rfc822/rfc822_parsedt.c

   1 /*
   2 ** Copyright 1998 - 1999 Double Precision, Inc.
   3 ** See COPYING for distribution information.
   4 */
   5
   6 /*
   7 ** $Id: rfc822_parsedt.c,v 1.4 2002/05/21 16:02:19 mrsam Exp $
   8 */
   9 #include        <stdio.h>
  10 #include        <string.h>
  11 #include        <ctype.h>
  12 #include        <time.h>
  13
  14 /*
  15 ** time_t rfc822_parsedate(const char *p)
  16 **
  17 ** p - contents of the Date: header, attempt to parse it into a time_t.
  18 **
  19 ** returns - time_t, or 0 if the date cannot be parsed
  20 */
  21
  22 static unsigned parsedig(const char **p)
  23 {
  24 unsigned i=0;
  25
  26         while (isdigit((int)(unsigned char)**p))
  27         {
  28                 i=i*10 + **p - '0';
  29                 ++*p;
  30         }
  31         return (i);
  32 }
  33
  34 static const char * const weekdays[7]={
  35         "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
  36         } ;
  37
  38 static const char * const mnames[13]={
  39         "Jan", "Feb", "Mar", "Apr",
  40         "May", "Jun", "Jul", "Aug",
  41         "Sep", "Oct", "Nov", "Dec", NULL};
  42
  43 #define leap(y) ( \
  44                         ((y) % 400) == 0 || \
  45                         (((y) % 4) == 0 && (y) % 100) )
  46
  47 static unsigned mlength[]={31,28,31,30,31,30,31,31,30,31,30,31};
  48 #define mdays(m,y)      ( (m) != 2 ? mlength[(m)-1] : leap(y) ? 29:28)
  49
  50 static const char * const zonenames[] = {
  51         "UT","GMT",
  52         "EST","EDT",
  53         "CST","CDT",
  54         "MST","MDT",
  55         "PST","PDT",
  56         "Z",
  57         "A", "B", "C", "D", "E", "F", "G", "H", "I", "K", "L", "M",
  58         "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y",
  59         NULL};
  60
  61 #define ZH(n)   ( (n) * 60 * 60 )
  62
  63 static int zoneoffset[] = {
  64         0, 0,
  65         ZH(-5), ZH(-4),
  66         ZH(-6), ZH(-5),
  67         ZH(-7), ZH(-6),
  68         ZH(-8), ZH(-7),
  69         0,
  70
  71         ZH(-1), ZH(-2), ZH(-3), ZH(-4), ZH(-5), ZH(-6), ZH(-7), ZH(-8), ZH(-9), ZH(-10), ZH(-11), ZH(-12),
  72         ZH(1), ZH(2), ZH(3), ZH(4), ZH(5), ZH(6), ZH(7), ZH(8), ZH(9), ZH(10), ZH(11), ZH(12) };
  73
  74 static unsigned parsekey(const char **mon, const char * const *ary)
  75 {
  76 unsigned m, j;
  77
  78         for (m=0; ary[m]; m++)
  79         {
  80                 for (j=0; ary[m][j]; j++)
  81                         if (tolower(ary[m][j]) != tolower((*mon)[j]))
  82                                 break;
  83                 if (!ary[m][j])
  84                 {
  85                         *mon += j;
  86                         return (m+1);
  87                 }
  88         }
  89         return (0);
  90 }
  91
  92 static int parsetime(const char **t)
  93 {
  94 unsigned h,m,s=0;
  95
  96         if (!isdigit((int)(unsigned char)**t))  return (-1);
  97         h=parsedig(t);
  98         if (h > 23)             return (-1);
  99         if (**t != ':')         return (-1);
 100         ++*t;
 101         if (!isdigit((int)(unsigned char)**t))  return (-1);
 102         m=parsedig(t);
 103         if (**t == ':')
 104         {
 105                 ++*t;
 106                 if (!isdigit((int)(unsigned char)**t))  return (-1);
 107                 s=parsedig(t);
 108         }
 109         if (m > 59 || s > 59)   return (-1);
 110         return (h * 60 * 60 + m * 60 + s);
 111 }
 112
 113 time_t rfc822_parsedt(const char *rfcdt)
 114 {
 115 unsigned day=0, mon=0, year;
 116 int secs;
 117 int offset;
 118 time_t t;
 119 unsigned y;
 120
 121         /* Ignore day of the week.  Tolerate "Tue, 25 Feb 1997 ... "
 122         ** without the comma.  Tolerate "Feb 25 1997 ...".
