From 6ad18ea8a3966e10b3d73b56663c502ef35e6f09 Mon Sep 17 00:00:00 2001
From: talha aamir <talha@talhaamir.xyz>
Date: Wed, 24 Sep 2025 21:27:03 +0500
Subject: Added files to git.

- Starting index buffer chapter of vulkan-tutorial
---
 arena.h | 110 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 110 insertions(+)
 create mode 100755 arena.h

(limited to 'arena.h')

diff --git a/arena.h b/arena.h
new file mode 100755
index 0000000..c7340a0
--- /dev/null
+++ b/arena.h
@@ -0,0 +1,110 @@
+#pragma once
+
+#include <string.h>
+
+#ifdef ARENA_TYPES
+#include <assert.h>
+#include <stdint.h>
+typedef uint8_t b8;
+#endif
+
+#ifndef ALIGNMENT
+#define ALIGNMENT (2*sizeof(void*))
+#endif
+
+struct Arena {
+  unsigned char* buffer;
+  size_t prev_offset;
+  size_t curr_offset;
+  size_t capacity;
+};
+typedef struct Arena Arena;
+
+struct TempArena {
+    Arena *a;
+    size_t saved_prev_offset;
+    size_t saved_curr_offset;
+};
+typedef struct TempArena TempArena;
+
+// definition
+b8 is_power_of_two(uintptr_t x);
+uintptr_t fast_modulo(uintptr_t p, uintptr_t a);
+uintptr_t align_forward(uintptr_t ptr, uintptr_t alignment);
+void arena_init(Arena* a, unsigned char *memory, size_t capacity);
+void* arena_alloc(Arena* a, size_t size);
+void arena_clear(Arena* a);
+
+TempArena temp_arena_start(Arena *a);
+void temp_arena_end(Arena* a);
+
+// implementation
+b8 is_power_of_two(uintptr_t x) {
+  return (x & (x-1)) == 0;
+}
+
+uintptr_t fast_modulo(uintptr_t p, uintptr_t a) { 
+  return (p & (a - 1)); 
+}
+
+uintptr_t align_forward(uintptr_t ptr, size_t alignment) {
+  uintptr_t p, a, modulo;
+
+  assert(is_power_of_two(alignment));
+
+  p = ptr;
+  a = (uintptr_t)alignment;
+  modulo = fast_modulo(p, a);
+
+  if (modulo != 0) {
+    p += (a - modulo);
+  }
+
+  return p;
+}
+
+void arena_init(Arena* a, unsigned char *memory, size_t capacity) {
+  a->buffer = memory;
+  a->prev_offset = 0;
+  a->curr_offset = 0;
+  a->capacity = capacity;
+}
+
+void* arena_alloc(Arena* a, size_t size) {
+  void *ptr = NULL;
+
+  assert(is_power_of_two(ALIGNMENT));
+
+  uintptr_t curr_ptr = (uintptr_t)a->buffer + a->curr_offset;
+  uintptr_t offset = align_forward(curr_ptr, ALIGNMENT);
+  offset = offset - (uintptr_t)a->buffer;
+  size_t next_offset = offset + size;
+
+  assert(next_offset <= a->capacity);
+
+  ptr = &a->buffer[offset];
+  a->prev_offset = a->curr_offset;
+  a->curr_offset = next_offset;
+  memset(ptr, 0, size);
+
+  return ptr;
+}
+
+void arena_clear(Arena* a) {
+  a->curr_offset = 0;
+  a->prev_offset = 0;
+}
+
+TempArena temp_arena_start(Arena* main) {
+    TempArena tmp = {};
+    tmp.a = main;
+    tmp.saved_prev_offset = main->prev_offset;
+    tmp.saved_curr_offset = main->curr_offset;
+
+    return tmp;
+}
+
+void temp_arena_end(TempArena tmp) {
+    tmp.a->prev_offset = tmp.saved_prev_offset;
+    tmp.a->curr_offset = tmp.saved_curr_offset;
+}
-- 
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