45 lines
1.0 KiB
Go
45 lines
1.0 KiB
Go
//go:build arm || 386
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package protocol
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import "unsafe"
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const xorWordMask32 uint32 = 0xADADADAD
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// XorInPlace is the 32-bit optimized path used by ARMv7/386 builds.
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// It aligns once, then processes 32 bytes per iteration with native uint32
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// operations instead of a byte-at-a-time loop.
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func XorInPlace(b []byte) {
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n := len(b)
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if n == 0 {
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return
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}
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i := 0
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for i < n && (uintptr(unsafe.Pointer(&b[i]))&3) != 0 {
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b[i] ^= XORKey
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i++
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}
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for ; i+32 <= n; i += 32 {
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p := unsafe.Pointer(&b[i])
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*(*uint32)(unsafe.Add(p, 0)) ^= xorWordMask32
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*(*uint32)(unsafe.Add(p, 4)) ^= xorWordMask32
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*(*uint32)(unsafe.Add(p, 8)) ^= xorWordMask32
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*(*uint32)(unsafe.Add(p, 12)) ^= xorWordMask32
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*(*uint32)(unsafe.Add(p, 16)) ^= xorWordMask32
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*(*uint32)(unsafe.Add(p, 20)) ^= xorWordMask32
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*(*uint32)(unsafe.Add(p, 24)) ^= xorWordMask32
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*(*uint32)(unsafe.Add(p, 28)) ^= xorWordMask32
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}
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for ; i+4 <= n; i += 4 {
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p := (*uint32)(unsafe.Pointer(&b[i]))
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*p ^= xorWordMask32
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}
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for ; i < n; i++ {
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b[i] ^= XORKey
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}
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}
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