calc7a.cpp

来自「Boost provides free peer-reviewed portab」· C++ 代码 · 共 126 行

/*=============================================================================
    Copyright (c) 2001-2007 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 "calc7.hpp"

# pragma warning(disable: 4800) // forcing value to bool 'true' or 'false'
                                // (performance warning)

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_not:
                stack_ptr[-1] = !bool(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_eq:
                --stack_ptr;
                stack_ptr[-1] = bool(stack_ptr[-1] == stack_ptr[0]);
                break;

            case op_neq:
                --stack_ptr;
                stack_ptr[-1] = bool(stack_ptr[-1] != stack_ptr[0]);
                break;

            case op_lt:
                --stack_ptr;
                stack_ptr[-1] = bool(stack_ptr[-1] < stack_ptr[0]);
                break;

            case op_lte:
                --stack_ptr;
                stack_ptr[-1] = bool(stack_ptr[-1] <= stack_ptr[0]);
                break;

            case op_gt:
                --stack_ptr;
                stack_ptr[-1] = bool(stack_ptr[-1] > stack_ptr[0]);
                break;

            case op_gte:
                --stack_ptr;
                stack_ptr[-1] = bool(stack_ptr[-1] >= stack_ptr[0]);
                break;

            case op_and:
                --stack_ptr;
                stack_ptr[-1] = bool(stack_ptr[-1]) && bool(stack_ptr[0]);
                break;

            case op_or:
                --stack_ptr;
                stack_ptr[-1] = bool(stack_ptr[-1]) || bool(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;

            case op_true:
                *stack_ptr++ = true;
                break;

            case op_false:
                *stack_ptr++ = false;
                break;

            case op_jump:
                pc = code.begin() + *pc;
                break;

            case op_jump_if:
                if (!bool(stack_ptr[-1]))
                    pc = code.begin() + *pc;
                else
                    ++pc;
                --stack_ptr;
                break;
        }
    }
}