mirror of
https://github.com/xtaci/kcp-go.git
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106 lines
2.5 KiB
Go
106 lines
2.5 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 kcp
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import (
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"runtime"
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"unsafe"
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)
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const wordSize = int(unsafe.Sizeof(uintptr(0)))
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const supportsUnaligned = runtime.GOARCH == "386" || runtime.GOARCH == "amd64" || runtime.GOARCH == "ppc64" || runtime.GOARCH == "ppc64le" || runtime.GOARCH == "s390x"
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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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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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wordBytes := w * wordSize
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fastXORWords(dst[:wordBytes], a[:wordBytes], b[:wordBytes])
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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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ex := n % 8
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for i := 0; i < ex; i++ {
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dst[i] = a[i] ^ b[i]
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}
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for i := ex; i < n; i += 8 {
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dst[i] = a[i] ^ b[i]
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dst[i+1] = a[i+1] ^ b[i+1]
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dst[i+2] = a[i+2] ^ b[i+2]
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dst[i+3] = a[i+3] ^ b[i+3]
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dst[i+4] = a[i+4] ^ b[i+4]
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dst[i+5] = a[i+5] ^ b[i+5]
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dst[i+6] = a[i+6] ^ b[i+6]
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dst[i+7] = a[i+7] ^ b[i+7]
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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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} else {
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// TODO(hanwen): if (dst, a, b) have common alignment
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// we could still try fastXORBytes. It is not clear
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// how often this happens, and it's only worth it if
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// the block encryption itself is hardware
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// accelerated.
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return safeXORBytes(dst, a, b)
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}
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}
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// fastXORWords XORs multiples of 4 or 8 bytes (depending on architecture.)
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// The arguments are assumed to be of equal length.
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func fastXORWords(dst, a, b []byte) {
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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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n := len(b) / wordSize
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ex := n % 8
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for i := 0; i < ex; i++ {
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dw[i] = aw[i] ^ bw[i]
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}
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for i := ex; i < n; i += 8 {
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dw[i] = aw[i] ^ bw[i]
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dw[i+1] = aw[i+1] ^ bw[i+1]
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dw[i+2] = aw[i+2] ^ bw[i+2]
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dw[i+3] = aw[i+3] ^ bw[i+3]
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dw[i+4] = aw[i+4] ^ bw[i+4]
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dw[i+5] = aw[i+5] ^ bw[i+5]
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dw[i+6] = aw[i+6] ^ bw[i+6]
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dw[i+7] = aw[i+7] ^ bw[i+7]
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}
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}
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func xorWords(dst, a, b []byte) {
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if supportsUnaligned {
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fastXORWords(dst, a, b)
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} else {
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safeXORBytes(dst, a, b)
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}
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}
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