Implement reallocation functionality for Arena allocator

src/core/mem/arena/mem_arena.c

@@ -96,13 +96,39 @@ void *wapp_mem_arena_alloc_aligned(Arena *arena, u64 size, u64 alignment) {
 }
 
 void *wapp_mem_arena_realloc(Arena *arena, void *ptr, u64 old_size, u64 new_size) {
+  if ((u8*)ptr < arena->buf || (u8*)ptr > arena->offset ||
+      arena->offset + new_size >= arena->buf + arena->capacity) {
     return NULL;
   }
 
-void *wapp_mem_arena_realloc_aligned(Arena *arena, void *ptr, u64 old_size, u64 new_size, u64 alignment) {
+  void *new_ptr = wapp_mem_arena_alloc(arena, new_size);
+  if (!new_ptr) {
     return NULL;
   }
 
+  u64 copy_size = new_size <= old_size ? new_size : old_size;
+  memcpy(new_ptr, ptr, copy_size);
+
+  return new_ptr;
+}
+
+void *wapp_mem_arena_realloc_aligned(Arena *arena, void *ptr, u64 old_size, u64 new_size, u64 alignment) {
+  if ((u8*)ptr < arena->buf || (u8*)ptr > arena->offset ||
+      arena->offset + new_size >= arena->buf + arena->capacity) {
+    return NULL;
+  }
+
+  void *new_ptr = wapp_mem_arena_alloc_aligned(arena, new_size, alignment);
+  if (!new_ptr) {
+    return NULL;
+  }
+
+  u64 copy_size = new_size <= old_size ? new_size : old_size;
+  memcpy(new_ptr, ptr, copy_size);
+
+  return new_ptr;
+}
+
 void wapp_mem_arena_clear(Arena *arena) {
   if (!arena) {
     return;