63 lines
1.2 KiB
Go
63 lines
1.2 KiB
Go
// Copyright 2013 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package stun
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import (
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"runtime"
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"unsafe"
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)
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// #nosec
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const wordSize = int(unsafe.Sizeof(uintptr(0)))
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var supportsUnaligned = runtime.GOARCH == "386" || runtime.GOARCH == "amd64"
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// fastXORBytes xors in bulk. It only works on architectures that
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// support unaligned read/writes.
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//
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// #nosec
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func fastXORBytes(dst, a, b []byte) int {
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n := len(a)
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if len(b) < n {
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n = len(b)
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}
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w := n / wordSize
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if w > 0 {
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dw := *(*[]uintptr)(unsafe.Pointer(&dst))
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aw := *(*[]uintptr)(unsafe.Pointer(&a))
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bw := *(*[]uintptr)(unsafe.Pointer(&b))
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for i := 0; i < w; i++ {
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dw[i] = aw[i] ^ bw[i]
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}
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}
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for i := n - n%wordSize; i < n; i++ {
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dst[i] = a[i] ^ b[i]
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}
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return n
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}
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func safeXORBytes(dst, a, b []byte) int {
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n := len(a)
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if len(b) < n {
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n = len(b)
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}
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for i := 0; i < n; i++ {
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dst[i] = a[i] ^ b[i]
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}
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return n
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}
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// xorBytes xors the bytes in a and b. The destination is assumed to have enough
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// space. Returns the number of bytes xor'd.
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func xorBytes(dst, a, b []byte) int {
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if supportsUnaligned {
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return fastXORBytes(dst, a, b)
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}
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return safeXORBytes(dst, a, b)
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}
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