1 files changed, 43 insertions, 0 deletions
diff --git a/src/arena.h b/src/arena.h
new file mode 100644
index 0000000..cd4aa17
--- /dev/null
+++ b/src/arena.h
@@ -0,0 +1,43 @@
+#ifndef ARENA_H
+#define ARENA_H
+
+//
+// This module defines a simple, fixed-size arena allocator.
+//
+
+#include <stddef.h> // size_t
+
+struct arena {
+	void *root;
+	size_t capacity;
+	size_t used;
+};
+
+// Initialize an arena with the given `capacity`.
+// Panics on failure to allocate.
+struct arena arena_create(size_t capacity);
+
+// These flags control the behavior of `arena_alloc`.
+#define ARENA_NO_ZERO      1
+#define ARENA_NO_PANIC     2
+
+// Allocate `size` bytes in `arena`.
+// The resulting memory is zeroed unless ARENA_NO_ZERO is passed.
+// Unless ARENA_NO_PANIC is specified, the resulting pointer is always valid.
+void *arena_alloc(struct arena *arena, size_t size, size_t alignment, unsigned flags);
+
+// Free the memory associated with the arena using the underlying allocator.
+void arena_destroy(struct arena *arena);
+
+//
+// The `new` macro makes the basic allocation case simple. It uses a bit of
+// preprocessor magic to simulate default argument values.
+//
+
+#define new(...) newx(__VA_ARGS__,new4,new3,new2)(__VA_ARGS__)
+#define newx(a1, a2, a3, a4, a5, ...) a5
+#define new2(arena, typ)                  (typ *)arena_alloc(arena,         sizeof(typ), _Alignof(typ), 0)
+#define new3(arena, typ, count)           (typ *)arena_alloc(arena, count * sizeof(typ), _Alignof(typ), 0)
+#define new4(arena, typ, count, flags)    (typ *)arena_alloc(arena, count * sizeof(typ), _Alignof(typ), flags)
+
+#endif