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https://github.com/rclone/rclone
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27b281ef69
This converts the ChunkedReader into an interface and provides two implementations one sequential and one parallel. This can be used to improve the performance of the VFS on high bandwidth or high latency links. Fixes #4760
48 lines
1.3 KiB
Go
48 lines
1.3 KiB
Go
// Package chunkedreader provides functionality for reading a stream in chunks.
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package chunkedreader
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import (
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"context"
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"errors"
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"io"
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"github.com/rclone/rclone/fs"
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)
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// io related errors returned by ChunkedReader
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var (
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ErrorFileClosed = errors.New("file already closed")
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ErrorInvalidSeek = errors.New("invalid seek position")
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)
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// ChunkedReader describes what a chunked reader can do.
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type ChunkedReader interface {
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io.Reader
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io.Seeker
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io.Closer
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fs.RangeSeeker
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Open() (ChunkedReader, error)
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}
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// New returns a ChunkedReader for the Object.
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//
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// An initialChunkSize of <= 0 will disable chunked reading.
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// If maxChunkSize is greater than initialChunkSize, the chunk size will be
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// doubled after each chunk read with a maximum of maxChunkSize.
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// A Seek or RangeSeek will reset the chunk size to it's initial value
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func New(ctx context.Context, o fs.Object, initialChunkSize int64, maxChunkSize int64, streams int) ChunkedReader {
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if initialChunkSize <= 0 {
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initialChunkSize = -1
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}
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if maxChunkSize != -1 && maxChunkSize < initialChunkSize {
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maxChunkSize = initialChunkSize
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}
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if streams < 0 {
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streams = 0
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}
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if streams <= 1 || o.Size() < 0 {
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return newSequential(ctx, o, initialChunkSize, maxChunkSize)
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}
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return newParallel(ctx, o, initialChunkSize, streams)
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}
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