51 lines
1.3 KiB
Go
51 lines
1.3 KiB
Go
//go:build amd64 || arm64
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package protocol
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import "unsafe"
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const xorWordMask uint64 = 0xADADADADADADADAD
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// XorInPlace is optimized for 64-bit targets (amd64/arm64).
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//
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// It aligns the input once, then XORs 64 bytes per loop iteration using
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// eight native 64-bit operations. This removes the encoding/binary call
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// overhead from the hot relay path and lets the compiler generate a tight
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// load/xor/store 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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// Align the pointer for native uint64 accesses. This is normally already
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// aligned for pooled relay buffers, but also makes this safe for subslices.
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for i < n && (uintptr(unsafe.Pointer(&b[i]))&7) != 0 {
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b[i] ^= XORKey
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i++
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}
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for ; i+64 <= n; i += 64 {
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p := unsafe.Pointer(&b[i])
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*(*uint64)(unsafe.Add(p, 0)) ^= xorWordMask
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*(*uint64)(unsafe.Add(p, 8)) ^= xorWordMask
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*(*uint64)(unsafe.Add(p, 16)) ^= xorWordMask
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*(*uint64)(unsafe.Add(p, 24)) ^= xorWordMask
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*(*uint64)(unsafe.Add(p, 32)) ^= xorWordMask
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*(*uint64)(unsafe.Add(p, 40)) ^= xorWordMask
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*(*uint64)(unsafe.Add(p, 48)) ^= xorWordMask
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*(*uint64)(unsafe.Add(p, 56)) ^= xorWordMask
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}
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for ; i+8 <= n; i += 8 {
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p := (*uint64)(unsafe.Pointer(&b[i]))
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*p ^= xorWordMask
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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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