gistfile1.cpp

#include <stdio.h>
#include <iostream>
#include <string>
#include <sstream>
#include <vector>
#include <stack>

#define MEMSIZE 30000
#define CODESIZE 30000

#include "xbyak/xbyak.h"

class BFVM : public Xbyak::CodeGenerator {
private:
    std::istream& input;
    int membuf[MEMSIZE];

    static const char* toLabel(char ch, int num)
    {
        static std::stringstream labelStream;
        labelStream.str("");
        labelStream << ch << num;
        return labelStream.str().c_str();
    }

public:
    BFVM(std::istream& input) :
        CodeGenerator(CODESIZE),
        input(input)
    {
        using namespace Xbyak;
        push(ebx);

        Reg32 mem(ebx);
        mov(mem, (int) membuf);

        char ch = 0;
        std::stack<int> labelStack;
        int labelNum = 0;
        std::string label;
        while(input.get(ch).good()) {
            switch(ch) {
                case '+':
                    mov(eax, ptr[mem]);
                    inc(eax);
                    mov(ptr[mem], eax);
                    break;
                case '-':
                    mov(eax, ptr[mem]);
                    dec(eax);
                    mov(ptr[mem], eax);
                    break;
                case '>':
                    add(mem, 4);
                    break;
                case '<':
                    add(mem, -4);
                    break;
                case ',':
                    call((void*) getchar);
                    mov(ptr[mem], eax);
                    break;
                case '.':
                    push(ptr[mem]);
                    call((void*) putchar);
                    add(esp, 4);
                    break;
                case '[':
                    L(toLabel('L', labelNum));
                    mov(eax, ptr[mem]);
                    test(eax, eax);
                    jz(toLabel('R', labelNum), T_NEAR);

                    labelStack.push(labelNum);
                    ++labelNum;
                    break;
                case ']':
                    int beginNum = labelStack.top();
                    labelStack.pop();

                    jmp(toLabel('L', beginNum), T_NEAR);
                    L(toLabel('R', beginNum));
                    break;
            }
        }
        pop(ebx);
        ret();
    }
    void execute()
    {
        void (*codes)() = (void (*)()) getCode();
        codes();
    }
};

int main()
{
    BFVM bf(std::cin);
    bf.execute();
    return 0;
}