//go:build (amd64 && !purego) || (arm64 && !purego)
// +build amd64,!purego arm64,!purego

package sm4

import (
	"crypto/cipher"
)

// Assert that sm4CipherAsm implements the xtsEncAble and xtsDecAble interfaces.
var _ xtsEncAble = (*sm4CipherNI)(nil)
var _ xtsDecAble = (*sm4CipherNI)(nil)

type xtsNI struct {
	b     *sm4CipherNI
	tweak [BlockSize]byte
	isGB  bool // if true, follows GB/T 17964-2021
	enc   int
}

func (b *sm4CipherNI) NewXTSEncrypter(encryptedTweak *[BlockSize]byte, isGB bool) cipher.BlockMode {
	var c xtsNI
	c.b = b
	c.enc = xtsEncrypt
	c.isGB = isGB
	copy(c.tweak[:], encryptedTweak[:])
	return &c
}

func (b *sm4CipherNI) NewXTSDecrypter(encryptedTweak *[BlockSize]byte, isGB bool) cipher.BlockMode {
	var c xtsNI
	c.b = b
	c.enc = xtsDecrypt
	c.isGB = isGB
	copy(c.tweak[:], encryptedTweak[:])
	return &c
}

func (x *xtsNI) BlockSize() int { return BlockSize }

func (x *xtsNI) CryptBlocks(dst, src []byte) {
	validateXtsInput(dst, src)
	if x.enc == xtsEncrypt {
		if x.isGB {
			encryptSm4XtsGB(&x.b.enc[0], &x.tweak, dst, src)
		} else {
			encryptSm4Xts(&x.b.enc[0], &x.tweak, dst, src)
		}
	} else {
		if x.isGB {
			decryptSm4XtsGB(&x.b.dec[0], &x.tweak, dst, src)
		} else {
			decryptSm4Xts(&x.b.dec[0], &x.tweak, dst, src)
		}
	}
}