/* Use CONVERT to convert *T to a broken down time in *TP.
If *T is out of range for conversion, adjust it so that
it is the nearest in-range value and then convert that. */
static struct tm *
ranged_convert (struct tm *(*convert) (const time_t *, struct tm *),
time_t *t, struct tm *tp)
{
struct tm *r = convert (t, tp);
if (!r && *t)
{
time_t bad = *t;
time_t ok = 0;
/* BAD is a known unconvertible time_t, and OK is a known good one.
Use binary search to narrow the range between BAD and OK until
they differ by 1. */
while (bad != (ok + ((bad < 0) ? -1 : 1)))
{
time_t mid = *t = time_t_avg(ok, bad);
r = convert(t, tp);
if (r)
ok = mid;
else
bad = mid;
}
if (!r && ok)
{
/* The last conversion attempt failed;
revert to the most recent successful attempt. */
*t = ok;
r = convert(t, tp);
}
}
return r;
}
/* Return 1 if A + B does not overflow. If time_t is unsigned and if
B's top bit is set, assume that the sum represents A - -B, and
return 1 if the subtraction does not wrap around. */
static int
time_t_add_ok(time_t a, time_t b)
{
if (! TYPE_SIGNED(time_t))
{
time_t sum = (a + b);
return ((sum < a) == (TIME_T_MIDPOINT <= b));
}
else if (WRAPV)
{
time_t sum = (a + b);
return ((sum < a) == (b < 0));
}
else
{
time_t avg = time_t_avg(a, b);
return (((TIME_T_MIN / 2) <= avg) && (avg <= (TIME_T_MAX / 2)));
}
}
/* Return 1 if A + B does not overflow. If time_t is unsigned and if
B's top bit is set, assume that the sum represents A - -B, and
return 1 if the subtraction does not wrap around. */
static int
time_t_add_ok (time_t a, time_t b)
{
if (! TYPE_SIGNED (time_t))
{
time_t sum = a + b;
return (sum < a) == (TIME_T_MIDPOINT <= b);
}
else if (WRAPV)
{
time_t sum = a + b;
return (sum < a) == (b < 0);
}
else
{
time_t avg = time_t_avg (a, b);
return TIME_T_MIN / 2 <= avg && avg <= TIME_T_MAX / 2;
}
}
