contrib/loaders/checksum/armv4_5_crc.s

   1 /***************************************************************************
   2  *   Copyright (C) 2010 by Spencer Oliver                                  *
   3  *   spen@spen-soft.co.uk                                                  *
   4  *                                                                         *
   5  *   This program is free software; you can redistribute it and/or modify  *
   6  *   it under the terms of the GNU General Public License as published by  *
   7  *   the Free Software Foundation; either version 2 of the License, or     *
   8  *   (at your option) any later version.                                   *
   9  *                                                                         *
  10  *   This program is distributed in the hope that it will be useful,       *
  11  *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
  12  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
  13  *   GNU General Public License for more details.                          *
  14  *                                                                         *
  15  *   You should have received a copy of the GNU General Public License     *
  16  *   along with this program; if not, write to the                         *
  17  *   Free Software Foundation, Inc.,                                       *
  18  *   51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.           *
  19  ***************************************************************************/
  20
  21 /*
  22         r0 - address in - crc out
  23         r1 - char count
  24 */
  25
  26         .text
  27         .arm
  28
  29 _start:
  30 main:
  31         mov             r2, r0
  32         mov             r0, #0xffffffff /* crc */
  33         mov             r3, r1
  34         mov             r4, #0
  35         b               ncomp
  36 nbyte:
  37         ldrb    r1, [r2, r4]
  38         ldr             r7, CRC32XOR
  39         eor             r0, r0, r1, asl #24
  40         mov             r5, #0
  41 loop:
  42         cmp             r0, #0
  43         mov             r6, r0, asl #1
  44         add             r5, r5, #1
  45         mov             r0, r6
  46         eorlt   r0, r6, r7
  47         cmp             r5, #8
  48         bne             loop
  49         add             r4, r4, #1
  50 ncomp:
  51         cmp             r4, r3
  52         bne             nbyte
  53 end:
  54         bkpt    #0
  55
  56 CRC32XOR:       .word   0x04c11db7
  57
  58         .end