aligned

aligned.go

package aligned

import (
    "fmt"
    "unsafe"
    "golang.org/x/sys/cpu"
)

const (
    cacheLineSize = unsafe.Sizeof(cpu.CacheLinePad{})
)

func malign(size, align uintptr) unsafe.Pointer {
	s := align * 2
	if size > align {
		s = align * (1 + (size+align-1)/align)
	}
	b := make([]byte, s)
	for i := range b[:uintptr(len(b))-size] {
		p := (unsafe.Pointer)(&b[i])
		if (uintptr)(p)%align == 0 {
			return p
		}
	}
	panic(fmt.Sprintf("mailgn(%d, %d): bug", size, align))
}

// Uint64 returns a cacheline-aligned uint64 that is guaranteed not
// to share the cacheline with any other data.
func Uint64() *uint64 {
	return (*uint64)(malign(unsafe.Sizeof(uint64(0)), cacheLineSize))
}

// Int64 returns a cacheline-aligned int64 that is guaranteed not
// to share the cacheline with any other data.
func Int64() *int64 {
	return (*int64)(malign(unsafe.Sizeof(int64(0)), cacheLineSize))
}

// Uint32 returns a cacheline-aligned uint32 that is guaranteed not
// to share the cacheline with any other data.
func Uint32() *uint32 {
	return (*uint32)(malign(unsafe.Sizeof(uint32(0)), cacheLineSize))
}

// Int32 returns a cacheline-aligned int32 that is guaranteed not
// to share the cacheline with any other data.
func Int32() *int32 {
	return (*int32)(malign(unsafe.Sizeof(int32(0)), cacheLineSize))
}

// Uintptr returns a cacheline-aligned uintptr that is guaranteed not
// to share the cacheline with any other data.
func Uintptr() *uintptr {
	return (*uintptr)(malign(unsafe.Sizeof(uintptr(0)), cacheLineSize))
}