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package htcat
import (
"io"
"sync"
)
type eagerReader struct {
closeNotify chan struct{}
rc io.ReadCloser
buf []byte
more *sync.Cond
begin int
end int
lastErr error
}
func newEagerReader(r io.ReadCloser, bufSz int64) *eagerReader {
er := eagerReader{
closeNotify: make(chan struct{}),
rc: r,
buf: make([]byte, bufSz, bufSz),
}
er.more = sync.NewCond(new(sync.Mutex))
go er.buffer()
return &er
}
func (er *eagerReader) buffer() {
for er.lastErr == nil && er.end != len(er.buf) {
var n int
er.more.L.Lock()
n, er.lastErr = er.rc.Read(er.buf[er.end:])
er.end += n
er.more.Broadcast()
er.more.L.Unlock()
}
}
func (er *eagerReader) writeOnce(dst io.Writer) (int64, error) {
// Make one attempt at writing bytes from the buffer to the
// destination.
//
// It may be necessary to wait for more bytes to arrive.
er.more.L.Lock()
defer er.more.L.Unlock()
for er.begin == er.end {
if er.lastErr != nil {
return 0, er.lastErr
}
if er.begin == len(er.buf) {
return 0, io.EOF
}
er.more.Wait()
}
n, err := dst.Write(er.buf[er.begin:er.end])
er.begin += n
return int64(n), err
}
func (er *eagerReader) WriteTo(dst io.Writer) (int64, error) {
var written int64
for {
n, err := er.writeOnce(dst)
written += n
switch err {
case io.EOF:
// Finished.
//
// The EOF originates from the Read half of
// the eagerReader, and it's not desirable
// emit that to the caller of WriteTo: it's
// assumed that a nil error and a return means
// that all bytes have been written.
return 0, nil
case nil:
// More bytes to be written still.
continue
default:
// Error encountered, stop execution.
return written, err
}
}
}
func (er *eagerReader) Close() error {
err := er.rc.Close()
er.closeNotify <- struct{}{}
return err
}
func (er *eagerReader) WaitClosed() {
<-er.closeNotify
}
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