reflect.Value, decodingNull bool) (Unmarshaler, encoding.TextUnmarshaler, reflect.Value) {
+	// If v is a named type and is addressable,
+	// start with its address, so that if the type has pointer methods,
+	// we find them.
+	if v.Kind() != reflect.Ptr && v.Type().Name() != "" && v.CanAddr() {
+		v = v.Addr()
+	}
+	for {
+		// Load value from interface, but only if the result will be
+		// usefully addressable.
+		if v.Kind() == reflect.Interface && !v.IsNil() {
+			e := v.Elem()
+			if e.Kind() == reflect.Ptr && !e.IsNil() && (!decodingNull || e.Elem().Kind() == reflect.Ptr) {
+				v = e
+				continue
+			}
+		}
+
+		if v.Kind() != reflect.Ptr {
+			break
+		}
+
+		if v.Elem().Kind() != reflect.Ptr && decodingNull && v.CanSet() {
+			break
+		}
+		if v.IsNil() {
+			v.Set(reflect.New(v.Type().Elem()))
+		}
+		if v.Type().NumMethod() > 0 {
+			if u, ok := v.Interface().(Unmarshaler); ok {
+				return u, nil, v
+			}
+			if u, ok := v.Interface().(encoding.TextUnmarshaler); ok {
+				return nil, u, v
+			}
+		}
+		v = v.Elem()
+	}
+	return nil, nil, v
+}
+
+// array consumes an array from d.data[d.off-1:], decoding into the value v.
+// the first byte of the array ('[') has been read already.
+func (d *decodeState) array(v reflect.Value) {
+	// Check for unmarshaler.
+	u, ut, pv := d.indirect(v, false)
+	if u != nil {
+		d.off--
+		err := u.UnmarshalJSON(d.next())
+		if err != nil {
+			d.error(err)
+		}
+		return
+	}
+	if ut != nil {
+		d.saveError(&UnmarshalTypeError{"array", v.Type(), int64(d.off)})
+		d.off--
+		d.next()
+		return
+	}
+
+	v = pv
+
+	// Check type of target.
+	switch v.Kind() {
+	case reflect.Interface:
+		if v.NumMethod() == 0 {
+			// Decoding into nil interface?  Switch to non-reflect code.
+			v.Set(reflect.ValueOf(d.arrayInterface()))
+			return
+		}
+		// Otherwise it's invalid.
+		fallthrough
+	default:
+		d.saveError(&UnmarshalTypeError{"array", v.Type(), int64(d.off)})
+		d.off--
+		d.next()
+		return
+	case reflect.Array:
+	case reflect.Slice:
+		break
+	}
+
+	i := 0
+	for {
+		// Look ahead for ] - can only happen on first iteration.
+		op := d.scanWhile(scanSkipSpace)
+		if op == scanEndArray {
+			break
+		}
+
+		// Back up so d.value can have the byte we just read.
+		d.off--
+		d.scan.undo(op)
+
+		// Get element of array, growing if necessary.
+		if v.Kind() == reflect.Slice {
+			// Grow slice if necessary
+			if i >= v.Cap() {
+				newcap := v.Cap() + v.Cap()/2
+				if newcap < 4 {
+					newcap = 4
+				}
+				newv := reflect.MakeSlice(v.Type(), v.Len(), newcap)
+				reflect.Copy(newv, v)
+				v.Set(newv)
+			}
+			if i >= v.Len() {
+				v.SetLen(i + 1)
+			}
+		}
+
+		if i < v.Len() {
+			// Decode into element.
+			d.value(v.Index(i))
+		} else {
+			// Ran out of fixed array: skip.
+			d.value(reflect.Value{})
+		}
+		i++
+
+		// Next token must be , or ].
+		op = d.scanWhile(scanSkipSpace)
+		if op == scanEndArray {
+			break
+		}
+		if op != scanArrayValue {
+			d.error(errPhase)
+		}
+	}
+
+	if i < v.Len() {
+		if v.Kind() == reflect.Array {
+			// Array. Zero the rest.
+			z := reflect.Zero(v.Type().Elem())
+			for ; i < v.Len(); i++ {
+				v.Index(i).Set(z)
+			}
+		} else {
+			v.SetLen(i)
+		}
+	}
+	if i == 0 && v.Kind() == reflect.Slice {
+		v.Set(reflect.MakeSlice(v.Type(), 0, 0))
+	}
+}
+
+var nullLiteral = []byte("null")
+var textUnmarshalerType = reflect.TypeOf(new(encoding.TextUnmarshaler)).Elem()
+
+// object consumes an object from d.data[d.off-1:], decoding into the value v.
+// the first byte ('{') of the object has been read already.
+func (d *decodeState) object(v reflect.Value) {
+	// Check for unmarshaler.
+	u, ut, pv := d.indirect(v, false)
+	if d.storeKeyed(pv) {
+		return
+	}
+	if u != nil {
+		d.off--
+		err := u.UnmarshalJSON(d.next())
+		if err != nil {
+			d.error(err)
+		}
+		return
+	}
+	if ut != nil {
+		d.saveError(&UnmarshalTypeError{"object", v.Type(), int64(d.off)})
+		d.off--
+		d.next() // skip over { } in input
+		return
+	}
+	v = pv
+
+	// Decoding into nil interface?  Switch to non-reflect code.
+	if v.Kind() == reflect.Interface && v.NumMethod() == 0 {
+		v.Set(reflect.ValueOf(d.objectInterface()))
+		return
+	}
+
+	// Check type of target:
+	//   struct or
+	//   map[string]T or map[encoding.TextUnmarshaler]T
+	switch v.Kind() {
+	case reflect.Map:
+		// Map key must either have string kind or be an encoding.TextUnmarshaler.
+		t := v.Type()
+		if t.Key().Kind() != reflect.String &&
+			!reflect.PtrTo(t.Key()).Implements(textUnmarshalerType) {
+			d.saveError(&UnmarshalTypeError{"object", v.Type(), int64(d.off)})
+			d.off--
+			d.next() // skip over { } in input
+			return
+		}
+		if v.IsNil() {
+			v.Set(reflect.MakeMap(t))
+		}
+	case reflect.Struct:
+
+	default:
+		d.saveError(&UnmarshalTypeError{"object", v.Type(), int64(d.off)})
+		d.off--
+		d.next() // skip over { } in input
+		return
+	}
+
+	var mapElem reflect.Value
+
+	empty := true
+	for {
+		// Read opening " of string key or closing }.
+		op := d.scanWhile(scanSkipSpace)
+		if op == scanEndObject {
+			if !empty && !d.ext.trailingCommas {
+				d.syntaxError("beginning of object key string")
+			}
+			break
+		}
+		empty = false
+		if op == scanBeginName {
+			if !d.ext.unquotedKeys {
+				d.syntaxError("beginning of object key string")
+			}
+		} else if op != scanBeginLiteral {
+			d.error(errPhase)
+		}
+		unquotedKey := op == scanBeginName
+
+		// Read key.
+		start := d.off - 1
+		op = d.scanWhile(scanContinue)
+		item := d.data[start : d.off-1]
+		var key []byte
+		if unquotedKey {
+			key = item
+			// TODO Fix code below to quote item when necessary.
+		} else {
+			var ok bool
+			key, ok = unquoteBytes(item)
+			if !ok {
+				d.error(errPhase)
+			}
+		}
+
+		// Figure out field corresponding to key.
+		var subv reflect.Value
+		destring := false // whether the value is wrapped in a string to be decoded first
+
+		if v.Kind() == reflect.Map {
+			elemType := v.Type().Elem()
+			if !mapElem.IsValid() {
+				mapElem = reflect.New(elemType).Elem()
+			} else {
+				mapElem.Set(reflect.Zero(elemType))
+			}
+			subv = mapElem
+		} else {
+			var f *field
+			fields := cachedTypeFields(v.Type())
+			for i := range fields {
+				ff := &fields[i]
+				if bytes.Equal(ff.nameBytes, key) {
+					f = ff
+					break
+				}
+				if f == nil && ff.equalFold(ff.nameBytes, key) {
+					f = ff
+				}
+			}
+			if f != nil {
+				subv = v
+				destring = f.quoted
+				for _, i := range f.index {
+					if subv.Kind() == reflect.Ptr {
+						if subv.IsNil() {
+							subv.Set(reflect.New(subv.Type().Elem()))
+						}
+						subv = subv.Elem()
+					}
+					subv = subv.Field(i)
+				}
+			}
+		}
+
+		// Read : before value.
+		if op == scanSkipSpace {
+			op = d.scanWhile(scanSkipSpace)
+		}
+		if op != scanObjectKey {
+			d.error(errPhase)
+		}
+
+		// Read value.
+		if destring {
+			switch qv := d.valueQuoted().(type) {
+			case nil:
+				d.literalStore(nullLiteral, subv, false)
+			case string:
+				d.literalStore([]byte(qv), subv, true)
+			default:
+				d.saveError(fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal unquoted value into %v", subv.Type()))
+			}
+		} else {
+			d.value(subv)
+		}
+
+		// Write value back to map;
+		// if using struct, subv points into struct already.
+		if v.Kind() == reflect.Map {
+			kt := v.Type().Key()
+			var kv reflect.Value
+			switch {
+			case kt.Kind() == reflect.String:
+				kv = reflect.ValueOf(key).Convert(v.Type().Key())
+			case reflect.PtrTo(kt).Implements(textUnmarshalerType):
+				kv = reflect.New(v.Type().Key())
+				d.literalStore(item, kv, true)
+				kv = kv.Elem()
+			default:
+				panic("json: Unexpected key type") // should never occur
+			}
+			v.SetMapIndex(kv, subv)
+		}
+
+		// Next token must be , or }.
+		op = d.scanWhile(scanSkipSpace)
+		if op == scanEndObject {
+			break
+		}
+		if op != scanObjectValue {
+			d.error(errPhase)
+		}
+	}
+}
+
+// isNull returns whether there's a null literal at the provided offset.
+func (d *decodeState) isNull(off int) bool {
+	if off+4 >= len(d.data) || d.data[off] != 'n' || d.data[off+1] != 'u' || d.data[off+2] != 'l' || d.data[off+3] != 'l' {
+		return false
+	}
+	d.nextscan.reset()
+	for i, c := range d.data[off:] {
+		if i > 4 {
+			return false
+		}
+		switch d.nextscan.step(&d.nextscan, c) {
+		case scanContinue, scanBeginName:
+			continue
+		}
+		break
+	}
+	return true
+}
+
+// name consumes a const or function from d.data[d.off-1:], decoding into the value v.
+// the first byte of the function name has been read already.
+func (d *decodeState) name(v reflect.Value) {
+	if d.isNull(d.off-1) {
+		d.literal(v)
+		return
+	}
+
+	// Check for unmarshaler.
+	u, ut, pv := d.indirect(v, false)
+	if d.storeKeyed(pv) {
+		return
+	}
+	if u != nil {
+		d.off--
+		err := u.UnmarshalJSON(d.next())
+		if err != nil {
+			d.error(err)
+		}
+		return
+	}
+	if ut != nil {
+		d.saveError(&UnmarshalTypeError{"object", v.Type(), int64(d.off)})
+		d.off--
+		d.next() // skip over function in input
+		return
+	}
+	v = pv
+
+	// Decoding into nil interface?  Switch to non-reflect code.
+	if v.Kind() == reflect.Interface && v.NumMethod() == 0 {
+		out := d.nameInterface()
+		if out == nil {
+			v.Set(reflect.Zero(v.Type()))
+		} else {
+			v.Set(reflect.ValueOf(out))
+		}
+		return
+	}
+
+	nameStart := d.off - 1
+
+	op := d.scanWhile(scanContinue)
+
+	name := d.data[nameStart : d.off-1]
+	if op != scanParam {
+		// Back up so the byte just read is consumed next.
+		d.off--
+		d.scan.undo(op)
+		if l, ok := d.convertLiteral(name); ok {
+			d.storeValue(v, l)
+			return
+		}
+		d.error(&SyntaxError{fmt.Sprintf("json: unknown constant %q", name), int64(d.off)})
+	}
+
+	funcName := string(name)
+	funcData := d.ext.funcs[funcName]
+	if funcData.key == "" {
+		d.error(fmt.Errorf("json: unknown function %q", funcName))
+	}
+
+	// Check type of target:
+	//   struct or
+	//   map[string]T or map[encoding.TextUnmarshaler]T
+	switch v.Kind() {
+	case reflect.Map:
+		// Map key must either have string kind or be an encoding.TextUnmarshaler.
+		t := v.Type()
+		if t.Key().Kind() != reflect.String &&
+			!reflect.PtrTo(t.Key()).Implements(textUnmarshalerType) {
+			d.saveError(&UnmarshalTypeError{"object", v.Type(), int64(d.off)})
+			d.off--
+			d.next() // skip over { } in input
+			return
+		}
+		if v.IsNil() {
+			v.Set(reflect.MakeMap(t))
+		}
+	case reflect.Struct:
+
+	default:
+		d.saveError(&UnmarshalTypeError{"object", v.Type(), int64(d.off)})
+		d.off--
+		d.next() // skip over { } in input
+		return
+	}
+
+	// TODO Fix case of func field as map.
+	//topv := v
+
+	// Figure out field corresponding to function.
+	key := []byte(funcData.key)
+	if v.Kind() == reflect.Map {
+		elemType := v.Type().Elem()
+		v = reflect.New(elemType).Elem()
+	} else {
+		var f *field
+		fields := cachedTypeFields(v.Type())
+		for i := range fields {
+			ff := &fields[i]
+			if bytes.Equal(ff.nameBytes, key) {
+				f = ff
+				break
+			}
+			if f == nil && ff.equalFold(ff.nameBytes, key) {
+				f = ff
+			}
+		}
+		if f != nil {
+			for _, i := range f.index {
+				if v.Kind() == reflect.Ptr {
+					if v.IsNil() {
+						v.Set(reflect.New(v.Type().Elem()))
+					}
+					v = v.Elem()
+				}
+				v = v.Field(i)
+			}
+			if v.Kind() == reflect.Ptr {
+				if v.IsNil() {
+					v.Set(reflect.New(v.Type().Elem()))
+				}
+				v = v.Elem()
+			}
+		}
+	}
+
+	// Check for unmarshaler on func field itself.
+	u, ut, pv = d.indirect(v, false)
+	if u != nil {
+		d.off = nameStart
+		err := u.UnmarshalJSON(d.next())
+		if err != nil {
+			d.error(err)
+		}
+		return
+	}
+
+	var mapElem reflect.Value
+
+	// Parse function arguments.
+	for i := 0; ; i++ {
+		// closing ) - can only happen on first iteration.
+		op := d.scanWhile(scanSkipSpace)
+		if op == scanEndParams {
+			break
+		}
+
+		// Back up so d.value can have the byte we just read.
+		d.off--
+		d.scan.undo(op)
+
+		if i >= len(funcData.args) {
+			d.error(fmt.Errorf("json: too many arguments for function %s", funcName))
+		}
+		key := []byte(funcData.args[i])
+
+		// Figure out field corresponding to key.
+		var subv reflect.Value
+		destring := false // whether the value is wrapped in a string to be decoded first
+
+		if v.Kind() == reflect.Map {
+			elemType := v.Type().Elem()
+			if !mapElem.IsValid() {
+				mapElem = reflect.New(elemType).Elem()
+			} else {
+				mapElem.Set(reflect.Zero(elemType))
+			}
+			subv = mapElem
+		} else {
+			var f *field
+			fields := cachedTypeFields(v.Type())
+			for i := range fields {
+				ff := &fields[i]
+				if bytes.Equal(ff.nameBytes, key) {
+					f = ff
+					break
+				}
+				if f == nil && ff.equalFold(ff.nameBytes, key) {
+					f = ff
+				}
+			}
+			if f != nil {
+				subv = v
+				destring = f.quoted
+				for _, i := range f.index {
+					if subv.Kind() == reflect.Ptr {
+						if subv.IsNil() {
+							subv.Set(reflect.New(subv.Type().Elem()))
+						}
+						subv = subv.Elem()
+					}
+					subv = subv.Field(i)
+				}
+			}
+		}
+
+		// Read value.
+		if destring {
+			switch qv := d.valueQuoted().(type) {
+			case nil:
+				d.literalStore(nullLiteral, subv, false)
+			case string:
+				d.literalStore([]byte(qv), subv, true)
+			default:
+				d.saveError(fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal unquoted value into %v", subv.Type()))
+			}
+		} else {
+			d.value(subv)
+		}
+
+		// Write value back to map;
+		// if using struct, subv points into struct already.
