6d3a4f1db8
When preparing a tutorial for netxlite, I figured it is easier to tell people "hey, this is the package you should use for all low-level networking stuff" rather than introducing people to a set of packages working together where some piece of functionality is here and some other piece is there. Part of https://github.com/ooni/probe/issues/1591
58 lines
1.4 KiB
Go
58 lines
1.4 KiB
Go
package netxlite
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import (
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"context"
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"io"
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)
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// ReadAllContext is like io.ReadAll but reads r in a
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// background goroutine. This function will return
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// earlier if the context is cancelled. In which case
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// we will continue reading from r in the background
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// goroutine, and we will discard the result. To stop
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// the long-running goroutine, you need to close the
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// connection bound to the r reader, if possible.
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func ReadAllContext(ctx context.Context, r io.Reader) ([]byte, error) {
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datach, errch := make(chan []byte, 1), make(chan error, 1) // buffers
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go func() {
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data, err := io.ReadAll(r)
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if err != nil {
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errch <- err
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return
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}
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datach <- data
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}()
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select {
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case data := <-datach:
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return data, nil
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case <-ctx.Done():
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return nil, ctx.Err()
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case err := <-errch:
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return nil, err
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}
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}
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// CopyContext is like io.Copy but may terminate earlier
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// when the context expires. This function has the same
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// caveats of ReadAllContext regarding the temporary leaking
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// of the background goroutine used to do I/O.
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func CopyContext(ctx context.Context, dst io.Writer, src io.Reader) (int64, error) {
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countch, errch := make(chan int64, 1), make(chan error, 1) // buffers
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go func() {
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count, err := io.Copy(dst, src)
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if err != nil {
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errch <- err
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return
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}
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countch <- count
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}()
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select {
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case count := <-countch:
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return count, nil
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case <-ctx.Done():
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return 0, ctx.Err()
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case err := <-errch:
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return 0, err
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}
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}
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