brain fuck c++

bf.cpp

// a simple brain-fuck interpretor
// see http:://en.wikipedia.org/wiki/Brainfuck
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <assert.h>
#include <vector>
#define BUFSIZE 30000

class State {
private:
    unsigned char data[BUFSIZE];
    size_t dataptr;
    std::vector<char> prg;
    size_t prgptr;
    void _exec();
public:
    State() : dataptr(0) {
        memset(data, 0, sizeof(data));
    }
    void read(char c) {
        prg.push_back(c);
    }
    void exec() {
        dataptr = 0;
        prgptr = 0;
        _exec();
    }
    char code() { return prg[prgptr]; }
};

void State::_exec()
{
    while (prgptr < prg.size()) {
        switch (code()) {
            case '+':
                data[dataptr]++; break;
            case '-':
                data[dataptr]--; break;
            case '>':
                dataptr++; break;
            case '<':
                dataptr--; break;
            case '.':
                putchar(data[dataptr]); break;
            case ',':
                data[dataptr] = getchar(); break;
            case '[':
                if (data[dataptr] == 0) {
                    int count = 0;
                    for (;;) {
                        prgptr += 1;
                        if (code() == '[') {
                            count += 1;
                        } else if (count == 0 && code() == ']') {
                            break;
                        } else if (count > 0 && code() == ']') {
                            count -= 1;
                        }
                    }
                    prgptr += 1;
                    continue;
                } else {
                    break;
                }
            case ']':
                if (data[dataptr] != 0) {
                    int count = 0;
                    for (;;) {
                        prgptr -= 1;
                        if (code() == ']') {
                            count += 1;
                        } else if (count == 0 && code() == '[') {
                            break;
                        } else if (count > 0 && code() == '[') {
                            count -= 1;
                        }
                    }
                    prgptr += 1;
                    continue;
                } else {
                    break;
                }
            default:
                break;
        }
        prgptr++;
    }
}

int main(int argc, char *argv[])
{
    assert(argc == 2);
    State stat;
    char *prg = argv[1];
    while (*prg != 0) {
        stat.read(*prg++);
    }
    stat.exec();
}

./bf  '++++++++[>++++[>++>+++>+++>+<<<<-]>+>+>->>+[<]<-]>>.>---.+++++++..+++.>>.<-.<.+++.------.--------.>>+.>++.'