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60 lines
2.5 KiB
Markdown
60 lines
2.5 KiB
Markdown
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# readahead
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Asynchronous read-ahead for Go readers
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This package will allow you to add readhead to any reader. This means a separate goroutine will perform reads from your upstream reader, so you can request from this reader without delay.
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This is helpful for splitting an input stream into concurrent processing, and also helps smooth out **bursts** of input or output.
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This should be fully transparent, except that once an error has been returned from the Reader, it will not recover. A panic will be caught and returned as an error.
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The readahead object also fulfills the [`io.WriterTo`](https://golang.org/pkg/io/#WriterTo) interface, which is likely to speed up `io.Copy` and other code that use the interface.
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See an introduction: [An Async Read-ahead Package for Go](https://blog.klauspost.com/an-async-read-ahead-package-for-go/)
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[![GoDoc][1]][2] [![Build Status][3]][4]
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[1]: https://godoc.org/github.com/klauspost/readahead?status.svg
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[2]: https://godoc.org/github.com/klauspost/readahead
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[3]: https://travis-ci.org/klauspost/readahead.svg
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[4]: https://travis-ci.org/klauspost/readahead
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# usage
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To get the package use `go get -u github.com/klauspost/readahead`.
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Here is a simple example that does file copy. Error handling has been omitted for brevity.
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```Go
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input, _ := os.Open("input.txt")
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output, _ := os.Create("output.txt")
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defer input.Close()
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defer output.Close()
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// Create a read-ahead Reader with default settings
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ra := readahead.NewReader(input)
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defer ra.Close()
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// Copy the content to our output
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_, _ = io.Copy(output, ra)
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```
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# settings
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You can finetune the read-ahead for your specific use case, and adjust the number of buffers and the size of each buffer.
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The default the size of each buffer is 1MB, and there are 4 buffers. Do not make your buffers too small since there is a small overhead for passing buffers between goroutines. Other than that you are free to experiment with buffer sizes.
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# contributions
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On this project contributions in terms of new features is limited to:
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* Features that are widely usable and
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* Features that have extensive tests
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This package is meant to be simple and stable, so therefore these strict requirements.
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The only feature I have considered is supporting the `io.Seeker` interface. I currently do not plan to add it myself, but if you can show a clean and well-tested way to implementing it, I will consider to merge it. If not, I will be happy to link to it.
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# license
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This package is released under the MIT license. See the supplied LICENSE file for more info.
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