code review 3183043: crypto/cipher: add CFB and OCFB mode.

src/pkg/crypto/cipher/cfb_test.go

 // 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 (
         "bytes"
         "crypto/aes"
         "crypto/rand"
         "testing"
 )
 
 func TestCFB(t *testing.T) {
         block, err := aes.NewCipher(commonKey128)
         if err != nil {
                 t.Error(err)
                 return
         }
 
         plaintext := []byte("this is the plaintext")
         iv := make([]byte, block.BlockSize())
         rand.Reader.Read(iv)
-        cfb := NewCFB(block, iv, false /* decrypting? */)
+        cfb := NewCFBEncrypter(block, iv)
         ciphertext := make([]byte, len(plaintext))
         cfb.XORKeyStream(ciphertext, plaintext)
 
-        cfbdec := NewCFB(block, iv, true /* decrypting? */)
+        cfbdec := NewCFBDecrypter(block, iv)
         plaintextCopy := make([]byte, len(plaintext))
         cfbdec.XORKeyStream(plaintextCopy, ciphertext)
 
         if !bytes.Equal(plaintextCopy, plaintext) {
                 t.Errorf("got: %x, want: %x", plaintextCopy, plaintext)
         }
 }