1 files changed, 27 insertions, 0 deletions
diff --git a/memory.c b/memory.c
new file mode 100644
index 0000000..cfb5dd4
--- /dev/null
+++ b/memory.c
@@ -0,0 +1,27 @@
+#include <assert.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "memory.h"
+
+Arena Arena_new(ptrdiff_t cap) {
+  Arena a = {0};
+  a.cap = cap;
+  a.beg = malloc(cap);
+  a.end = a.beg ? a.beg + cap : 0;
+  return a;
+}
+
+// Magic to allow optimisation __attribute((malloc, alloc_size(2, 4),
+// alloc_align(3)))
+void *alloc(Arena *a, ptrdiff_t count, int size, int align) {
+  int padding = -(uintptr_t)a->beg & (align - 1);
+  assert(count < (a->end - a->beg - padding) / size);
+  void *cursor = a->beg + padding;
+  a->beg += padding + count * size;
+  return memset(cursor, 0, count * size);
+}
+
+int Arena_get_used(Arena a) { return a.cap - (a.end - a.beg); }