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// 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()

}