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1 /* Copyright (C) 1993, 1994 Free Software Foundation, Inc. |
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2 Contributed by Noel Cragg (noel@cs.oberlin.edu), with fixes by |
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3 Michael E. Calwas (calwas@ttd.teradyne.com) and |
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4 Wade Hampton (tasi029@tmn.com). |
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5 |
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6 |
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7 NOTE: The canonical source of this file is maintained with the GNU C Library. |
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8 Bugs can be reported to bug-glibc@prep.ai.mit.edu. |
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9 |
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10 This program is free software; you can redistribute it and/or modify it |
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11 under the terms of the GNU General Public License as published by the |
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12 Free Software Foundation; either version 2, or (at your option) any |
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13 later version. |
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14 |
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15 This program is distributed in the hope that it will be useful, |
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16 but WITHOUT ANY WARRANTY; without even the implied warranty of |
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17 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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18 GNU General Public License for more details. |
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19 |
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20 You should have received a copy of the GNU General Public License |
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21 along with this program; if not, write to the Free Software |
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22 Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */ |
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23 |
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24 /* Define this to have a standalone program to test this implementation of |
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25 mktime. */ |
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26 /* #define DEBUG */ |
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27 |
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28 #ifdef HAVE_CONFIG_H |
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29 #include <config.h> |
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30 #endif |
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31 |
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32 #include <sys/types.h> /* Some systems define `time_t' here. */ |
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33 #include <time.h> |
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34 |
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35 |
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36 #ifndef __isleap |
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37 /* Nonzero if YEAR is a leap year (every 4 years, |
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38 except every 100th isn't, and every 400th is). */ |
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39 #define __isleap(year) \ |
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40 ((year) % 4 == 0 && ((year) % 100 != 0 || (year) % 400 == 0)) |
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41 #endif |
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42 |
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43 #ifndef __P |
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44 #if defined (__GNUC__) || (defined (__STDC__) && __STDC__) |
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45 #define __P(args) args |
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46 #else |
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47 #define __P(args) () |
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48 #endif /* GCC. */ |
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49 #endif /* Not __P. */ |
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50 |
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51 /* How many days are in each month. */ |
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52 const unsigned short int __mon_lengths[2][12] = |
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53 { |
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54 /* Normal years. */ |
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55 { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 }, |
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56 /* Leap years. */ |
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57 { 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 } |
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58 }; |
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59 |
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60 |
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61 static int times_through_search; /* This library routine should never |
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62 hang -- make sure we always return |
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63 when we're searching for a value */ |
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64 |
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65 |
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66 #ifdef DEBUG |
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67 |
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68 #include <stdio.h> |
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69 #include <ctype.h> |
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70 |
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71 int debugging_enabled = 0; |
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72 |
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187
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73 /* Print the values in a `struct tm'. */ |
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74 static void |
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75 printtm (it) |
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76 struct tm *it; |
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77 { |
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78 printf ("%02d/%02d/%04d %02d:%02d:%02d (%s) yday:%03d dst:%d gmtoffset:%ld", |
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79 it->tm_mon + 1, |
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80 it->tm_mday, |
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81 it->tm_year + 1900, |
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82 it->tm_hour, |
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83 it->tm_min, |
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84 it->tm_sec, |
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85 it->tm_zone, |
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86 it->tm_yday, |
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87 it->tm_isdst, |
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88 it->tm_gmtoff); |
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89 } |
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90 #endif |
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91 |
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92 |
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93 static time_t |
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94 dist_tm (t1, t2) |
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95 struct tm *t1; |
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96 struct tm *t2; |
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97 { |
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98 time_t distance = 0; |
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99 unsigned long int v1, v2; |
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100 int diff_flag = 0; |
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101 |
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102 v1 = v2 = 0; |
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103 |
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104 #define doit(x, secs) \ |
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105 v1 += t1->x * secs; \ |
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106 v2 += t2->x * secs; \ |
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107 if (!diff_flag) \ |
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108 { \ |
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109 if (t1->x < t2->x) \ |
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110 diff_flag = -1; \ |
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111 else if (t1->x > t2->x) \ |
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112 diff_flag = 1; \ |
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113 } |
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114 |
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115 doit (tm_year, 31536000); /* Okay, not all years have 365 days. */ |
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116 doit (tm_mon, 2592000); /* Okay, not all months have 30 days. */ |
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117 doit (tm_mday, 86400); |
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118 doit (tm_hour, 3600); |
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119 doit (tm_min, 60); |
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120 doit (tm_sec, 1); |
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121 |
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122 #undef doit |
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123 |
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124 /* We should also make sure that the sign of DISTANCE is correct -- if |
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125 DIFF_FLAG is positive, the distance should be positive and vice versa. */ |
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126 |
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127 distance = (v1 > v2) ? (v1 - v2) : (v2 - v1); |
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128 if (diff_flag < 0) |
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129 distance = -distance; |
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130 |