+		if v.Kind() == reflect.Map {
+			kt := v.Type().Key()
+			var kv reflect.Value
+			switch {
+			case kt.Kind() == reflect.String:
+				kv = reflect.ValueOf(key).Convert(v.Type().Key())
+			case reflect.PtrTo(kt).Implements(textUnmarshalerType):
+				kv = reflect.New(v.Type().Key())
+				d.literalStore(key, kv, true)
+				kv = kv.Elem()
+			default:
+				panic("json: Unexpected key type") // should never occur
+			}
+			v.SetMapIndex(kv, subv)
+		}
+
+		// Next token must be , or ).
+		op = d.scanWhile(scanSkipSpace)
+		if op == scanEndParams {
+			break
+		}
+		if op != scanParam {
+			d.error(errPhase)
+		}
+	}
+}
+
+// keyed attempts to decode an object or function using a keyed doc extension,
+// and returns the value and true on success, or nil and false otherwise.
+func (d *decodeState) keyed() (interface{}, bool) {
+	if len(d.ext.keyed) == 0 {
+		return nil, false
+	}
+
+	unquote := false
+
+	// Look-ahead first key to check for a keyed document extension.
+	d.nextscan.reset()
+	var start, end int
+	for i, c := range d.data[d.off-1:] {
+		switch op := d.nextscan.step(&d.nextscan, c); op {
+		case scanSkipSpace, scanContinue, scanBeginObject:
+			continue
+		case scanBeginLiteral, scanBeginName:
+			unquote = op == scanBeginLiteral
+			start = i
+			continue
+		}
+		end = i
+		break
+	}
+
+	name := d.data[d.off-1+start : d.off-1+end]
+
+	var key []byte
+	var ok bool
+	if unquote {
+		key, ok = unquoteBytes(name)
+		if !ok {
+			d.error(errPhase)
+		}
+	} else {
+		funcData, ok := d.ext.funcs[string(name)]
+		if !ok {
+			return nil, false
+		}
+		key = []byte(funcData.key)
+	}
+
+	decode, ok := d.ext.keyed[string(key)]
+	if !ok {
+		return nil, false
+	}
+
+	d.off--
+	out, err := decode(d.next())
+	if err != nil {
+		d.error(err)
+	}
+	return out, true
+}
+
+func (d *decodeState) storeKeyed(v reflect.Value) bool {
+	keyed, ok := d.keyed()
+	if !ok {
+		return false
+	}
+	d.storeValue(v, keyed)
+	return true
+}
+
+var (
+	trueBytes = []byte("true")
+	falseBytes = []byte("false")
+	nullBytes = []byte("null")
+)
+
+func (d *decodeState) storeValue(v reflect.Value, from interface{}) {
+	switch from {
+	case nil:
+		d.literalStore(nullBytes, v, false)
+		return
+	case true:
+		d.literalStore(trueBytes, v, false)
+		return
+	case false:
+		d.literalStore(falseBytes, v, false)
+		return
+	}
+	fromv := reflect.ValueOf(from)
+	for fromv.Kind() == reflect.Ptr && !fromv.IsNil() {
+		fromv = fromv.Elem()
+	}
+	fromt := fromv.Type()
+	for v.Kind() == reflect.Ptr && !v.IsNil() {
+		v = v.Elem()
+	}
+	vt := v.Type()
+	if fromt.AssignableTo(vt) {
+		v.Set(fromv)
+	} else if fromt.ConvertibleTo(vt) {
+		v.Set(fromv.Convert(vt))
+	} else {
+		d.saveError(&UnmarshalTypeError{"object", v.Type(), int64(d.off)})
+	}
+}
+
+func (d *decodeState) convertLiteral(name []byte) (interface{}, bool) {
+	if len(name) == 0 {
+		return nil, false
+	}
+	switch name[0] {
+	case 't':
+		if bytes.Equal(name, trueBytes) {
+			return true, true
+		}
+	case 'f':
+		if bytes.Equal(name, falseBytes) {
+			return false, true
+		}
+	case 'n':
+		if bytes.Equal(name, nullBytes) {
+			return nil, true
+		}
+	}
+	if l, ok := d.ext.consts[string(name)]; ok {
+		return l, true
+	}
+	return nil, false
+}
+
+// literal consumes a literal from d.data[d.off-1:], decoding into the value v.
+// The first byte of the literal has been read already
+// (that's how the caller knows it's a literal).
+func (d *decodeState) literal(v reflect.Value) {
+	// All bytes inside literal return scanContinue op code.
+	start := d.off - 1
+	op := d.scanWhile(scanContinue)
+
+	// Scan read one byte too far; back up.
+	d.off--
+	d.scan.undo(op)
+
+	d.literalStore(d.data[start:d.off], v, false)
+}
+
+// convertNumber converts the number literal s to a float64 or a Number
+// depending on the setting of d.useNumber.
+func (d *decodeState) convertNumber(s string) (interface{}, error) {
+	if d.useNumber {
+		return Number(s), nil
+	}
+	f, err := strconv.ParseFloat(s, 64)
+	if err != nil {
+		return nil, &UnmarshalTypeError{"number " + s, reflect.TypeOf(0.0), int64(d.off)}
+	}
+	return f, nil
+}
+
+var numberType = reflect.TypeOf(Number(""))
+
+// literalStore decodes a literal stored in item into v.
+//
+// fromQuoted indicates whether this literal came from unwrapping a
+// string from the ",string" struct tag option. this is used only to
+// produce more helpful error messages.
+func (d *decodeState) literalStore(item []byte, v reflect.Value, fromQuoted bool) {
+	// Check for unmarshaler.
+	if len(item) == 0 {
+		//Empty string given
+		d.saveError(fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into %v", item, v.Type()))
+		return
+	}
+	wantptr := item[0] == 'n' // null
+	u, ut, pv := d.indirect(v, wantptr)
+	if u != nil {
+		err := u.UnmarshalJSON(item)
+		if err != nil {
+			d.error(err)
+		}
+		return
+	}
+	if ut != nil {
+		if item[0] != '"' {
+			if fromQuoted {
+				d.saveError(fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into %v", item, v.Type()))
+			} else {
+				d.saveError(&UnmarshalTypeError{"string", v.Type(), int64(d.off)})
+			}
+			return
+		}
+		s, ok := unquoteBytes(item)
+		if !ok {
+			if fromQuoted {
+				d.error(fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into %v", item, v.Type()))
+			} else {
+				d.error(errPhase)
+			}
+		}
+		err := ut.UnmarshalText(s)
+		if err != nil {
+			d.error(err)
+		}
+		return
+	}
+
+	v = pv
+
+	switch c := item[0]; c {
+	case 'n': // null
+		switch v.Kind() {
+		case reflect.Interface, reflect.Ptr, reflect.Map, reflect.Slice:
+			v.Set(reflect.Zero(v.Type()))
+			// otherwise, ignore null for primitives/string
+		}
+	case 't', 'f': // true, false
+		value := c == 't'
+		switch v.Kind() {
+		default:
+			if fromQuoted {
+				d.saveError(fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into %v", item, v.Type()))
+			} else {
+				d.saveError(&UnmarshalTypeError{"bool", v.Type(), int64(d.off)})
+			}
+		case reflect.Bool:
+			v.SetBool(value)
+		case reflect.Interface:
+			if v.NumMethod() == 0 {
+				v.Set(reflect.ValueOf(value))
+			} else {
+				d.saveError(&UnmarshalTypeError{"bool", v.Type(), int64(d.off)})
+			}
+		}
+
+	case '"': // string
+		s, ok := unquoteBytes(item)
+		if !ok {
+			if fromQuoted {
+				d.error(fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into %v", item, v.Type()))
+			} else {
+				d.error(errPhase)
+			}
+		}
+		switch v.Kind() {
+		default:
+			d.saveError(&UnmarshalTypeError{"string", v.Type(), int64(d.off)})
+		case reflect.Slice:
+			if v.Type().Elem().Kind() != reflect.Uint8 {
+				d.saveError(&UnmarshalTypeError{"string", v.Type(), int64(d.off)})
+				break
+			}
+			b := make([]byte, base64.StdEncoding.DecodedLen(len(s)))
+			n, err := base64.StdEncoding.Decode(b, s)
+			if err != nil {
+				d.saveError(err)
+				break
+			}
+			v.SetBytes(b[:n])
+		case reflect.String:
+			v.SetString(string(s))
+		case reflect.Interface:
+			if v.NumMethod() == 0 {
+				v.Set(reflect.ValueOf(string(s)))
+			} else {
+				d.saveError(&UnmarshalTypeError{"string", v.Type(), int64(d.off)})
+			}
+		}
+
+	default: // number
+		if c != '-' && (c < '0' || c > '9') {
+			if fromQuoted {
+				d.error(fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into %v", item, v.Type()))
+			} else {
+				d.error(errPhase)
+			}
+		}
+		s := string(item)
+		switch v.Kind() {
+		default:
+			if v.Kind() == reflect.String && v.Type() == numberType {
+				v.SetString(s)
+				if !isValidNumber(s) {
+					d.error(fmt.Errorf("json: invalid number literal, trying to unmarshal %q into Number", item))
+				}
+				break
+			}
+			if fromQuoted {
+				d.error(fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into %v", item, v.Type()))
+			} else {
+				d.error(&UnmarshalTypeError{"number", v.Type(), int64(d.off)})
+			}
+		case reflect.Interface:
+			n, err := d.convertNumber(s)
+			if err != nil {
+				d.saveError(err)
+				break
+			}
+			if v.NumMethod() != 0 {
+				d.saveError(&UnmarshalTypeError{"number", v.Type(), int64(d.off)})
+				break
+			}
+			v.Set(reflect.ValueOf(n))
+
+		case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+			n, err := strconv.ParseInt(s, 10, 64)
+			if err != nil || v.OverflowInt(n) {
+				d.saveError(&UnmarshalTypeError{"number " + s, v.Type(), int64(d.off)})
+				break
+			}
+			v.SetInt(n)
+
+		case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+			n, err := strconv.ParseUint(s, 10, 64)
+			if err != nil || v.OverflowUint(n) {
+				d.saveError(&UnmarshalTypeError{"number " + s, v.Type(), int64(d.off)})
+				break
+			}
+			v.SetUint(n)
+
+		case reflect.Float32, reflect.Float64:
+			n, err := strconv.ParseFloat(s, v.Type().Bits())
+			if err != nil || v.OverflowFloat(n) {
+				d.saveError(&UnmarshalTypeError{"number " + s, v.Type(), int64(d.off)})
+				break
+			}
+			v.SetFloat(n)
+		}
+	}
+}
+
+// The xxxInterface routines build up a value to be stored
+// in an empty interface. They are not strictly necessary,
+// but they avoid the weight of reflection in this common case.
+
+// valueInterface is like value but returns interface{}
+func (d *decodeState) valueInterface() interface{} {
+	switch d.scanWhile(scanSkipSpace) {
+	default:
+		d.error(errPhase)
+		panic("unreachable")
+	case scanBeginArray:
+		return d.arrayInterface()
+	case scanBeginObject:
+		return d.objectInterface()
+	case scanBeginLiteral:
+		return d.literalInterface()
+	case scanBeginName:
+		return d.nameInterface()
+	}
+}
+
+func (d *decodeState) syntaxError(expected string) {
+	msg := fmt.Sprintf("invalid character '%c' looking for %s", d.data[d.off-1], expected)
+	d.error(&SyntaxError{msg, int64(d.off)})
+}
+
+// arrayInterface is like array but returns []interface{}.
+func (d *decodeState) arrayInterface() []interface{} {
+	var v = make([]interface{}, 0)
+	for {
+		// Look ahead for ] - can only happen on first iteration.
+		op := d.scanWhile(scanSkipSpace)
+		if op == scanEndArray {
+			if len(v) > 0 && !d.ext.trailingCommas {
+				d.syntaxError("beginning of value")
+			}
+			break
+		}
+
+		// Back up so d.value can have the byte we just read.
+		d.off--
+		d.scan.undo(op)
+
+		v = append(v, d.valueInterface())
+
+		// Next token must be , or ].
+		op = d.scanWhile(scanSkipSpace)
+		if op == scanEndArray {
+			break
+		}
+		if op != scanArrayValue {
+			d.error(errPhase)
+		}
+	}
+	return v
+}
+
+// objectInterface is like object but returns map[string]interface{}.
+func (d *decodeState) objectInterface() interface{} {
+	v, ok := d.keyed()
+	if ok {
+		return v
+	}
+
+	m := make(map[string]interface{})
+	for {
+		// Read opening " of string key or closing }.
+		op := d.scanWhile(scanSkipSpace)
+		if op == scanEndObject {
+			if len(m) > 0 && !d.ext.trailingCommas {
+				d.syntaxError("beginning of object key string")
+			}
+			break
+		}
+		if op == scanBeginName {
+			if !d.ext.unquotedKeys {
+				d.syntaxError("beginning of object key string")
+			}
+		} else if op != scanBeginLiteral {
+			d.error(errPhase)
+		}
+		unquotedKey := op == scanBeginName
+
+		// Read string key.
+		start := d.off - 1
+		op = d.scanWhile(scanContinue)
+		item := d.data[start : d.off-1]
+		var key string
+		if unquotedKey {
+			key = string(item)
+		} else {
+			var ok bool
+			key, ok = unquote(item)
+			if !ok {
+				d.error(errPhase)
+			}
+		}
+
+		// Read : before value.
+		if op == scanSkipSpace {
+			op = d.scanWhile(scanSkipSpace)
+		}
+		if op != scanObjectKey {
+			d.error(errPhase)
+		}
+
+		// Read value.
+		m[key] = d.valueInterface()
+
+		// Next token must be , or }.
+		op = d.scanWhile(scanSkipSpace)
+		if op == scanEndObject {
+			break
+		}
+		if op != scanObjectValue {
+			d.error(errPhase)
+		}
+	}
+	return m
+}
+
+// literalInterface is like literal but returns an interface value.
+func (d *decodeState) literalInterface() interface{} {
+	// All bytes inside literal return scanContinue op code.
+	start := d.off - 1
+	op := d.scanWhile(scanContinue)
+
+	// Scan read one byte too far; back up.
+	d.off--
+	d.scan.undo(op)
+	item := d.data[start:d.off]
+
+	switch c := item[0]; c {
+	case 'n': // null
+		return nil
+
+	case 't', 'f': // true, false
+		return c == 't'
+
+	case '"': // string
+		s, ok := unquote(item)
+		if !ok {
+			d.error(errPhase)
+		}
+		return s
+
+	default: // number
+		if c != '-' && (c < '0' || c > '9') {
+			d.error(errPhase)
+		}
+		n, err := d.convertNumber(string(item))
+		if err != nil {
+			d.saveError(err)
+		}
+		return n
+	}
+}
+
+// nameInterface is like function but returns map[string]interface{}.
+func (d *decodeState) nameInterface() interface{} {
+	v, ok := d.keyed()
+	if ok {
+		return v
+	}
+
+	nameStart := d.off - 1
+
+	op := d.scanWhile(scanContinue)
+
+	name := d.data[nameStart : d.off-1]
+	if op != scanParam {
+		// Back up so the byte just read is consumed next.
+		d.off--
+		d.scan.undo(op)
+		if l, ok := d.convertLiteral(name); ok {
+			return l
+		}
+		d.error(&SyntaxError{fmt.Sprintf("json: unknown constant %q", name), int64(d.off)})
+	}
+
+	funcName := string(name)
+	funcData := d.ext.funcs[funcName]
+	if funcData.key == "" {
+		d.error(fmt.Errorf("json: unknown function %q", funcName))
+	}
+
+	m := make(map[string]interface{})
+	for i := 0; ; i++ {
+		// Look ahead for ) - can only happen on first iteration.
+		op := d.scanWhile(scanSkipSpace)
+		if op == scanEndParams {
+			break
+		}
+
+		// Back up so d.value can have the byte we just read.
+		d.off--
+		d.scan.undo(op)
+
+		if i >= len(funcData.args) {
+			d.error(fmt.Errorf("json: too many arguments for function %s", funcName))
+		}
+		m[funcData.args[i]] = d.valueInterface()
+
+		// Next token must be , or ).
+		op = d.scanWhile(scanSkipSpace)
+		if op == scanEndParams {
+			break
+		}
+		if op != scanParam {
+			d.error(errPhase)
+		}
+	}
+	return map[string]interface{}{funcData.key: m}
+}
+
+// getu4 decodes \uXXXX from the beginning of s, returning the hex value,
+// or it returns -1.
+func getu4(s []byte) rune {
+	if len(s) < 6 || s[0] != '\\' || s[1] != 'u' {
+		return -1
+	}
+	r, err := strconv.ParseUint(string(s[2:6]), 16, 64)
+	if err != nil {
+		return -1
+	}
+	return rune(r)
+}
+
+// unquote converts a quoted JSON string literal s into an actual string t.
+// The rules are different than for Go, so cannot use strconv.Unquote.
