4 files changed, 81 insertions, 1 deletions
diff --git a/lib/build.sh b/lib/build.sh
index 8cf9d11..725c237 100755
--- a/lib/build.sh
+++ b/lib/build.sh
@@ -8,7 +8,7 @@ fail() {
 CC=cc
 CFLAGS="-std=c99 -Wall -Wextra -Wpedantic -D_POSIX_C_SOURCE=200809L"
 LDFLAGS="-fPIC"
-SOURCES="test.c vec2.c world.c"
+SOURCES="test.c vec2.c world.c log.c"
 output="build"
 
 for arg ; do
diff --git a/lib/log.c b/lib/log.c
new file mode 100644
index 0000000..51ab107
--- /dev/null
+++ b/lib/log.c
@@ -0,0 +1,56 @@
+#include <stdarg.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <time.h>
+
+#include "log.h"
+
+/* Message buffer */
+#define MBUF_SIZE 512
+
+static void (*log_output)(int level, const char *source, int line, const char *msg) = NULL;
+static int min_level = LOGL_INFO;
+
+void
+dp_log_set_output(void (*output)(int, const char *, int, const char *))
+{
+	log_output = output;
+}
+
+void
+dp_log_set_level(int level)
+{
+	min_level = level;
+}
+
+void
+dp_log_write(int level, const char *source, int line, const char *fmt, ...)
+{
+	char mbuf[MBUF_SIZE];
+	char *msg;
+	va_list va;
+	int len;
+
+	if (level < min_level)
+		return;
+	if (!log_output)
+		return;
+
+	msg = mbuf;
+	va_start(va, fmt);
+	len = vsnprintf(msg, MBUF_SIZE, fmt, va);
+	va_end(va);
+
+	if (len >= MBUF_SIZE)
+	{
+		msg = (char *)malloc(len + 1);
+		va_start(va, fmt);
+		len = vsnprintf(msg, len + 1, fmt, va);
+		va_end(va);
+	}
+
+	log_output(level, source, line, msg);
+
+	if (msg != mbuf)
+		free(msg);
+}
diff --git a/lib/log.h b/lib/log.h
new file mode 100644
index 0000000..e1cdcb8
--- /dev/null
+++ b/lib/log.h
@@ -0,0 +1,23 @@
+#include <stdio.h>
+
+enum { LOGL_TRACE, LOGL_DEBUG, LOGL_INFO, LOGL_WARN, LOGL_ERROR, LOGL_FATAL };
+
+/*
+ * log_info("Hello %s!", "World");
+ * log_warn("warning");
+ */
+#define log_trace(...) dp_log_write(LOGL_TRACE, __FILE__, __LINE__, __VA_ARGS__)
+#define log_debug(...) dp_log_write(LOGL_DEBUG, __FILE__, __LINE__, __VA_ARGS__)
+#define log_info(...) dp_log_write(LOGL_INFO, __FILE__, __LINE__, __VA_ARGS__)
+#define log_warn(...) dp_log_write(LOGL_WARN, __FILE__, __LINE__, __VA_ARGS__)
+#define log_error(...) dp_log_write(LOGL_ERROR, __FILE__, __LINE__, __VA_ARGS__)
+#define log_fatal(...) dp_log_write(LOGL_FATAL, __FILE__, __LINE__, __VA_ARGS__)
+
+void dp_log_set_output(void (*)(int level, const char *source, int line, const char *msg));
+
+/*
+ * Sets the minimum log level. Level is inclusive.
+ */
+void dp_log_set_level(int level);
+
+void dp_log_write(int level, const char *source, int line, const char *fmt, ...);
diff --git a/lib/world.c b/lib/world.c
index 954aa94..34d7489 100644
--- a/lib/world.c
+++ b/lib/world.c
@@ -3,6 +3,7 @@
 
 #include "types.h"
 #include "world.h"
+#include "log.h"
 
 struct world {
 	struct entity entities[WORLD_MAX_ENTITIES];