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131 if (times_through_search > 20) /* Arbitrary # of calls, but makes sure we |
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132 never hang if there's a problem with |
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133 this algorithm. */ |
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134 { |
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135 distance = diff_flag; |
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136 } |
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137 |
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138 /* We need this DIFF_FLAG business because it is forseeable that the |
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139 distance may be zero when, in actuality, the two structures are |
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140 different. This is usually the case when the dates are 366 days apart |
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141 and one of the years is a leap year. */ |
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142 |
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143 if (distance == 0 && diff_flag) |
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144 distance = 86400 * diff_flag; |
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145 |
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146 return distance; |
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147 } |
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148 |
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149 |
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150 /* MKTIME converts the values in a struct tm to a time_t. The values |
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151 in tm_wday and tm_yday are ignored; other values can be put outside |
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152 of legal ranges since they will be normalized. This routine takes |
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153 care of that normalization. */ |
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154 |
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155 void |
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156 do_normalization (tmptr) |
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157 struct tm *tmptr; |
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187
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158 { |
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159 |
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160 #define normalize(foo,x,y,bar); \ |
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161 while (tmptr->foo < x) \ |
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162 { \ |
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163 tmptr->bar--; \ |
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164 tmptr->foo = (y - (x - tmptr->foo) + 1); \ |
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165 } \ |
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166 while (tmptr->foo > y) \ |
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167 { \ |
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168 tmptr->foo = (x + (tmptr->foo - y) - 1); \ |
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169 tmptr->bar++; \ |
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170 } |
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171 |
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172 normalize (tm_sec, 0, 59, tm_min); |
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173 normalize (tm_min, 0, 59, tm_hour); |
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174 normalize (tm_hour, 0, 23, tm_mday); |
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175 |
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176 /* Do the month first, so day range can be found. */ |
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177 normalize (tm_mon, 0, 11, tm_year); |
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178 |
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179 /* Since the day range modifies the month, we should be careful how |
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180 we reference the array of month lengths -- it is possible that |
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181 the month will go negative, hence the modulo... |
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182 |
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183 Also, tm_year is the year - 1900, so we have to 1900 to have it |
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184 work correctly. */ |
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185 |
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187
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186 normalize (tm_mday, 1, |
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187 __mon_lengths[__isleap (tmptr->tm_year + 1900)] |
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188 [((tmptr->tm_mon < 0) |
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189 ? (12 + (tmptr->tm_mon % 12)) |
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190 : (tmptr->tm_mon % 12)) ], |
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191 tm_mon); |
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192 |
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193 /* Do the month again, because the day may have pushed it out of range. */ |
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194 normalize (tm_mon, 0, 11, tm_year); |
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195 |
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196 /* Do the day again, because the month may have changed the range. */ |
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197 normalize (tm_mday, 1, |
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198 __mon_lengths[__isleap (tmptr->tm_year + 1900)] |
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199 [((tmptr->tm_mon < 0) |
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200 ? (12 + (tmptr->tm_mon % 12)) |
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201 : (tmptr->tm_mon % 12)) ], |
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202 tm_mon); |
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203 |
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204 #ifdef DEBUG |
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205 if (debugging_enabled) |
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206 { |
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207 printf (" After normalizing:\n "); |
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208 printtm (tmptr); |
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209 putchar ('\n'); |
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210 } |
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187
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211 #endif |
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212 |
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213 } |
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214 |
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215 |
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216 /* Here's where the work gets done. */ |
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217 |
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218 #define BAD_STRUCT_TM ((time_t) -1) |
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219 |
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220 time_t |
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221 _mktime_internal (timeptr, producer) |
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222 struct tm *timeptr; |
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223 struct tm *(*producer) __P ((const time_t *)); |
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224 { |
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225 struct tm our_tm; /* our working space */ |
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226 struct tm *me = &our_tm; /* a pointer to the above */ |
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227 time_t result; /* the value we return */ |
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228 |
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229 *me = *timeptr; /* copy the struct tm that was passed |
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230 in by the caller */ |
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231 |
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232 |
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233 /***************************/ |
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234 /* Normalize the structure */ |
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235 /***************************/ |
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236 |
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237 /* This routine assumes that the value of TM_ISDST is -1, 0, or 1. |
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238 If the user didn't pass it in that way, fix it. */ |
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239 |
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240 if (me->tm_isdst > 0) |
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241 me->tm_isdst = 1; |
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242 else if (me->tm_isdst < 0) |
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243 me->tm_isdst = -1; |
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244 |
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245 do_normalization (me); |
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246 |
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247 /* Get out of here if it's not possible to represent this struct. |
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248 If any of the values in the normalized struct tm are negative, |
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249 our algorithms won't work. Luckily, we only need to check the |
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250 year at this point; normalization guarantees that all values will |
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251 be in correct ranges EXCEPT the year. */ |
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252 |
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253 if (me->tm_year < 0) |
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254 return BAD_STRUCT_TM; |
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255 |
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256 /*************************************************/ |
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257 /* Find the appropriate time_t for the structure */ |
