attempted to move to region based arena allocator

src/arena_allocator.c

@@ -3,30 +3,55 @@
 #include <stddef.h>
 #include <stdlib.h>
 
-#define DEFAULT_ARENA_SIZE 1048576 /* 8 * 1024 * 1024 = 8MB */
+#define DEFAUL_REGION_SIZE 1048576 /* 8 * 1024 * 1024 = 8MB */
+
+Region *new_region(size_t capacity) {
+  if (capacity == 0) {
+    capacity = DEFAUL_REGION_SIZE;
+  }
+  Region *region = malloc(capacity);
+  assert(region != NULL);
+  *region = (Region){.next = NULL,
+                     .capacity = capacity + sizeof(Region),
+                     .cursor = sizeof(Region) - 1};
+  return region;
+}
 
 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;
+  Region *region = new_region(capacity);
+  Arena arena = {.begin = region, .end = region};
+  return arena;
 }
 
 void arena_deinit(Arena *arena) {
-  free(arena->data);
-  *arena = (Arena){.capacity = 0, .size = 0, .data = NULL};
+  assert(arena->begin != NULL && arena->end != NULL);
+  Region *region = arena->begin;
+  while (region != NULL) {
+    Region *next_region = region->next;
+    free(region);
+    region = next_region;
+  }
+  *arena = (Arena){.begin = NULL, .end = NULL};
 }
 
 void *arena_alloc(Arena *arena, size_t size) {
-  assert(arena->size + size <= arena->capacity);
-  void *result = &arena->data[arena->size];
-  arena->size += size;
+  Region *region = arena->end;
+  assert(region != NULL);
+
+  if (region->cursor + size > region->capacity) {
+    if (size < DEFAUL_REGION_SIZE)
+      size = DEFAUL_REGION_SIZE;
+    region->next = new_region(size);
+    arena->end = region->next;
+    region = region->next;
+  }
+
+  void *result = &region->data[region->cursor];
+  region->cursor += size;
   return result;
 }
 
-void *arena_clear(Arena *arena) {
-  arena->size = 0;
-  return arena->data;
-}
+//void *arena_clear(Arena *arena) {
+//  arena->size = 0;
+//  return arena->data;
+//}

src/arena_allocator.h

@@ -1,15 +1,23 @@
 #pragma once
 
 #include <stddef.h>
+#include <stdint.h>
+
+typedef struct Region_s Region;
+struct Region_s {
+  Region *next;
+  size_t capacity;
+  size_t cursor;
+  uintptr_t data[];
+};
 
 typedef struct {
-  size_t capacity;
-  size_t size;
-  unsigned char *data;
+  Region *begin;
+  Region *end;
 } 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);
+//void *arena_clear(Arena *arena);