debug: add a logging module

src/log.c

@@ -0,0 +1,38 @@
+#include <errno.h>
+#include <stdarg.h>
+#include <string.h>
+
+#include "log.h"
+
+static FILE* logger_out = NULL;
+
+void log_init(FILE* fd) {
+  if (logger_out) (void)fclose(logger_out);
+  logger_out = fd;
+}
+
+void log_puts(const char* msg) {
+  if (!logger_out) return;
+  (void)fputs(msg, logger_out);
+}
+
+void log_printf(const char* fmt, ...) {
+  if (!logger_out) return;
+
+  va_list args;
+  va_start(args, fmt);
+
+  (void)vfprintf(logger_out, fmt, args);
+
+  va_end(args);
+}
+
+// NOLINTNEXTLINE(readability-identifier-length)
+void log_perror(const char* s) {
+  if (!logger_out) return;
+
+  if (s)
+    (void)fprintf(logger_out, "%s: %s", s, strerror(errno));
+  else
+    (void)fprintf(logger_out, "%s", strerror(errno));
+}