- /***************************************************************************
- * Copyright (C) 2010 by Spencer Oliver *
- * spen@spen-soft.co.uk *
- * *
- * 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 2 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, write to the *
- * Free Software Foundation, Inc., *
- * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. *
- ***************************************************************************/
-
- .global main
- .text
- .set noreorder
-
- /* params:
- * $a0 address in
- * $a1 byte count
- * vars
- * $a0 crc
- * $a1 crc data byte
- * temps:
- * t3 v0 a3 a2 t0 v1
- */
-
- .ent main
- main:
- addiu $t4, $a0, 0 /* address in */
- addiu $t2, $a1, 0 /* count */
-
- addiu $a0, $zero, 0xffffffff /* a0 crc - result */
-
- beq $zero, $zero, ncomp
- addiu $t3, $zero, 0 /* clear bytes read */
-
- nbyte:
- lb $a1, ($t4) /* load byte from source address */
- addi $t4, $t4, 1 /* inc byte count */
-
- crc:
- sll $a1, $a1, 24
- lui $v0, 0x04c1
- xor $a0, $a0, $a1
- ori $a3, $v0, 0x1db7
- addu $a2, $zero, $zero /* clear bit count */
- loop:
- sll $t0, $a0, 1
- addiu $a2, $a2, 1 /* inc bit count */
- slti $a0, $a0, 0
- xor $t1, $t0, $a3
- movn $t0, $t1, $a0
- slti $v1, $a2, 8 /* 8bits processed */
- bne $v1, $zero, loop
- addu $a0, $t0, $zero
-
- ncomp:
- bne $t2, $t3, nbyte /* all bytes processed */
- addiu $t3, $t3, 1
-
- wait:
- sdbbp
-
- .end main
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