+func unquote(s []byte) (t string, ok bool) {
+	s, ok = unquoteBytes(s)
+	t = string(s)
+	return
+}
+
+func unquoteBytes(s []byte) (t []byte, ok bool) {
+	if len(s) < 2 || s[0] != '"' || s[len(s)-1] != '"' {
+		return
+	}
+	s = s[1 : len(s)-1]
+
+	// Check for unusual characters. If there are none,
+	// then no unquoting is needed, so return a slice of the
+	// original bytes.
+	r := 0
+	for r < len(s) {
+		c := s[r]
+		if c == '\\' || c == '"' || c < ' ' {
+			break
+		}
+		if c < utf8.RuneSelf {
+			r++
+			continue
+		}
+		rr, size := utf8.DecodeRune(s[r:])
+		if rr == utf8.RuneError && size == 1 {
+			break
+		}
+		r += size
+	}
+	if r == len(s) {
+		return s, true
+	}
+
+	b := make([]byte, len(s)+2*utf8.UTFMax)
+	w := copy(b, s[0:r])
+	for r < len(s) {
+		// Out of room?  Can only happen if s is full of
+		// malformed UTF-8 and we're replacing each
+		// byte with RuneError.
+		if w >= len(b)-2*utf8.UTFMax {
+			nb := make([]byte, (len(b)+utf8.UTFMax)*2)
+			copy(nb, b[0:w])
+			b = nb
+		}
+		switch c := s[r]; {
+		case c == '\\':
+			r++
+			if r >= len(s) {
+				return
+			}
+			switch s[r] {
+			default:
+				return
+			case '"', '\\', '/', '\'':
+				b[w] = s[r]
+				r++
+				w++
+			case 'b':
+				b[w] = '\b'
+				r++
+				w++
+			case 'f':
+				b[w] = '\f'
+				r++
+				w++
+			case 'n':
+				b[w] = '\n'
+				r++
+				w++
+			case 'r':
+				b[w] = '\r'
+				r++
+				w++
+			case 't':
+				b[w] = '\t'
+				r++
+				w++
+			case 'u':
+				r--
+				rr := getu4(s[r:])
+				if rr < 0 {
+					return
+				}
+				r += 6
+				if utf16.IsSurrogate(rr) {
+					rr1 := getu4(s[r:])
+					if dec := utf16.DecodeRune(rr, rr1); dec != unicode.ReplacementChar {
+						// A valid pair; consume.
+						r += 6
+						w += utf8.EncodeRune(b[w:], dec)
+						break
+					}
+					// Invalid surrogate; fall back to replacement rune.
+					rr = unicode.ReplacementChar
+				}
+				w += utf8.EncodeRune(b[w:], rr)
+			}
+
+		// Quote, control characters are invalid.
+		case c == '"', c < ' ':
+			return
+
+		// ASCII
+		case c < utf8.RuneSelf:
+			b[w] = c
+			r++
+			w++
+
+		// Coerce to well-formed UTF-8.
+		default:
+			rr, size := utf8.DecodeRune(s[r:])
+			r += size
+			w += utf8.EncodeRune(b[w:], rr)
+		}
+	}
+	return b[0:w], true
+}
diff --git a/vendor/gopkg.in/mgo.v2/internal/json/encode.go b/vendor/gopkg.in/mgo.v2/internal/json/encode.go
new file mode 100644
index 0000000..67a0f00
--- /dev/null
+++ b/vendor/gopkg.in/mgo.v2/internal/json/encode.go
@@ -0,0 +1,1256 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package json implements encoding and decoding of JSON as defined in
+// RFC 4627. The mapping between JSON and Go values is described
+// in the documentation for the Marshal and Unmarshal functions.
+//
+// See "JSON and Go" for an introduction to this package:
+// https://golang.org/doc/articles/json_and_go.html
+package json
+
+import (
+	"bytes"
+	"encoding"
+	"encoding/base64"
+	"fmt"
+	"math"
+	"reflect"
+	"runtime"
+	"sort"
+	"strconv"
+	"strings"
+	"sync"
+	"unicode"
+	"unicode/utf8"
+)
+
+// Marshal returns the JSON encoding of v.
+//
+// Marshal traverses the value v recursively.
+// If an encountered value implements the Marshaler interface
+// and is not a nil pointer, Marshal calls its MarshalJSON method
+// to produce JSON. If no MarshalJSON method is present but the
+// value implements encoding.TextMarshaler instead, Marshal calls
+// its MarshalText method.
+// The nil pointer exception is not strictly necessary
+// but mimics a similar, necessary exception in the behavior of
+// UnmarshalJSON.
+//
+// Otherwise, Marshal uses the following type-dependent default encodings:
+//
+// Boolean values encode as JSON booleans.
+//
+// Floating point, integer, and Number values encode as JSON numbers.
+//
+// String values encode as JSON strings coerced to valid UTF-8,
+// replacing invalid bytes with the Unicode replacement rune.
+// The angle brackets "<" and ">" are escaped to "\u003c" and "\u003e"
+// to keep some browsers from misinterpreting JSON output as HTML.
+// Ampersand "&" is also escaped to "\u0026" for the same reason.
+// This escaping can be disabled using an Encoder with DisableHTMLEscaping.
+//
+// Array and slice values encode as JSON arrays, except that
+// []byte encodes as a base64-encoded string, and a nil slice
+// encodes as the null JSON value.
+//
+// Struct values encode as JSON objects. Each exported struct field
+// becomes a member of the object unless
+//   - the field's tag is "-", or
+//   - the field is empty and its tag specifies the "omitempty" option.
+// The empty values are false, 0, any
+// nil pointer or interface value, and any array, slice, map, or string of
+// length zero. The object's default key string is the struct field name
+// but can be specified in the struct field's tag value. The "json" key in
+// the struct field's tag value is the key name, followed by an optional comma
+// and options. Examples:
+//
+//   // Field is ignored by this package.
+//   Field int `json:"-"`
+//
+//   // Field appears in JSON as key "myName".
+//   Field int `json:"myName"`
+//
+//   // Field appears in JSON as key "myName" and
+//   // the field is omitted from the object if its value is empty,
+//   // as defined above.
+//   Field int `json:"myName,omitempty"`
+//
+//   // Field appears in JSON as key "Field" (the default), but
+//   // the field is skipped if empty.
+//   // Note the leading comma.
+//   Field int `json:",omitempty"`
+//
+// The "string" option signals that a field is stored as JSON inside a
+// JSON-encoded string. It applies only to fields of string, floating point,
+// integer, or boolean types. This extra level of encoding is sometimes used
+// when communicating with JavaScript programs:
+//
+//    Int64String int64 `json:",string"`
+//
+// The key name will be used if it's a non-empty string consisting of
+// only Unicode letters, digits, dollar signs, percent signs, hyphens,
+// underscores and slashes.
+//
+// Anonymous struct fields are usually marshaled as if their inner exported fields
+// were fields in the outer struct, subject to the usual Go visibility rules amended
+// as described in the next paragraph.
+// An anonymous struct field with a name given in its JSON tag is treated as
+// having that name, rather than being anonymous.
+// An anonymous struct field of interface type is treated the same as having
+// that type as its name, rather than being anonymous.
+//
+// The Go visibility rules for struct fields are amended for JSON when
+// deciding which field to marshal or unmarshal. If there are
+// multiple fields at the same level, and that level is the least
+// nested (and would therefore be the nesting level selected by the
+// usual Go rules), the following extra rules apply:
+//
+// 1) Of those fields, if any are JSON-tagged, only tagged fields are considered,
+// even if there are multiple untagged fields that would otherwise conflict.
+// 2) If there is exactly one field (tagged or not according to the first rule), that is selected.
+// 3) Otherwise there are multiple fields, and all are ignored; no error occurs.
+//
+// Handling of anonymous struct fields is new in Go 1.1.
+// Prior to Go 1.1, anonymous struct fields were ignored. To force ignoring of
+// an anonymous struct field in both current and earlier versions, give the field
+// a JSON tag of "-".
+//
+// Map values encode as JSON objects. The map's key type must either be a string
+// or implement encoding.TextMarshaler.  The map keys are used as JSON object
+// keys, subject to the UTF-8 coercion described for string values above.
+//
+// Pointer values encode as the value pointed to.
+// A nil pointer encodes as the null JSON value.
+//
+// Interface values encode as the value contained in the interface.
+// A nil interface value encodes as the null JSON value.
+//
+// Channel, complex, and function values cannot be encoded in JSON.
+// Attempting to encode such a value causes Marshal to return
+// an UnsupportedTypeError.
+//
+// JSON cannot represent cyclic data structures and Marshal does not
+// handle them. Passing cyclic structures to Marshal will result in
+// an infinite recursion.
+//
+func Marshal(v interface{}) ([]byte, error) {
+	e := &encodeState{}
+	err := e.marshal(v, encOpts{escapeHTML: true})
+	if err != nil {
+		return nil, err
+	}
+	return e.Bytes(), nil
+}
+
+// MarshalIndent is like Marshal but applies Indent to format the output.
+func MarshalIndent(v interface{}, prefix, indent string) ([]byte, error) {
+	b, err := Marshal(v)
+	if err != nil {
+		return nil, err
+	}
+	var buf bytes.Buffer
+	err = Indent(&buf, b, prefix, indent)
+	if err != nil {
+		return nil, err
+	}
+	return buf.Bytes(), nil
+}
+
+// HTMLEscape appends to dst the JSON-encoded src with <, >, &, U+2028 and U+2029
+// characters inside string literals changed to \u003c, \u003e, \u0026, \u2028, \u2029
+// so that the JSON will be safe to embed inside HTML <script> tags.
+// For historical reasons, web browsers don't honor standard HTML
+// escaping within <script> tags, so an alternative JSON encoding must
+// be used.
+func HTMLEscape(dst *bytes.Buffer, src []byte) {
+	// The characters can only appear in string literals,
+	// so just scan the string one byte at a time.
+	start := 0
+	for i, c := range src {
+		if c == '<' || c == '>' || c == '&' {
+			if start < i {
+				dst.Write(src[start:i])
+			}
+			dst.WriteString(`\u00`)
+			dst.WriteByte(hex[c>>4])
+			dst.WriteByte(hex[c&0xF])
+			start = i + 1
+		}
+		// Convert U+2028 and U+2029 (E2 80 A8 and E2 80 A9).
+		if c == 0xE2 && i+2 < len(src) && src[i+1] == 0x80 && src[i+2]&^1 == 0xA8 {
+			if start < i {
+				dst.Write(src[start:i])
+			}
+			dst.WriteString(`\u202`)
+			dst.WriteByte(hex[src[i+2]&0xF])
+			start = i + 3
+		}
+	}
+	if start < len(src) {
+		dst.Write(src[start:])
+	}
+}
+
+// Marshaler is the interface implemented by types that
+// can marshal themselves into valid JSON.
+type Marshaler interface {
+	MarshalJSON() ([]byte, error)
+}
+
+// An UnsupportedTypeError is returned by Marshal when attempting
+// to encode an unsupported value type.
+type UnsupportedTypeError struct {
+	Type reflect.Type
+}
+
+func (e *UnsupportedTypeError) Error() string {
+	return "json: unsupported type: " + e.Type.String()
+}
+
+type UnsupportedValueError struct {
+	Value reflect.Value
+	Str   string
+}
+
+func (e *UnsupportedValueError) Error() string {
+	return "json: unsupported value: " + e.Str
+}
+
+// Before Go 1.2, an InvalidUTF8Error was returned by Marshal when
+// attempting to encode a string value with invalid UTF-8 sequences.
+// As of Go 1.2, Marshal instead coerces the string to valid UTF-8 by
+// replacing invalid bytes with the Unicode replacement rune U+FFFD.
+// This error is no longer generated but is kept for backwards compatibility
+// with programs that might mention it.
+type InvalidUTF8Error struct {
+	S string // the whole string value that caused the error
+}
+
+func (e *InvalidUTF8Error) Error() string {
+	return "json: invalid UTF-8 in string: " + strconv.Quote(e.S)
+}
+
+type MarshalerError struct {
+	Type reflect.Type
+	Err  error
+}
+
+func (e *MarshalerError) Error() string {
+	return "json: error calling MarshalJSON for type " + e.Type.String() + ": " + e.Err.Error()
+}
+
+var hex = "0123456789abcdef"
+
+// An encodeState encodes JSON into a bytes.Buffer.
+type encodeState struct {
+	bytes.Buffer // accumulated output
+	scratch      [64]byte
+	ext          Extension
+}
+
+var encodeStatePool sync.Pool
+
+func newEncodeState() *encodeState {
+	if v := encodeStatePool.Get(); v != nil {
+		e := v.(*encodeState)
+		e.Reset()
+		return e
+	}
+	return new(encodeState)
+}
+
+func (e *encodeState) marshal(v interface{}, opts encOpts) (err error) {
+	defer func() {
+		if r := recover(); r != nil {
+			if _, ok := r.(runtime.Error); ok {
+				panic(r)
+			}
+			if s, ok := r.(string); ok {
+				panic(s)
+			}
+			err = r.(error)
+		}
+	}()
+	e.reflectValue(reflect.ValueOf(v), opts)
+	return nil
+}
+
+func (e *encodeState) error(err error) {
+	panic(err)
+}
+
+func isEmptyValue(v reflect.Value) bool {
+	switch v.Kind() {
+	case reflect.Array, reflect.Map, reflect.Slice, reflect.String:
+		return v.Len() == 0
+	case reflect.Bool:
+		return !v.Bool()
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		return v.Int() == 0
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		return v.Uint() == 0
+	case reflect.Float32, reflect.Float64:
+		return v.Float() == 0
+	case reflect.Interface, reflect.Ptr:
+		return v.IsNil()
+	}
+	return false
+}
+
+func (e *encodeState) reflectValue(v reflect.Value, opts encOpts) {
+	valueEncoder(v)(e, v, opts)
+}
+
+type encOpts struct {
+	// quoted causes primitive fields to be encoded inside JSON strings.
+	quoted bool
+	// escapeHTML causes '<', '>', and '&' to be escaped in JSON strings.
+	escapeHTML bool
+}
+
+type encoderFunc func(e *encodeState, v reflect.Value, opts encOpts)
+
+var encoderCache struct {
+	sync.RWMutex
+	m map[reflect.Type]encoderFunc
+}
+
+func valueEncoder(v reflect.Value) encoderFunc {
+	if !v.IsValid() {
+		return invalidValueEncoder
+	}
+	return typeEncoder(v.Type())
+}
+
+func typeEncoder(t reflect.Type) encoderFunc {
+	encoderCache.RLock()
+	f := encoderCache.m[t]
+	encoderCache.RUnlock()
+	if f != nil {
+		return f
+	}
+
+	// To deal with recursive types, populate the map with an
+	// indirect func before we build it. This type waits on the
+	// real func (f) to be ready and then calls it. This indirect
+	// func is only used for recursive types.
+	encoderCache.Lock()
+	if encoderCache.m == nil {
+		encoderCache.m = make(map[reflect.Type]encoderFunc)
+	}
+	var wg sync.WaitGroup
+	wg.Add(1)
+	encoderCache.m[t] = func(e *encodeState, v reflect.Value, opts encOpts) {
+		wg.Wait()
+		f(e, v, opts)
+	}
+	encoderCache.Unlock()
+
+	// Compute fields without lock.
+	// Might duplicate effort but won't hold other computations back.
+	innerf := newTypeEncoder(t, true)
+	f = func(e *encodeState, v reflect.Value, opts encOpts) {
+		encode, ok := e.ext.encode[v.Type()]
+		if !ok {
+			innerf(e, v, opts)
+			return
+		}
+
+		b, err := encode(v.Interface())
+		if err == nil {
+			// copy JSON into buffer, checking validity.
+			err = compact(&e.Buffer, b, opts.escapeHTML)
+		}
+		if err != nil {
+			e.error(&MarshalerError{v.Type(), err})
+		}
+	}
+	wg.Done()
+	encoderCache.Lock()
+	encoderCache.m[t] = f
+	encoderCache.Unlock()
+	return f
+}
+
+var (
+	marshalerType     = reflect.TypeOf(new(Marshaler)).Elem()
+	textMarshalerType = reflect.TypeOf(new(encoding.TextMarshaler)).Elem()
+)
+
+// newTypeEncoder constructs an encoderFunc for a type.
+// The returned encoder only checks CanAddr when allowAddr is true.
