go-ethereum/common/bitutil/or_generic.go

// 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) || purego

package bitutil

import "unsafe"

func orBytes(dst, a, b []byte) int {
	if supportsUnaligned {
		return fastORBytes(dst, a, b)
	}
	return safeORBytes(dst, a, b)
}

// fastORBytes ors in bulk. It only works on architectures that support
// unaligned read/writes.
func fastORBytes(dst, a, b []byte) int {
	n := len(a)
	if len(b) < n {
		n = len(b)
	}
	w := n / wordSize
	if w > 0 {
		dw := *(*[]uintptr)(unsafe.Pointer(&dst))
		aw := *(*[]uintptr)(unsafe.Pointer(&a))
		bw := *(*[]uintptr)(unsafe.Pointer(&b))
		for i := 0; i < w; i++ {
			dw[i] = aw[i] | bw[i]
		}
	}
	for i := n - n%wordSize; i < n; i++ {
		dst[i] = a[i] | b[i]
	}
	return n
}