cs440-final/integer.cpp

#include <algorithm>
#include <cassert>
#include <cstddef>
#include <iostream>
#include <limits>
#include <sstream>
#include <string>
#define todo(msg)                                                              \
  std::cerr << msg << std::endl;                                               \
  assert(false);
// TODO: try to maximize rvalue usage to reuse resources
// "Use rvalue references to reuse the resources of temporaries when possible,
// particularly for binary operands."

class Integer {
  using byte = unsigned char;
  // bytes are litle endian
  byte *bytes;
  bool isNegative;
  std::size_t size;

public:
  Integer(long long num = 0)
      : bytes{new byte[sizeof(long long)]}, isNegative{num < 0},
        size{sizeof(long long)} {
    for (std::size_t i = 0; i < size; i++) {
      bytes[i] = num % 256;
      num /= 256;
    }
  }
  Integer(Integer const &rhs)
      : bytes{new byte[rhs.size]}, isNegative{rhs.isNegative}, size{rhs.size} {
    for (std::size_t i = 0; i < size; i++) {
      bytes[i] = rhs.bytes[i];
    }
  }
  Integer(Integer &&rhs)
      : bytes{rhs.bytes}, isNegative{rhs.isNegative}, size{rhs.size} {
    rhs.bytes = nullptr;
  }
  ~Integer() {
    delete[] bytes;
    bytes = nullptr;
  }
  Integer &operator=(Integer const &rhs) {
    delete[] bytes;

    bytes = new byte[rhs.size];
    size = rhs.size;
    isNegative = rhs.isNegative;
    for (std::size_t i = 0; i < size; i++) {
      bytes[i] = rhs.bytes[i];
    }
    return *this;
  }
  Integer &operator=(Integer &&rhs) {
    bytes = rhs.bytes;
    rhs.bytes = nullptr;
    size = rhs.size;
    isNegative = rhs.isNegative;
    return *this;
  }
  void expand() {
    byte *new_buf = new byte[size + 1];
    std::copy(bytes, bytes + size, new_buf);
    size++;
    delete[] bytes;
    bytes = new_buf;
  }
  std::size_t true_size() const {
    std::size_t ret = size;
    if (bytes == nullptr) {
      return 0;
    }
    while (bytes[ret - 1] == 0 && ret > 1) {
      ret--;
    }
    return ret;
  }
  friend bool abs_lt(Integer const &lhs, Integer const &rhs) {
    std::size_t true_lhs_size = lhs.true_size();
    std::size_t true_rhs_size = rhs.true_size();
    if (true_lhs_size != true_rhs_size) {
      return true_lhs_size < true_rhs_size;
    }
    if (true_lhs_size == 0) {
      return false;
    }

    auto idx = true_lhs_size - 1;
    while (idx >= 0) {
      if (lhs.bytes[idx] != rhs.bytes[idx]) {
        return lhs.bytes[idx] < rhs.bytes[idx];
      }
    }
    return false;
  }
  friend Integer &operator+=(Integer &lhs, Integer const &rhs) {
    // TODO: negative numbers
    bool overflow = false;
    for (std::size_t i = 0; i < std::min(lhs.size, rhs.size); i++) {
      if (std::numeric_limits<byte>::max() - lhs.bytes[i] <= rhs.bytes[i]) {
        overflow = true;
      } else if (std::numeric_limits<byte>::max() - lhs.bytes[i] -
                     (rhs.bytes[i]) <=
                 (overflow ? 1 : 0)) {
        overflow = true;
      }
      lhs.bytes[i] += rhs.bytes[i] + (overflow ? 1 : 0);
    }
    if (overflow) {
      std::size_t idx = std::min(lhs.size, rhs.size);
      if (idx == lhs.size) {
        lhs.expand();
      }
      lhs.bytes[idx]++;
      if (lhs.bytes[idx] == 0) {
        idx++;
        if (idx == lhs.size) {
          lhs.expand();
        }
        lhs.bytes[idx]++;
      }
    }
    return lhs;
  }
  friend Integer &operator-=(Integer &lhs, Integer const &rhs) {
    todo("-=");
    return lhs;
  }
  friend Integer &operator*=(Integer &lhs, Integer const &rhs) {
    Integer tmp = std::move(lhs);
    Integer tmp_r = rhs;
    lhs = 0;
    while (tmp_r > 0) {
      lhs += tmp;
      tmp_r -= 1;
    }
    return lhs;
  }
  friend Integer &operator/=(Integer &lhs, Integer const &rhs) {
    Integer tmp = std::move(lhs);
    lhs = 0;
    while (tmp > rhs) {
      tmp -= rhs;
      lhs += 1;
    }
    return lhs;
  }
  friend Integer &operator%=(Integer &lhs, Integer const &rhs) {
    while (lhs > rhs) {
      lhs -= rhs;
    }
    return lhs;
  }
  friend Integer operator+(Integer const &lhs, Integer const &rhs) {
    Integer ret{lhs};
    ret += rhs;
    return ret;
  }
  friend Integer operator-(Integer const &lhs, Integer const &rhs) {
    Integer ret{lhs};
    ret -= rhs;
    return ret;
  }
  friend Integer operator*(Integer const &lhs, Integer const &rhs) {
    Integer ret{lhs};
    ret *= rhs;
    return ret;
  }
  friend Integer operator/(Integer const &lhs, Integer const &rhs) {
    Integer ret{lhs};
    ret /= rhs;
    return ret;
  }
  friend Integer operator%(Integer const &lhs, Integer const &rhs) {
    Integer ret{lhs};
    ret %= rhs;
    return ret;
  }
  friend Integer operator%(Integer const &lhs, byte rhs) {
    if (lhs.size == 0 || lhs.bytes == nullptr) {
      return 0;
    }
    return lhs.bytes[0] % rhs;
  }
  friend Integer operator-(Integer const &val) {
    Integer ret = val;
    ret.isNegative = !ret.isNegative;
    return ret;
  }
  friend bool operator<(Integer const &lhs, Integer const &rhs) {
    if (lhs.isNegative != rhs.isNegative) {
      return lhs.isNegative;
    } else {
      return abs_lt(lhs, rhs);
    }
  }
  friend bool operator>(Integer const &lhs, Integer const &rhs) {
    return rhs < lhs;
  }
  friend bool operator==(Integer const &lhs, Integer const &rhs) {
    auto l_true = lhs.true_size();
    return l_true == rhs.true_size() &&
           std::equal(lhs.bytes, lhs.bytes + l_true, rhs.bytes);
  }

  friend std::ostream &operator<<(std::ostream &lhs, Integer const &rhs) {
    if (rhs == 0) {
      lhs << 0;
      return lhs;
    }

    Integer discard = rhs;
    std::stringstream to_output{};
    while (discard != 0) {
      to_output << discard % 10;
      discard /= 10;
    }
    std::string out;
    to_output >> out;
    std::reverse(out.begin(), out.end());
    lhs << out;
    return lhs;
  }

  explicit operator unsigned long() {
    unsigned long ret = 0;
    for (std::size_t i = 0; i < std::min(size, sizeof(unsigned long)); i++) {
      ret += (static_cast<unsigned long>(this->bytes[i]) << (i * 8));
    }
    return ret;
  }
};

int main(void) {
  for (std::size_t i = 0; i <= 8584148901; i++) {
    unsigned long n = i * i;
    n = i + i;
    n = i - i;
    n = i / i;
  }
}