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// Copyright 2014 Google Inc. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package storage
import (
"errors"
"fmt"
"io"
"unicode/utf8"
"golang.org/x/net/context"
"google.golang.org/api/googleapi"
raw "google.golang.org/api/storage/v1"
)
// A Writer writes a Cloud Storage object.
type Writer struct {
// ObjectAttrs are optional attributes to set on the object. Any attributes
// must be initialized before the first Write call. Nil or zero-valued
// attributes are ignored.
ObjectAttrs
// ChunkSize controls the maximum number of bytes of the object that the
// Writer will attempt to send to the server in a single request. Objects
// smaller than the size will be sent in a single request, while larger
// objects will be split over multiple requests. The size will be rounded up
// to the nearest multiple of 256K. If zero, chunking will be disabled and
// the object will be uploaded in a single request.
//
// ChunkSize will default to a reasonable value. Any custom configuration
// must be done before the first Write call.
ChunkSize int
ctx context.Context
o *ObjectHandle
opened bool
pw *io.PipeWriter
donec chan struct{} // closed after err and obj are set.
err error
obj *ObjectAttrs
}
func (w *Writer) open() error {
attrs := w.ObjectAttrs
// Check the developer didn't change the object Name (this is unfortunate, but
// we don't want to store an object under the wrong name).
if attrs.Name != w.o.object {
return fmt.Errorf("storage: Writer.Name %q does not match object name %q", attrs.Name, w.o.object)
}
if !utf8.ValidString(attrs.Name) {
return fmt.Errorf("storage: object name %q is not valid UTF-8", attrs.Name)
}
pr, pw := io.Pipe()
w.pw = pw
w.opened = true
if w.ChunkSize < 0 {
return errors.New("storage: Writer.ChunkSize must non-negative")
}
mediaOpts := []googleapi.MediaOption{
googleapi.ChunkSize(w.ChunkSize),
}
if c := attrs.ContentType; c != "" {
mediaOpts = append(mediaOpts, googleapi.ContentType(c))
}
go func() {
defer close(w.donec)
call := w.o.c.raw.Objects.Insert(w.o.bucket, attrs.toRawObject(w.o.bucket)).
Media(pr, mediaOpts...).
Projection("full").
Context(w.ctx)
var resp *raw.Object
err := applyConds("NewWriter", w.o.gen, w.o.conds, call)
if err == nil {
err = runWithRetry(w.ctx, func() error { resp, err = call.Do(); return err })
}
if err != nil {
w.err = err
pr.CloseWithError(w.err)
return
}
w.obj = newObject(resp)
}()
return nil
}
// Write appends to w. It implements the io.Writer interface.
func (w *Writer) Write(p []byte) (n int, err error) {
if w.err != nil {
return 0, w.err
}
if !w.opened {
if err := w.open(); err != nil {
return 0, err
}
}
return w.pw.Write(p)
}
// Close completes the write operation and flushes any buffered data.
// If Close doesn't return an error, metadata about the written object
// can be retrieved by calling Object.
func (w *Writer) Close() error {
if !w.opened {
if err := w.open(); err != nil {
return err
}
}
if err := w.pw.Close(); err != nil {
return err
}
<-w.donec
return w.err
}
// CloseWithError aborts the write operation with the provided error.
// CloseWithError always returns nil.
func (w *Writer) CloseWithError(err error) error {
if !w.opened {
return nil
}
return w.pw.CloseWithError(err)
}
// Attrs returns metadata about a successfully-written object.
// It's only valid to call it after Close returns nil.
func (w *Writer) Attrs() *ObjectAttrs {
return w.obj
}
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