+func newTypeEncoder(t reflect.Type, allowAddr bool) encoderFunc {
+	if t.Implements(marshalerType) {
+		return marshalerEncoder
+	}
+	if t.Kind() != reflect.Ptr && allowAddr {
+		if reflect.PtrTo(t).Implements(marshalerType) {
+			return newCondAddrEncoder(addrMarshalerEncoder, newTypeEncoder(t, false))
+		}
+	}
+
+	if t.Implements(textMarshalerType) {
+		return textMarshalerEncoder
+	}
+	if t.Kind() != reflect.Ptr && allowAddr {
+		if reflect.PtrTo(t).Implements(textMarshalerType) {
+			return newCondAddrEncoder(addrTextMarshalerEncoder, newTypeEncoder(t, false))
+		}
+	}
+
+	switch t.Kind() {
+	case reflect.Bool:
+		return boolEncoder
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		return intEncoder
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		return uintEncoder
+	case reflect.Float32:
+		return float32Encoder
+	case reflect.Float64:
+		return float64Encoder
+	case reflect.String:
+		return stringEncoder
+	case reflect.Interface:
+		return interfaceEncoder
+	case reflect.Struct:
+		return newStructEncoder(t)
+	case reflect.Map:
+		return newMapEncoder(t)
+	case reflect.Slice:
+		return newSliceEncoder(t)
+	case reflect.Array:
+		return newArrayEncoder(t)
+	case reflect.Ptr:
+		return newPtrEncoder(t)
+	default:
+		return unsupportedTypeEncoder
+	}
+}
+
+func invalidValueEncoder(e *encodeState, v reflect.Value, _ encOpts) {
+	e.WriteString("null")
+}
+
+func marshalerEncoder(e *encodeState, v reflect.Value, opts encOpts) {
+	if v.Kind() == reflect.Ptr && v.IsNil() {
+		e.WriteString("null")
+		return
+	}
+	m := v.Interface().(Marshaler)
+	b, err := m.MarshalJSON()
+	if err == nil {
+		// copy JSON into buffer, checking validity.
+		err = compact(&e.Buffer, b, opts.escapeHTML)
+	}
+	if err != nil {
+		e.error(&MarshalerError{v.Type(), err})
+	}
+}
+
+func addrMarshalerEncoder(e *encodeState, v reflect.Value, _ encOpts) {
+	va := v.Addr()
+	if va.IsNil() {
+		e.WriteString("null")
+		return
+	}
+	m := va.Interface().(Marshaler)
+	b, err := m.MarshalJSON()
+	if err == nil {
+		// copy JSON into buffer, checking validity.
+		err = compact(&e.Buffer, b, true)
+	}
+	if err != nil {
+		e.error(&MarshalerError{v.Type(), err})
+	}
+}
+
+func textMarshalerEncoder(e *encodeState, v reflect.Value, opts encOpts) {
+	if v.Kind() == reflect.Ptr && v.IsNil() {
+		e.WriteString("null")
+		return
+	}
+	m := v.Interface().(encoding.TextMarshaler)
+	b, err := m.MarshalText()
+	if err != nil {
+		e.error(&MarshalerError{v.Type(), err})
+	}
+	e.stringBytes(b, opts.escapeHTML)
+}
+
+func addrTextMarshalerEncoder(e *encodeState, v reflect.Value, opts encOpts) {
+	va := v.Addr()
+	if va.IsNil() {
+		e.WriteString("null")
+		return
+	}
+	m := va.Interface().(encoding.TextMarshaler)
+	b, err := m.MarshalText()
+	if err != nil {
+		e.error(&MarshalerError{v.Type(), err})
+	}
+	e.stringBytes(b, opts.escapeHTML)
+}
+
+func boolEncoder(e *encodeState, v reflect.Value, opts encOpts) {
+	if opts.quoted {
+		e.WriteByte('"')
+	}
+	if v.Bool() {
+		e.WriteString("true")
+	} else {
+		e.WriteString("false")
+	}
+	if opts.quoted {
+		e.WriteByte('"')
+	}
+}
+
+func intEncoder(e *encodeState, v reflect.Value, opts encOpts) {
+	b := strconv.AppendInt(e.scratch[:0], v.Int(), 10)
+	if opts.quoted {
+		e.WriteByte('"')
+	}
+	e.Write(b)
+	if opts.quoted {
+		e.WriteByte('"')
+	}
+}
+
+func uintEncoder(e *encodeState, v reflect.Value, opts encOpts) {
+	b := strconv.AppendUint(e.scratch[:0], v.Uint(), 10)
+	if opts.quoted {
+		e.WriteByte('"')
+	}
+	e.Write(b)
+	if opts.quoted {
+		e.WriteByte('"')
+	}
+}
+
+type floatEncoder int // number of bits
+
+func (bits floatEncoder) encode(e *encodeState, v reflect.Value, opts encOpts) {
+	f := v.Float()
+	if math.IsInf(f, 0) || math.IsNaN(f) {
+		e.error(&UnsupportedValueError{v, strconv.FormatFloat(f, 'g', -1, int(bits))})
+	}
+	b := strconv.AppendFloat(e.scratch[:0], f, 'g', -1, int(bits))
+	if opts.quoted {
+		e.WriteByte('"')
+	}
+	e.Write(b)
+	if opts.quoted {
+		e.WriteByte('"')
+	}
+}
+
+var (
+	float32Encoder = (floatEncoder(32)).encode
+	float64Encoder = (floatEncoder(64)).encode
+)
+
+func stringEncoder(e *encodeState, v reflect.Value, opts encOpts) {
+	if v.Type() == numberType {
+		numStr := v.String()
+		// In Go1.5 the empty string encodes to "0", while this is not a valid number literal
+		// we keep compatibility so check validity after this.
+		if numStr == "" {
+			numStr = "0" // Number's zero-val
+		}
+		if !isValidNumber(numStr) {
+			e.error(fmt.Errorf("json: invalid number literal %q", numStr))
+		}
+		e.WriteString(numStr)
+		return
+	}
+	if opts.quoted {
+		sb, err := Marshal(v.String())
+		if err != nil {
+			e.error(err)
+		}
+		e.string(string(sb), opts.escapeHTML)
+	} else {
+		e.string(v.String(), opts.escapeHTML)
+	}
+}
+
+func interfaceEncoder(e *encodeState, v reflect.Value, opts encOpts) {
+	if v.IsNil() {
+		e.WriteString("null")
+		return
+	}
+	e.reflectValue(v.Elem(), opts)
+}
+
+func unsupportedTypeEncoder(e *encodeState, v reflect.Value, _ encOpts) {
+	e.error(&UnsupportedTypeError{v.Type()})
+}
+
+type structEncoder struct {
+	fields    []field
+	fieldEncs []encoderFunc
+}
+
+func (se *structEncoder) encode(e *encodeState, v reflect.Value, opts encOpts) {
+	e.WriteByte('{')
+	first := true
+	for i, f := range se.fields {
+		fv := fieldByIndex(v, f.index)
+		if !fv.IsValid() || f.omitEmpty && isEmptyValue(fv) {
+			continue
+		}
+		if first {
+			first = false
+		} else {
+			e.WriteByte(',')
+		}
+		e.string(f.name, opts.escapeHTML)
+		e.WriteByte(':')
+		opts.quoted = f.quoted
+		se.fieldEncs[i](e, fv, opts)
+	}
+	e.WriteByte('}')
+}
+
+func newStructEncoder(t reflect.Type) encoderFunc {
+	fields := cachedTypeFields(t)
+	se := &structEncoder{
+		fields:    fields,
+		fieldEncs: make([]encoderFunc, len(fields)),
+	}
+	for i, f := range fields {
+		se.fieldEncs[i] = typeEncoder(typeByIndex(t, f.index))
+	}
+	return se.encode
+}
+
+type mapEncoder struct {
+	elemEnc encoderFunc
+}
+
+func (me *mapEncoder) encode(e *encodeState, v reflect.Value, opts encOpts) {
+	if v.IsNil() {
+		e.WriteString("null")
+		return
+	}
+	e.WriteByte('{')
+
+	// Extract and sort the keys.
+	keys := v.MapKeys()
+	sv := make([]reflectWithString, len(keys))
+	for i, v := range keys {
+		sv[i].v = v
+		if err := sv[i].resolve(); err != nil {
+			e.error(&MarshalerError{v.Type(), err})
+		}
+	}
+	sort.Sort(byString(sv))
+
+	for i, kv := range sv {
+		if i > 0 {
+			e.WriteByte(',')
+		}
+		e.string(kv.s, opts.escapeHTML)
+		e.WriteByte(':')
+		me.elemEnc(e, v.MapIndex(kv.v), opts)
+	}
+	e.WriteByte('}')
+}
+
+func newMapEncoder(t reflect.Type) encoderFunc {
+	if t.Key().Kind() != reflect.String && !t.Key().Implements(textMarshalerType) {
+		return unsupportedTypeEncoder
+	}
+	me := &mapEncoder{typeEncoder(t.Elem())}
+	return me.encode
+}
+
+func encodeByteSlice(e *encodeState, v reflect.Value, _ encOpts) {
+	if v.IsNil() {
+		e.WriteString("null")
+		return
+	}
+	s := v.Bytes()
+	e.WriteByte('"')
+	if len(s) < 1024 {
+		// for small buffers, using Encode directly is much faster.
+		dst := make([]byte, base64.StdEncoding.EncodedLen(len(s)))
+		base64.StdEncoding.Encode(dst, s)
+		e.Write(dst)
+	} else {
+		// for large buffers, avoid unnecessary extra temporary
+		// buffer space.
+		enc := base64.NewEncoder(base64.StdEncoding, e)
+		enc.Write(s)
+		enc.Close()
+	}
+	e.WriteByte('"')
+}
+
+// sliceEncoder just wraps an arrayEncoder, checking to make sure the value isn't nil.
+type sliceEncoder struct {
+	arrayEnc encoderFunc
+}
+
+func (se *sliceEncoder) encode(e *encodeState, v reflect.Value, opts encOpts) {
+	if v.IsNil() {
+		e.WriteString("null")
+		return
+	}
+	se.arrayEnc(e, v, opts)
+}
+
+func newSliceEncoder(t reflect.Type) encoderFunc {
+	// Byte slices get special treatment; arrays don't.
+	if t.Elem().Kind() == reflect.Uint8 &&
+		!t.Elem().Implements(marshalerType) &&
+		!t.Elem().Implements(textMarshalerType) {
+		return encodeByteSlice
+	}
+	enc := &sliceEncoder{newArrayEncoder(t)}
+	return enc.encode
+}
+
+type arrayEncoder struct {
+	elemEnc encoderFunc
+}
+
+func (ae *arrayEncoder) encode(e *encodeState, v reflect.Value, opts encOpts) {
+	e.WriteByte('[')
+	n := v.Len()
+	for i := 0; i < n; i++ {
+		if i > 0 {
+			e.WriteByte(',')
+		}
+		ae.elemEnc(e, v.Index(i), opts)
+	}
+	e.WriteByte(']')
+}
+
+func newArrayEncoder(t reflect.Type) encoderFunc {
+	enc := &arrayEncoder{typeEncoder(t.Elem())}
+	return enc.encode
+}
+
+type ptrEncoder struct {
+	elemEnc encoderFunc
+}
+
+func (pe *ptrEncoder) encode(e *encodeState, v reflect.Value, opts encOpts) {
+	if v.IsNil() {
+		e.WriteString("null")
+		return
+	}
+	pe.elemEnc(e, v.Elem(), opts)
+}
+
+func newPtrEncoder(t reflect.Type) encoderFunc {
+	enc := &ptrEncoder{typeEncoder(t.Elem())}
+	return enc.encode
+}
+
+type condAddrEncoder struct {
+	canAddrEnc, elseEnc encoderFunc
+}
+
+func (ce *condAddrEncoder) encode(e *encodeState, v reflect.Value, opts encOpts) {
+	if v.CanAddr() {
+		ce.canAddrEnc(e, v, opts)
+	} else {
+		ce.elseEnc(e, v, opts)
+	}
+}
+
+// newCondAddrEncoder returns an encoder that checks whether its value
+// CanAddr and delegates to canAddrEnc if so, else to elseEnc.
+func newCondAddrEncoder(canAddrEnc, elseEnc encoderFunc) encoderFunc {
+	enc := &condAddrEncoder{canAddrEnc: canAddrEnc, elseEnc: elseEnc}
+	return enc.encode
+}
+
+func isValidTag(s string) bool {
+	if s == "" {
+		return false
+	}
+	for _, c := range s {
+		switch {
+		case strings.ContainsRune("!#$%&()*+-./:<=>?@[]^_{|}~ ", c):
+			// Backslash and quote chars are reserved, but
+			// otherwise any punctuation chars are allowed
+			// in a tag name.
+		default:
+			if !unicode.IsLetter(c) && !unicode.IsDigit(c) {
+				return false
+			}
+		}
+	}
+	return true
+}
+
+func fieldByIndex(v reflect.Value, index []int) reflect.Value {
+	for _, i := range index {
+		if v.Kind() == reflect.Ptr {
+			if v.IsNil() {
+				return reflect.Value{}
+			}
+			v = v.Elem()
+		}
+		v = v.Field(i)
+	}
+	return v
+}
+
+func typeByIndex(t reflect.Type, index []int) reflect.Type {
+	for _, i := range index {
+		if t.Kind() == reflect.Ptr {
+			t = t.Elem()
+		}
+		t = t.Field(i).Type
+	}
+	return t
+}
+
+type reflectWithString struct {
+	v reflect.Value
+	s string
+}
+
+func (w *reflectWithString) resolve() error {
+	if w.v.Kind() == reflect.String {
+		w.s = w.v.String()
+		return nil
+	}
+	buf, err := w.v.Interface().(encoding.TextMarshaler).MarshalText()
+	w.s = string(buf)
+	return err
+}
+
+// byString is a slice of reflectWithString where the reflect.Value is either
+// a string or an encoding.TextMarshaler.
+// It implements the methods to sort by string.
+type byString []reflectWithString
+
+func (sv byString) Len() int           { return len(sv) }
+func (sv byString) Swap(i, j int)      { sv[i], sv[j] = sv[j], sv[i] }
+func (sv byString) Less(i, j int) bool { return sv[i].s < sv[j].s }
+
+// NOTE: keep in sync with stringBytes below.
+func (e *encodeState) string(s string, escapeHTML bool) int {
+	len0 := e.Len()
+	e.WriteByte('"')
+	start := 0
+	for i := 0; i < len(s); {
+		if b := s[i]; b < utf8.RuneSelf {
+			if 0x20 <= b && b != '\\' && b != '"' &&
+				(!escapeHTML || b != '<' && b != '>' && b != '&') {
+				i++
+				continue
+			}
+			if start < i {
+				e.WriteString(s[start:i])
+			}
+			switch b {
+			case '\\', '"':
+				e.WriteByte('\\')
+				e.WriteByte(b)
+			case '\n':
+				e.WriteByte('\\')
+				e.WriteByte('n')
+			case '\r':
+				e.WriteByte('\\')
+				e.WriteByte('r')
+			case '\t':
+				e.WriteByte('\\')
+				e.WriteByte('t')
+			default:
+				// This encodes bytes < 0x20 except for \t, \n and \r.
+				// If escapeHTML is set, it also escapes <, >, and &
+				// because they can lead to security holes when
+				// user-controlled strings are rendered into JSON
+				// and served to some browsers.
+				e.WriteString(`\u00`)
+				e.WriteByte(hex[b>>4])
+				e.WriteByte(hex[b&0xF])
+			}
+			i++
+			start = i
+			continue
+		}
+		c, size := utf8.DecodeRuneInString(s[i:])
+		if c == utf8.RuneError && size == 1 {
+			if start < i {
+				e.WriteString(s[start:i])
+			}
+			e.WriteString(`\ufffd`)
+			i += size
+			start = i
+			continue
+		}
+		// U+2028 is LINE SEPARATOR.
+		// U+2029 is PARAGRAPH SEPARATOR.
+		// They are both technically valid characters in JSON strings,
+		// but don't work in JSONP, which has to be evaluated as JavaScript,
+		// and can lead to security holes there. It is valid JSON to
+		// escape them, so we do so unconditionally.
+		// See http://timelessrepo.com/json-isnt-a-javascript-subset for discussion.
+		if c == '\u2028' || c == '\u2029' {
+			if start < i {
+				e.WriteString(s[start:i])
+			}
+			e.WriteString(`\u202`)
+			e.WriteByte(hex[c&0xF])
+			i += size
+			start = i
+			continue
+		}
+		i += size
+	}
+	if start < len(s) {
+		e.WriteString(s[start:])
+	}
+	e.WriteByte('"')
+	return e.Len() - len0
+}
+
+// NOTE: keep in sync with string above.
