From 554fd8c5195424bdbcabf5de30fdc183aba391bd Mon Sep 17 00:00:00 2001
From: upstream source tree <ports@midipix.org>
Date: Sun, 15 Mar 2015 20:14:05 -0400
Subject: obtained gcc-4.6.4.tar.bz2 from upstream website; verified
 gcc-4.6.4.tar.bz2.sig; imported gcc-4.6.4 source tree from verified upstream
 tarball.

downloading a git-generated archive based on the 'upstream' tag
should provide you with a source tree that is binary identical
to the one extracted from the above tarball.

if you have obtained the source via the command 'git clone',
however, do note that line-endings of files in your working
directory might differ from line-endings of the respective
files in the upstream repository.
---
 libgo/go/crypto/block/ctr.go | 67 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 67 insertions(+)
 create mode 100644 libgo/go/crypto/block/ctr.go

(limited to 'libgo/go/crypto/block/ctr.go')

diff --git a/libgo/go/crypto/block/ctr.go b/libgo/go/crypto/block/ctr.go
new file mode 100644
index 000000000..5d65c0c9a
--- /dev/null
+++ b/libgo/go/crypto/block/ctr.go
@@ -0,0 +1,67 @@
+// Copyright 2009 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.
+
+// Counter (CTR) mode.
+
+// CTR converts a block cipher into a stream cipher by
+// repeatedly encrypting an incrementing counter and
+// xoring the resulting stream of data with the input.
+
+// See NIST SP 800-38A, pp 13-15
+
+package block
+
+import (
+	"io"
+)
+
+type ctrStream struct {
+	c   Cipher
+	ctr []byte
+	out []byte
+}
+
+func newCTRStream(c Cipher, ctr []byte) *ctrStream {
+	x := new(ctrStream)
+	x.c = c
+	x.ctr = dup(ctr)
+	x.out = make([]byte, len(ctr))
+	return x
+}
+
+func (x *ctrStream) Next() []byte {
+	// Next block is encryption of counter.
+	x.c.Encrypt(x.out, x.ctr)
+
+	// Increment counter
+	for i := len(x.ctr) - 1; i >= 0; i-- {
+		x.ctr[i]++
+		if x.ctr[i] != 0 {
+			break
+		}
+	}
+
+	return x.out
+}
+
+// NewCTRReader returns a reader that reads data from r, decrypts (or encrypts)
+// it using c in counter (CTR) mode with the initialization vector iv.
+// The returned Reader does not buffer and has no block size.
+// In CTR mode, encryption and decryption are the same operation:
+// a CTR reader applied to an encrypted stream produces a decrypted
+// stream and vice versa.
+func NewCTRReader(c Cipher, iv []byte, r io.Reader) io.Reader {
+	return newXorReader(newCTRStream(c, iv), r)
+}
+
+// NewCTRWriter returns a writer that encrypts (or decrypts) data using c
+// in counter (CTR) mode with the initialization vector iv
+// and writes the encrypted data to w.
+// The returned Writer does not buffer and has no block size.
+// In CTR mode, encryption and decryption are the same operation:
+// a CTR writer applied to an decrypted stream produces an encrypted
+// stream and vice versa.
+func NewCTRWriter(c Cipher, iv []byte, w io.Writer) io.Writer {
+	return newXorWriter(newCTRStream(c, iv), w)
+}
-- 
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