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

src/pkg/crypto/cipher/ocfb_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 TestOCFB(t *testing.T) {
+        block, err := aes.NewCipher(commonKey128)
+        if err != nil {
+                t.Error(err)
+                return
+        }
+
+        plaintext := []byte("this is the plaintext")
+        randData := make([]byte, block.BlockSize())
+        rand.Reader.Read(randData)
+        ocfb, prefix := NewOCFBEncrypter(block, randData)
+        ciphertext := make([]byte, len(plaintext))
+        ocfb.XORKeyStream(ciphertext, plaintext)
+
+        ocfbdec := NewOCFBDecrypter(block, prefix)
+        if ocfbdec == nil {
+                t.Error("NewOCFBDecrypter failed")
+                return
+        }
+        plaintextCopy := make([]byte, len(plaintext))
+        ocfbdec.XORKeyStream(plaintextCopy, ciphertext)
+
+        if !bytes.Equal(plaintextCopy, plaintext) {
+                t.Errorf("got: %x, want: %x", plaintextCopy, plaintext)
+        }
+}