xapian-applications/omega/datetime.cc

   1 /** @file
   2  * @brief Parse and format date/time strings
   3  */
   4 /* Copyright (c) 2013,2014,2015,2016,2019 Olly Betts
   5  *
   6  * Permission is hereby granted, free of charge, to any person obtaining a copy
   7  * of this software and associated documentation files (the "Software"), to
   8  * deal in the Software without restriction, including without limitation the
   9  * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
  10  * sell copies of the Software, and to permit persons to whom the Software is
  11  * furnished to do so, subject to the following conditions:
  12  *
  13  * The above copyright notice and this permission notice shall be included in
  14  * all copies or substantial portions of the Software.
  15  *
  16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  17  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  19  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  20  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  21  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  22  * IN THE SOFTWARE.
  23  */
  24
  25 #include <config.h>
  26
  27 #include "datetime.h"
  28
  29 #include "timegm.h"
  30
  31 #include <algorithm>
  32 #include <cstdlib>
  33
  34 using namespace std;
  35
  36 time_t
  37 parse_datetime(const string & s)
  38 {
  39     struct tm t;
  40     const char * p = s.c_str();
  41     char * q;
  42     if (s.find('T') != string::npos || s.find('-') != string::npos) {
  43         // E.g. "2013-01-17T09:10:55Z"
  44         t.tm_year = strtoul(p, &q, 10) - 1900;
  45         p = q;
  46         if (*p == '-') {
  47             t.tm_mon = strtoul(p + 1, &q, 10) - 1;
  48             p = q;
  49         } else {
  50             t.tm_mon = 0;
  51         }
  52         if (*p == '-') {
  53             t.tm_mday = strtoul(p + 1, &q, 10);
  54             p = q;
  55         } else {
  56             t.tm_mday = 1;
  57         }
  58         if (*p == 'T') {
  59             t.tm_hour = strtoul(p + 1, &q, 10);
  60             p = q;
  61             if (*p == ':') {
  62                 t.tm_min = strtoul(p + 1, &q, 10);
  63                 p = q;
  64             } else {
  65                 t.tm_min = 0;
  66             }
  67             if (*p == ':') {
  68                 t.tm_sec = strtoul(p + 1, &q, 10);
  69                 p = q;
  70             } else {
  71                 t.tm_sec = 0;
  72             }
  73         } else {
  74             t.tm_hour = t.tm_min = t.tm_sec = 0;
  75         }
  76         if (*p == 'Z') {
  77             // FIXME: always assume UTC for now...
  78         }
  79     } else {
  80         // As produced by LibreOffice HTML export.
  81         // E.g.
  82         // "20130117;09105500" == 2013-01-17T09:10:55
  83         // "20070903;200000000000" == 2007-09-03T00:02:00
  84         // "20070831;5100000000000" == 2007-08-31T00:51:00
  85         unsigned long v = strtoul(p, &q, 10);
  86         if (v == 0) {
  87             // LibreOffice sometimes exports "0;0".  A date of "0" is
  88             // clearly invalid.
  89             return time_t(-1);
  90         }
  91         p = q;
  92         t.tm_mday = v % 100;
  93         v /= 100;
  94         t.tm_mon = v % 100 - 1;
  95         t.tm_year = v / 100 - 1900;
  96         if (*p == ';') {
  97             ++p;
  98             v = strtoul(p, &q, 10);
  99             v /= (q - p > 10) ? 1000000000 : 100;
 100             t.tm_sec = v % 100;
 101             v /= 100;
 102             t.tm_min = v % 100;
 103             t.tm_hour = v / 100;
 104         } else {
 105             t.tm_hour = t.tm_min = t.tm_sec = 0;
 106         }
 107     }
 108     t.tm_isdst = -1;
 109
 110     return timegm(&t);
 111 }
 112
 113 // Write exactly w chars to buffer p representing integer v.
 114 //
 115 // The result is left padded with zeros if v < pow(10, w - 1).
 116 //
 117 // If v >= pow(10, w), then the output will show v % pow(10, w) (i.e. the
 118 // most significant digits are lost).
 119 static void
 120 format_int_fixed_width(char* p, int v, int w)
 121 {
 122     while (--w >= 0) {
 123         p[w] = '0' + (v % 10);
 124         v /= 10;
 125     }
 126 }
 127
 128 string
 129 date_to_string(int year, int month, int day)
 130 {
 131     year = std::clamp(year, 0, 9999);
 132     month = std::clamp(month, 1, 12);
 133     day = std::clamp(day, 1, 31);
 134     char buf[8];
 135     format_int_fixed_width(buf, year, 4);
 136     format_int_fixed_width(buf + 4, month, 2);
 137     format_int_fixed_width(buf + 6, day, 2);
 138     return string(buf, 8);
 139 }