xxtea

xxtea.go

package xxtea

import (
	"unsafe"
)

const _DELTA = 0x9e3779b9

func EncryptBytes(m []byte, k *[4]uint32) {
	if len(m) < 8 {
		return
	}
	vptr := uintptr(unsafe.Pointer(&m[0]))
	n := uint32(len(m) / 4)
	vlast := vptr + uintptr(n*4-4)
	rounds := 6 + 52/n
	sum := uint32(0)
	z := *(*uint32)(unsafe.Pointer(vlast))
	for {
		sum += _DELTA
		e := (sum >> 2) & 3
		p := uint32(0)
		for ; p < n-1; p++ {
			v := (*[2]uint32)(unsafe.Pointer(vptr + uintptr(p*4)))
			y := v[1]
			v[0] += (((z>>5 ^ y<<2) + (y>>3 ^ z<<4)) ^ ((sum ^ y) + (k[((p&3)^e)&3] ^ z)))
			z = v[0]
		}
		y := *(*uint32)(unsafe.Pointer(vptr))
		*(*uint32)(unsafe.Pointer(vlast)) += (((z>>5 ^ y<<2) + (y>>3 ^ z<<4)) ^ ((sum ^ y) + (k[((p&3)^e)&3] ^ z)))
		z = *(*uint32)(unsafe.Pointer(vlast))
		rounds--
		if rounds == 0 {
			break
		}
	}
}

func DecryptBytes(m []byte, k *[4]uint32) {
	if len(m) < 8 {
		return
	}
	vptr := uintptr(unsafe.Pointer(&m[0]))
	n := uint32(len(m) / 4)
	vlast := vptr + uintptr(n*4-4)
	rounds := 6 + 52/n
	sum := uint32(rounds * _DELTA)
	y := *(*uint32)(unsafe.Pointer(vptr))
	var z uint32
	for {
		e := (sum >> 2) & 3
		p := n - 1
		for ; p > 0; p-- {
			v := (*[2]uint32)(unsafe.Pointer(vptr + uintptr(p*4) - 4))
			z = v[0]
			v[1] -= (((z>>5 ^ y<<2) + (y>>3 ^ z<<4)) ^ ((sum ^ y) + (k[((p&3)^e)&3] ^ z)))
			y = v[1]
		}
		z = *(*uint32)(unsafe.Pointer(vlast))
		*(*uint32)(unsafe.Pointer(vptr)) -= (((z>>5 ^ y<<2) + (y>>3 ^ z<<4)) ^ ((sum ^ y) + (k[((p&3)^e)&3] ^ z)))
		y = *(*uint32)(unsafe.Pointer(vptr))
		sum -= _DELTA
		rounds--
		if rounds == 0 {
			break
		}
	}
}

func Encrypt(v []uint32, k *[4]uint32) {
	if len(v) <= 1 {
		return
	}
	n := len(v)
	rounds := 6 + 52/n
	sum := uint32(0)
	z := v[n-1]
	for {
		sum += _DELTA
		e := (sum >> 2) & 3
		p := 0
		for ; p < n-1; p++ {
			y := v[p+1]
			v[p] += (((z>>5 ^ y<<2) + (y>>3 ^ z<<4)) ^ ((sum ^ y) + (k[uint32(p&3)^e] ^ z)))
			z = v[p]
		}
		y := v[0]
		v[n-1] += (((z>>5 ^ y<<2) + (y>>3 ^ z<<4)) ^ ((sum ^ y) + (k[uint32(p&3)^e] ^ z)))
		z = v[n-1]
		rounds--
		if rounds == 0 {
			break
		}
	}
}

func Decrypt(v []uint32, k *[4]uint32) {
	if len(v) <= 1 {
		return
	}
	n := len(v)
	rounds := 6 + 52/n
	sum := uint32(rounds * _DELTA)
	y := v[0]
	var z uint32
	for {
		e := (sum >> 2) & 3
		p := n - 1
		for ; p > 0; p-- {
			z = v[p-1]
			v[p] -= (((z>>5 ^ y<<2) + (y>>3 ^ z<<4)) ^ ((sum ^ y) + (k[uint32(p&3)^e] ^ z)))
			y = v[p]
		}
		z = v[n-1]
		v[0] -= (((z>>5 ^ y<<2) + (y>>3 ^ z<<4)) ^ ((sum ^ y) + (k[uint32(p&3)^e] ^ z)))
		y = v[0]
		sum -= _DELTA
		rounds--
		if rounds == 0 {
			break
		}
	}
}