diplodocus.org Git - nmh/blob - docs/historical/mh-nov-1983/cmds/emitl.c

   1 /*
   2  * Routine to convert a localtime(3) format date back into
   3  * a system format date.
   4  *
   5  * Hats off to Bob Kridle for the insight that the way to do
   6  * this is by binary search of the system date space.
   7  */
   8
   9 #include <sys/time.h>
  10
  11 struct tm *localtime();
  12
  13 long
  14 emitl(dp)
  15         struct tm *dp;
  16 {
  17         long conv;
  18         register int i, bit;
  19         struct tm dcopy;
  20
  21         dcopy = *dp;
  22         dp = &dcopy;
  23         conv = 0;
  24         for (i = 31; i >= 0; i--) {
  25                 bit = 1 << i;
  26                 conv |= bit;
  27                 if (dcmp(localtime(&conv), dp) > 0)
  28                         conv &= ~bit;
  29         }
  30         return(conv);
  31 }
  32
  33 /*
  34  * Compare two localtime dates, return result.
  35  */
  36
  37 #define DECIDE(a) \
  38         if (dp->a > dp2->a) \
  39                 return(1); \
  40         if (dp->a < dp2->a) \
  41                 return(-1)
  42
  43 static
  44 dcmp(dp, dp2)
  45         register struct tm *dp, *dp2;
  46 {
  47
  48         DECIDE(tm_year);
  49         DECIDE(tm_mon);
  50         DECIDE(tm_mday);
  51         DECIDE(tm_hour);
  52         DECIDE(tm_min);
  53         DECIDE(tm_sec);
  54         return(0);
  55 }