Gecko [ 167.86.127.34 ]

Name	Size	Permission
benchmark_test.go	3.46 KB	-rw-r--r--
cbc.go	4.42 KB	-rw-r--r--
cbc_aes_test.go	2.93 KB	-rw-r--r--
cfb.go	1.94 KB	-rw-r--r--
cfb_test.go	2.77 KB	-rw-r--r--
cipher.go	2.49 KB	-rw-r--r--
cipher_test.go	2.2 KB	-rw-r--r--
common_test.go	1.24 KB	-rw-r--r--
ctr.go	2.12 KB	-rw-r--r--
ctr_aes_test.go	2.98 KB	-rw-r--r--
ctr_test.go	1.13 KB	-rw-r--r--
example_test.go	11.78 KB	-rw-r--r--
export_test.go	242 B	-rw-r--r--
gcm.go	13.82 KB	-rw-r--r--
gcm_test.go	21.3 KB	-rw-r--r--
io.go	1.46 KB	-rw-r--r--
ofb.go	1.6 KB	-rw-r--r--
ofb_test.go	2.95 KB	-rw-r--r--
xor_amd64.go	642 B	-rw-r--r--
xor_amd64.s	1.31 KB	-rw-r--r--
xor_generic.go	2.33 KB	-rw-r--r--
xor_ppc64x.go	641 B	-rw-r--r--
xor_ppc64x.s	2.03 KB	-rw-r--r--
xor_test.go	1.6 KB	-rw-r--r--

Code Editor : xor_generic.go

// Copyright 2013 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.

// +build !amd64,!ppc64,!ppc64le

package cipher

import (
	"runtime"
	"unsafe"
)

// xorBytes xors the bytes in a and b. The destination should have enough
// space, otherwise xorBytes will panic. Returns the number of bytes xor'd.
func xorBytes(dst, a, b []byte) int {
	n := len(a)
	if len(b) < n {
		n = len(b)
	}
	if n == 0 {
		return 0
	}

switch {
	case supportsUnaligned:
		fastXORBytes(dst, a, b, n)
	default:
		// TODO(hanwen): if (dst, a, b) have common alignment
		// we could still try fastXORBytes. It is not clear
		// how often this happens, and it's only worth it if
		// the block encryption itself is hardware
		// accelerated.
		safeXORBytes(dst, a, b, n)
	}
	return n
}

const wordSize = int(unsafe.Sizeof(uintptr(0)))
const supportsUnaligned = runtime.GOARCH == "386" || runtime.GOARCH == "ppc64" || runtime.GOARCH == "ppc64le" || runtime.GOARCH == "s390x"

// fastXORBytes xors in bulk. It only works on architectures that
// support unaligned read/writes.
// n needs to be smaller or equal than the length of a and b.
func fastXORBytes(dst, a, b []byte, n int) {
	// Assert dst has enough space
	_ = dst[n-1]

w := n / wordSize
	if w > 0 {
		dw := *(*[]uintptr)(unsafe.Pointer(&dst))
		aw := *(*[]uintptr)(unsafe.Pointer(&a))
		bw := *(*[]uintptr)(unsafe.Pointer(&b))
		for i := 0; i < w; i++ {
			dw[i] = aw[i] ^ bw[i]
		}
	}

for i := (n - n%wordSize); i < n; i++ {
		dst[i] = a[i] ^ b[i]
	}
}

// n needs to be smaller or equal than the length of a and b.
func safeXORBytes(dst, a, b []byte, n int) {
	for i := 0; i < n; i++ {
		dst[i] = a[i] ^ b[i]
	}
}

// fastXORWords XORs multiples of 4 or 8 bytes (depending on architecture.)
// The arguments are assumed to be of equal length.
func fastXORWords(dst, a, b []byte) {
	dw := *(*[]uintptr)(unsafe.Pointer(&dst))
	aw := *(*[]uintptr)(unsafe.Pointer(&a))
	bw := *(*[]uintptr)(unsafe.Pointer(&b))
	n := len(b) / wordSize
	for i := 0; i < n; i++ {
		dw[i] = aw[i] ^ bw[i]
	}
}

// fastXORWords XORs multiples of 4 or 8 bytes (depending on architecture.)
// The slice arguments a and b are assumed to be of equal length.
func xorWords(dst, a, b []byte) {
	if supportsUnaligned {
		fastXORWords(dst, a, b)
	} else {
		safeXORBytes(dst, a, b, len(b))
	}
}

${this.title}

Code Editor : xor_generic.go