annotate src/strcmp.c @ 428:3ecd8885ac67 r21-2-22

Import from CVS: tag r21-2-22
author cvs
date Mon, 13 Aug 2007 11:28:15 +0200
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children abe6d1db359e
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428
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1 /* This file is part of XEmacs.
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2
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3 XEmacs is free software; you can redistribute it and/or modify it
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4 under the terms of the GNU General Public License as published by the
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5 Free Software Foundation; either version 2, or (at your option) any
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6 later version.
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7
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8 XEmacs is distributed in the hope that it will be useful, but WITHOUT
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9 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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10 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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11 for more details.
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12
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13 You should have received a copy of the GNU General Public License
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14 along with XEmacs; see the file COPYING. If not, write to
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15 the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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16 Boston, MA 02111-1307, USA. */
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17
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18 /* Synched up with: Not in FSF. */
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19
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20 /* In SunOS 4.1.1 the strcmp and strncmp functions reference memory
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21 past the last byte of the string! This will core dump if the memory
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22 following the last byte is not mapped.
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23
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24 Here are correct versions by hbs@lucid.com.
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25 */
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26
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27 # include <config.h>
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28 # ifndef REGISTER /* Strictly enforced in 20.3 */
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29 # define REGISTER
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30 # endif
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31
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32 #include <string.h>
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33 #define ALIGNED(x) (!(((unsigned long) (x)) & (sizeof (unsigned long) - 1)))
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34
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35 #define MAGIC 0x7efefeff
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36 #define HIGH_BIT_P(c) ((c) & hi_bit)
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37 #define HAS_ZERO(c) (((((c) + magic) ^ (c)) & not_magic) != not_magic)
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38
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39 /* CONST IS LOSING, but const is part of the interface of strcmp */
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40 int
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41 strcmp (const char *x, const char *y)
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42 {
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43 if (x == y)
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44 return 0;
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45 else if (ALIGNED (x) && ALIGNED (y))
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46 {
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47 CONST unsigned long *x1 = (CONST unsigned long *) x;
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48 CONST unsigned long *y1 = (CONST unsigned long *) y;
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49 unsigned long c;
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50 unsigned long magic = MAGIC;
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51 unsigned long not_magic = ~magic;
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52 unsigned long hi_bit = 0x80000000;
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53
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54 while ((c = *x1) == *y1)
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55 {
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56 if (HAS_ZERO(c))
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57 {
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58 if (!HIGH_BIT_P (c))
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59 return 0;
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60 else
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61 {
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62 x = (CONST char *) x1;
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63 y = (CONST char *) y1;
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64 goto slow_loop;
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65 }
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66 }
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67
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68 x1++;
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69 y1++;
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70 }
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71
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72 x = (CONST char *) x1;
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73 y = (CONST char *) y1;
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74 goto slow_loop;
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75 }
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76 else
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77 {
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78 char c;
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79
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80 slow_loop:
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81
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82 while ((c = *x) == *y)
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83 {
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84 if (c == (char) 0) return 0;
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85 x++;
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86 y++;
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87 }
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88 return (*x - *y);
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89 }
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90 }
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91
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92
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93 int
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94 strncmp (CONST char *x, CONST char *y, size_t n)
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95 {
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96 if ((x == y) || (n <= 0))
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97 return 0;
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98 else if (ALIGNED (x) && ALIGNED (y))
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99 {
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100 CONST unsigned long *x1 = (CONST unsigned long *) x;
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101 CONST unsigned long *y1 = (CONST unsigned long *) y;
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102 unsigned long c;
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103 unsigned long magic = MAGIC;
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104 unsigned long not_magic = ~magic;
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105 unsigned long hi_bit = 0x80000000;
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106
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107 while ((c = *x1) == *y1)
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108 {
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109 n -= sizeof (unsigned long);
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110 if (n <= 0)
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111 return 0;
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112
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113 if (HAS_ZERO(c))
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114 {
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115 if (!HIGH_BIT_P (c))
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116 return 0;
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117 else
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118 {
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119 x = (CONST char *) x1;
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120 y = (CONST char *) y1;
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121 goto slow_loop;
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122 }
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123 }
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124
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125 x1++;
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126 y1++;
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127 }
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128
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129 x = (CONST char *) x1;
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130 y = (CONST char *) y1;
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131 goto slow_loop;
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132 }
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133 else
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134 {
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135 char c;
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136
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137 slow_loop:
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138
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139 while ((c = *x) == *y)
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140 {
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141 n--;
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142 if (n <= 0)
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143 return 0;
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144 if (c == (char) 0)
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145 return 0;
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146 x++;
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147 y++;
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148 }
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149 return (*x - *y);
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150 }
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151 }