#define ARENA_HEADER_SIZE 128
#define ARENA_COMMIT_SIZE (64 * 1024)
#define ARENA_RESERVE_SIZE (64 * 1024 * 1024)

struct Arena {
  Arena *prev;
  Arena *cur;
  u64 base_pos;
  u64 pos;
  u64 cmt;
  u64 res;
  u64 align;
  u64 mem_used;
  u64 mem_peak_used;
  b8 grow;
};

struct Temp {
  Arena *arena;
  u64 pos;
};