libgo/go/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 // A StreamWriter has no internal buffering; Close does not need
  29 // to be called to flush write data.
  30 type StreamWriter struct {
  31         S   Stream
  32         W   io.Writer
  33         Err error // unused
  34 }
  35
  36 func (w StreamWriter) Write(src []byte) (n int, err error) {
  37         c := make([]byte, len(src))
  38         w.S.XORKeyStream(c, src)
  39         n, err = w.W.Write(c)
  40         if n != len(src) {
  41                 if err == nil { // should never happen
  42                         err = io.ErrShortWrite
  43                 }
  44         }
  45         return
  46 }
  47
  48 // Close closes the underlying Writer and returns its Close return value, if the Writer
  49 // is also an io.Closer. Otherwise it returns nil.
  50 func (w StreamWriter) Close() error {
  51         if c, ok := w.W.(io.Closer); ok {
  52                 return c.Close()
  53         }
  54         return nil
  55 }