| /*************************************************************************** |
| * __________ __ ___. |
| * Open \______ \ ____ ____ | | _\_ |__ _______ ___ |
| * Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ / |
| * Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < < |
| * Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \ |
| * \/ \/ \/ \/ \/ |
| * $Id$ |
| * |
| * Copyright (C) 2005 by Jens Arnold |
| * |
| * 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 software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY |
| * KIND, either express or implied. |
| * |
| ****************************************************************************/ |
| #include "config.h" |
| |
| .section .icode,"ax",@progbits |
| |
| .align 2 |
| .global _strlen |
| .type _strlen,@function |
| |
| /* Works out the length of a string |
| * This version is optimized for speed |
| * |
| * arguments: |
| * r4 - start address |
| * |
| * return value: |
| * r0 - string length |
| * |
| * register usage: |
| * r0 - current address |
| * r1 - current value (byte/long) |
| * r2 - mask for alignment / zero (for cmp/str) |
| * r4 - start address |
| * |
| */ |
| |
| _strlen: |
| mov r4,r0 /* r0 = start address */ |
| tst #3,r0 /* long aligned? */ |
| bt .start_l /* yes, jump directly to the longword loop */ |
| |
| /* not long aligned: check the first 3 bytes */ |
| mov.b @r0+,r1 /* fetch first byte */ |
| tst r1,r1 /* byte == 0 ? */ |
| bt .hitzero /* yes, string end found */ |
| mov.b @r0+,r1 /* fetch second byte */ |
| mov #3,r2 /* prepare mask: r2 = 0..00000011b */ |
| tst r1,r1 /* byte == 0 ? */ |
| bt .hitzero /* yes, string end found */ |
| mov.b @r0+,r1 /* fetch third byte */ |
| not r2,r2 /* prepare mask: r2 = 1..11111100b */ |
| tst r1,r1 /* byte == 0 ? */ |
| bt .hitzero /* yes, string end found */ |
| |
| /* not yet found, fall through into longword loop */ |
| and r2,r0 /* align down to long bound */ |
| |
| /* main loop: check longwords */ |
| .start_l: |
| mov #0,r2 /* zero longword for cmp/str */ |
| .loop_l: |
| mov.l @r0+,r1 /* fetch long word */ |
| cmp/str r1,r2 /* any zero byte within? */ |
| bf .loop_l /* no, loop */ |
| add #-4,r0 /* set address back to start of this longword */ |
| |
| /* the last longword contains the string end: figure out the byte */ |
| mov.b @r0+,r1 /* fetch first byte */ |
| tst r1,r1 /* byte == 0 ? */ |
| bt .hitzero /* yes, string end found */ |
| mov.b @r0+,r1 /* fetch second byte */ |
| tst r1,r1 /* byte == 0 ? */ |
| bt .hitzero /* yes, string end found */ |
| mov.b @r0+,r1 /* fetch third byte */ |
| tst r1,r1 /* byte == 0 ? */ |
| bt .hitzero /* yes, string end found */ |
| rts /* must be the fourth byte */ |
| sub r4,r0 /* len = string_end - string_start */ |
| |
| .hitzero: |
| add #-1,r0 /* undo address increment */ |
| rts |
| sub r4,r0 /* len = string_end - string_start */ |
| |
| .end: |
| .size _strlen,.end-_strlen |
| |