common/log: improve time prefix

Same as [1].

[1]: https://github.com/swaywm/wlroots/pull/2052

1 files changed, 30 insertions, 8 deletions

diff --git a/common/log.c b/common/log.c
index 17648e44..59cb9b71 100644
--- a/common/log.c
+++ b/common/log.c
@@ -36,6 +36,7 @@ bool _sway_assert(bool condition, const char *format, ...) {
 
 static bool colored = true;
 static sway_log_importance_t log_importance = SWAY_ERROR;
+static struct timespec start_time = {-1, -1};
 
 static const char *verbosity_colors[] = {
         [SWAY_SILENT] = "",
@@ -44,20 +45,39 @@ static const char *verbosity_colors[] = {
         [SWAY_DEBUG ] = "\x1B[1;30m",
 };
 
+static void timespec_sub(struct timespec *r, const struct timespec *a,
+                const struct timespec *b) {
+        const long NSEC_PER_SEC = 1000000000;
+        r->tv_sec = a->tv_sec - b->tv_sec;
+        r->tv_nsec = a->tv_nsec - b->tv_nsec;
+        if (r->tv_nsec < 0) {
+                r->tv_sec--;
+                r->tv_nsec += NSEC_PER_SEC;
+        }
+}
+
+static void init_start_time(void) {
+        if (start_time.tv_sec >= 0) {
+                return;
+        }
+        clock_gettime(CLOCK_MONOTONIC, &start_time);
+}
+
 static void sway_log_stderr(sway_log_importance_t verbosity, const char *fmt,
                 va_list args) {
+        init_start_time();
+
         if (verbosity > log_importance) {
                 return;
         }
-        // prefix the time to the log message
-        struct tm result;
-        time_t t = time(NULL);
-        struct tm *tm_info = localtime_r(&t, &result);
-        char buffer[26];
 
-        // generate time prefix
-        strftime(buffer, sizeof(buffer), "%F %T - ", tm_info);
-        fprintf(stderr, "%s", buffer);
+        struct timespec ts = {0};
+        clock_gettime(CLOCK_MONOTONIC, &ts);
+        timespec_sub(&ts, &ts, &start_time);
+
+        fprintf(stderr, "%02d:%02d:%02d.%03ld ", (int)(ts.tv_sec / 60 / 60),
+                (int)(ts.tv_sec / 60 % 60), (int)(ts.tv_sec % 60),
+                ts.tv_nsec / 1000000);
 
         unsigned c = (verbosity < SWAY_LOG_IMPORTANCE_LAST) ? verbosity :
                 SWAY_LOG_IMPORTANCE_LAST - 1;
@@ -75,6 +95,8 @@ static void sway_log_stderr(sway_log_importance_t verbosity, const char *fmt,
 }
 
 void sway_log_init(sway_log_importance_t verbosity, terminate_callback_t callback) {
+        init_start_time();
+
         if (verbosity < SWAY_LOG_IMPORTANCE_LAST) {
                 log_importance = verbosity;
         }