From 3913d1778318cd0c6bfb871148d38abb33ec7fd3 Mon Sep 17 00:00:00 2001
From: nasr <nsrddyn@gmail.com>
Date: Wed, 28 Jan 2026 13:13:40 +0100
Subject: checkpoint

---
 library/arena.c | 81 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 81 insertions(+)
 create mode 100644 library/arena.c

(limited to 'library/arena.c')

diff --git a/library/arena.c b/library/arena.c
new file mode 100644
index 0000000..39711d5
--- /dev/null
+++ b/library/arena.c
@@ -0,0 +1,81 @@
+#include <assert.h>
+#include <dirent.h>
+#include <fcntl.h>
+#include <stdint.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+#include "arena.h"
+
+mem_arena *
+arena_create(u64 capacity)
+{
+  mem_arena *arena = mmap(0, capacity, PROT_READ | PROT_WRITE | PROT_EXEC,
+    MAP_SHARED | MAP_ANONYMOUS, -1, 0);
+  if (arena == MAP_FAILED)
+  {
+    assert(0);
+  }
+
+  arena->capacity = capacity;
+  arena->pos = ARENA_BASE_POS;
+
+  return arena;
+}
+
+// make it a void pointer to allow implicit conversion
+void
+arena_destroy(mem_arena *arena)
+{
+  munmap(arena, arena->capacity);
+}
+
+void *
+arena_push(mem_arena *arena, u64 size, b32 non_zero)
+{
+  u64 pos_aligned = ALIGN_UP_POW2(arena->pos, ARENA_ALIGN);
+  u64 new_pos = pos_aligned + size;
+
+  if (new_pos > arena->capacity)
+  {
+    assert(0);
+    return NULL;
+  }
+
+  arena->pos = new_pos;
+  // cast to u8 to be able to do pointer arithemtic
+  u8 *out = (u8 *)arena + pos_aligned;
+
+  if (!non_zero)
+  {
+    memset(out, 0, size);
+  }
+  return out;
+}
+void
+arena_pop(mem_arena *arena, u64 size)
+{
+  size = MIN(size, arena->pos - ARENA_BASE_POS);
+  arena->pos -= size;
+}
+
+void
+arena_pop_to(mem_arena *arena, u64 pos)
+{
+  u64 size = pos < arena->pos ? arena->pos - pos : 0;
+  arena_pop(arena, size);
+}
+
+void
+arena_clear(mem_arena *arena)
+{
+  arena_pop_to(arena, ARENA_BASE_POS);
+}
+
+#define PUSH_STRUCT(arena, T) (T *)arena_push((arena), sizeof(T), 0)
+#define PUSH_STRUCT_NZ(arena, T) (T *)arena_push((arena), sizeof(T), 1)
+#define PUSH_ARRAY(arena, T, n) (T *)arena_push((arena), sizeof(T) * (n), 0)
+#define PUSH_ARRAY_NZ(arena, T, n) (T *)arena_push((arena), sizeof(T) * (n), 1)
+
-- 
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