From 5944fcda92f47bea10b69b9b5a06aa3e9dcb6fa1 Mon Sep 17 00:00:00 2001
From: Warwick <warwick.l.e.new@gmail.com>
Date: Fri, 15 Aug 2025 13:08:38 +0100
Subject: [PATCH] Added simple arena allocator from my other game engine.

---
 src/arena_allocator.c | 32 ++++++++++++++++++++++++++++++++
 src/arena_allocator.h | 15 +++++++++++++++
 src/main.c            | 11 ++++++-----
 3 files changed, 53 insertions(+), 5 deletions(-)
 create mode 100644 src/arena_allocator.c
 create mode 100644 src/arena_allocator.h

diff --git a/src/arena_allocator.c b/src/arena_allocator.c
new file mode 100644
index 0000000..591dd8d
--- /dev/null
+++ b/src/arena_allocator.c
@@ -0,0 +1,32 @@
+#include "arena_allocator.h"
+#include <assert.h>
+#include <stddef.h>
+#include <stdlib.h>
+
+#define DEFAULT_ARENA_SIZE 1048576 /* 8 * 1024 * 1024 : 8MB*/
+
+Arena arena_init(size_t capacity) {
+  if (capacity == 0) {
+    capacity = DEFAULT_ARENA_SIZE;
+  }
+  Arena result = {.capacity = capacity, .size = 0, .data = malloc(capacity)};
+  assert(result.data != NULL);
+  return result;
+}
+
+void arena_deinit(Arena *arena) {
+  free(arena->data);
+  *arena = (Arena){.capacity = 0, .size = 0, .data = NULL};
+}
+
+void *arena_alloc(Arena *arena, size_t size) {
+  assert(arena->size + size <= arena->capacity);
+  void *result = &arena->data[arena->size];
+  arena->size += size;
+  return result;
+}
+
+void *arena_clear(Arena *arena) {
+  arena->size = 0;
+  return arena->data;
+}
diff --git a/src/arena_allocator.h b/src/arena_allocator.h
new file mode 100644
index 0000000..981f76c
--- /dev/null
+++ b/src/arena_allocator.h
@@ -0,0 +1,15 @@
+#pragma once
+
+#include <stddef.h>
+
+typedef struct {
+  size_t capacity;
+  size_t size;
+  unsigned char *data;
+} Arena;
+
+Arena arena_init(size_t capacity);
+void arena_deinit(Arena *arena);
+
+void *arena_alloc(Arena *arena, size_t size);
+void *arena_clear(Arena *arena);
diff --git a/src/main.c b/src/main.c
index 5e2147c..f4abd11 100644
--- a/src/main.c
+++ b/src/main.c
@@ -1,10 +1,12 @@
-#include "SDL3/SDL_init.h"
-#include "SDL3/SDL_log.h"
-#include "SDL3/SDL_render.h"
-#include "SDL3/SDL_video.h"
+#include <SDL3/SDL_init.h>
+#include <SDL3/SDL_log.h>
+#include <SDL3/SDL_render.h>
+#include <SDL3/SDL_video.h>
 #include <GL/glew.h>
 #include <stdlib.h>
 
+#include "arena_allocator.h"
+
 // settings
 const unsigned int SCR_WIDTH = 800;
 const unsigned int SCR_HEIGHT = 600;
@@ -104,7 +106,6 @@ int main(int argc, char *argv[]) {
       -0.5f, 0.5f,  0.0f  // top left
   };
   unsigned int indices[] = {
-      // note that we start from 0!
       0, 1, 3, // first Triangle
       1, 2, 3  // second Triangle
   };