1 | /* |
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2 | * strncpy.S -- strncmp function. On at least some MIPS chips, you get better |
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3 | * code by hand unrolling the loops, and by using store words to zero the |
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4 | * remainder of the buffer than the default newlib C version. |
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5 | * |
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6 | * Copyright (c) 2001 Red Hat, Inc. |
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7 | * |
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8 | * The authors hereby grant permission to use, copy, modify, distribute, |
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9 | * and license this software and its documentation for any purpose, provided |
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10 | * that existing copyright notices are retained in all copies and that this |
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11 | * notice is included verbatim in any distributions. No written agreement, |
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12 | * license, or royalty fee is required for any of the authorized uses. |
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13 | * Modifications to this software may be copyrighted by their authors |
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14 | * and need not follow the licensing terms described here, provided that |
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15 | * the new terms are clearly indicated on the first page of each file where |
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16 | * they apply. */ |
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17 | |
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18 | #include <string.h> |
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19 | #include <stddef.h> |
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20 | #include <stdlib.h> |
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21 | #include <stdint.h> |
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22 | |
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23 | #if !defined(__GNUC__) || (__GNUC__ < 3) |
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24 | #define __builtin_expect(a,b) a |
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25 | |
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26 | #else |
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27 | #ifdef __mips64 |
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28 | /* Don't use limits test for the size of long, in order to allow the use of |
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29 | 64-bit stores on MIPS3 machines, even if -mlong32 was used. */ |
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30 | typedef unsigned word_type __attribute__ ((mode (DI))); |
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31 | #else |
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32 | typedef unsigned word_type __attribute__ ((mode (SI))); |
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33 | #endif |
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34 | |
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35 | typedef unsigned si_type __attribute__ ((mode (SI))); |
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36 | typedef unsigned hi_type __attribute__ ((mode (HI))); |
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37 | |
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38 | #ifndef UNROLL_FACTOR |
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39 | #define UNROLL_FACTOR 4 |
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40 | |
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41 | #elif (UNROLL_FACTOR != 2) && (UNROLL_FACTOR != 4) |
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42 | #error "UNROLL_FACTOR must be 2 or 4" |
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43 | #endif |
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44 | #endif |
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45 | |
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46 | char * |
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47 | strncpy (char *dst0, const char *src0, size_t count) |
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48 | { |
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49 | #if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__) || defined(__mips16) || !defined(__GNUC__) || (__GNUC__ < 3) |
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50 | char *dst, *end; |
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51 | const char *src; |
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52 | int ch; |
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53 | |
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54 | dst = dst0; |
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55 | src = src0; |
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56 | end = dst + count; |
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57 | while (dst != end) |
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58 | { |
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59 | *dst++ = ch = *src++; |
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60 | if (__builtin_expect (ch == '\0', 0)) |
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61 | { |
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62 | while (dst != end) |
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63 | *dst++ = '\0'; |
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64 | |
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65 | break; |
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66 | } |
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67 | } |
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68 | |
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69 | return dst0; |
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70 | |
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71 | #else |
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72 | unsigned char *dst; |
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73 | unsigned char *dst_end; |
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74 | unsigned char *end; |
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75 | const unsigned char *src; |
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76 | int ch0, ch1; |
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77 | #if UNROLL_FACTOR > 2 |
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78 | int ch2, ch3; |
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79 | #endif |
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80 | int ch; |
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81 | int odd_bytes; |
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82 | size_t long_count; |
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83 | |
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84 | dst = (unsigned char *)dst0; |
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85 | src = (unsigned const char *)src0; |
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86 | /* Take care of any odd bytes in the source data because we |
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87 | * want to unroll where we read ahead 2 or 4 bytes at a time and then |
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88 | * check each byte for the null terminator. This can result in |
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89 | * a segfault for the case where the source pointer is unaligned, |
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90 | * the null terminator is in valid memory, but reading 2 or 4 bytes at a |
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91 | * time blindly eventually goes outside of valid memory. */ |
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92 | while (((uintptr_t) src & (UNROLL_FACTOR - 1)) != 0 && count > 0) |
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93 | { |
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94 | *dst++ = ch = *src++; |
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95 | --count; |
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96 | if (ch == '\0') |
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97 | { |
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98 | end = dst + count; |
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99 | while (dst != end) |
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100 | *dst++ = '\0'; |
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101 | |
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102 | return dst0; |
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103 | } |
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104 | } |
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105 | |
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106 | if (__builtin_expect (count >= 4, 1)) |
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107 | { |
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108 | odd_bytes = (count & (UNROLL_FACTOR - 1)); |
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109 | count -= odd_bytes; |
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110 | |
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111 | do |
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112 | { |
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113 | ch0 = src[0]; |
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114 | ch1 = src[1]; |
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115 | #if UNROLL_FACTOR > 2 |
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116 | ch2 = src[2]; |
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117 | ch3 = src[3]; |
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118 | #endif |
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119 | src += UNROLL_FACTOR; |
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120 | count -= UNROLL_FACTOR; |
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121 | |
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122 | dst[0] = ch0; |
