Better way to avoid glibc dependency.

Returns us to something amost identical to the original code.
Sigh.  Timezones are a swamp.

All regression tests pass.

1 files changed, 30 insertions, 0 deletions

diff --git a/gpsutils.c b/gpsutils.c
index 6b72776f..b02975fe 100644
--- a/gpsutils.c
+++ b/gpsutils.c
@@ -308,6 +308,36 @@ timestamp_t timestamp(void)
 #endif
 }
 
+time_t mkgmtime(register struct tm * t)
+/* struct tm to seconds since Unix epoch */
+{
+    register int year;
+    register time_t result;
+    static const int cumdays[MONTHSPERYEAR] =
+	{ 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334 };
+
+    /*@ +matchanyintegral @*/
+    year = 1900 + t->tm_year + t->tm_mon / MONTHSPERYEAR;
+    result = (year - 1970) * 365 + cumdays[t->tm_mon % MONTHSPERYEAR];
+    result += (year - 1968) / 4;
+    result -= (year - 1900) / 100;
+    result += (year - 1600) / 400;
+    if ((year % 4) == 0 && ((year % 100) != 0 || (year % 400) == 0) &&
+	(t->tm_mon % MONTHSPERYEAR) < 2)
+	result--;
+    result += t->tm_mday - 1;
+    result *= 24;
+    result += t->tm_hour;
+    result *= 60;
+    result += t->tm_min;
+    result *= 60;
+    result += t->tm_sec;
+    if (t->tm_isdst == 1)
+	result -= 3600;
+    /*@ -matchanyintegral @*/
+    return (result);
+}
+
 timestamp_t iso8601_to_unix( /*@in@*/ char *isotime)
 /* ISO8601 UTC to Unix UTC */
 {