Add functions for converting to/from a struct timespec, and for setting

the system clock

src/libiso8601/000_TopHeader.h

@@ -11,6 +11,7 @@
 /* standard includes, or includes needed for type declarations */
 #include <time.h>
 #include <stdint.h>
+#include <sys/time.h>
 
 /* options for text editors
 kate: replace-trailing-space-save true; space-indent true; tab-width 4;

src/libiso8601/400_c_library.c

@@ -44,6 +44,33 @@ void iso8601_now(struct iso8601_date* date, struct iso8601_details* details)
 
 
 
+int iso8601_set_sysclock(const struct iso8601_date* date)
+{
+    static int use_settimeofday = 0;
+    struct timeval tv;
+    struct timespec ts;
+
+    /* not all systems have clock_settime implemented */
+    if(use_settimeofday) goto try_settimeofday;
+
+    /* try setting clock */
+    iso8601_to_ts(&ts, date);
+    if(clock_settime(CLOCK_REALTIME, &ts)) {
+        if(errno == EPERM) return -1;
+        use_settimeofday = 1;
+        goto try_settimeofday;
+    }
+    
+    return 0;
+
+    /* fallback using settimeofday() */
+  try_settimeofday:
+    iso8601_to_tv(&tv, date);
+    return settimeofday(&tv, 0);
+}
+
+
+
 void iso8601_from_ts(struct iso8601_date* date, const struct timespec* ts)
 {
     ldiv_t qr;
@@ -64,6 +91,26 @@ void iso8601_to_ts(struct timespec* ts, const struct iso8601_date* date)
 
 
 
+void iso8601_from_tv(struct iso8601_date* date, const struct timeval* tv)
+{
+    ldiv_t qr;
+
+    qr = ldiv(tv->tv_sec, 86400);
+    date->day = EPOCH_GDAY + qr.quot;
+    date->sec = qr.rem;
+    date->nsec = tv->tv_usec * 1000;
+}
+
+
+
+void iso8601_to_tv(struct timeval* tv, const struct iso8601_date* date)
+{
+    tv->tv_sec = 86400L * (date->day - EPOCH_GDAY) + date->sec;
+    tv->tv_usec = date->nsec / 1000;
+}
+
+
+
 void iso8601_from_time_t(struct iso8601_date* date, const time_t* t)
 {
     ldiv_t qr;

src/libiso8601/400_c_library.h

@@ -29,10 +29,29 @@ void iso8601_now(struct iso8601_date* date, struct iso8601_details* details);
 
 
 
+/*! \brief Set the system clock.
+
+\param date Date to set.
+\retval 0 on success.
+\retval -1 on error (and see \a errno).
+
+Attempts to set the system clock using \c clock_settime(), falling back to \c settimeofday(). The
+user will need the \c CAP_SYS_TIME capability to set the clock, otherwise \a errno will be set to
+\c EPERM.
+
+*/
+int iso8601_set_sysclock(const struct iso8601_date* date);
+
+
+
 /*! \brief Convert from a struct timespec. */
 void iso8601_from_ts(struct iso8601_date* date, const struct timespec* ts);
 /*! \brief Convert to a struct timespec. */
 void iso8601_to_ts(struct timespec* ts, const struct iso8601_date* date);
+/*! \brief Convert from a struct timeval. */
+void iso8601_from_tv(struct iso8601_date* date, const struct timeval* tv);
+/*! \brief Convert to a struct timeval. */
+void iso8601_to_tv(struct timeval* tv, const struct iso8601_date* date);
 /*! \brief Convert from a time_t. */
 void iso8601_from_time_t(struct iso8601_date* date, const time_t* t);
 /*! \brief Convert to a time_t. */