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258 /*************************************************/ |
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259 |
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260 /* Modified b-search -- make intelligent guesses as to where the |
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261 time might lie along the timeline, assuming that our target time |
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262 lies a linear distance (w/o considering time jumps of a |
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263 particular region). |
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264 |
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265 Assume that time does not fluctuate at all along the timeline -- |
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266 e.g., assume that a day will always take 86400 seconds, etc. -- |
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267 and come up with a hypothetical value for the time_t |
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268 representation of the struct tm TARGET, in relation to the guess |
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269 variable -- it should be pretty close! |
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270 |
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271 After testing this, the maximum number of iterations that I had |
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272 on any number that I tried was 3! Not bad. |
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273 |
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274 The reason this is not a subroutine is that we will modify some |
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275 fields in the struct tm (yday and mday). I've never felt good |
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276 about side-effects when writing structured code... */ |
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277 |
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278 { |
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279 struct tm *guess_tm; |
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280 time_t guess = 0; |
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281 time_t distance = 0; |
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282 time_t last_distance = 0; |
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283 |
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284 times_through_search = 0; |
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285 |
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286 do |
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287 { |
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288 guess += distance; |
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289 |
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290 times_through_search++; |
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291 |
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292 guess_tm = (*producer) (&guess); |
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293 |
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294 #ifdef DEBUG |
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295 if (debugging_enabled) |
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296 { |
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297 printf (" Guessing time_t == %d\n ", (int) guess); |
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298 printtm (guess_tm); |
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299 putchar ('\n'); |
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300 } |
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301 #endif |
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302 |
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303 /* How far is our guess from the desired struct tm? */ |
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304 distance = dist_tm (me, guess_tm); |
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305 |
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306 /* Handle periods of time where a period of time is skipped. |
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307 For example, 2:15 3 April 1994 does not exist, because DST |
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308 is in effect. The distance function will alternately |
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309 return values of 3600 and -3600, because it doesn't know |
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310 that the requested time doesn't exist. In these situations |
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311 (even if the skip is not exactly an hour) the distances |
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312 returned will be the same, but alternating in sign. We |
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313 want the later time, so check to see that the distance is |
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314 oscillating and we've chosen the correct of the two |
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315 possibilities. |
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316 |
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317 Useful: 3 Apr 94 765356300, 30 Oct 94 783496000 */ |
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318 |
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319 if ((distance == -last_distance) && (distance < last_distance)) |
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320 { |
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321 /* If the caller specified that the DST flag was off, it's |
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322 not possible to represent this time. */ |
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323 if (me->tm_isdst == 0) |
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324 { |
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325 #ifdef DEBUG |
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326 printf (" Distance is oscillating -- dst flag nixes struct!\n"); |
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327 #endif |
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328 return BAD_STRUCT_TM; |
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329 } |
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330 |
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331 #ifdef DEBUG |
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332 printf (" Distance is oscillating -- chose the later time.\n"); |
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333 #endif |
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334 distance = 0; |
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335 } |
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336 |
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337 if ((distance == 0) && (me->tm_isdst != -1) |
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338 && (me->tm_isdst != guess_tm->tm_isdst)) |
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339 { |
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340 /* If we're in this code, we've got the right time but the |
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341 wrong daylight savings flag. We need to move away from |
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342 the time that we have and approach the other time from |
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343 the other direction. That is, if I've requested the |
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344 non-DST version of a time and I get the DST version |
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345 instead, I want to put us forward in time and search |
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346 backwards to get the other time. I checked all of the |
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347 configuration files for the tz package -- no entry |
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348 saves more than two hours, so I think we'll be safe by |
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349 moving 24 hours in one direction. IF THE AMOUNT OF |
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350 TIME SAVED IN THE CONFIGURATION FILES CHANGES, THIS |
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351 VALUE MAY NEED TO BE ADJUSTED. Luckily, we can never |
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352 have more than one level of overlaps, or this would |
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353 never work. */ |
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354 |
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355 #define SKIP_VALUE 86400 |
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356 |
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357 if (guess_tm->tm_isdst == 0) |
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358 /* we got the later one, but want the earlier one */ |
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359 distance = -SKIP_VALUE; |
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360 else |
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361 distance = SKIP_VALUE; |
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362 |
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363 #ifdef DEBUG |
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364 printf (" Got the right time, wrong DST value -- adjusting\n"); |
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365 #endif |
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366 } |
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367 |
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368 last_distance = distance; |
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369 |
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370 } while (distance != 0); |
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371 |
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372 /* Check to see that the dst flag matches */ |
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373 |
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374 if (me->tm_isdst != -1) |
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375 { |
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376 if (me->tm_isdst != guess_tm->tm_isdst) |
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377 { |
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378 #ifdef DEBUG |
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379 printf (" DST flag doesn't match! FIXME?\n"); |
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380 #endif |
