Speed up UTC mktime by using library timegm if available instead of our slow implementation.

2 files changed, 33 insertions, 0 deletions

diff --git a/missing_d/ChangeLog b/missing_d/ChangeLog
index bc54838f..2d69087a 100644
--- a/missing_d/ChangeLog
+++ b/missing_d/ChangeLog
@@ -1,3 +1,7 @@
+2018-12-12         Andrew J. Schorr     <aschorr@telemetry-investments.com>
+
+	* timegm.c: New file implementing timegm.
+
 2018-10-03         Arnold D. Robbins     <arnold@skeeve.com>
 
 	* intprops.h, verify.h: Removed. The copy in ../support is
diff --git a/missing_d/timegm.c b/missing_d/timegm.c
new file mode 100644
index 00000000..f7b780de
--- /dev/null
+++ b/missing_d/timegm.c
@@ -0,0 +1,29 @@
+#include <time.h>
+#include <stdlib.h>
+
+static time_t
+timegm(struct tm *tm)
+{
+	time_t ret;
+	char *tz = getenv("TZ");
+	const char *tzreq = "UTC+0";	/* more portable than ""? */
+
+	if (tz)
+		tz = estrdup(tz, strlen(tz));
+	if (setenv("TZ", tzreq, 1) < 0) {
+		warning(_("setenv(TZ, %s) failed (%s)"), tzreq, strerror(errno));
+		return -1;
+	}
+	tzset();
+	ret = mktime(tm);
+	if (tz) {
+		if (setenv("TZ", tz, 1) < 0)
+			fatal(_("setenv(TZ, %s) restoration failed (%s)"), tz, strerror(errno));
+		free(tz);
+	} else {
+		if (unsetenv("TZ") < 0)
+			fatal(_("unsetenv(TZ) failed (%s)"), strerror(errno));
+	}
+	tzset();
+	return ret;
+}