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1 //=========================================================================== |
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2 // |
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3 // memchr.cxx |
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4 // |
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5 // ANSI standard memchr() routine |
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6 // |
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7 //=========================================================================== |
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8 //####COPYRIGHTBEGIN#### |
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9 // |
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10 // ------------------------------------------- |
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11 // The contents of this file are subject to the Cygnus eCos Public License |
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12 // Version 1.0 (the "License"); you may not use this file except in |
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13 // compliance with the License. You may obtain a copy of the License at |
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14 // http://sourceware.cygnus.com/ecos |
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15 // |
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16 // Software distributed under the License is distributed on an "AS IS" |
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17 // basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See the |
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18 // License for the specific language governing rights and limitations under |
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19 // the License. |
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20 // |
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21 // The Original Code is eCos - Embedded Cygnus Operating System, released |
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22 // September 30, 1998. |
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23 // |
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24 // The Initial Developer of the Original Code is Cygnus. Portions created |
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25 // by Cygnus are Copyright (C) 1998 Cygnus Solutions. All Rights Reserved. |
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26 // ------------------------------------------- |
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27 // |
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28 //####COPYRIGHTEND#### |
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29 //=========================================================================== |
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30 //#####DESCRIPTIONBEGIN#### |
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31 // |
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32 // Author(s): jlarmour |
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33 // Contributors: jlarmour@cygnus.co.uk |
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34 // Date: 1998-02-13 |
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35 // Purpose: |
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36 // Description: |
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37 // Usage: |
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38 // |
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39 //####DESCRIPTIONEND#### |
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40 // |
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41 //=========================================================================== |
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42 |
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43 // CONFIGURATION |
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44 |
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45 #include <pkgconf/libc.h> // Configuration header |
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46 |
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47 // Include the C library? |
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48 #ifdef CYGPKG_LIBC |
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49 |
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50 // INCLUDES |
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51 |
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52 #include <cyg/infra/cyg_type.h> // Common type definitions |
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53 #include <cyg/infra/cyg_trac.h> // Tracing support |
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54 #include <cyg/infra/cyg_ass.h> // Assertion support |
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55 #include <string.h> // Header for this file |
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56 #include <stddef.h> // Compiler definitions such as size_t, NULL etc. |
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57 #include "clibincl/stringsupp.hxx" // Useful string function support and |
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58 // prototypes |
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59 |
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60 // EXPORTED SYMBOLS |
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61 |
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62 externC void * |
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63 memchr( const void *s, int c, size_t n ) CYGPRI_LIBC_WEAK_ALIAS("_memchr"); |
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64 |
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65 // FUNCTIONS |
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66 |
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67 void * |
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68 _memchr( const void *s, int c, size_t n ) |
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69 { |
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70 CYG_REPORT_FUNCNAMETYPE( "_memchr", "returning addr %08x" ); |
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71 CYG_REPORT_FUNCARG3( "s=%08x, c=%d, n=%d", s, c, n ); |
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72 |
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73 CYG_CHECK_DATA_PTR( s, "s is not a valid pointer!" ); |
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74 |
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75 #if defined(CYGIMP_LIBC_STRING_PREFER_SMALL_TO_FAST) || defined(__OPTIMIZE_SIZE__) |
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76 const unsigned char *src = (const unsigned char *) s; |
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77 |
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78 while (n--) |
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79 { |
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80 if (*src == c) |
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81 { |
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82 CYG_REPORT_RETVAL( src ); |
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83 return (void *) src; |
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84 } // if |
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85 src++; |
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86 } |
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87 CYG_REPORT_RETVAL( NULL ); |
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88 return NULL; |
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89 #else |
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90 const unsigned char *src = (const unsigned char *) s; |
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91 CYG_WORD *aligned_src; |
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92 CYG_WORD buffer; |
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93 CYG_WORD mask; |
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94 cyg_ucount8 i; |
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95 |
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96 // If the size is small, or src is unaligned, then |
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97 // use the bytewise loop. We can hope this is rare. |
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98 if (CYG_LIBC_STR_OPT_TOO_SMALL (n) || CYG_LIBC_STR_UNALIGNED (src)) |
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99 { |
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100 while (n--) |
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101 { |
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102 if (*src == c) |
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103 { |
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104 CYG_REPORT_RETVAL( src ); |
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105 return (void *) src; |
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106 } // if |
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107 src++; |
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108 } |
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109 CYG_REPORT_RETVAL( NULL ); |
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110 return NULL; |
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111 } |
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112 |
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113 // The fast code reads the ASCII one word at a time and only |
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114 // performs the bytewise search on word-sized segments if they |
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115 // contain the search character, which is detected by XORing |
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116 // the word-sized segment with a word-sized block of the search |
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117 // character and then detecting for the presence of NULL in the |
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118 // result. |
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119 |
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120 aligned_src = (CYG_WORD *) src; |
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121 mask = 0; |
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122 for (i = 0; i < CYG_LIBC_STR_OPT_LITTLEBLOCKSIZE; i++) |
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123 mask = (mask << 8) + c; |
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124 |
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125 while (n > CYG_LIBC_STR_OPT_LITTLEBLOCKSIZE) |
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126 { |
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127 buffer = *aligned_src; |
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128 buffer ^= mask; |
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129 if (CYG_LIBC_STR_DETECTNULL (buffer)) |
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130 { |
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131 src = (unsigned char*) aligned_src; |
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132 for ( i = 0; i < CYG_LIBC_STR_OPT_LITTLEBLOCKSIZE; i++ ) |
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133 { |
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134 if (*src == c) |
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135 { |
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136 CYG_REPORT_RETVAL( src ); |
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137 return (void *) src; |
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138 } // if |
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139 src++; |
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140 } |
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141 } |
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142 n -= CYG_LIBC_STR_OPT_LITTLEBLOCKSIZE; |
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143 aligned_src++; |
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144 } |
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145 |
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146 // If there are fewer than CYG_LIBC_STR_OPT_LITTLEBLOCKSIZE characters |
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147 // left, then we resort to the bytewise loop. |
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148 |
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149 src = (const unsigned char *) aligned_src; |
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150 while (n--) |
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151 { |
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152 if (*src == c) |
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153 { |
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154 CYG_REPORT_RETVAL( src ); |
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155 return (void *) src; |
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156 } // if |
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157 src++; |
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158 } |
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159 |
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160 CYG_REPORT_RETVAL( NULL ); |
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161 return NULL; |
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162 #endif // not defined(CYGIMP_LIBC_STRING_PREFER_SMALL_TO_FAST) || |
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163 // defined(__OPTIMIZE_SIZE__) |
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164 } // _memchr() |
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165 |
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166 #endif // ifdef CYGPKG_LIBC |
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167 |
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168 // EOF memchr.cxx |
