add an arena allocator first impl

1 files changed, 26 insertions, 0 deletions

diff --git a/src/std/mem.c b/src/std/mem.c
new file mode 100644
index 0000000..c30f76d
--- /dev/null
+++ b/src/std/mem.c
@@ -0,0 +1,26 @@
+#include "mem.h"
+#include <stddef.h>
+#include <stdint.h>
+#include <string.h>
+#include "log.h"
+
+#ifndef DEFAULT_ALIGNMENT
+#define DEFAULT_ALIGNMENT (2 * sizeof(void*))
+#endif
+
+void* arena_alloc_align(arena* a, size_t size, size_t align) {
+  ptrdiff_t padding = -(uintptr_t)a->begin & (align - 1);
+  ptrdiff_t available = a->end - a->begin - padding;
+  TRACE("Padding %td available %td", padding, available);
+  if (available < 0 || (ptrdiff_t)size > available) {
+    ERROR_EXIT("Arena ran out of memory\n");
+  }
+  void* p = a->begin + padding;
+  a->begin += padding + size;
+  return memset(p, 0, size);
+}
+void* arena_alloc(arena* a, size_t size) { return arena_alloc_align(a, size, DEFAULT_ALIGNMENT); }
+
+arena arena_create(void* backing_buffer, size_t capacity) {
+  return (arena){ .begin = backing_buffer, .end = backing_buffer + (ptrdiff_t)capacity };
+}
\ No newline at end of file