Source file src/pkg/crypto/cipher/io.go

     1	// Copyright 2010 The Go Authors. All rights reserved.
     2	// Use of this source code is governed by a BSD-style
     3	// license that can be found in the LICENSE file.
     4	
     5	package cipher
     6	
     7	import "io"
     8	
     9	// The Stream* objects are so simple that all their members are public. Users
    10	// can create them themselves.
    11	
    12	// StreamReader wraps a Stream into an io.Reader. It calls XORKeyStream
    13	// to process each slice of data which passes through.
    14	type StreamReader struct {
    15		S Stream
    16		R io.Reader
    17	}
    18	
    19	func (r StreamReader) Read(dst []byte) (n int, err error) {
    20		n, err = r.R.Read(dst)
    21		r.S.XORKeyStream(dst[:n], dst[:n])
    22		return
    23	}
    24	
    25	// StreamWriter wraps a Stream into an io.Writer. It calls XORKeyStream
    26	// to process each slice of data which passes through. If any Write call
    27	// returns short then the StreamWriter is out of sync and must be discarded.
    28	type StreamWriter struct {
    29		S   Stream
    30		W   io.Writer
    31		Err error
    32	}
    33	
    34	func (w StreamWriter) Write(src []byte) (n int, err error) {
    35		if w.Err != nil {
    36			return 0, w.Err
    37		}
    38		c := make([]byte, len(src))
    39		w.S.XORKeyStream(c, src)
    40		n, err = w.W.Write(c)
    41		if n != len(src) {
    42			if err == nil { // should never happen
    43				err = io.ErrShortWrite
    44			}
    45			w.Err = err
    46		}
    47		return
    48	}
    49	
    50	func (w StreamWriter) Close() error {
    51		// This saves us from either requiring a WriteCloser or having a
    52		// StreamWriterCloser.
    53		return w.W.(io.Closer).Close()
    54	}