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