1 /* 2 * Copyright (c) 2017 Imagination Technologies. 3 * 4 * All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 10 * * Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * * Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer 14 * in the documentation and/or other materials provided with 15 * the distribution. 16 * * Neither the name of Imagination Technologies nor the names of its 17 * contributors may be used to endorse or promote products derived 18 * from this software without specific prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 21 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 22 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 23 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 24 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 25 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 26 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 27 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 28 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 29 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 30 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 31 */ 32 33 #include <string.h> 34 35 #define op_t unsigned long int 36 #define op_size sizeof (op_t) 37 38 #if __mips64 || __mips_isa_rev >= 2 39 static inline size_t __attribute__ ((always_inline)) 40 do_bytes (const char *base, const char *p, op_t inval) 41 { 42 op_t outval = 0; 43 #if __mips64 44 __asm__ volatile ( 45 "dsbh %1, %0 \n\t" 46 "dshd %0, %1 \n\t" 47 "dclz %1, %0 \n\t" 48 : "+r" (inval), "+r" (outval) 49 ); 50 #else 51 __asm__ volatile ( 52 "wsbh %1, %0 \n\t" 53 "rotr %0, %1, 16 \n\t" 54 "clz %1, %0 \n\t" 55 : "+r" (inval), "+r" (outval) 56 ); 57 #endif 58 p += (outval >> 3); 59 return (size_t) (p - base); 60 } 61 62 #define DO_WORD(in, val) { \ 63 op_t tmp = ((val - mask_1) & ~val) & mask_128; \ 64 if (tmp) \ 65 return do_bytes(str, (const char *)(in), tmp); \ 66 } 67 #else 68 static inline size_t __attribute__ ((always_inline)) 69 do_bytes (const char *base, const char *p) 70 { 71 for (; *p; ++p); 72 return (size_t) (p - base); 73 } 74 75 #define DO_WORD(in, val) { \ 76 if (((val - mask_1) & ~val) & mask_128) { \ 77 return do_bytes(str, (const char *)(in)); \ 78 } \ 79 } 80 #endif 81 82 size_t strnlen (const char *str, size_t n) { 83 if (n != 0) { 84 const char *p = (const char *) str; 85 const op_t *w; 86 op_t mask_1, mask_128; 87 88 for (; n > 0 && ((size_t) p % op_size) != 0; --n, ++p) { 89 if (!(*p)) 90 return (p - str); 91 } 92 93 w = (const op_t *) p; 94 95 __asm__ volatile ( 96 "li %0, 0x01010101 \n\t" 97 : "=r" (mask_1) 98 ); 99 #if __mips64 100 mask_1 |= mask_1 << 32; 101 #endif 102 mask_128 = mask_1 << 7; 103 104 /* 105 * Check op_size byteswize after initial alignment 106 */ 107 while (n >= 4 * op_size) { 108 const op_t w0 = w[0]; 109 const op_t w1 = w[1]; 110 const op_t w2 = w[2]; 111 const op_t w3 = w[3]; 112 DO_WORD(w + 0, w0) 113 DO_WORD(w + 1, w1) 114 DO_WORD(w + 2, w2) 115 DO_WORD(w + 3, w3) 116 w += 4; 117 n -= 4 * op_size; 118 } 119 120 while (n >= op_size) { 121 DO_WORD(w, w[0]); 122 w++; 123 n -= op_size; 124 } 125 126 /* 127 * Check bytewize for remaining bytes 128 */ 129 p = (const char *) w; 130 for (; n > 0; --n, ++p) { 131 if (!(*p)) 132 return (p - str); 133 } 134 135 return (p - str); 136 } 137 138 return 0; 139 } 140
