Subversion Repositories openrisc

// Copyright 2010 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package cipher

import "io"

// The Stream* objects are so simple that all their members are public. Users
// can create them themselves.

// StreamReader wraps a Stream into an io.Reader. It calls XORKeyStream
// to process each slice of data which passes through.
type StreamReader struct {
        S Stream
        R io.Reader
}

func (r StreamReader) Read(dst []byte) (n int, err error) {
        n, err = r.R.Read(dst)
        r.S.XORKeyStream(dst[:n], dst[:n])
        return
}

// StreamWriter wraps a Stream into an io.Writer. It calls XORKeyStream
// to process each slice of data which passes through. If any Write call
// returns short then the StreamWriter is out of sync and must be discarded.
type StreamWriter struct {
        S   Stream
        W   io.Writer
        Err error
}

func (w StreamWriter) Write(src []byte) (n int, err error) {
        if w.Err != nil {
                return 0, w.Err
        }
        c := make([]byte, len(src))
        w.S.XORKeyStream(c, src)
        n, err = w.W.Write(c)
        if n != len(src) {
                if err == nil { // should never happen
                        err = io.ErrShortWrite
                }
                w.Err = err
        }
        return
}

func (w StreamWriter) Close() error {
        // This saves us from either requiring a WriteCloser or having a
        // StreamWriterCloser.
        return w.W.(io.Closer).Close()
}