add arenaGetAddressOffset helper

src/util.h

@@ -33,12 +33,15 @@ struct MemoryArena
 MemoryArena* arenaInit(size_t initial_size = DEFAULT_ARENA_SIZE);
 
 void arenaFree(MemoryArena*& arena);
+
 u32 arenaGetFreeSize(MemoryArena* arena);
 
 #define ARENA_ALLOC(arena, type, count) \
 	(type*) arenaAllocateBlock(arena, sizeof(type) * count)
 void* arenaAllocateBlock(MemoryArena* arena, size_t block_size);
 
+void* arenaGetAddressOffset(void* address, u32 offset);
+
 #define MAX_NAME_LENGTH 256
 char* arenaCopyCStr(MemoryArena* arena,
 	const char* input,
@@ -46,7 +49,9 @@ char* arenaCopyCStr(MemoryArena* arena,
 
 #define UTIL_ALLOC(count, type) (type*) utilAllocate(count, sizeof(type))
 void* utilAllocate(u32 count, u32 type_size);
+
 char* utilAllocateCStr(const char* str, u32 max_len = 256);
+
 void utilSafeFree(void* p);
 
 #endif // UTIL_H
@@ -115,6 +120,12 @@ arenaAllocateBlock(MemoryArena* arena, size_t block_size)
 	return ret;
 }
 
+void*
+arenaGetAddressOffset(void* address, u32 offset)
+{
+	return (void*) ((u8*) address + offset);
+}
+
 char*
 arenaCopyCStr(MemoryArena* arena, const char* input, u32 max_len)
 {