move time string function to timer.c

1 files changed, 49 insertions, 2 deletions

diff --git a/src/timer.c b/src/timer.c
index 3a763a0..254f3da 100644
--- a/src/timer.c
+++ b/src/timer.c
@@ -2,11 +2,12 @@
  * @file timer.c
  * @author Gertjan van den Burg
  * @date January, 2014
- * @brief Function for calculating time difference
+ * @brief Utility functions relating to time
  *
  * @details
  * This file contains a simple function for calculating the time in seconds
- * elapsed between two clock() calls.
+ * elapsed between two clock() calls. It also contains a function for
+ * generating a string of the current time, used in writing output files.
  */
 
 #include <time.h>
@@ -24,3 +25,49 @@ double elapsed_time(clock_t s_time, clock_t e_time)
 {
 	return ((double) (e_time - s_time))/((double) CLOCKS_PER_SEC);
 }
+
+/**
+ * @brief Get time string with UTC offset
+ *
+ * @details
+ * Create a string for the current system time. Include an offset of UTC for
+ * consistency. The format of the generated string is "DDD MMM D HH:MM:SS 
+ * YYYY (UTC +HH:MM)", e.g. "Fri Aug 9, 12:34:56 2013 (UTC +02:00)".
+ *
+ * @param[in,out] 	buffer 	allocated string buffer, on exit contains
+ * 				formatted string
+ *
+ */
+void get_time_string(char *buffer)
+{
+	int diff, hours, minutes;
+	char timestr[MAX_LINE_LENGTH];
+	time_t current_time, lt, gt;
+	struct tm *lclt;
+
+	// get current time (in epoch)
+	current_time = time(NULL);
+	if (current_time == ((time_t)-1)) {
+		fprintf(stderr, "Failed to compute the current time.\n");
+		return;
+	}
+
+	// convert time to local time and create a string
+	lclt = localtime(&current_time);
+	strftime(timestr, MAX_LINE_LENGTH, "%c", lclt);
+	if (timestr == NULL) {
+		fprintf(stderr, "Failed to convert time to string.\n");
+		return;
+	}
+
+	// calculate the UTC offset including DST
+	lt = mktime(localtime(&current_time));
+	gt = mktime(gmtime(&current_time));
+	diff = -difftime(gt, lt);
+	hours = (diff/3600);
+	minutes = (diff%3600)/60;
+	if (lclt->tm_isdst == 1)
+		hours++;
+
+	sprintf(buffer, "%s (UTC %+03i:%02i)", timestr, hours, minutes);
+}