| // 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" |
| ) |
| |
| // ResumableBuffer buffers data from an io.Reader to support uploading media in retryable chunks. |
| type ResumableBuffer 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 NewResumableBuffer(media io.Reader, chunkSize int) *ResumableBuffer { |
| return &ResumableBuffer{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 (rb *ResumableBuffer) 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 rb.err == nil && len(rb.chunk) == 0 { |
| rb.err = rb.loadChunk() |
| } |
| return bytes.NewReader(rb.chunk), rb.off, len(rb.chunk), rb.err |
| } |
| |
| // loadChunk will read from media into chunk, up to the capacity of chunk. |
| func (rb *ResumableBuffer) loadChunk() error { |
| bufSize := cap(rb.chunk) |
| rb.chunk = rb.chunk[:bufSize] |
| |
| read := 0 |
| var err error |
| for err == nil && read < bufSize { |
| var n int |
| n, err = rb.media.Read(rb.chunk[read:]) |
| read += n |
| } |
| rb.chunk = rb.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 (rb *ResumableBuffer) Next() { |
| rb.off += int64(len(rb.chunk)) |
| rb.chunk = rb.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 |
| } |