+func (e *encodeState) stringBytes(s []byte, escapeHTML bool) int {
+	len0 := e.Len()
+	e.WriteByte('"')
+	start := 0
+	for i := 0; i < len(s); {
+		if b := s[i]; b < utf8.RuneSelf {
+			if 0x20 <= b && b != '\\' && b != '"' &&
+				(!escapeHTML || b != '<' && b != '>' && b != '&') {
+				i++
+				continue
+			}
+			if start < i {
+				e.Write(s[start:i])
+			}
+			switch b {
+			case '\\', '"':
+				e.WriteByte('\\')
+				e.WriteByte(b)
+			case '\n':
+				e.WriteByte('\\')
+				e.WriteByte('n')
+			case '\r':
+				e.WriteByte('\\')
+				e.WriteByte('r')
+			case '\t':
+				e.WriteByte('\\')
+				e.WriteByte('t')
+			default:
+				// This encodes bytes < 0x20 except for \t, \n and \r.
+				// If escapeHTML is set, it also escapes <, >, and &
+				// because they can lead to security holes when
+				// user-controlled strings are rendered into JSON
+				// and served to some browsers.
+				e.WriteString(`\u00`)
+				e.WriteByte(hex[b>>4])
+				e.WriteByte(hex[b&0xF])
+			}
+			i++
+			start = i
+			continue
+		}
+		c, size := utf8.DecodeRune(s[i:])
+		if c == utf8.RuneError && size == 1 {
+			if start < i {
+				e.Write(s[start:i])
+			}
+			e.WriteString(`\ufffd`)
+			i += size
+			start = i
+			continue
+		}
+		// U+2028 is LINE SEPARATOR.
+		// U+2029 is PARAGRAPH SEPARATOR.
+		// They are both technically valid characters in JSON strings,
+		// but don't work in JSONP, which has to be evaluated as JavaScript,
+		// and can lead to security holes there. It is valid JSON to
+		// escape them, so we do so unconditionally.
+		// See http://timelessrepo.com/json-isnt-a-javascript-subset for discussion.
+		if c == '\u2028' || c == '\u2029' {
+			if start < i {
+				e.Write(s[start:i])
+			}
+			e.WriteString(`\u202`)
+			e.WriteByte(hex[c&0xF])
+			i += size
+			start = i
+			continue
+		}
+		i += size
+	}
+	if start < len(s) {
+		e.Write(s[start:])
+	}
+	e.WriteByte('"')
+	return e.Len() - len0
+}
+
+// A field represents a single field found in a struct.
+type field struct {
+	name      string
+	nameBytes []byte                 // []byte(name)
+	equalFold func(s, t []byte) bool // bytes.EqualFold or equivalent
+
+	tag       bool
+	index     []int
+	typ       reflect.Type
+	omitEmpty bool
+	quoted    bool
+}
+
+func fillField(f field) field {
+	f.nameBytes = []byte(f.name)
+	f.equalFold = foldFunc(f.nameBytes)
+	return f
+}
+
+// byName sorts field by name, breaking ties with depth,
+// then breaking ties with "name came from json tag", then
+// breaking ties with index sequence.
+type byName []field
+
+func (x byName) Len() int { return len(x) }
+
+func (x byName) Swap(i, j int) { x[i], x[j] = x[j], x[i] }
+
+func (x byName) Less(i, j int) bool {
+	if x[i].name != x[j].name {
+		return x[i].name < x[j].name
+	}
+	if len(x[i].index) != len(x[j].index) {
+		return len(x[i].index) < len(x[j].index)
+	}
+	if x[i].tag != x[j].tag {
+		return x[i].tag
+	}
+	return byIndex(x).Less(i, j)
+}
+
+// byIndex sorts field by index sequence.
+type byIndex []field
+
+func (x byIndex) Len() int { return len(x) }
+
+func (x byIndex) Swap(i, j int) { x[i], x[j] = x[j], x[i] }
+
+func (x byIndex) Less(i, j int) bool {
+	for k, xik := range x[i].index {
+		if k >= len(x[j].index) {
+			return false
+		}
+		if xik != x[j].index[k] {
+			return xik < x[j].index[k]
+		}
+	}
+	return len(x[i].index) < len(x[j].index)
+}
+
+// typeFields returns a list of fields that JSON should recognize for the given type.
+// The algorithm is breadth-first search over the set of structs to include - the top struct
+// and then any reachable anonymous structs.
+func typeFields(t reflect.Type) []field {
+	// Anonymous fields to explore at the current level and the next.
+	current := []field{}
+	next := []field{{typ: t}}
+
+	// Count of queued names for current level and the next.
+	count := map[reflect.Type]int{}
+	nextCount := map[reflect.Type]int{}
+
+	// Types already visited at an earlier level.
+	visited := map[reflect.Type]bool{}
+
+	// Fields found.
+	var fields []field
+
+	for len(next) > 0 {
+		current, next = next, current[:0]
+		count, nextCount = nextCount, map[reflect.Type]int{}
+
+		for _, f := range current {
+			if visited[f.typ] {
+				continue
+			}
+			visited[f.typ] = true
+
+			// Scan f.typ for fields to include.
+			for i := 0; i < f.typ.NumField(); i++ {
+				sf := f.typ.Field(i)
+				if sf.PkgPath != "" && !sf.Anonymous { // unexported
+					continue
+				}
+				tag := sf.Tag.Get("json")
+				if tag == "-" {
+					continue
+				}
+				name, opts := parseTag(tag)
+				if !isValidTag(name) {
+					name = ""
+				}
+				index := make([]int, len(f.index)+1)
+				copy(index, f.index)
+				index[len(f.index)] = i
+
+				ft := sf.Type
+				if ft.Name() == "" && ft.Kind() == reflect.Ptr {
+					// Follow pointer.
+					ft = ft.Elem()
+				}
+
+				// Only strings, floats, integers, and booleans can be quoted.
+				quoted := false
+				if opts.Contains("string") {
+					switch ft.Kind() {
+					case reflect.Bool,
+						reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
+						reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64,
+						reflect.Float32, reflect.Float64,
+						reflect.String:
+						quoted = true
+					}
+				}
+
+				// Record found field and index sequence.
+				if name != "" || !sf.Anonymous || ft.Kind() != reflect.Struct {
+					tagged := name != ""
+					if name == "" {
+						name = sf.Name
+					}
+					fields = append(fields, fillField(field{
+						name:      name,
+						tag:       tagged,
+						index:     index,
+						typ:       ft,
+						omitEmpty: opts.Contains("omitempty"),
+						quoted:    quoted,
+					}))
+					if count[f.typ] > 1 {
+						// If there were multiple instances, add a second,
+						// so that the annihilation code will see a duplicate.
+						// It only cares about the distinction between 1 or 2,
+						// so don't bother generating any more copies.
+						fields = append(fields, fields[len(fields)-1])
+					}
+					continue
+				}
+
+				// Record new anonymous struct to explore in next round.
+				nextCount[ft]++
+				if nextCount[ft] == 1 {
+					next = append(next, fillField(field{name: ft.Name(), index: index, typ: ft}))
+				}
+			}
+		}
+	}
+
+	sort.Sort(byName(fields))
+
+	// Delete all fields that are hidden by the Go rules for embedded fields,
+	// except that fields with JSON tags are promoted.
+
+	// The fields are sorted in primary order of name, secondary order
+	// of field index length. Loop over names; for each name, delete
+	// hidden fields by choosing the one dominant field that survives.
+	out := fields[:0]
+	for advance, i := 0, 0; i < len(fields); i += advance {
+		// One iteration per name.
+		// Find the sequence of fields with the name of this first field.
+		fi := fields[i]
+		name := fi.name
+		for advance = 1; i+advance < len(fields); advance++ {
+			fj := fields[i+advance]
+			if fj.name != name {
+				break
+			}
+		}
+		if advance == 1 { // Only one field with this name
+			out = append(out, fi)
+			continue
+		}
+		dominant, ok := dominantField(fields[i : i+advance])
+		if ok {
+			out = append(out, dominant)
+		}
+	}
+
+	fields = out
+	sort.Sort(byIndex(fields))
+
+	return fields
+}
+
+// dominantField looks through the fields, all of which are known to
+// have the same name, to find the single field that dominates the
+// others using Go's embedding rules, modified by the presence of
+// JSON tags. If there are multiple top-level fields, the boolean
+// will be false: This condition is an error in Go and we skip all
+// the fields.
+func dominantField(fields []field) (field, bool) {
+	// The fields are sorted in increasing index-length order. The winner
+	// must therefore be one with the shortest index length. Drop all
+	// longer entries, which is easy: just truncate the slice.
+	length := len(fields[0].index)
+	tagged := -1 // Index of first tagged field.
+	for i, f := range fields {
+		if len(f.index) > length {
+			fields = fields[:i]
+			break
+		}
+		if f.tag {
+			if tagged >= 0 {
+				// Multiple tagged fields at the same level: conflict.
+				// Return no field.
+				return field{}, false
+			}
+			tagged = i
+		}
+	}
+	if tagged >= 0 {
+		return fields[tagged], true
+	}
+	// All remaining fields have the same length. If there's more than one,
+	// we have a conflict (two fields named "X" at the same level) and we
+	// return no field.
+	if len(fields) > 1 {
+		return field{}, false
+	}
+	return fields[0], true
+}
+
+var fieldCache struct {
+	sync.RWMutex
+	m map[reflect.Type][]field
+}
+
+// cachedTypeFields is like typeFields but uses a cache to avoid repeated work.
+func cachedTypeFields(t reflect.Type) []field {
+	fieldCache.RLock()
+	f := fieldCache.m[t]
+	fieldCache.RUnlock()
+	if f != nil {
+		return f
+	}
+
+	// Compute fields without lock.
+	// Might duplicate effort but won't hold other computations back.
+	f = typeFields(t)
+	if f == nil {
+		f = []field{}
+	}
+
+	fieldCache.Lock()
+	if fieldCache.m == nil {
+		fieldCache.m = map[reflect.Type][]field{}
+	}
+	fieldCache.m[t] = f
+	fieldCache.Unlock()
+	return f
+}
diff --git a/vendor/gopkg.in/mgo.v2/internal/json/extension.go b/vendor/gopkg.in/mgo.v2/internal/json/extension.go
new file mode 100644
index 0000000..1c8fd45
--- /dev/null
+++ b/vendor/gopkg.in/mgo.v2/internal/json/extension.go
@@ -0,0 +1,95 @@
+package json
+
+import (
+	"reflect"
+)
+
+// Extension holds a set of additional rules to be used when unmarshaling
+// strict JSON or JSON-like content.
+type Extension struct {
+	funcs  map[string]funcExt
+	consts map[string]interface{}
+	keyed  map[string]func([]byte) (interface{}, error)
+	encode map[reflect.Type]func(v interface{}) ([]byte, error)
+
+	unquotedKeys   bool
+	trailingCommas bool
+}
+
+type funcExt struct {
+	key  string
+	args []string
+}
+
+// Extend changes the decoder behavior to consider the provided extension.
+func (dec *Decoder) Extend(ext *Extension) { dec.d.ext = *ext }
+
+// Extend changes the encoder behavior to consider the provided extension.
+func (enc *Encoder) Extend(ext *Extension) { enc.ext = *ext }
+
+// Extend includes in e the extensions defined in ext.
+func (e *Extension) Extend(ext *Extension) {
+	for name, fext := range ext.funcs {
+		e.DecodeFunc(name, fext.key, fext.args...)
+	}
+	for name, value := range ext.consts {
+		e.DecodeConst(name, value)
+	}
+	for key, decode := range ext.keyed {
+		e.DecodeKeyed(key, decode)
+	}
+	for typ, encode := range ext.encode {
+		if e.encode == nil {
+			e.encode = make(map[reflect.Type]func(v interface{}) ([]byte, error))
+		}
+		e.encode[typ] = encode
+	}
+}
+
+// DecodeFunc defines a function call that may be observed inside JSON content.
+// A function with the provided name will be unmarshaled as the document
+// {key: {args[0]: ..., args[N]: ...}}.
+func (e *Extension) DecodeFunc(name string, key string, args ...string) {
+	if e.funcs == nil {
+		e.funcs = make(map[string]funcExt)
+	}
+	e.funcs[name] = funcExt{key, args}
+}
+
+// DecodeConst defines a constant name that may be observed inside JSON content
+// and will be decoded with the provided value.
+func (e *Extension) DecodeConst(name string, value interface{}) {
+	if e.consts == nil {
+		e.consts = make(map[string]interface{})
+	}
+	e.consts[name] = value
+}
+
+// DecodeKeyed defines a key that when observed as the first element inside a
+// JSON document triggers the decoding of that document via the provided
+// decode function.
+func (e *Extension) DecodeKeyed(key string, decode func(data []byte) (interface{}, error)) {
+	if e.keyed == nil {
+		e.keyed = make(map[string]func([]byte) (interface{}, error))
+	}
+	e.keyed[key] = decode
+}
+
+// DecodeUnquotedKeys defines whether to accept map keys that are unquoted strings.
+func (e *Extension) DecodeUnquotedKeys(accept bool) {
+	e.unquotedKeys = accept
+}
+
+// DecodeTrailingCommas defines whether to accept trailing commas in maps and arrays.
+func (e *Extension) DecodeTrailingCommas(accept bool) {
+	e.trailingCommas = accept
+}
+
+// EncodeType registers a function to encode values with the same type of the
+// provided sample.
+func (e *Extension) EncodeType(sample interface{}, encode func(v interface{}) ([]byte, error)) {
+	if e.encode == nil {
+		e.encode = make(map[reflect.Type]func(v interface{}) ([]byte, error))
+	}
+	e.encode[reflect.TypeOf(sample)] = encode
+}
diff --git a/vendor/gopkg.in/mgo.v2/internal/json/fold.go b/vendor/gopkg.in/mgo.v2/internal/json/fold.go
new file mode 100644
index 0000000..9e17012
--- /dev/null
+++ b/vendor/gopkg.in/mgo.v2/internal/json/fold.go
@@ -0,0 +1,143 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package json
+
+import (
+	"bytes"
+	"unicode/utf8"
+)
+
+const (
+	caseMask     = ^byte(0x20) // Mask to ignore case in ASCII.
+	kelvin       = '\u212a'
+	smallLongEss = '\u017f'
+)
+
+// foldFunc returns one of four different case folding equivalence
+// functions, from most general (and slow) to fastest:
+//
+// 1) bytes.EqualFold, if the key s contains any non-ASCII UTF-8
+// 2) equalFoldRight, if s contains special folding ASCII ('k', 'K', 's', 'S')
+// 3) asciiEqualFold, no special, but includes non-letters (including _)
+// 4) simpleLetterEqualFold, no specials, no non-letters.
+//
+// The letters S and K are special because they map to 3 runes, not just 2:
+//  * S maps to s and to U+017F 'ſ' Latin small letter long s
+//  * k maps to K and to U+212A 'K' Kelvin sign
+// See https://play.golang.org/p/tTxjOc0OGo
+//
+// The returned function is specialized for matching against s and
+// should only be given s. It's not curried for performance reasons.
+func foldFunc(s []byte) func(s, t []byte) bool {
+	nonLetter := false
+	special := false // special letter
+	for _, b := range s {
+		if b >= utf8.RuneSelf {
+			return bytes.EqualFold
+		}
+		upper := b & caseMask
+		if upper < 'A' || upper > 'Z' {
+			nonLetter = true
+		} else if upper == 'K' || upper == 'S' {
+			// See above for why these letters are special.
+			special = true
+		}
+	}
+	if special {
+		return equalFoldRight
+	}
+	if nonLetter {
+		return asciiEqualFold
+	}
+	return simpleLetterEqualFold
+}
+
+// equalFoldRight is a specialization of bytes.EqualFold when s is
+// known to be all ASCII (including punctuation), but contains an 's',
+// 'S', 'k', or 'K', requiring a Unicode fold on the bytes in t.
+// See comments on foldFunc.
+func equalFoldRight(s, t []byte) bool {
+	for _, sb := range s {
+		if len(t) == 0 {
+			return false
+		}
+		tb := t[0]
+		if tb < utf8.RuneSelf {
+			if sb != tb {
+				sbUpper := sb & caseMask
+				if 'A' <= sbUpper && sbUpper <= 'Z' {
+					if sbUpper != tb&caseMask {
+						return false
+					}
+				} else {
+					return false
+				}
+			}
+			t = t[1:]
+			continue
+		}
+		// sb is ASCII and t is not. t must be either kelvin
+		// sign or long s; sb must be s, S, k, or K.
+		tr, size := utf8.DecodeRune(t)
+		switch sb {
+		case 's', 'S':
+			if tr != smallLongEss {
+				return false
+			}
+		case 'k', 'K':
+			if tr != kelvin {
+				return false
+			}
+		default:
+			return false
+		}
+		t = t[size:]
+
+	}
+	if len(t) > 0 {
+		return false
+	}
+	return true
+}
+
+// asciiEqualFold is a specialization of bytes.EqualFold for use when
+// s is all ASCII (but may contain non-letters) and contains no
+// special-folding letters.
