simple stable growable array

stable_dynamic_array.h

#pragma once
#include "common.h"
#include "dynamic_array.h"

template <typename T>
struct Stable_Dynamic_Array {
    // this is your usual unstable growable array like std::vector
    Dynamic_Array<T *> blocks;
    int count;
    int cap;

    void push(T elem) {
        if (count >= cap) {
            //NOTE(chen): equivalent to 2^N growth, same as dynamic_array
            int new_block_size = cap + 1;
            cap += new_block_size;
            T *new_block = (T *)calloc(new_block_size, sizeof(T));
            blocks.push(new_block);
        }

        ++count;
        operator[](count-1) = elem;
    }

    T &operator[](int index) {
        assert(index >= 0 && index < count); 
        int block_index = 31 - nlz(u32(index+1)); // effectively floor(log2(index+1))
        int local_index = index - ((1 << block_index) - 1);
        return blocks[block_index][local_index];
    }

    T operator[](int index) const {
        assert(index >= 0 && index < count); 
        int block_index = 31 - nlz(u32(index+1)); // effectively floor(log2(index+1))
        int local_index = index - ((1 << block_index) - 1);
        return blocks[block_index][local_index];
    }
};

template <typename T>
void free(Stable_Dynamic_Array<T> array) {
    for (int i = 0; i < array.blocks.count; ++i) {
        free(array.blocks[i]);
    }
    free(array.blocks);
}