| lh | 9ed821d | 2023-04-07 01:36:19 -0700 | [diff] [blame^] | 1 | /* Copyright (C) 1998 Free Software Foundation, Inc. |
| 2 | This file is part of the GNU C Library. |
| 3 | Code contributed by Matthew Wilcox <willy@odie.barnet.ac.uk> |
| 4 | |
| 5 | The GNU C Library is free software; you can redistribute it and/or |
| 6 | modify it under the terms of the GNU Lesser General Public |
| 7 | License as published by the Free Software Foundation; either |
| 8 | version 2.1 of the License, or (at your option) any later version. |
| 9 | |
| 10 | The GNU C Library 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 GNU |
| 13 | Lesser General Public License for more details. |
| 14 | |
| 15 | You should have received a copy of the GNU Lesser General Public |
| 16 | License along with the GNU C Library; if not, write to the Free |
| 17 | Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA |
| 18 | 02111-1307 USA. */ |
| 19 | |
| 20 | #include <features.h> |
| 21 | #include <endian.h> |
| 22 | #include <sys/syscall.h> |
| 23 | #include <bits/arm_asm.h> |
| 24 | |
| 25 | /* size_t strlen(const char *S) |
| 26 | * entry: r0 -> string |
| 27 | * exit: r0 = len |
| 28 | */ |
| 29 | |
| 30 | .text |
| 31 | .global strlen |
| 32 | .type strlen,%function |
| 33 | .align 4 |
| 34 | |
| 35 | #if defined(THUMB1_ONLY) |
| 36 | /* A simple implementation for when the ARM implementation can't be used. */ |
| 37 | .thumb_func |
| 38 | strlen: |
| 39 | mov r2, #0 |
| 40 | 1: |
| 41 | ldrb r1, [r0, r2] |
| 42 | add r2, r2, #1 |
| 43 | cmp r1, #0 |
| 44 | bne 1b |
| 45 | sub r0, r2, #1 |
| 46 | bx lr |
| 47 | #else |
| 48 | strlen: |
| 49 | bic r1, r0, $3 @ addr of word containing first byte |
| 50 | ldr r2, [r1], $4 @ get the first word |
| 51 | ands r3, r0, $3 @ how many bytes are duff? |
| 52 | rsb r0, r3, $0 @ get - that number into counter. |
| 53 | beq Laligned @ skip into main check routine if no |
| 54 | @ more |
| 55 | #if __BYTE_ORDER == __BIG_ENDIAN |
| 56 | orr r2, r2, $0xff000000 @ set this byte to non-zero |
| 57 | subs r3, r3, $1 @ any more to do? |
| 58 | IT(t, gt) |
| 59 | orrgt r2, r2, $0x00ff0000 @ if so, set this byte |
| 60 | subs r3, r3, $1 @ more? |
| 61 | IT(t, gt) |
| 62 | orrgt r2, r2, $0x0000ff00 @ then set. |
| 63 | #else |
| 64 | orr r2, r2, $0x000000ff @ set this byte to non-zero |
| 65 | subs r3, r3, $1 @ any more to do? |
| 66 | IT(t, gt) |
| 67 | orrgt r2, r2, $0x0000ff00 @ if so, set this byte |
| 68 | subs r3, r3, $1 @ more? |
| 69 | IT(t, gt) |
| 70 | orrgt r2, r2, $0x00ff0000 @ then set. |
| 71 | #endif |
| 72 | Laligned: @ here, we have a word in r2. Does it |
| 73 | tst r2, $0x000000ff @ contain any zeroes? |
| 74 | IT(tttt, ne) |
| 75 | tstne r2, $0x0000ff00 @ |
| 76 | tstne r2, $0x00ff0000 @ |
| 77 | tstne r2, $0xff000000 @ |
| 78 | addne r0, r0, $4 @ if not, the string is 4 bytes longer |
| 79 | IT(t, ne) |
| 80 | ldrne r2, [r1], $4 @ and we continue to the next word |
| 81 | bne Laligned @ |
| 82 | Llastword: @ drop through to here once we find a |
| 83 | #if __BYTE_ORDER == __BIG_ENDIAN |
| 84 | tst r2, $0xff000000 @ word that has a zero byte in it |
| 85 | IT(tttt, ne) |
| 86 | addne r0, r0, $1 @ |
| 87 | tstne r2, $0x00ff0000 @ and add up to 3 bytes on to it |
| 88 | addne r0, r0, $1 @ |
| 89 | tstne r2, $0x0000ff00 @ (if first three all non-zero, 4th |
| 90 | IT(t, ne) |
| 91 | addne r0, r0, $1 @ must be zero) |
| 92 | #else |
| 93 | tst r2, $0x000000ff @ |
| 94 | IT(tttt, ne) |
| 95 | addne r0, r0, $1 @ |
| 96 | tstne r2, $0x0000ff00 @ and add up to 3 bytes on to it |
| 97 | addne r0, r0, $1 @ |
| 98 | tstne r2, $0x00ff0000 @ (if first three all non-zero, 4th |
| 99 | IT(t, ne) |
| 100 | addne r0, r0, $1 @ must be zero) |
| 101 | #endif |
| 102 | #if defined(__USE_BX__) |
| 103 | bx lr |
| 104 | #else |
| 105 | mov pc,lr |
| 106 | #endif |
| 107 | #endif |
| 108 | |
| 109 | .size strlen,.-strlen |
| 110 | |
| 111 | libc_hidden_def(strlen) |