+// See comments on foldFunc.
+func asciiEqualFold(s, t []byte) bool {
+	if len(s) != len(t) {
+		return false
+	}
+	for i, sb := range s {
+		tb := t[i]
+		if sb == tb {
+			continue
+		}
+		if ('a' <= sb && sb <= 'z') || ('A' <= sb && sb <= 'Z') {
+			if sb&caseMask != tb&caseMask {
+				return false
+			}
+		} else {
+			return false
+		}
+	}
+	return true
+}
+
+// simpleLetterEqualFold is a specialization of bytes.EqualFold for
+// use when s is all ASCII letters (no underscores, etc) and also
+// doesn't contain 'k', 'K', 's', or 'S'.
+// See comments on foldFunc.
+func simpleLetterEqualFold(s, t []byte) bool {
+	if len(s) != len(t) {
+		return false
+	}
+	for i, b := range s {
+		if b&caseMask != t[i]&caseMask {
+			return false
+		}
+	}
+	return true
+}
diff --git a/vendor/gopkg.in/mgo.v2/internal/json/indent.go b/vendor/gopkg.in/mgo.v2/internal/json/indent.go
new file mode 100644
index 0000000..fba1954
--- /dev/null
+++ b/vendor/gopkg.in/mgo.v2/internal/json/indent.go
@@ -0,0 +1,141 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package json
+
+import "bytes"
+
+// Compact appends to dst the JSON-encoded src with
+// insignificant space characters elided.
+func Compact(dst *bytes.Buffer, src []byte) error {
+	return compact(dst, src, false)
+}
+
+func compact(dst *bytes.Buffer, src []byte, escape bool) error {
+	origLen := dst.Len()
+	var scan scanner
+	scan.reset()
+	start := 0
+	for i, c := range src {
+		if escape && (c == '<' || c == '>' || c == '&') {
+			if start < i {
+				dst.Write(src[start:i])
+			}
+			dst.WriteString(`\u00`)
+			dst.WriteByte(hex[c>>4])
+			dst.WriteByte(hex[c&0xF])
+			start = i + 1
+		}
+		// Convert U+2028 and U+2029 (E2 80 A8 and E2 80 A9).
+		if c == 0xE2 && i+2 < len(src) && src[i+1] == 0x80 && src[i+2]&^1 == 0xA8 {
+			if start < i {
+				dst.Write(src[start:i])
+			}
+			dst.WriteString(`\u202`)
+			dst.WriteByte(hex[src[i+2]&0xF])
+			start = i + 3
+		}
+		v := scan.step(&scan, c)
+		if v >= scanSkipSpace {
+			if v == scanError {
+				break
+			}
+			if start < i {
+				dst.Write(src[start:i])
+			}
+			start = i + 1
+		}
+	}
+	if scan.eof() == scanError {
+		dst.Truncate(origLen)
+		return scan.err
+	}
+	if start < len(src) {
+		dst.Write(src[start:])
+	}
+	return nil
+}
+
+func newline(dst *bytes.Buffer, prefix, indent string, depth int) {
+	dst.WriteByte('\n')
+	dst.WriteString(prefix)
+	for i := 0; i < depth; i++ {
+		dst.WriteString(indent)
+	}
+}
+
+// Indent appends to dst an indented form of the JSON-encoded src.
+// Each element in a JSON object or array begins on a new,
+// indented line beginning with prefix followed by one or more
+// copies of indent according to the indentation nesting.
+// The data appended to dst does not begin with the prefix nor
+// any indentation, to make it easier to embed inside other formatted JSON data.
+// Although leading space characters (space, tab, carriage return, newline)
+// at the beginning of src are dropped, trailing space characters
+// at the end of src are preserved and copied to dst.
+// For example, if src has no trailing spaces, neither will dst;
+// if src ends in a trailing newline, so will dst.
+func Indent(dst *bytes.Buffer, src []byte, prefix, indent string) error {
+	origLen := dst.Len()
+	var scan scanner
+	scan.reset()
+	needIndent := false
+	depth := 0
+	for _, c := range src {
+		scan.bytes++
+		v := scan.step(&scan, c)
+		if v == scanSkipSpace {
+			continue
+		}
+		if v == scanError {
+			break
+		}
+		if needIndent && v != scanEndObject && v != scanEndArray {
+			needIndent = false
+			depth++
+			newline(dst, prefix, indent, depth)
+		}
+
+		// Emit semantically uninteresting bytes
+		// (in particular, punctuation in strings) unmodified.
+		if v == scanContinue {
+			dst.WriteByte(c)
+			continue
+		}
+
+		// Add spacing around real punctuation.
+		switch c {
+		case '{', '[':
+			// delay indent so that empty object and array are formatted as {} and [].
+			needIndent = true
+			dst.WriteByte(c)
+
+		case ',':
+			dst.WriteByte(c)
+			newline(dst, prefix, indent, depth)
+
+		case ':':
+			dst.WriteByte(c)
+			dst.WriteByte(' ')
+
+		case '}', ']':
+			if needIndent {
+				// suppress indent in empty object/array
+				needIndent = false
+			} else {
+				depth--
+				newline(dst, prefix, indent, depth)
+			}
+			dst.WriteByte(c)
+
+		default:
+			dst.WriteByte(c)
+		}
+	}
+	if scan.eof() == scanError {
+		dst.Truncate(origLen)
+		return scan.err
+	}
+	return nil
+}
diff --git a/vendor/gopkg.in/mgo.v2/internal/json/scanner.go b/vendor/gopkg.in/mgo.v2/internal/json/scanner.go
new file mode 100644
index 0000000..9708043
--- /dev/null
+++ b/vendor/gopkg.in/mgo.v2/internal/json/scanner.go
@@ -0,0 +1,697 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package json
+
+// JSON value parser state machine.
+// Just about at the limit of what is reasonable to write by hand.
+// Some parts are a bit tedious, but overall it nicely factors out the
+// otherwise common code from the multiple scanning functions
+// in this package (Compact, Indent, checkValid, nextValue, etc).
+//
+// This file starts with two simple examples using the scanner
+// before diving into the scanner itself.
+
+import "strconv"
+
+// checkValid verifies that data is valid JSON-encoded data.
+// scan is passed in for use by checkValid to avoid an allocation.
+func checkValid(data []byte, scan *scanner) error {
+	scan.reset()
+	for _, c := range data {
+		scan.bytes++
+		if scan.step(scan, c) == scanError {
+			return scan.err
+		}
+	}
+	if scan.eof() == scanError {
+		return scan.err
+	}
+	return nil
+}
+
+// nextValue splits data after the next whole JSON value,
+// returning that value and the bytes that follow it as separate slices.
+// scan is passed in for use by nextValue to avoid an allocation.
+func nextValue(data []byte, scan *scanner) (value, rest []byte, err error) {
+	scan.reset()
+	for i, c := range data {
+		v := scan.step(scan, c)
+		if v >= scanEndObject {
+			switch v {
+			// probe the scanner with a space to determine whether we will
+			// get scanEnd on the next character. Otherwise, if the next character
+			// is not a space, scanEndTop allocates a needless error.
+			case scanEndObject, scanEndArray, scanEndParams:
+				if scan.step(scan, ' ') == scanEnd {
+					return data[:i+1], data[i+1:], nil
+				}
+			case scanError:
+				return nil, nil, scan.err
+			case scanEnd:
+				return data[:i], data[i:], nil
+			}
+		}
+	}
+	if scan.eof() == scanError {
+		return nil, nil, scan.err
+	}
+	return data, nil, nil
+}
+
+// A SyntaxError is a description of a JSON syntax error.
+type SyntaxError struct {
+	msg    string // description of error
+	Offset int64  // error occurred after reading Offset bytes
+}
+
+func (e *SyntaxError) Error() string { return e.msg }
+
+// A scanner is a JSON scanning state machine.
+// Callers call scan.reset() and then pass bytes in one at a time
+// by calling scan.step(&scan, c) for each byte.
+// The return value, referred to as an opcode, tells the
+// caller about significant parsing events like beginning
+// and ending literals, objects, and arrays, so that the
+// caller can follow along if it wishes.
+// The return value scanEnd indicates that a single top-level
+// JSON value has been completed, *before* the byte that
+// just got passed in.  (The indication must be delayed in order
+// to recognize the end of numbers: is 123 a whole value or
+// the beginning of 12345e+6?).
+type scanner struct {
+	// The step is a func to be called to execute the next transition.
+	// Also tried using an integer constant and a single func
+	// with a switch, but using the func directly was 10% faster
+	// on a 64-bit Mac Mini, and it's nicer to read.
+	step func(*scanner, byte) int
+
+	// Reached end of top-level value.
+	endTop bool
+
+	// Stack of what we're in the middle of - array values, object keys, object values.
+	parseState []int
+
+	// Error that happened, if any.
+	err error
+
+	// 1-byte redo (see undo method)
+	redo      bool
+	redoCode  int
+	redoState func(*scanner, byte) int
+
+	// total bytes consumed, updated by decoder.Decode
+	bytes int64
+}
+
+// These values are returned by the state transition functions
+// assigned to scanner.state and the method scanner.eof.
+// They give details about the current state of the scan that
+// callers might be interested to know about.
+// It is okay to ignore the return value of any particular
+// call to scanner.state: if one call returns scanError,
+// every subsequent call will return scanError too.
+const (
+	// Continue.
+	scanContinue     = iota // uninteresting byte
+	scanBeginLiteral        // end implied by next result != scanContinue
+	scanBeginObject         // begin object
+	scanObjectKey           // just finished object key (string)
+	scanObjectValue         // just finished non-last object value
+	scanEndObject           // end object (implies scanObjectValue if possible)
+	scanBeginArray          // begin array
+	scanArrayValue          // just finished array value
+	scanEndArray            // end array (implies scanArrayValue if possible)
+	scanBeginName           // begin function call
+	scanParam               // begin function argument
+	scanEndParams           // end function call
+	scanSkipSpace           // space byte; can skip; known to be last "continue" result
+
+	// Stop.
+	scanEnd   // top-level value ended *before* this byte; known to be first "stop" result
+	scanError // hit an error, scanner.err.
+)
+
+// These values are stored in the parseState stack.
+// They give the current state of a composite value
+// being scanned. If the parser is inside a nested value
+// the parseState describes the nested state, outermost at entry 0.
+const (
+	parseObjectKey   = iota // parsing object key (before colon)
+	parseObjectValue        // parsing object value (after colon)
+	parseArrayValue         // parsing array value
+	parseName               // parsing unquoted name
+	parseParam              // parsing function argument value
+)
+
+// reset prepares the scanner for use.
+// It must be called before calling s.step.
+func (s *scanner) reset() {
+	s.step = stateBeginValue
+	s.parseState = s.parseState[0:0]
+	s.err = nil
+	s.redo = false
+	s.endTop = false
+}
+
+// eof tells the scanner that the end of input has been reached.
+// It returns a scan status just as s.step does.
+func (s *scanner) eof() int {
+	if s.err != nil {
+		return scanError
+	}
+	if s.endTop {
+		return scanEnd
+	}
+	s.step(s, ' ')
+	if s.endTop {
+		return scanEnd
+	}
+	if s.err == nil {
+		s.err = &SyntaxError{"unexpected end of JSON input", s.bytes}
+	}
+	return scanError
+}
+
+// pushParseState pushes a new parse state p onto the parse stack.
+func (s *scanner) pushParseState(p int) {
+	s.parseState = append(s.parseState, p)
+}
+
+// popParseState pops a parse state (already obtained) off the stack
+// and updates s.step accordingly.
+func (s *scanner) popParseState() {
+	n := len(s.parseState) - 1
+	s.parseState = s.parseState[0:n]
+	s.redo = false
+	if n == 0 {
+		s.step = stateEndTop
+		s.endTop = true
+	} else {
+		s.step = stateEndValue
+	}
+}
+
+func isSpace(c byte) bool {
+	return c == ' ' || c == '\t' || c == '\r' || c == '\n'
+}
+
+// stateBeginValueOrEmpty is the state after reading `[`.
+func stateBeginValueOrEmpty(s *scanner, c byte) int {
+	if c <= ' ' && isSpace(c) {
+		return scanSkipSpace
+	}
+	if c == ']' {
+		return stateEndValue(s, c)
+	}
+	return stateBeginValue(s, c)
+}
+
+// stateBeginValue is the state at the beginning of the input.
+func stateBeginValue(s *scanner, c byte) int {
+	if c <= ' ' && isSpace(c) {
+		return scanSkipSpace
+	}
+	switch c {
+	case '{':
+		s.step = stateBeginStringOrEmpty
+		s.pushParseState(parseObjectKey)
+		return scanBeginObject
+	case '[':
+		s.step = stateBeginValueOrEmpty
+		s.pushParseState(parseArrayValue)
+		return scanBeginArray
+	case '"':
+		s.step = stateInString
+		return scanBeginLiteral
+	case '-':
+		s.step = stateNeg
+		return scanBeginLiteral
+	case '0': // beginning of 0.123
+		s.step = state0
+		return scanBeginLiteral
+	case 'n':
+		s.step = stateNew0
+		return scanBeginName
+	}
+	if '1' <= c && c <= '9' { // beginning of 1234.5
+		s.step = state1
+		return scanBeginLiteral
+	}
+	if isName(c) {
+		s.step = stateName
+		return scanBeginName
+	}
+	return s.error(c, "looking for beginning of value")
+}
+
+func isName(c byte) bool {
+	return c == '$' || c == '_' || 'a' <= c && c <= 'z' || 'A' <= c && c <= 'Z' || '0' <= c && c <= '9'
+}
+
+// stateBeginStringOrEmpty is the state after reading `{`.
+func stateBeginStringOrEmpty(s *scanner, c byte) int {
+	if c <= ' ' && isSpace(c) {
+		return scanSkipSpace
+	}
+	if c == '}' {
+		n := len(s.parseState)
+		s.parseState[n-1] = parseObjectValue
+		return stateEndValue(s, c)
+	}
+	return stateBeginString(s, c)
+}
+
+// stateBeginString is the state after reading `{"key": value,`.
+func stateBeginString(s *scanner, c byte) int {
+	if c <= ' ' && isSpace(c) {
+		return scanSkipSpace
+	}
+	if c == '"' {
+		s.step = stateInString
+		return scanBeginLiteral
+	}
+	if isName(c) {
+		s.step = stateName
+		return scanBeginName
+	}
+	return s.error(c, "looking for beginning of object key string")
+}
+
+// stateEndValue is the state after completing a value,
+// such as after reading `{}` or `true` or `["x"`.
+func stateEndValue(s *scanner, c byte) int {
+	n := len(s.parseState)
+	if n == 0 {
+		// Completed top-level before the current byte.
+		s.step = stateEndTop
+		s.endTop = true
+		return stateEndTop(s, c)
+	}
+	if c <= ' ' && isSpace(c) {
+		s.step = stateEndValue
+		return scanSkipSpace
+	}
+	ps := s.parseState[n-1]
+	switch ps {
+	case parseObjectKey:
+		if c == ':' {
+			s.parseState[n-1] = parseObjectValue
+			s.step = stateBeginValue
+			return scanObjectKey
+		}
+		return s.error(c, "after object key")
+	case parseObjectValue:
+		if c == ',' {
+			s.parseState[n-1] = parseObjectKey
+			s.step = stateBeginStringOrEmpty
+			return scanObjectValue
+		}
+		if c == '}' {
+			s.popParseState()
+			return scanEndObject
+		}
+		return s.error(c, "after object key:value pair")
+	case parseArrayValue:
+		if c == ',' {
+			s.step = stateBeginValueOrEmpty
+			return scanArrayValue
+		}
+		if c == ']' {
+			s.popParseState()
+			return scanEndArray
+		}
+		return s.error(c, "after array element")
+	case parseParam:
+		if c == ',' {
+			s.step = stateBeginValue
+			return scanParam
+		}
+		if c == ')' {
+			s.popParseState()
+			return scanEndParams
+		}
+		return s.error(c, "after array element")
+	}
+	return s.error(c, "")
+}
+
+// stateEndTop is the state after finishing the top-level value,
+// such as after reading `{}` or `[1,2,3]`.
+// Only space characters should be seen now.
+func stateEndTop(s *scanner, c byte) int {
+	if c != ' ' && c != '\t' && c != '\r' && c != '\n' {
+		// Complain about non-space byte on next call.
+		s.error(c, "after top-level value")
+	}
+	return scanEnd
+}
+
+// stateInString is the state after reading `"`.
+func stateInString(s *scanner, c byte) int {
+	if c == '"' {
+		s.step = stateEndValue
+		return scanContinue
+	}
+	if c == '\\' {
+		s.step = stateInStringEsc
+		return scanContinue
+	}
+	if c < 0x20 {
+		return s.error(c, "in string literal")
+	}
+	return scanContinue
+}
+
+// stateInStringEsc is the state after reading `"\` during a quoted string.
