brainfuck.cc

// Copyright (c) 2018 SAKATA Sinji. Released under the MIT license.

#include <fstream>
#include <iostream>
#include <iterator>
#include <string>
#include <vector>

using namespace std;

const int DataSize = 30000;

enum OP_CODE {
  OP_ADD_PTR = 0,
  OP_ADD_DATA,
  OP_READ,
  OP_OUT,
  OP_JUMP,
  OP_JUMP_BK,
};

const string code_s[] = {
    "addptr", "adddata", "read", "out", "jump", "jumpbk",
};

struct Operation {
  OP_CODE op;
  int value;
};

using Program = vector<Operation>;

Program parse(const string &code) {
  int cp = 0;
  int pp = 0;
  vector<int> bracket_pp;
  Program program;
  program.push_back({OP_ADD_DATA, 0});

  while (cp < code.length()) {
    int jump_to;
    switch (code[cp]) {
    case '>':
      if (program.back().op != OP_ADD_PTR) {
        program.push_back({OP_ADD_PTR, 0});
      }
      program.back().value++;
      break;
    case '<':
      if (program.back().op != OP_ADD_PTR) {
        program.push_back({OP_ADD_PTR, 0});
      }
      program.back().value--;
      break;
    case '+':
      if (program.back().op != OP_ADD_DATA) {
        program.push_back({OP_ADD_DATA, 0});
      }
      program.back().value++;
      break;
    case '-':
      if (program.back().op != OP_ADD_DATA) {
        program.push_back({OP_ADD_DATA, 0});
      }
      program.back().value--;
      break;
    case '.':
      program.push_back({OP_OUT, 1});
      break;
    case ',':
      program.push_back({OP_READ, 1});
      break;
    case '[':
      bracket_pp.push_back(program.size());
      program.push_back({OP_JUMP, 0});
      break;
    case ']':
      jump_to = bracket_pp.back();
      bracket_pp.pop_back();
      program[jump_to].value = program.size();
      program.push_back({OP_JUMP_BK, jump_to});
      break;
    default:
      break; // ignore
    }
    cp++;
  }
  return program;
}

void print_op(const Operation &o) {
  cout << code_s[o.op] << " " << o.value << endl;
}

void print_program(const Program &program) {
  int line = 0;
  for (const auto &o : program) {
    cout << line << ":";
    print_op(o);
    line++;
  }
}

void eval(const Program &program) {
  int pp = 0;
  int ptr = 0;
  uint8_t data[DataSize] = {};

  while (pp < program.size()) {
    OP_CODE op = program[pp].op;
    int value = program[pp].value;
    // print_op(program[pp]);
    switch (op) {
    case OP_ADD_DATA:
      data[ptr] += value;
      break;
    case OP_ADD_PTR:
      ptr += value;
      break;
    case OP_READ:
      cin >> data[ptr];
      break;
    case OP_OUT:
      cout << data[ptr];
      break;
    case OP_JUMP:
      if (data[ptr] == 0)
        pp = value;
      break;
    case OP_JUMP_BK:
      if (data[ptr] != 0)
        pp = value;
      break;
    }
    pp++;
  }
}

void eval(const string &code) {
  int cp = 0;
  int ptr = 0;
  uint8_t data[DataSize] = {};

  while (cp < code.length()) {
    switch (code[cp]) {
    case '>':
      ptr++;
      break;
    case '<':
      ptr--;
      break;
    case '+':
      data[ptr]++;
      break;
    case '-':
      data[ptr]--;
      break;
    case '.':
      putchar(data[ptr]);
      break;
    case ',':
      cin >> data[ptr];
      break;
    case '[':
      if (data[ptr] == 0) {
        int bracket_cnt = 0;
        while (code[++cp] != ']' || bracket_cnt != 0) {
          if (code[cp] == '[')
            bracket_cnt++;
          else if (code[cp] == ']')
            bracket_cnt--;
        }
      }
      break;
    case ']':
      if (data[ptr] != 0) {
        int bracket_cnt = 0;
        while (code[--cp] != '[' || bracket_cnt != 0) {
          if (code[cp] == ']')
            bracket_cnt++;
          else if (code[cp] == '[')
            bracket_cnt--;
        }
      }
      break;
    default:; // ignore
    }
    cp++;
  }
}

int main(int argc, char *argv[]) {
  if (argc != 2) {
    cerr << "require source code" << endl;
    return -1;
  }

  string src(argv[1]);
  ifstream ifs(src);
  if (ifs.fail()) {
    std::cerr << src << ": Not found." << std::endl;
    return -1;
  }
  istreambuf_iterator<char> it(ifs);
  istreambuf_iterator<char> last;
  string code(it, last);

  Program program = parse(code);
  // print_program(program);
  eval(program);
  // eval(code);
  return 0;
}