mirror of https://github.com/Xhofe/alist
36 lines
1.2 KiB
Go
36 lines
1.2 KiB
Go
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package utils
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import (
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"context"
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"io"
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)
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// here is some syntaxic sugar inspired by the Tomas Senart's video,
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// it allows me to inline the Reader interface
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type readerFunc func(p []byte) (n int, err error)
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func (rf readerFunc) Read(p []byte) (n int, err error) { return rf(p) }
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// CopyWithCtx slightly modified function signature:
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// - context has been added in order to propagate cancelation
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// - I do not return the number of bytes written, has it is not useful in my use case
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func CopyWithCtx(ctx context.Context, out io.Writer, in io.Reader) error {
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// Copy will call the Reader and Writer interface multiple time, in order
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// to copy by chunk (avoiding loading the whole file in memory).
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// I insert the ability to cancel before read time as it is the earliest
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// possible in the call process.
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_, err := io.Copy(out, readerFunc(func(p []byte) (int, error) {
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// golang non-blocking channel: https://gobyexample.com/non-blocking-channel-operations
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select {
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// if context has been canceled
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case <-ctx.Done():
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// stop process and propagate "context canceled" error
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return 0, ctx.Err()
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default:
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// otherwise just run default io.Reader implementation
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return in.Read(p)
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}
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}))
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return err
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}
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