+func stateInStringEsc(s *scanner, c byte) int {
+	switch c {
+	case 'b', 'f', 'n', 'r', 't', '\\', '/', '"':
+		s.step = stateInString
+		return scanContinue
+	case 'u':
+		s.step = stateInStringEscU
+		return scanContinue
+	}
+	return s.error(c, "in string escape code")
+}
+
+// stateInStringEscU is the state after reading `"\u` during a quoted string.
+func stateInStringEscU(s *scanner, c byte) int {
+	if '0' <= c && c <= '9' || 'a' <= c && c <= 'f' || 'A' <= c && c <= 'F' {
+		s.step = stateInStringEscU1
+		return scanContinue
+	}
+	// numbers
+	return s.error(c, "in \\u hexadecimal character escape")
+}
+
+// stateInStringEscU1 is the state after reading `"\u1` during a quoted string.
+func stateInStringEscU1(s *scanner, c byte) int {
+	if '0' <= c && c <= '9' || 'a' <= c && c <= 'f' || 'A' <= c && c <= 'F' {
+		s.step = stateInStringEscU12
+		return scanContinue
+	}
+	// numbers
+	return s.error(c, "in \\u hexadecimal character escape")
+}
+
+// stateInStringEscU12 is the state after reading `"\u12` during a quoted string.
+func stateInStringEscU12(s *scanner, c byte) int {
+	if '0' <= c && c <= '9' || 'a' <= c && c <= 'f' || 'A' <= c && c <= 'F' {
+		s.step = stateInStringEscU123
+		return scanContinue
+	}
+	// numbers
+	return s.error(c, "in \\u hexadecimal character escape")
+}
+
+// stateInStringEscU123 is the state after reading `"\u123` during a quoted string.
+func stateInStringEscU123(s *scanner, c byte) int {
+	if '0' <= c && c <= '9' || 'a' <= c && c <= 'f' || 'A' <= c && c <= 'F' {
+		s.step = stateInString
+		return scanContinue
+	}
+	// numbers
+	return s.error(c, "in \\u hexadecimal character escape")
+}
+
+// stateNeg is the state after reading `-` during a number.
+func stateNeg(s *scanner, c byte) int {
+	if c == '0' {
+		s.step = state0
+		return scanContinue
+	}
+	if '1' <= c && c <= '9' {
+		s.step = state1
+		return scanContinue
+	}
+	return s.error(c, "in numeric literal")
+}
+
+// state1 is the state after reading a non-zero integer during a number,
+// such as after reading `1` or `100` but not `0`.
+func state1(s *scanner, c byte) int {
+	if '0' <= c && c <= '9' {
+		s.step = state1
+		return scanContinue
+	}
+	return state0(s, c)
+}
+
+// state0 is the state after reading `0` during a number.
+func state0(s *scanner, c byte) int {
+	if c == '.' {
+		s.step = stateDot
+		return scanContinue
+	}
+	if c == 'e' || c == 'E' {
+		s.step = stateE
+		return scanContinue
+	}
+	return stateEndValue(s, c)
+}
+
+// stateDot is the state after reading the integer and decimal point in a number,
+// such as after reading `1.`.
+func stateDot(s *scanner, c byte) int {
+	if '0' <= c && c <= '9' {
+		s.step = stateDot0
+		return scanContinue
+	}
+	return s.error(c, "after decimal point in numeric literal")
+}
+
+// stateDot0 is the state after reading the integer, decimal point, and subsequent
+// digits of a number, such as after reading `3.14`.
+func stateDot0(s *scanner, c byte) int {
+	if '0' <= c && c <= '9' {
+		return scanContinue
+	}
+	if c == 'e' || c == 'E' {
+		s.step = stateE
+		return scanContinue
+	}
+	return stateEndValue(s, c)
+}
+
+// stateE is the state after reading the mantissa and e in a number,
+// such as after reading `314e` or `0.314e`.
+func stateE(s *scanner, c byte) int {
+	if c == '+' || c == '-' {
+		s.step = stateESign
+		return scanContinue
+	}
+	return stateESign(s, c)
+}
+
+// stateESign is the state after reading the mantissa, e, and sign in a number,
+// such as after reading `314e-` or `0.314e+`.
+func stateESign(s *scanner, c byte) int {
+	if '0' <= c && c <= '9' {
+		s.step = stateE0
+		return scanContinue
+	}
+	return s.error(c, "in exponent of numeric literal")
+}
+
+// stateE0 is the state after reading the mantissa, e, optional sign,
+// and at least one digit of the exponent in a number,
+// such as after reading `314e-2` or `0.314e+1` or `3.14e0`.
+func stateE0(s *scanner, c byte) int {
+	if '0' <= c && c <= '9' {
+		return scanContinue
+	}
+	return stateEndValue(s, c)
+}
+
+// stateNew0 is the state after reading `n`.
+func stateNew0(s *scanner, c byte) int {
+	if c == 'e' {
+		s.step = stateNew1
+		return scanContinue
+	}
+	s.step = stateName
+	return stateName(s, c)
+}
+
+// stateNew1 is the state after reading `ne`.
+func stateNew1(s *scanner, c byte) int {
+	if c == 'w' {
+		s.step = stateNew2
+		return scanContinue
+	}
+	s.step = stateName
+	return stateName(s, c)
+}
+
+// stateNew2 is the state after reading `new`.
+func stateNew2(s *scanner, c byte) int {
+	s.step = stateName
+	if c == ' ' {
+		return scanContinue
+	}
+	return stateName(s, c)
+}
+
+// stateName is the state while reading an unquoted function name.
+func stateName(s *scanner, c byte) int {
+	if isName(c) {
+		return scanContinue
+	}
+	if c == '(' {
+		s.step = stateParamOrEmpty
+		s.pushParseState(parseParam)
+		return scanParam
+	}
+	return stateEndValue(s, c)
+}
+
+// stateParamOrEmpty is the state after reading `(`.
+func stateParamOrEmpty(s *scanner, c byte) int {
+	if c <= ' ' && isSpace(c) {
+		return scanSkipSpace
+	}
+	if c == ')' {
+		return stateEndValue(s, c)
+	}
+	return stateBeginValue(s, c)
+}
+
+// stateT is the state after reading `t`.
+func stateT(s *scanner, c byte) int {
+	if c == 'r' {
+		s.step = stateTr
+		return scanContinue
+	}
+	return s.error(c, "in literal true (expecting 'r')")
+}
+
+// stateTr is the state after reading `tr`.
+func stateTr(s *scanner, c byte) int {
+	if c == 'u' {
+		s.step = stateTru
+		return scanContinue
+	}
+	return s.error(c, "in literal true (expecting 'u')")
+}
+
+// stateTru is the state after reading `tru`.
+func stateTru(s *scanner, c byte) int {
+	if c == 'e' {
+		s.step = stateEndValue
+		return scanContinue
+	}
+	return s.error(c, "in literal true (expecting 'e')")
+}
+
+// stateF is the state after reading `f`.
+func stateF(s *scanner, c byte) int {
+	if c == 'a' {
+		s.step = stateFa
+		return scanContinue
+	}
+	return s.error(c, "in literal false (expecting 'a')")
+}
+
+// stateFa is the state after reading `fa`.
+func stateFa(s *scanner, c byte) int {
+	if c == 'l' {
+		s.step = stateFal
+		return scanContinue
+	}
+	return s.error(c, "in literal false (expecting 'l')")
+}
+
+// stateFal is the state after reading `fal`.
+func stateFal(s *scanner, c byte) int {
+	if c == 's' {
+		s.step = stateFals
+		return scanContinue
+	}
+	return s.error(c, "in literal false (expecting 's')")
+}
+
+// stateFals is the state after reading `fals`.
+func stateFals(s *scanner, c byte) int {
+	if c == 'e' {
+		s.step = stateEndValue
+		return scanContinue
+	}
+	return s.error(c, "in literal false (expecting 'e')")
+}
+
+// stateN is the state after reading `n`.
+func stateN(s *scanner, c byte) int {
+	if c == 'u' {
+		s.step = stateNu
+		return scanContinue
+	}
+	return s.error(c, "in literal null (expecting 'u')")
+}
+
+// stateNu is the state after reading `nu`.
+func stateNu(s *scanner, c byte) int {
+	if c == 'l' {
+		s.step = stateNul
+		return scanContinue
+	}
+	return s.error(c, "in literal null (expecting 'l')")
+}
+
+// stateNul is the state after reading `nul`.
+func stateNul(s *scanner, c byte) int {
+	if c == 'l' {
+		s.step = stateEndValue
+		return scanContinue
+	}
+	return s.error(c, "in literal null (expecting 'l')")
+}
+
+// stateError is the state after reaching a syntax error,
+// such as after reading `[1}` or `5.1.2`.
+func stateError(s *scanner, c byte) int {
+	return scanError
+}
+
+// error records an error and switches to the error state.
+func (s *scanner) error(c byte, context string) int {
+	s.step = stateError
+	s.err = &SyntaxError{"invalid character " + quoteChar(c) + " " + context, s.bytes}
+	return scanError
+}
+
+// quoteChar formats c as a quoted character literal
+func quoteChar(c byte) string {
+	// special cases - different from quoted strings
+	if c == '\'' {
+		return `'\''`
+	}
+	if c == '"' {
+		return `'"'`
+	}
+
+	// use quoted string with different quotation marks
+	s := strconv.Quote(string(c))
+	return "'" + s[1:len(s)-1] + "'"
+}
+
+// undo causes the scanner to return scanCode from the next state transition.
+// This gives callers a simple 1-byte undo mechanism.
+func (s *scanner) undo(scanCode int) {
+	if s.redo {
+		panic("json: invalid use of scanner")
+	}
+	s.redoCode = scanCode
+	s.redoState = s.step
+	s.step = stateRedo
+	s.redo = true
+}
+
+// stateRedo helps implement the scanner's 1-byte undo.
+func stateRedo(s *scanner, c byte) int {
+	s.redo = false
+	s.step = s.redoState
+	return s.redoCode
+}
diff --git a/vendor/gopkg.in/mgo.v2/internal/json/stream.go b/vendor/gopkg.in/mgo.v2/internal/json/stream.go
new file mode 100644
index 0000000..e023702
--- /dev/null
+++ b/vendor/gopkg.in/mgo.v2/internal/json/stream.go
@@ -0,0 +1,510 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package json
+
+import (
+	"bytes"
+	"errors"
+	"io"
+)
+
+// A Decoder reads and decodes JSON values from an input stream.
+type Decoder struct {
+	r     io.Reader
+	buf   []byte
+	d     decodeState
+	scanp int // start of unread data in buf
+	scan  scanner
+	err   error
+
+	tokenState int
+	tokenStack []int
+}
+
+// NewDecoder returns a new decoder that reads from r.
+//
+// The decoder introduces its own buffering and may
+// read data from r beyond the JSON values requested.
+func NewDecoder(r io.Reader) *Decoder {
+	return &Decoder{r: r}
+}
+
+// UseNumber causes the Decoder to unmarshal a number into an interface{} as a
+// Number instead of as a float64.
+func (dec *Decoder) UseNumber() { dec.d.useNumber = true }
+
+// Decode reads the next JSON-encoded value from its
+// input and stores it in the value pointed to by v.
+//
+// See the documentation for Unmarshal for details about
+// the conversion of JSON into a Go value.
+func (dec *Decoder) Decode(v interface{}) error {
+	if dec.err != nil {
+		return dec.err
+	}
+
+	if err := dec.tokenPrepareForDecode(); err != nil {
+		return err
+	}
+
+	if !dec.tokenValueAllowed() {
+		return &SyntaxError{msg: "not at beginning of value"}
+	}
+
+	// Read whole value into buffer.
+	n, err := dec.readValue()
+	if err != nil {
+		return err
+	}
+	dec.d.init(dec.buf[dec.scanp : dec.scanp+n])
+	dec.scanp += n
+
+	// Don't save err from unmarshal into dec.err:
+	// the connection is still usable since we read a complete JSON
+	// object from it before the error happened.
+	err = dec.d.unmarshal(v)
+
+	// fixup token streaming state
+	dec.tokenValueEnd()
+
+	return err
+}
+
+// Buffered returns a reader of the data remaining in the Decoder's
+// buffer. The reader is valid until the next call to Decode.
+func (dec *Decoder) Buffered() io.Reader {
+	return bytes.NewReader(dec.buf[dec.scanp:])
+}
+
+// readValue reads a JSON value into dec.buf.
+// It returns the length of the encoding.
+func (dec *Decoder) readValue() (int, error) {
+	dec.scan.reset()
+
+	scanp := dec.scanp
+	var err error
+Input:
+	for {
+		// Look in the buffer for a new value.
+		for i, c := range dec.buf[scanp:] {
+			dec.scan.bytes++
+			v := dec.scan.step(&dec.scan, c)
+			if v == scanEnd {
+				scanp += i
+				break Input
+			}
+			// scanEnd is delayed one byte.
+			// We might block trying to get that byte from src,
+			// so instead invent a space byte.
+			if (v == scanEndObject || v == scanEndArray) && dec.scan.step(&dec.scan, ' ') == scanEnd {
+				scanp += i + 1
+				break Input
+			}
+			if v == scanError {
+				dec.err = dec.scan.err
+				return 0, dec.scan.err
+			}
+		}
+		scanp = len(dec.buf)
+
+		// Did the last read have an error?
+		// Delayed until now to allow buffer scan.
+		if err != nil {
+			if err == io.EOF {
+				if dec.scan.step(&dec.scan, ' ') == scanEnd {
+					break Input
+				}
+				if nonSpace(dec.buf) {
+					err = io.ErrUnexpectedEOF
+				}
+			}
+			dec.err = err
+			return 0, err
+		}
+
+		n := scanp - dec.scanp
+		err = dec.refill()
+		scanp = dec.scanp + n
+	}
+	return scanp - dec.scanp, nil
+}
+
+func (dec *Decoder) refill() error {
+	// Make room to read more into the buffer.
+	// First slide down data already consumed.
+	if dec.scanp > 0 {
+		n := copy(dec.buf, dec.buf[dec.scanp:])
+		dec.buf = dec.buf[:n]
+		dec.scanp = 0
+	}
+
+	// Grow buffer if not large enough.
+	const minRead = 512
+	if cap(dec.buf)-len(dec.buf) < minRead {
+		newBuf := make([]byte, len(dec.buf), 2*cap(dec.buf)+minRead)
+		copy(newBuf, dec.buf)
+		dec.buf = newBuf
+	}
+
+	// Read. Delay error for next iteration (after scan).
+	n, err := dec.r.Read(dec.buf[len(dec.buf):cap(dec.buf)])
+	dec.buf = dec.buf[0 : len(dec.buf)+n]
+
+	return err
+}
+
+func nonSpace(b []byte) bool {
+	for _, c := range b {
+		if !isSpace(c) {
+			return true
+		}
+	}
+	return false
+}
+
+// An Encoder writes JSON values to an output stream.
+type Encoder struct {
+	w          io.Writer
+	err        error
+	escapeHTML bool
+
+	indentBuf    *bytes.Buffer
+	indentPrefix string
+	indentValue  string
+
+	ext Extension
+}
+
+// NewEncoder returns a new encoder that writes to w.
+func NewEncoder(w io.Writer) *Encoder {
+	return &Encoder{w: w, escapeHTML: true}
+}
+
+// Encode writes the JSON encoding of v to the stream,
+// followed by a newline character.
+//
+// See the documentation for Marshal for details about the
+// conversion of Go values to JSON.
+func (enc *Encoder) Encode(v interface{}) error {
+	if enc.err != nil {
+		return enc.err
+	}
+	e := newEncodeState()
+	e.ext = enc.ext
+	err := e.marshal(v, encOpts{escapeHTML: enc.escapeHTML})
+	if err != nil {
+		return err
+	}
+
+	// Terminate each value with a newline.
+	// This makes the output look a little nicer
+	// when debugging, and some kind of space
+	// is required if the encoded value was a number,
+	// so that the reader knows there aren't more
+	// digits coming.
+	e.WriteByte('\n')
+
+	b := e.Bytes()
+	if enc.indentBuf != nil {
+		enc.indentBuf.Reset()
+		err = Indent(enc.indentBuf, b, enc.indentPrefix, enc.indentValue)
+		if err != nil {
+			return err
+		}
+		b = enc.indentBuf.Bytes()
+	}
+	if _, err = enc.w.Write(b); err != nil {
+		enc.err = err
+	}
+	encodeStatePool.Put(e)
+	return err
+}
+
+// Indent sets the encoder to format each encoded value with Indent.
