#include "stack.h"
#include "chip8.h"

#include <assert.h>

static void
chip8_stack_in_bounds (struct chip8 *chip8)
{
	assert (chip8->registers.SP < sizeof (chip8->stack.stack));
}

void
chip8_stack_push (struct chip8 *chip8, unsigned short val)
{
	chip8->registers.SP += 1;
	chip8_stack_in_bounds (chip8);

	chip8->stack.stack[chip8->registers.SP] = val;
}

unsigned short
chip8_stack_pop (struct chip8 *chip8)
{
	chip8_stack_in_bounds (chip8);

	unsigned short result = chip8->stack.stack[chip8->registers.SP];
	chip8->registers.SP -= 1;
	return result; // we don't set the program counter
}