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package ioutils
import (
"context"
"io"
)
// CopyCtx copies from src to dst until either EOF is reached on src or a context is cancelled.
// The writer is not closed when the context is cancelled.
//
// After CopyCtx exits due to context cancellation, the goroutine that performed
// the copy may still be running if either the reader or writer blocks.
func CopyCtx(ctx context.Context, dst io.Writer, src io.Reader) (n int64, err error) {
copyDone := make(chan struct{})
src = &readerCtx{ctx: ctx, r: src}
go func() {
n, err = io.Copy(dst, src)
close(copyDone)
}()
select {
case <-ctx.Done():
return -1, ctx.Err()
case <-copyDone:
}
return n, err
}
type readerCtx struct {
ctx context.Context
r io.Reader
}
// NewCtxReader wraps the given reader with a reader that doesn't proceed with
// reading if the context is done.
//
// Note: Read will still block if the underlying reader blocks.
func NewCtxReader(ctx context.Context, r io.Reader) io.Reader {
return &readerCtx{ctx: ctx, r: r}
}
func (r *readerCtx) Read(p []byte) (n int, err error) {
if err := r.ctx.Err(); err != nil {
return 0, err
}
n, outErr := r.r.Read(p)
if err := r.ctx.Err(); err != nil {
return 0, err
}
return n, outErr
}
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