+func (enc *Encoder) Indent(prefix, indent string) {
+	enc.indentBuf = new(bytes.Buffer)
+	enc.indentPrefix = prefix
+	enc.indentValue = indent
+}
+
+// DisableHTMLEscaping causes the encoder not to escape angle brackets
+// ("<" and ">") or ampersands ("&") in JSON strings.
+func (enc *Encoder) DisableHTMLEscaping() {
+	enc.escapeHTML = false
+}
+
+// RawMessage is a raw encoded JSON value.
+// It implements Marshaler and Unmarshaler and can
+// be used to delay JSON decoding or precompute a JSON encoding.
+type RawMessage []byte
+
+// MarshalJSON returns *m as the JSON encoding of m.
+func (m *RawMessage) MarshalJSON() ([]byte, error) {
+	return *m, nil
+}
+
+// UnmarshalJSON sets *m to a copy of data.
+func (m *RawMessage) UnmarshalJSON(data []byte) error {
+	if m == nil {
+		return errors.New("json.RawMessage: UnmarshalJSON on nil pointer")
+	}
+	*m = append((*m)[0:0], data...)
+	return nil
+}
+
+var _ Marshaler = (*RawMessage)(nil)
+var _ Unmarshaler = (*RawMessage)(nil)
+
+// A Token holds a value of one of these types:
+//
+//	Delim, for the four JSON delimiters [ ] { }
+//	bool, for JSON booleans
+//	float64, for JSON numbers
+//	Number, for JSON numbers
+//	string, for JSON string literals
+//	nil, for JSON null
+//
+type Token interface{}
+
+const (
+	tokenTopValue = iota
+	tokenArrayStart
+	tokenArrayValue
+	tokenArrayComma
+	tokenObjectStart
+	tokenObjectKey
+	tokenObjectColon
+	tokenObjectValue
+	tokenObjectComma
+)
+
+// advance tokenstate from a separator state to a value state
+func (dec *Decoder) tokenPrepareForDecode() error {
+	// Note: Not calling peek before switch, to avoid
+	// putting peek into the standard Decode path.
+	// peek is only called when using the Token API.
+	switch dec.tokenState {
+	case tokenArrayComma:
+		c, err := dec.peek()
+		if err != nil {
+			return err
+		}
+		if c != ',' {
+			return &SyntaxError{"expected comma after array element", 0}
+		}
+		dec.scanp++
+		dec.tokenState = tokenArrayValue
+	case tokenObjectColon:
+		c, err := dec.peek()
+		if err != nil {
+			return err
+		}
+		if c != ':' {
+			return &SyntaxError{"expected colon after object key", 0}
+		}
+		dec.scanp++
+		dec.tokenState = tokenObjectValue
+	}
+	return nil
+}
+
+func (dec *Decoder) tokenValueAllowed() bool {
+	switch dec.tokenState {
+	case tokenTopValue, tokenArrayStart, tokenArrayValue, tokenObjectValue:
+		return true
+	}
+	return false
+}
+
+func (dec *Decoder) tokenValueEnd() {
+	switch dec.tokenState {
+	case tokenArrayStart, tokenArrayValue:
+		dec.tokenState = tokenArrayComma
+	case tokenObjectValue:
+		dec.tokenState = tokenObjectComma
+	}
+}
+
+// A Delim is a JSON array or object delimiter, one of [ ] { or }.
+type Delim rune
+
+func (d Delim) String() string {
+	return string(d)
+}
+
+// Token returns the next JSON token in the input stream.
+// At the end of the input stream, Token returns nil, io.EOF.
+//
+// Token guarantees that the delimiters [ ] { } it returns are
+// properly nested and matched: if Token encounters an unexpected
+// delimiter in the input, it will return an error.
+//
+// The input stream consists of basic JSON values—bool, string,
+// number, and null—along with delimiters [ ] { } of type Delim
+// to mark the start and end of arrays and objects.
+// Commas and colons are elided.
+func (dec *Decoder) Token() (Token, error) {
+	for {
+		c, err := dec.peek()
+		if err != nil {
+			return nil, err
+		}
+		switch c {
+		case '[':
+			if !dec.tokenValueAllowed() {
+				return dec.tokenError(c)
+			}
+			dec.scanp++
+			dec.tokenStack = append(dec.tokenStack, dec.tokenState)
+			dec.tokenState = tokenArrayStart
+			return Delim('['), nil
+
+		case ']':
+			if dec.tokenState != tokenArrayStart && dec.tokenState != tokenArrayComma {
+				return dec.tokenError(c)
+			}
+			dec.scanp++
+			dec.tokenState = dec.tokenStack[len(dec.tokenStack)-1]
+			dec.tokenStack = dec.tokenStack[:len(dec.tokenStack)-1]
+			dec.tokenValueEnd()
+			return Delim(']'), nil
+
+		case '{':
+			if !dec.tokenValueAllowed() {
+				return dec.tokenError(c)
+			}
+			dec.scanp++
+			dec.tokenStack = append(dec.tokenStack, dec.tokenState)
+			dec.tokenState = tokenObjectStart
+			return Delim('{'), nil
+
+		case '}':
+			if dec.tokenState != tokenObjectStart && dec.tokenState != tokenObjectComma {
+				return dec.tokenError(c)
+			}
+			dec.scanp++
+			dec.tokenState = dec.tokenStack[len(dec.tokenStack)-1]
+			dec.tokenStack = dec.tokenStack[:len(dec.tokenStack)-1]
+			dec.tokenValueEnd()
+			return Delim('}'), nil
+
+		case ':':
+			if dec.tokenState != tokenObjectColon {
+				return dec.tokenError(c)
+			}
+			dec.scanp++
+			dec.tokenState = tokenObjectValue
+			continue
+
+		case ',':
+			if dec.tokenState == tokenArrayComma {
+				dec.scanp++
+				dec.tokenState = tokenArrayValue
+				continue
+			}
+			if dec.tokenState == tokenObjectComma {
+				dec.scanp++
+				dec.tokenState = tokenObjectKey
+				continue
+			}
+			return dec.tokenError(c)
+
+		case '"':
+			if dec.tokenState == tokenObjectStart || dec.tokenState == tokenObjectKey {
+				var x string
+				old := dec.tokenState
+				dec.tokenState = tokenTopValue
+				err := dec.Decode(&x)
+				dec.tokenState = old
+				if err != nil {
+					clearOffset(err)
+					return nil, err
+				}
+				dec.tokenState = tokenObjectColon
+				return x, nil
+			}
+			fallthrough
+
+		default:
+			if !dec.tokenValueAllowed() {
+				return dec.tokenError(c)
+			}
+			var x interface{}
+			if err := dec.Decode(&x); err != nil {
+				clearOffset(err)
+				return nil, err
+			}
+			return x, nil
+		}
+	}
+}
+
+func clearOffset(err error) {
+	if s, ok := err.(*SyntaxError); ok {
+		s.Offset = 0
+	}
+}
+
+func (dec *Decoder) tokenError(c byte) (Token, error) {
+	var context string
+	switch dec.tokenState {
+	case tokenTopValue:
+		context = " looking for beginning of value"
+	case tokenArrayStart, tokenArrayValue, tokenObjectValue:
+		context = " looking for beginning of value"
+	case tokenArrayComma:
+		context = " after array element"
+	case tokenObjectKey:
+		context = " looking for beginning of object key string"
+	case tokenObjectColon:
+		context = " after object key"
+	case tokenObjectComma:
+		context = " after object key:value pair"
+	}
+	return nil, &SyntaxError{"invalid character " + quoteChar(c) + " " + context, 0}
+}
+
+// More reports whether there is another element in the
+// current array or object being parsed.
+func (dec *Decoder) More() bool {
+	c, err := dec.peek()
+	return err == nil && c != ']' && c != '}'
+}
+
+func (dec *Decoder) peek() (byte, error) {
+	var err error
+	for {
+		for i := dec.scanp; i < len(dec.buf); i++ {
+			c := dec.buf[i]
+			if isSpace(c) {
+				continue
+			}
+			dec.scanp = i
+			return c, nil
+		}
+		// buffer has been scanned, now report any error
+		if err != nil {
+			return 0, err
+		}
+		err = dec.refill()
+	}
+}
+
+/*
+TODO
+
+// EncodeToken writes the given JSON token to the stream.
+// It returns an error if the delimiters [ ] { } are not properly used.
+//
+// EncodeToken does not call Flush, because usually it is part of
+// a larger operation such as Encode, and those will call Flush when finished.
+// Callers that create an Encoder and then invoke EncodeToken directly,
+// without using Encode, need to call Flush when finished to ensure that
+// the JSON is written to the underlying writer.
+func (e *Encoder) EncodeToken(t Token) error  {
+	...
+}
+
+*/
diff --git a/vendor/gopkg.in/mgo.v2/internal/json/tags.go b/vendor/gopkg.in/mgo.v2/internal/json/tags.go
new file mode 100644
index 0000000..c38fd51
--- /dev/null
+++ b/vendor/gopkg.in/mgo.v2/internal/json/tags.go
@@ -0,0 +1,44 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package json
+
+import (
+	"strings"
+)
+
+// tagOptions is the string following a comma in a struct field's "json"
+// tag, or the empty string. It does not include the leading comma.
+type tagOptions string
+
+// parseTag splits a struct field's json tag into its name and
+// comma-separated options.
+func parseTag(tag string) (string, tagOptions) {
+	if idx := strings.Index(tag, ","); idx != -1 {
+		return tag[:idx], tagOptions(tag[idx+1:])
+	}
+	return tag, tagOptions("")
+}
+
+// Contains reports whether a comma-separated list of options
+// contains a particular substr flag. substr must be surrounded by a
+// string boundary or commas.
+func (o tagOptions) Contains(optionName string) bool {
+	if len(o) == 0 {
+		return false
+	}
+	s := string(o)
+	for s != "" {
+		var next string
+		i := strings.Index(s, ",")
+		if i >= 0 {
+			s, next = s[:i], s[i+1:]
+		}
+		if s == optionName {
+			return true
+		}
+		s = next
+	}
+	return false
+}
diff --git a/vendor/gopkg.in/mgo.v2/internal/sasl/sasl_windows.c b/vendor/gopkg.in/mgo.v2/internal/sasl/sasl_windows.c
index dd6a88a..c359fd6 100644
--- a/vendor/gopkg.in/mgo.v2/internal/sasl/sasl_windows.c
+++ b/vendor/gopkg.in/mgo.v2/internal/sasl/sasl_windows.c
@@ -10,14 +10,18 @@ SECURITY_STATUS SEC_ENTRY sspi_acquire_credentials_handle(CredHandle *cred_handl
 	auth_identity.Flags = SEC_WINNT_AUTH_IDENTITY_ANSI;
 	auth_identity.User = (LPSTR) username;
 	auth_identity.UserLength = strlen(username);
-	auth_identity.Password = (LPSTR) password;
-	auth_identity.PasswordLength = strlen(password);
+	auth_identity.Password = NULL;
+	auth_identity.PasswordLength = 0;
+	if(password){
+		auth_identity.Password = (LPSTR) password;
+		auth_identity.PasswordLength = strlen(password);
+	}
 	auth_identity.Domain = (LPSTR) domain;
 	auth_identity.DomainLength = strlen(domain);
 	return call_sspi_acquire_credentials_handle(NULL, SSPI_PACKAGE_NAME, SECPKG_CRED_OUTBOUND, NULL, &auth_identity, NULL, NULL, cred_handle, &ignored);
 }
 
-int sspi_step(CredHandle *cred_handle, int has_context, CtxtHandle *context, PVOID *buffer, ULONG *buffer_length, char *target)
+int sspi_step(CredHandle *cred_handle, int has_context, CtxtHandle *context, PVOID buffer, ULONG buffer_length, PVOID *out_buffer, ULONG *out_buffer_length,  char *target)
 {
 	SecBufferDesc inbuf;
 	SecBuffer in_bufs[1];
@@ -30,8 +34,8 @@ int sspi_step(CredHandle *cred_handle, int has_context, CtxtHandle *context, PVO
 		inbuf.ulVersion = SECBUFFER_VERSION;
 		inbuf.cBuffers = 1;
 		inbuf.pBuffers = in_bufs;
-		in_bufs[0].pvBuffer = *buffer;
-		in_bufs[0].cbBuffer = *buffer_length;
+		in_bufs[0].pvBuffer = buffer;
+		in_bufs[0].cbBuffer = buffer_length;
 		in_bufs[0].BufferType = SECBUFFER_TOKEN;
 	}
 
@@ -57,9 +61,9 @@ int sspi_step(CredHandle *cred_handle, int has_context, CtxtHandle *context, PVO
 	          &context_attr,
 	          NULL);
 
-	*buffer = malloc(out_bufs[0].cbBuffer);
-	*buffer_length = out_bufs[0].cbBuffer;
-	memcpy(*buffer, out_bufs[0].pvBuffer, *buffer_length);
+	*out_buffer = malloc(out_bufs[0].cbBuffer);
+	*out_buffer_length = out_bufs[0].cbBuffer;
+	memcpy(*out_buffer, out_bufs[0].pvBuffer, *out_buffer_length);
 
 	return ret;
 }
diff --git a/vendor/gopkg.in/mgo.v2/internal/sasl/sasl_windows.go b/vendor/gopkg.in/mgo.v2/internal/sasl/sasl_windows.go
index 3302cfe..d8ec001 100644
--- a/vendor/gopkg.in/mgo.v2/internal/sasl/sasl_windows.go
+++ b/vendor/gopkg.in/mgo.v2/internal/sasl/sasl_windows.go
@@ -101,6 +101,8 @@ func (ss *saslSession) Step(serverData []byte) (clientData []byte, done bool, er
 	}
 	var buffer C.PVOID
 	var bufferLength C.ULONG
+	var outBuffer C.PVOID
+	var outBufferLength C.ULONG
 	if len(serverData) > 0 {
 		buffer = (C.PVOID)(unsafe.Pointer(&serverData[0]))
 		bufferLength = C.ULONG(len(serverData))
@@ -108,20 +110,20 @@ func (ss *saslSession) Step(serverData []byte) (clientData []byte, done bool, er
 	var status C.int
 	if ss.authComplete {
 		// Step 3: last bit of magic to use the correct server credentials
-		status = C.sspi_send_client_authz_id(&ss.context, &buffer, &bufferLength, ss.cstr(ss.userPlusRealm))
+		status = C.sspi_send_client_authz_id(&ss.context, &outBuffer, &outBufferLength, ss.cstr(ss.userPlusRealm))
 	} else {
 		// Step 1 + Step 2: set up security context with the server and TGT
-		status = C.sspi_step(&ss.credHandle, ss.hasContext, &ss.context, &buffer, &bufferLength, ss.cstr(ss.target))
+		status = C.sspi_step(&ss.credHandle, ss.hasContext, &ss.context, buffer, bufferLength, &outBuffer, &outBufferLength, ss.cstr(ss.target))
 	}
-	if buffer != C.PVOID(nil) {
-		defer C.free(unsafe.Pointer(buffer))
+	if outBuffer != C.PVOID(nil) {
+		defer C.free(unsafe.Pointer(outBuffer))
 	}
 	if status != C.SEC_E_OK && status != C.SEC_I_CONTINUE_NEEDED {
 		ss.errored = true
 		return nil, false, ss.handleSSPIErrorCode(status)
 	}
 
-	clientData = C.GoBytes(unsafe.Pointer(buffer), C.int(bufferLength))
+	clientData = C.GoBytes(unsafe.Pointer(outBuffer), C.int(outBufferLength))
 	if status == C.SEC_E_OK {
 		ss.authComplete = true
 		return clientData, true, nil
diff --git a/vendor/gopkg.in/mgo.v2/internal/sasl/sasl_windows.h b/vendor/gopkg.in/mgo.v2/internal/sasl/sasl_windows.h
index 94321b2..a6b0395 100644
--- a/vendor/gopkg.in/mgo.v2/internal/sasl/sasl_windows.h
+++ b/vendor/gopkg.in/mgo.v2/internal/sasl/sasl_windows.h
@@ -3,5 +3,5 @@
 #include "sspi_windows.h"
 
 SECURITY_STATUS SEC_ENTRY sspi_acquire_credentials_handle(CredHandle* cred_handle, char* username, char* password, char* domain);
-int sspi_step(CredHandle* cred_handle, int has_context, CtxtHandle* context, PVOID* buffer, ULONG* buffer_length, char* target);
+int sspi_step(CredHandle* cred_handle, int has_context, CtxtHandle* context, PVOID buffer, ULONG buffer_length, PVOID* out_buffer, ULONG* out_buffer_length, char* target);
 int sspi_send_client_authz_id(CtxtHandle* context, PVOID* buffer, ULONG* buffer_length, char* user_plus_realm);