--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libsci/log.c	Thu Aug 04 16:47:10 2022 +0200
@@ -0,0 +1,88 @@
+/*
+ * log.c -- logging routines
+ *
+ * Copyright (c) 2020-2022 David Demelier <markand@malikania.fr>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <assert.h>
+#include <stdio.h>
+#include <syslog.h>
+#include <time.h>
+
+#include "log.h"
+
+/* TODO: replace. */
+static struct {
+	enum log_level verbosity;
+} config = {
+	.verbosity = LOG_LEVEL_DEBUG
+};
+
+static int syslog_levels[] = {
+	[LOG_LEVEL_DEBUG]       = LOG_DEBUG,
+	[LOG_LEVEL_INFO]        = LOG_INFO,
+	[LOG_LEVEL_WARNING]     = LOG_WARNING
+};
+
+static const char * const levelsyms[] = {
+	[LOG_LEVEL_DEBUG]       = "D",
+	[LOG_LEVEL_INFO]        = "I",
+	[LOG_LEVEL_WARNING]     = "W"
+};
+
+void
+log_open(const char *name)
+{
+	openlog(name, 0, LOG_USER);
+}
+
+void
+log_write(enum log_level level, const char *fmt, ...)
+{
+	assert(level >= LOG_LEVEL_WARNING && level <= LOG_LEVEL_DEBUG);
+	assert(fmt);
+
+	if (config.verbosity >= level) {
+		va_list ap;
+
+		va_start(ap, fmt);
+		log_vwrite(level, fmt, ap);
+		va_end(ap);
+	}
+}
+
+void
+log_vwrite(enum log_level level, const char *fmt, va_list ap)
+{
+	assert(level >= LOG_LEVEL_WARNING && level <= LOG_LEVEL_DEBUG);
+	assert(fmt);
+
+	char line[BUFSIZ] = {0}, timebuf[32] = {0};
+	time_t timestamp = time(NULL);
+	struct tm *tm = localtime(&timestamp);
+
+	vsnprintf(line, sizeof (line), fmt, ap);
+	syslog(syslog_levels[level], "%s", line);
+
+	strftime(timebuf, sizeof (timebuf), "%F %T", tm);
+	printf("%s %s %s\n", timebuf, levelsyms[level], line);
+}
+
+void
+log_finish(void)
+{
+	if (config.verbosity > 0)
+		closelog();
+}