gistfile1.cpp

#include <stdio.h>
#include <sstream>
#include <stack>

#define MEMSIZE 30000
#define CODESIZE 30000

#include "xbyak/xbyak.h"

class BFVM : public Xbyak::CodeGenerator {
private:
    FILE *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(FILE *input) :
        CodeGenerator(CODESIZE),
        input(input)
    {
        using namespace Xbyak;
        push(ebx);
        push(esi);
        push(edi);

        Reg32 mem(ebx);
        Reg32 ptrGetchar(esi);
        Reg32 ptrPutchar(edi);
        mov(eax, 0);
        mov(mem, (int) membuf);
        mov(ptrGetchar, (int) getchar);
        mov(ptrPutchar, (int) putchar);

        char ch = 0, nextch = 0;
        int opMemCount = 0;
        int opPtrCount = 0;
        std::stack<int> labelStack;
        int labelNum = 0;
        std::string label;
        do {
            nextch = getc(input);
            switch(ch) {
                case '+':
                case '-':
                    opMemCount += ch=='+' ? 1 : -1;
                    if ((nextch!='+' && nextch!='-') && opMemCount!=0) {
                        switch(opMemCount) {
                            case 1:
                                inc(eax);
                                break;
                            case -1:
                                dec(eax);
                                break;
                            default:
                                add(eax, opMemCount);
                                break;
                        }
                        opMemCount = 0;
                    }
                    break;
                case '>':
                case '<':
                    opPtrCount += ch=='>' ? 1 : -1;
                    if ((nextch!='>' && nextch!='<') && opPtrCount!=0) {
                        mov(dword [mem], eax);
                        add(mem, 4*opPtrCount);
                        mov(eax, dword [mem]);
                        opPtrCount = 0;
                    }
                    break;
                case ',':
                    call(ptrGetchar);
                    break;
                case '.':
                    push(eax);
                    call(ptrPutchar);
                    pop(eax);
                    break;
                case '[':
                    L(toLabel('L', labelNum));
                    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;
            }
            ch = nextch;
        } while (ch != EOF);

        pop(edi);
        pop(esi);
        pop(ebx);
        ret();
    }
    void execute()
    {
        void (*codes)() = (void (*)()) getCode();
        codes();
        fflush(stdout);
        fprintf(stderr, "\nsize of x86-code: %d\n", getSize());
    }
};

int main()
{
    BFVM bf(stdin);
    bf.execute();
    return 0;
}