From 5976d6b5a6b85c9e92290a2752d57f1f47910541 Mon Sep 17 00:00:00 2001
From: kilroy <>
Date: Sun, 30 Nov 2025 22:37:18 -0500
Subject: [PATCH] Added basic arena implementation w/ linear allocator

---
 include/arena.h | 27 +++++++++++++++++++
 src/arena.c     | 69 +++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 96 insertions(+)
 create mode 100644 include/arena.h
 create mode 100644 src/arena.c

diff --git a/include/arena.h b/include/arena.h
new file mode 100644
index 0000000..bcef97a
--- /dev/null
+++ b/include/arena.h
@@ -0,0 +1,27 @@
+#ifndef ARENA_H
+#define ARENA_H
+
+#include <stdint.h>
+
+typedef struct {
+    uint8_t *buffer;
+    size_t capacity;
+    size_t offset;
+} Arena;
+
+Arena *ArenaInit(size_t capacity);
+void ArenaDestroy(Arena *arena);
+
+void *ArenaAlloc(Arena *arena, size_t size);
+void *ArenaAllocZero(Arena *arena, size_t size);
+
+void ArenaFree(Arena *arena, size_t size);
+void ArenaFreeAndNullify(Arena *arena, size_t size, void **ptrAddress);
+
+// Fundamentally returns how many bytes have been allocated
+size_t ArenaGetOffset(Arena *arena);
+
+void ArenaSetOffsetBack(Arena *arena, size_t offset);
+void ArenaClear(Arena *arena);
+
+#endif // ARENA_H
\ No newline at end of file
diff --git a/src/arena.c b/src/arena.c
new file mode 100644
index 0000000..1d02d68
--- /dev/null
+++ b/src/arena.c
@@ -0,0 +1,69 @@
+#include "../include/arena.h"
+
+//#include <string.h>
+#include <stdint.h>
+#include <stdio.h>
+
+Arena *ArenaInit(size_t capacity)
+{
+    Arena arena;
+    arena.buffer = malloc(capacity);
+    arena.capacity = capacity;
+    arena.offset = 0;
+    return &arena;
+}
+
+void ArenaDestroy(Arena *arena)
+{
+    free(arena->buffer);
+    arena->buffer = NULL;
+    arena->capacity = 0;
+    arena->offset = 0;
+}
+
+void *ArenaAlloc(Arena *arena, size_t size)
+{
+    void *ptr = arena->buffer + arena->offset;
+    arena->offset += size;
+    return ptr;
+}
+void *ArenaAllocZero(Arena *arena, size_t size)
+{
+    void *ptr = arena->buffer + arena->offset;
+    arena->offset += size;
+    // should I just use memset?
+    for (void *i = ptr; i != ptr + size; ++i) {
+        *(uint8_t*)i = 0;
+    }
+    return ptr;
+}
+
+void ArenaFree(Arena *arena, size_t size)
+{
+    arena->offset -= size;
+}
+
+// Frees the memory in the arena *and* sets the pointer to null
+void ArenaFreeAndNullify(Arena *arena, size_t size, void **ptrAddress)
+{
+    arena->offset -= size;
+    *ptrAddress = NULL;
+}
+
+// Fundamentally returns how many bytes have been allocated
+size_t ArenaGetOffset(Arena *arena)
+{
+    return arena->offset;
+}
+
+void ArenaSetOffsetBack(Arena *arena, size_t offset)
+{
+    if (offset > arena->offset) {
+        *(int*)0 = 0; // Should crash here
+    }
+    arena->offset = offset;
+}
+void ArenaClear(Arena *arena)
+{
+    arena->offset = 0;
+}
\ No newline at end of file