1 files changed, 82 insertions, 0 deletions
diff --git a/arena.c b/arena.c
new file mode 100644
index 0000000..9e15c2a
--- /dev/null
+++ b/arena.c
@@ -0,0 +1,82 @@
+#include <assert.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "arena.h"
+
+union align {
+	long long int l;
+	long double d;
+	void *p;
+};
+
+/* alignment for a long-ish builtin type? */
+#define ALIGN (sizeof(union align))
+/* ensure it's a power of two */
+static_assert(ALIGN && !(ALIGN & (ALIGN - 1)), "ALIGN not power of two");
+
+static unsigned char *data;
+static size_t total;
+static size_t used;
+
+/*
+ * round up to nearest multiple of ALIGN
+ */
+static size_t
+round_up(size_t minimum)
+{
+	return (minimum + ALIGN - 1) & ~(ALIGN - 1);
+}
+
+int
+ar_setup(size_t total_size)
+{
+	assert(data == NULL);
+
+	size_t adjusted = round_up(total_size);
+
+	void *p = calloc(1, adjusted);
+	if (p == NULL) {
+		return -1;
+	}
+
+	data = p;
+	total = adjusted;
+
+	return 0;
+}
+
+void *
+ar_alloc(size_t object_size)
+{
+	assert(data != NULL);
+
+	size_t adjusted = round_up(object_size);
+	if (used + adjusted > total) {
+		return NULL;
+	}
+
+	void *p = data + used;
+	used += adjusted;
+
+	return p;
+}
+
+void
+ar_free(void)
+{
+	assert(data != NULL);
+
+	memset(data, 0, total);
+	used = 0;
+}
+
+void
+ar_cleanup(void)
+{
+	assert(data != NULL);
+	free(data);
+	data = NULL;
+	total = 0;
+	used = 0;
+}