| /* |

| ** This file is in the public domain, so clarified as of |

| ** 1996-06-05 by Arthur David Olson. |

| */ |

| |

| /*LINTLIBRARY*/ |

| |

| #include "private.h" /* for time_t and TYPE_SIGNED */ |

| |

| double ATTRIBUTE_CONST |

| difftime(const time_t time1, const time_t time0) |

| { |

| /* |

| ** If (sizeof (double) > sizeof (time_t)) simply convert and subtract |

| ** (assuming that the larger type has more precision). |

| */ |

| if (sizeof (double) > sizeof (time_t)) |

| return (double) time1 - (double) time0; |

| if (!TYPE_SIGNED(time_t)) { |

| /* |

| ** The difference of two unsigned values can't overflow |

| ** if the minuend is greater than or equal to the subtrahend. |

| */ |

| if (time1 >= time0) |

| return time1 - time0; |

| else return -(double) (time0 - time1); |

| } |

| /* |

| ** Handle cases where both time1 and time0 have the same sign |

| ** (meaning that their difference cannot overflow). |

| */ |

| if ((time1 < 0) == (time0 < 0)) |

| return time1 - time0; |

| /* |

| ** time1 and time0 have opposite signs. |

| ** Punt if uintmax_t is too narrow. |

| ** This suffers from double rounding; attempt to lessen that |

| ** by using long double temporaries. |

| */ |

| if (sizeof (uintmax_t) < sizeof (time_t)) |

| return (long double) time1 - (long double) time0; |

| /* |

| ** Stay calm...decent optimizers will eliminate the complexity below. |

| */ |

| if (time1 >= 0 /* && time0 < 0 */) |

| return (uintmax_t) time1 + (uintmax_t) (-1 - time0) + 1; |

| return -(double) ((uintmax_t) time0 + (uintmax_t) (-1 - time1) + 1); |

| } |