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123 | if (ch0 == '\0') |
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124 | goto found_null0; |
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125 | |
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126 | dst[1] = ch1; |
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127 | if (ch1 == '\0') |
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128 | goto found_null1; |
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129 | |
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130 | #if UNROLL_FACTOR > 2 |
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131 | dst[2] = ch2; |
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132 | if (ch2 == '\0') |
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133 | goto found_null2; |
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134 | |
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135 | dst[3] = ch3; |
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136 | if (ch3 == '\0') |
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137 | goto found_null3; |
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138 | #endif |
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139 | |
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140 | dst += UNROLL_FACTOR; |
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141 | } |
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142 | while (count); |
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143 | |
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144 | /* fall through, count == 0, no null found, deal with last bytes */ |
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145 | count = odd_bytes; |
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146 | } |
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147 | |
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148 | end = dst + count; |
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149 | while (dst != end) |
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150 | { |
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151 | *dst++ = ch = *src++; |
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152 | if (ch == '\0') |
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153 | { |
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154 | while (dst != end) |
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155 | *dst++ = '\0'; |
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156 | |
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157 | break; |
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158 | } |
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159 | } |
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160 | |
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161 | return dst0; |
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162 | |
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163 | /* Found null byte in first byte, count has been decremented by 4, null has |
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164 | been stored in dst[0]. */ |
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165 | found_null0: |
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166 | count++; /* add 1 to cover remaining byte */ |
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167 | dst -= 1; /* adjust dst += 4 gets correct ptr */ |
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168 | /* fall through */ |
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169 | |
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170 | /* Found null byte in second byte, count has been decremented by 4, null has |
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171 | been stored in dst[1]. */ |
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172 | found_null1: |
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173 | #if UNROLL_FACTOR > 2 |
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174 | count++; /* add 1 to cover remaining byte */ |
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175 | dst -= 1; /* adjust dst += 4 gets correct ptr */ |
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176 | /* fall through */ |
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177 | |
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178 | /* Found null byte in third byte, count has been decremented by 4, null has |
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179 | been stored in dst[2]. */ |
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180 | found_null2: |
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181 | count++; /* add 1 to cover remaining byte */ |
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182 | dst -= 1; /* adjust dst += 4 gets correct ptr */ |
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183 | /* fall through */ |
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184 | |
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185 | /* Found null byte in fourth byte, count is accurate, dst has not been |
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186 | updated yet. */ |
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187 | found_null3: |
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188 | #endif |
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189 | count += odd_bytes; /* restore odd byte count */ |
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190 | dst += UNROLL_FACTOR; |
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191 | |
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192 | /* Zero fill remainder of the array. Unroll the loop, and use word/dword |
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193 | stores where we can. */ |
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194 | while (count && (((long)dst) & (sizeof (word_type) - 1)) != 0) |
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195 | { |
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196 | count--; |
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197 | *dst++ = 0; |
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198 | } |
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199 | |
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200 | while (count >= UNROLL_FACTOR*sizeof (word_type)) |
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201 | { |
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202 | count -= UNROLL_FACTOR*sizeof (word_type); |
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203 | dst += UNROLL_FACTOR*sizeof (word_type); |
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204 | #if UNROLL_FACTOR > 2 |
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205 | ((word_type *)(void *)dst)[-4] = 0; |
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206 | ((word_type *)(void *)dst)[-3] = 0; |
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207 | #endif |
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208 | ((word_type *)(void *)dst)[-2] = 0; |
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209 | ((word_type *)(void *)dst)[-1] = 0; |
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210 | } |
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211 | |
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212 | #if UNROLL_FACTOR > 2 |
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213 | if (count >= 2*sizeof (word_type)) |
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214 | { |
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215 | count -= 2*sizeof (word_type); |
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216 | ((word_type *)(void *)dst)[0] = 0; |
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217 | ((word_type *)(void *)dst)[1] = 0; |
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218 | dst += 2*sizeof (word_type); |
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219 | } |
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220 | #endif |
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221 | |
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222 | if (count >= sizeof (word_type)) |
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223 | { |
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224 | count -= sizeof (word_type); |
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225 | ((word_type *)(void *)dst)[0] = 0; |
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226 | dst += sizeof (word_type); |
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227 | } |
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228 | |
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229 | #ifdef __mips64 |
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230 | if (count >= sizeof (si_type)) |
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231 | { |
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232 | count -= sizeof (si_type); |
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233 | ((si_type *)(void *)dst)[0] = 0; |
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234 | dst += sizeof (si_type); |
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235 | } |
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236 | #endif |
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237 | |
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238 | if (count >= sizeof (hi_type)) |
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239 | { |
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240 | count -= sizeof (hi_type); |
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241 | ((hi_type *)(void *)dst)[0] = 0; |
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242 | dst += sizeof (hi_type); |
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243 | } |
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244 | |
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245 | if (count) |
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246 | *dst = '\0'; |
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247 | |
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248 | return dst0; |
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249 | #endif |
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250 | } |
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