#ifndef ARENA_H
#define ARENA_H

#include <stdint.h>

#include "typ.h"

typedef struct {
	char *beg, *end;
} Arena;

#define new(a, t)\
	zeroed(alloc(a, sizeof(t), _Alignof(t)), sizeof(t))

#define new_arr(a, t, n)\
	alloc(a, sizeof(t) * n, _Alignof(t))

#define resize(a, p, old, new)\
	re_alloc(a, p, (old) * sizeof(*(p)), (new) * sizeof(*(p)),\
			_Alignof(__typeof__(*(p))))

void *alloc(Arena *a, isize n, isize align);
void *re_alloc(Arena *a, void *ptr, isize old, isize new, isize align);
void *zeroed(void *p, usize n);

#ifdef ARENA_IMPL

#include <stdio.h>
#include <stdlib.h>

void *alloc(Arena *a, isize n, isize align) {
	char *p = a->beg + (-(uintptr_t)a->beg & (align - 1));
	if (p + n >= a->end) {
		fprintf(stderr, "out of arena memory!\n");
		abort();
	}
	a->beg = p + n;
	return p;
}

void *zeroed(void *p, usize n) {
	memset(p, 0, n);
	return p;
}

void *re_alloc(Arena *a, void *ptr, isize old, isize new, isize align) {
	if (ptr && a->beg - old == ptr && a->beg - old + new < a->end) {
		a->beg = a->beg - old + new;
		return ptr;
	} else {
		void *p = alloc(a, new, align);
		if (ptr) memcpy(p, ptr, old);
		return p;
	}
}

#endif
#endif