lukechampine
63 lines
1.3 KiB
Go
63 lines
1.3 KiB
Go
// +build 386 amd64,!go1.7 ppc64 ppc64le s390x
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package fastxor
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import (
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"unsafe"
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)
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const wordSize = int(unsafe.Sizeof(uintptr(0)))
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// Bytes stores (a xor b) in dst, stopping when the end of any slice is
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// reached. It returns the number of bytes xor'd.
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func Bytes(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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if n == 0 {
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return 0
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}
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// Assert dst has enough space
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_ = dst[n-1]
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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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// Byte xors each byte in a with b and stores the result in dst, stopping when
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// the end of either dst or a is reached. It returns the number of bytes
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// xor'd.
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func Byte(dst, a []byte, b byte) int {
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n := len(a)
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if len(dst) < n {
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n = len(dst)
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}
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for i := 0; i < n; i++ {
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dst[i] = a[i] ^ b
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}
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return n
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}
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// Block stores (a xor b) in dst, where a, b, and dst all have length 16.
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func Block(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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dw[0] = aw[0] ^ bw[0]
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dw[1] = aw[1] ^ bw[1]
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}
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