bfvm.cpp

#include <iostream>
#include <fstream>
#include <vector>
#include <stack>

int main(int argc, char* argv[]) {
    if (argc != 2) {
        std::cerr << "Usage: bfvm <filename.bfp>" << std::endl;
        return 1;
    }

    std::string filename = argv[1];
    std::ifstream in(filename, std::ios::binary);
    if (!in) {
        std::cerr << "Error opening file: " << filename << std::endl;
        return 1;
    }

    std::vector<char> code;
    char ch;
    while (in.get(ch)) {
        code.push_back(ch);
    }
    in.close();

    // Precompute matching brackets
    std::vector<int> matching(code.size(), -1);
    std::stack<int> stk;
    for (size_t i = 0; i < code.size(); ++i) {
        if (code[i] == 6) { // [
            stk.push(i);
        } else if (code[i] == 7) { // ]
            if (!stk.empty()) {
                int start = stk.top();
                stk.pop();
                matching[start] = i;
                matching[i] = start;
            }
        }
    }

    // VM
    const int DATA_SIZE = 30000;
    std::vector<char> data(DATA_SIZE, 0);
    size_t dp = 0;
    size_t ip = 0;

    while (ip < code.size()) {
        char instr = code[ip];
        switch (instr) {
            case 0: // >
                dp = (dp + 1) % DATA_SIZE;
                break;
            case 1: // <
                dp = (dp - 1 + DATA_SIZE) % DATA_SIZE;
                break;
            case 2: // +
                data[dp]++;
                break;
            case 3: // -
                data[dp]--;
                break;
            case 4: // .
                std::cout << data[dp];
                break;
            case 5: // ,
                data[dp] = std::cin.get();
                break;
            case 6: // [
                if (data[dp] == 0) {
                    ip = matching[ip];
                }
                break;
            case 7: // ]
                if (data[dp] != 0) {
                    ip = matching[ip];
                }
                break;
        }
        ip++;
    }

    return 0;
}