#include "arena.h"
#include <stdint.h>
#include <stdlib.h>
#include <string.h>

void arena_init(Arena* a)
{
    a->data = NULL;
    a->size = 0;
    a->capacity = 0;
}

void* arena_alloc(Arena* a, size_t size)
{
    // simple alignment to 8 bytes
    size = (size + 7) & ~((size_t)7);

    if (a->size + size > a->capacity) {
        size_t new_cap = a->capacity ? a->capacity * 2 : 1024;

        while (new_cap < a->size + size)
            new_cap *= 2;

        uint8_t* new_data = realloc(a->data, new_cap);
        if (!new_data)
            return NULL;

        a->data = new_data;
        a->capacity = new_cap;
    }

    void* ptr = a->data + a->size;
    a->size += size;
    return ptr;
}

void arena_free(Arena* a)
{
    free(a->data);
    a->data = NULL;
    a->size = 0;
    a->capacity = 0;
}