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package main
import "io"
type countingReader struct {
io.Reader
N int
}
func (r *countingReader) Read(p []byte) (int, error) {
n, err := r.Reader.Read(p)
r.N += n
return n, err
}
type countingWriter struct {
io.Writer
N int
}
func (w *countingWriter) Write(p []byte) (int, error) {
n, err := w.Writer.Write(p)
w.N += n
return n, err
}
type prependReader struct {
io.ReadCloser
prepend []byte
}
func NewPrependReader(r io.ReadCloser, prepend []byte) *prependReader {
return &prependReader{r, prepend}
}
func (r *prependReader) Read(p []byte) (int, error) {
if r.prepend != nil {
n := copy(p, r.prepend)
if n != len(r.prepend) {
return n, io.ErrShortBuffer
}
r.prepend = nil
return n, nil
}
return r.ReadCloser.Read(p)
}
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