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381 return BAD_STRUCT_TM; |
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382 } |
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383 } |
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384 |
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385 result = guess; /* Success! */ |
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386 |
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387 /* On successful completion, the values of tm_wday and tm_yday |
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388 have to be set appropriately. */ |
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389 |
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390 /* me->tm_yday = guess_tm->tm_yday; |
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391 me->tm_mday = guess_tm->tm_mday; */ |
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392 |
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393 *me = *guess_tm; |
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394 } |
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395 |
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396 /* Update the caller's version of the structure */ |
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397 |
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187
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398 *timeptr = *me; |
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399 |
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400 return result; |
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401 } |
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187
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402 |
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403 time_t |
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295
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404 #ifdef DEBUG /* make it work even if the system's |
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405 libc has it's own mktime routine */ |
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406 my_mktime (timeptr) |
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407 #else |
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187
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408 mktime (timeptr) |
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295
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409 #endif |
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187
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410 struct tm *timeptr; |
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411 { |
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412 return _mktime_internal (timeptr, localtime); |
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413 } |
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414 |
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415 #ifdef DEBUG |
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416 void |
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417 main (argc, argv) |
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418 int argc; |
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419 char *argv[]; |
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420 { |
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421 int time; |
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422 int result_time; |
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423 struct tm *tmptr; |
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424 |
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425 if (argc == 1) |
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426 { |
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427 long q; |
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428 |
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429 printf ("starting long test...\n"); |
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430 |
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295
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431 for (q = 10000000; q < 1000000000; q += 599) |
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187
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432 { |
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295
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433 struct tm *tm = localtime ((time_t *) &q); |
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187
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434 if ((q % 10000) == 0) { printf ("%ld\n", q); fflush (stdout); } |
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295
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435 if (q != my_mktime (tm)) |
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187
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436 { printf ("failed for %ld\n", q); fflush (stdout); } |
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437 } |
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438 |
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439 printf ("test finished\n"); |
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440 |
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441 exit (0); |
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442 } |
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443 |
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444 if (argc != 2) |
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445 { |
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446 printf ("wrong # of args\n"); |
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447 exit (0); |
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448 } |
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449 |
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450 debugging_enabled = 1; /* We want to see the info */ |
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451 |
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452 ++argv; |
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453 time = atoi (*argv); |
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454 |
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295
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455 tmptr = localtime ((time_t *) &time); |
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456 printf ("Localtime tells us that a time_t of %d represents\n ", time); |
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457 printtm (tmptr); |
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458 putchar ('\n'); |
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187
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459 |
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295
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460 printf (" Given localtime's return val, mktime returns %d which is\n ", |
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461 (int) my_mktime (tmptr)); |
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187
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462 printtm (tmptr); |
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295
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463 putchar ('\n'); |
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187
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464 |
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295
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465 #if 0 |
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187
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466 tmptr->tm_sec -= 20; |
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467 tmptr->tm_min -= 20; |
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468 tmptr->tm_hour -= 20; |
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469 tmptr->tm_mday -= 20; |
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470 tmptr->tm_mon -= 20; |
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471 tmptr->tm_year -= 20; |
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472 tmptr->tm_gmtoff -= 20000; /* This has no effect! */ |
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473 tmptr->tm_zone = NULL; /* Nor does this! */ |
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474 tmptr->tm_isdst = -1; |
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295
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475 #endif |
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476 |
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477 tmptr->tm_hour += 1; |
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478 tmptr->tm_isdst = -1; |
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187
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479 |
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295
|
480 printf ("\n\nchanged ranges: "); |
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187
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481 printtm (tmptr); |
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295
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482 putchar ('\n'); |
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483 |
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484 result_time = my_mktime (tmptr); |
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485 printf ("\nmktime: %d\n", result_time); |
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187
|
486 |
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295
|
487 tmptr->tm_isdst = 0; |
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|
488 |
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489 printf ("\n\nchanged ranges: "); |
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490 printtm (tmptr); |
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|
491 putchar ('\n'); |
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492 |
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493 result_time = my_mktime (tmptr); |
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187
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494 printf ("\nmktime: %d\n", result_time); |
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495 } |
|
|
496 #endif /* DEBUG */ |
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295
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497 |
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498 |
|
|
499 /* |
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500 Local Variables: |
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501 compile-command: "gcc -g mktime.c -o mktime -DDEBUG" |
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502 End: |
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|
503 */ |