 123         */
 124
 125         while (!day || !mon)
 126         {
 127                 if (!*rfcdt)    return (0);
 128                 if (isalpha((int)(unsigned char)*rfcdt))
 129                 {
 130                         if (mon)        return (0);
 131                         mon=parsekey(&rfcdt, mnames);
 132                         if (!mon)
 133                                 while (*rfcdt && isalpha((int)(unsigned char)*rfcdt))
 134                                         ++rfcdt;
 135                         continue;
 136                 }
 137
 138                 if (isdigit((int)(unsigned char)*rfcdt))
 139                 {
 140                         if (day)        return (0);
 141                         day=parsedig(&rfcdt);
 142                         if (!day)       return (0);
 143                         continue;
 144                 }
 145                 ++rfcdt;
 146         }
 147
 148         while (*rfcdt && isspace((int)(unsigned char)*rfcdt))
 149                 ++rfcdt;
 150         if (!isdigit((int)(unsigned char)*rfcdt))       return (0);
 151         year=parsedig(&rfcdt);
 152         if (year < 70)  year += 2000;
 153         if (year < 100) year += 1900;
 154
 155         while (*rfcdt && isspace((int)(unsigned char)*rfcdt))
 156                 ++rfcdt;
 157
 158         if (day == 0 || mon == 0 || mon > 12 || day > mdays(mon,year))
 159                 return (0);
 160
 161         secs=parsetime(&rfcdt);
 162         if (secs < 0)   return (0);
 163
 164         offset=0;
 165
 166         /* RFC822 sez no parenthesis, but I've seen (EST) */
 167
 168         while ( *rfcdt )
 169         {
 170                 if (isalnum((int)(unsigned char)*rfcdt) || *rfcdt == '+' || *rfcdt == '-')
 171                         break;
 172                 ++rfcdt;
 173         }
 174
 175         if (isalpha((int)(unsigned char)*rfcdt))
 176         {
 177         int     n=parsekey(&rfcdt, zonenames);
 178
 179                 if (n > 0)      offset= zoneoffset[n-1];
 180         }
 181         else
 182         {
 183         int     sign=1;
 184         unsigned n;
 185
 186                 switch (*rfcdt) {
 187                 case '-':
 188                         sign= -1;
 189                 case '+':
 190                         ++rfcdt;
 191                 }
 192
 193                 if (isdigit((int)(unsigned char)*rfcdt))
 194                 {
 195                         n=parsedig(&rfcdt);
 196                         if (n > 2359 || (n % 100) > 59) n=0;
 197                         offset = sign * ( (n % 100) * 60 + n / 100 * 60 * 60);
 198                 }
 199         }
 200
 201         if (year < 1970)        return (0);
 202         if (year > 9999)        return (0);
 203
 204         t=0;
 205         for (y=1970; y<year; y++)
 206         {
 207                 if ( leap(y) )
 208                 {
 209                         if (year-y >= 4)
 210                         {
 211                                 y += 3;
 212                                 t += ( 365*3+366 ) * 24 * 60 * 60;
 213                                 continue;
 214                         }
 215                         t += 24 * 60 * 60;
 216                 }
 217                 t += 365 * 24 * 60 * 60;
 218         }
 219
 220         for (y=1; y < mon; y++)
 221                 t += mdays(y, year) * 24 * 60 * 60;
 222
 223         return ( t + (day-1) * 24 * 60 * 60 + secs - offset );
 224 }
 225
 226 const char *rfc822_mkdt(time_t t)
 227 {
 228 static char buf[80];
 229 struct  tm *tmptr=gmtime(&t);
 230
 231         buf[0]=0;
 232         if (tmptr)
 233         {
 234                 sprintf(buf, "%s, %02d %s %04d %02d:%02d:%02d GMT",
 235                         weekdays[tmptr->tm_wday],
 236                         tmptr->tm_mday,
 237                         mnames[tmptr->tm_mon],
 238                         tmptr->tm_year + 1900,
 239                         tmptr->tm_hour,
 240                         tmptr->tm_min,
 241                         tmptr->tm_sec);
 242         }
 243         return (buf);
 244 }