ggstd 0.1.0

// Copyright 2023 The rust-ggstd authors. All rights reserved.
// Copyright 2013 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

//go:build (!amd64 && !arm64 && !ppc64 && !ppc64le) || purego

// import (
// 	"runtime"
// 	"unsafe"
// )

// const wordSize = unsafe.Sizeof(uintptr(0))

// const supportsUnaligned = runtime.GOARCH == "386" ||
// 	runtime.GOARCH == "amd64" ||
// 	runtime.GOARCH == "ppc64" ||
// 	runtime.GOARCH == "ppc64le" ||
// 	runtime.GOARCH == "s390x"

// func xorBytes(dstb, xb, yb *byte, n int) {
// 	// xorBytes assembly is written using pointers and n. Back to slices.
// 	dst := unsafe.Slice(dstb, n)
// 	x := unsafe.Slice(xb, n)
// 	y := unsafe.Slice(yb, n)

// 	if supportsUnaligned || aligned(dstb, xb, yb) {
// 		xorLoop(words(dst), words(x), words(y))
// 		if uintptr(n)%wordSize == 0 {
// 			return
// 		}
// 		done := n &^ int(wordSize-1)
// 		dst = dst[done:]
// 		x = x[done:]
// 		y = y[done:]
// 	}
// 	xorLoop(dst, x, y)
// }

// // aligned reports whether dst, x, and y are all word-aligned pointers.
// func aligned(dst, x, y *byte) bool {
// 	return (uintptr(unsafe.Pointer(dst))|uintptr(unsafe.Pointer(x))|uintptr(unsafe.Pointer(y)))&(wordSize-1) == 0
// }

// // words returns a []uintptr pointing at the same data as x,
// // with any trailing partial word removed.
// func words(x []byte) []uintptr {
// 	n := uintptr(len(x)) / wordSize
// 	if n == 0 {
// 		// Avoid creating a *uintptr that refers to data smaller than a uintptr;
// 		// see issue 59334.
// 		return nil
// 	}
// 	return unsafe.Slice((*uintptr)(unsafe.Pointer(&x[0])), n)
// }

pub fn xor_loop(dst: &mut [u8], x: &[u8], y: &[u8]) {
    // func xorLoop[T byte | uintptr](dst, x, y []T) {
    assert!(x.len() >= dst.len());
    assert!(y.len() >= dst.len());
    for i in 0..dst.len() {
        dst[i] = x[i] ^ y[i];
    }
}

pub fn xor_loop_inplace(dst: &mut [u8], y: &[u8]) {
    assert!(y.len() >= dst.len());
    for i in 0..dst.len() {
        dst[i] ^= y[i];
    }
}