borgware-2d/random/memxor.S

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/* memxor.S */
/*
This file is part of the Crypto-avr-lib/microcrypt-lib.
Copyright (C) 2008 Daniel Otte (daniel.otte@rub.de)
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
/*
* File: memxor.S
* Author: Daniel Otte
* Date: 2008-08-07
* License: GPLv3 or later
* Description: memxor, XORing one block into another
*
*/
/*
* void memxor(void* dest, const void* src, uint16_t n);
*/
/*
* param dest is passed in r24:r25
* param src is passed in r22:r23
* param n is passed in r20:r21
*/
.global memxor
memxor:
movw r30, r24
movw r26, r22
movw r24, r20
tst r24
brne 1f
tst r25
breq 2f
1:
ld r20, X+
ld r21, Z
eor r20, r21
st Z+, r20
sbiw r24, 1
brne 1b
2:
ret