77 lines
2.3 KiB
Go
77 lines
2.3 KiB
Go
// Copyright 2016 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 gensupport
|
|
|
|
import (
|
|
"bytes"
|
|
"io"
|
|
|
|
"google.golang.org/api/googleapi"
|
|
)
|
|
|
|
// MediaBuffer buffers data from an io.Reader to support uploading media in retryable chunks.
|
|
type MediaBuffer struct {
|
|
media io.Reader
|
|
|
|
chunk []byte // The current chunk which is pending upload. The capacity is the chunk size.
|
|
err error // Any error generated when populating chunk by reading media.
|
|
|
|
// The absolute position of chunk in the underlying media.
|
|
off int64
|
|
}
|
|
|
|
func NewMediaBuffer(media io.Reader, chunkSize int) *MediaBuffer {
|
|
return &MediaBuffer{media: media, chunk: make([]byte, 0, chunkSize)}
|
|
}
|
|
|
|
// Chunk returns the current buffered chunk, the offset in the underlying media
|
|
// from which the chunk is drawn, and the size of the chunk.
|
|
// Successive calls to Chunk return the same chunk between calls to Next.
|
|
func (mb *MediaBuffer) Chunk() (chunk io.Reader, off int64, size int, err error) {
|
|
// There may already be data in chunk if Next has not been called since the previous call to Chunk.
|
|
if mb.err == nil && len(mb.chunk) == 0 {
|
|
mb.err = mb.loadChunk()
|
|
}
|
|
return bytes.NewReader(mb.chunk), mb.off, len(mb.chunk), mb.err
|
|
}
|
|
|
|
// loadChunk will read from media into chunk, up to the capacity of chunk.
|
|
func (mb *MediaBuffer) loadChunk() error {
|
|
bufSize := cap(mb.chunk)
|
|
mb.chunk = mb.chunk[:bufSize]
|
|
|
|
read := 0
|
|
var err error
|
|
for err == nil && read < bufSize {
|
|
var n int
|
|
n, err = mb.media.Read(mb.chunk[read:])
|
|
read += n
|
|
}
|
|
mb.chunk = mb.chunk[:read]
|
|
return err
|
|
}
|
|
|
|
// Next advances to the next chunk, which will be returned by the next call to Chunk.
|
|
// Calls to Next without a corresponding prior call to Chunk will have no effect.
|
|
func (mb *MediaBuffer) Next() {
|
|
mb.off += int64(len(mb.chunk))
|
|
mb.chunk = mb.chunk[0:0]
|
|
}
|
|
|
|
type readerTyper struct {
|
|
io.Reader
|
|
googleapi.ContentTyper
|
|
}
|
|
|
|
// ReaderAtToReader adapts a ReaderAt to be used as a Reader.
|
|
// If ra implements googleapi.ContentTyper, then the returned reader
|
|
// will also implement googleapi.ContentTyper, delegating to ra.
|
|
func ReaderAtToReader(ra io.ReaderAt, size int64) io.Reader {
|
|
r := io.NewSectionReader(ra, 0, size)
|
|
if typer, ok := ra.(googleapi.ContentTyper); ok {
|
|
return readerTyper{r, typer}
|
|
}
|
|
return r
|
|
}
|