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/*
*
* Copyright 2014, Google Inc.
* 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.
*
*/
// Package metadata define the structure of the metadata supported by gRPC library.
// Please refer to http://www.grpc.io/docs/guides/wire.html for more information about custom-metadata.
package metadata // import "google.golang.org/grpc/metadata"
import (
"encoding/base64"
"fmt"
"strings"
"golang.org/x/net/context"
)
const (
binHdrSuffix = "-bin"
)
// encodeKeyValue encodes key and value qualified for transmission via gRPC.
// Transmitting binary headers violates HTTP/2 spec.
// TODO(zhaoq): Maybe check if k is ASCII also.
func encodeKeyValue(k, v string) (string, string) {
k = strings.ToLower(k)
if strings.HasSuffix(k, binHdrSuffix) {
val := base64.StdEncoding.EncodeToString([]byte(v))
v = string(val)
}
return k, v
}
// DecodeKeyValue returns the original key and value corresponding to the
// encoded data in k, v.
// If k is a binary header and v contains comma, v is split on comma before decoded,
// and the decoded v will be joined with comma before returned.
func DecodeKeyValue(k, v string) (string, string, error) {
if !strings.HasSuffix(k, binHdrSuffix) {
return k, v, nil
}
vvs := strings.Split(v, ",")
for i, vv := range vvs {
val, err := base64.StdEncoding.DecodeString(vv)
if err != nil {
return "", "", err
}
vvs[i] = string(val)
}
return k, strings.Join(vvs, ","), nil
}
// MD is a mapping from metadata keys to values. Users should use the following
// two convenience functions New and Pairs to generate MD.
type MD map[string][]string
// New creates a MD from given key-value map.
// Keys are automatically converted to lowercase. And for keys having "-bin" as suffix, their values will be applied Base64 encoding.
func New(m map[string]string) MD {
md := MD{}
for k, v := range m {
key, val := encodeKeyValue(k, v)
md[key] = append(md[key], val)
}
return md
}
// Pairs returns an MD formed by the mapping of key, value ...
// Pairs panics if len(kv) is odd.
// Keys are automatically converted to lowercase. And for keys having "-bin" as suffix, their values will be appplied Base64 encoding.
func Pairs(kv ...string) MD {
if len(kv)%2 == 1 {
panic(fmt.Sprintf("metadata: Pairs got the odd number of input pairs for metadata: %d", len(kv)))
}
md := MD{}
var k string
for i, s := range kv {
if i%2 == 0 {
k = s
continue
}
key, val := encodeKeyValue(k, s)
md[key] = append(md[key], val)
}
return md
}
// Len returns the number of items in md.
func (md MD) Len() int {
return len(md)
}
// Copy returns a copy of md.
func (md MD) Copy() MD {
return Join(md)
}
// Join joins any number of MDs into a single MD.
// The order of values for each key is determined by the order in which
// the MDs containing those values are presented to Join.
func Join(mds ...MD) MD {
out := MD{}
for _, md := range mds {
for k, v := range md {
out[k] = append(out[k], v...)
}
}
return out
}
type mdKey struct{}
// NewContext creates a new context with md attached.
func NewContext(ctx context.Context, md MD) context.Context {
return context.WithValue(ctx, mdKey{}, md)
}
// FromContext returns the MD in ctx if it exists.
// The returned md should be immutable, writing to it may cause races.
// Modification should be made to the copies of the returned md.
func FromContext(ctx context.Context) (md MD, ok bool) {
md, ok = ctx.Value(mdKey{}).(MD)
return
}
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