#include "arena.h"
#include "macros.h"
#include "sys.h"

struct arena alloc_arena(u64 capacity)
{
	/* TODO(pryazha): Find reasonable maximum capacity through testing */
	assert(capacity <= (u64)gigabytes(16));
	if (!capacity)
		capacity = kilobytes(4);
	void *memory = sys_alloc(capacity);
	assert(memory);
	return (struct arena){memory, capacity, 0};
}

void release_arena(struct arena *arena)
{
	assert(arena);
	sys_free(arena->memory, arena->capacity);
	arena->memory = 0;
	arena->capacity = 0;
	arena->used = 0;
}

void *push_arena(struct arena *arena, u64 size)
{
	assert(arena);
	assert(arena->used + size <= arena->capacity);
	void *memory = arena->memory + arena->used;
	arena->used += size;
	return memory;
}

void pop_arena(struct arena *arena, u64 size)
{
	assert(arena);
	arena->used -= min(size, arena->used);
}