1 files changed, 80 insertions, 0 deletions
diff --git a/common/log.c b/common/log.c
new file mode 100644
index 0000000..1474dcc
--- /dev/null
+++ b/common/log.c
@@ -0,0 +1,80 @@
+#include <errno.h>
+#include <stdarg.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+#include <unistd.h>
+
+#include "log.h"
+
+const long NSEC_PER_SEC = 1000000000;
+
+static enum libseat_log_level current_log_level;
+static struct timespec start_time = {-1, -1};
+static bool colored = false;
+
+static const char *verbosity_colors[] = {
+	[LIBSEAT_SILENT] = "",
+	[LIBSEAT_ERROR] = "\x1B[1;31m",
+	[LIBSEAT_INFO] = "\x1B[1;34m",
+	[LIBSEAT_DEBUG] = "\x1B[1;90m",
+};
+
+static const char *verbosity_headers[] = {
+	[LIBSEAT_SILENT] = "",
+	[LIBSEAT_ERROR] = "[ERROR]",
+	[LIBSEAT_INFO] = "[INFO]",
+	[LIBSEAT_DEBUG] = "[DEBUG]",
+};
+
+static void timespec_sub(struct timespec *r, const struct timespec *a, const struct timespec *b) {
+	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;
+	}
+}
+
+void libseat_log_init(enum libseat_log_level level) {
+	if (start_time.tv_sec >= 0) {
+		return;
+	}
+	clock_gettime(CLOCK_MONOTONIC, &start_time);
+	current_log_level = level;
+	colored = isatty(STDERR_FILENO);
+}
+
+void _libseat_logf(enum libseat_log_level level, const char *fmt, ...) {
+	int stored_errno = errno;
+	va_list args;
+	if (level < current_log_level) {
+		return;
+	}
+
+	struct timespec ts = {0};
+	clock_gettime(CLOCK_MONOTONIC, &ts);
+	timespec_sub(&ts, &ts, &start_time);
+	unsigned c = (level < LIBSEAT_LOG_LEVEL_LAST) ? level : LIBSEAT_LOG_LEVEL_LAST - 1;
+
+	const char *prefix, *postfix;
+
+	if (colored) {
+		prefix = verbosity_colors[c];
+		postfix = "\x1B[0m\n";
+	} else {
+		prefix = verbosity_headers[c];
+		postfix = "\n";
+	}
+
+	fprintf(stderr, "%02d:%02d:%02d.%03ld %s ", (int)(ts.tv_sec / 60 / 60),
+		(int)(ts.tv_sec / 60 % 60), (int)(ts.tv_sec % 60), ts.tv_nsec / 1000000, prefix);
+
+	va_start(args, fmt);
+	vfprintf(stderr, fmt, args);
+	va_end(args);
+
+	fprintf(stderr, "%s", postfix);
+	errno = stored_errno;
+}