/*=============================================================================
    Copyright (c) 2001-2010 Joel de Guzman

    Distributed under the Boost Software License, Version 1.0. (See accompanying
    file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
=============================================================================*/
#include "calc6.hpp"

void vmachine::execute(std::vector<int> const& code, int nvars)
{
    std::vector<int>::const_iterator pc = code.begin();
    std::vector<int>::iterator locals = stack.begin();
    stack_ptr = stack.begin() + nvars;

    while (pc != code.end())
    {
        switch (*pc++)
        {
            case op_neg:
                stack_ptr[-1] = -stack_ptr[-1];
                break;

            case op_add:
                --stack_ptr;
                stack_ptr[-1] += stack_ptr[0];
                break;

            case op_sub:
                --stack_ptr;
                stack_ptr[-1] -= stack_ptr[0];
                break;

            case op_mul:
                --stack_ptr;
                stack_ptr[-1] *= stack_ptr[0];
                break;

            case op_div:
                --stack_ptr;
                stack_ptr[-1] /= stack_ptr[0];
                break;

            case op_load:
                *stack_ptr++ = locals[*pc++];
                break;

            case op_store:
                --stack_ptr;
                locals[*pc++] = stack_ptr[0];
                break;

            case op_int:
                *stack_ptr++ = *pc++;
                break;
        }
    }
}