func CopyBuffer(dst Writer, src Reader, buf []byte) (written int64, err error) {
	if buf != nil && len(buf) == 0 {
		panic("empty buffer in CopyBuffer")
	}
	return copyBuffer(dst, src, buf)
}

// copyBuffer is the actual implementation of Copy and CopyBuffer.
// if buf is nil, one is allocated.
func copyBuffer(dst Writer, src Reader, buf []byte) (written int64, err error) {

			output := strings.Repeat(test.enc, multiplier)

			var buf bytes.Buffer
			enc := NewEncoder(&buf)
			r := struct{ io.Reader }{bytes.NewReader(input)} // io.Reader only; not io.WriterTo
			if n, err := io.CopyBuffer(enc, r, make([]byte, 7)); n != int64(len(input)) || err != nil {
				t.Errorf("encoder.Write(%q*%d) = (%d, %v), want (%d, nil)", test.dec, multiplier, n, err, len(input))
				continue
			}

			}
			// os.File.ReadFrom will allocate its own copy buffer if we let io.Copy use it.
			type writerOnly struct{ io.Writer }
			remainingSize, err := io.CopyBuffer(writerOnly{file}, p, copyBuf)
			if err != nil {
				return nil, err
			}
			fh.tmpfile = file.Name()
			fh.Size = int64(b.Len()) + remainingSize
			fh.tmpoff = fileOff
			fileOff += fh.Size

			r, idxCB := newS2CompressReader(bytes.NewReader(tt.data), int64(len(tt.data)), false)
			defer r.Close()

			var rdrBuf bytes.Buffer
			_, err := io.CopyBuffer(&rdrBuf, r, buf)
			if err != nil {
				t.Fatal(err)
			}
			r.Close()
			idx := idxCB()
			if !tt.wantIdx && len(idx) > 0 {
				t.Errorf("index returned above threshold")
			}
			if tt.wantIdx {

func Copy(dst io.Writer, src io.Reader) (written int64, err error) {
	bufp := copyBufPool.Get().(*[]byte)
	buf := *bufp
	defer copyBufPool.Put(bufp)

	return io.CopyBuffer(dst, src, buf)
}

// SameFile returns if the files are same.
func SameFile(fi1, fi2 os.FileInfo) bool {
	if !os.SameFile(fi1, fi2) {
		return false
	}
	if !fi1.ModTime().Equal(fi2.ModTime()) {

// connections like "unixpacket".
// We assume that the maximum packet size is at least 1024.
func chunkedCopy(w io.Writer, r io.Reader) error {
	b := make([]byte, 1024)
	_, err := io.CopyBuffer(struct{ io.Writer }{w}, struct{ io.Reader }{r}, b)
	return err

		if err != nil {
			return err
		}
		// Check if we have a response ready or a filler byte.
		switch tmp[0] {
		case 0:
			// 0 is unbuffered, copy the rest.
			_, err := io.CopyBuffer(w, respBody, buf)
			if err == io.EOF {
				return nil
			}
			return err
		case 1:
			errorText, err := io.ReadAll(respBody)
			if err != nil {
				return err
			}

//
// This function is only intended for use in writeBody.
func (t *transferWriter) doBodyCopy(dst io.Writer, src io.Reader) (n int64, err error) {
	buf := getCopyBuf()
	defer putCopyBuf(buf)

	n, err = io.CopyBuffer(dst, src, buf)
	if err != nil && err != io.EOF {
		t.bodyReadError = err
	}
	return
}

// unwrapBody unwraps the body's inner reader if it's a

	if !ok {
		return io.CopyBuffer(writerOnly{w}, src, buf)
	}

	// Copy the first sniffLen bytes before switching to ReadFrom.
	// This ensures we don't start writing the response before the
	// source is available (see golang.org/issue/5660) and provides
	// enough bytes to perform Content-Type sniffing when required.
	if !w.cw.wroteHeader {
		n0, err := io.CopyBuffer(writerOnly{w}, io.LimitReader(src, sniffLen), buf)

			srv := Server(sconn, serverConfig)
			if err := srv.Handshake(); err != nil {
				panic(fmt.Errorf("handshake: %v", err))
			}
			if _, err := io.CopyBuffer(srv, srv, buf); err != nil {
				panic(fmt.Errorf("copy buffer: %v", err))
			}
		}
	}()

	b.SetBytes(totalBytes)
	clientConfig := testConfig.Clone()