bsnes-libretro/nall/serializer.hpp

#ifndef NALL_SERIALIZER_HPP
#define NALL_SERIALIZER_HPP

//serializer: a class designed to save and restore the state of classes.
//
//benefits:
//- data() will be portable in size (it is not necessary to specify type sizes.)
//- data() will be portable in endianness (always stored internally as little-endian.)
//- one serialize function can both save and restore class states.
//
//caveats:
//- only plain-old-data can be stored. complex classes must provide serialize(serializer&);
//- floating-point usage is not portable across different implementations

#include <type_traits>
#include <utility>
#include <nall/stdint.hpp>
#include <nall/utility.hpp>

namespace nall {

struct serializer;

template<typename T>
struct has_serialize {
  template<typename C> static auto test(decltype(std::declval<C>().serialize(std::declval<serializer&>()))*) -> char;
  template<typename C> static auto test(...) -> long;
  static const bool value = sizeof(test<T>(0)) == sizeof(char);
};

struct serializer {
  enum mode_t { Load, Save, Size };

  auto mode() const -> mode_t {
    return _mode;
  }

  auto data() const -> const uint8_t* {
    return _data;
  }

  auto size() const -> unsigned {
    return _size;
  }

  auto capacity() const -> unsigned {
    return _capacity;
  }

  template<typename T> auto floatingpoint(T& value) -> serializer& {
    enum { size = sizeof(T) };
    //this is rather dangerous, and not cross-platform safe;
    //but there is no standardized way to export FP-values
    uint8_t* p = (uint8_t*)&value;
    if(_mode == Save) {
      for(unsigned n = 0; n < size; n++) _data[_size++] = p[n];
    } else if(_mode == Load) {
      for(unsigned n = 0; n < size; n++) p[n] = _data[_size++];
    } else {
      _size += size;
    }
    return *this;
  }

  template<typename T> auto integer(T& value) -> serializer& {
    enum { size = std::is_same<bool, T>::value ? 1 : sizeof(T) };
    if(_mode == Save) {
      for(unsigned n = 0; n < size; n++) _data[_size++] = (uintmax_t)value >> (n << 3);
    } else if(_mode == Load) {
      value = 0;
      for(unsigned n = 0; n < size; n++) value |= (uintmax_t)_data[_size++] << (n << 3);
    } else if(_mode == Size) {
      _size += size;
    }
    return *this;
  }

  template<typename T, int N> auto array(T (&array)[N]) -> serializer& {
    for(unsigned n = 0; n < N; n++) operator()(array[n]);
    return *this;
  }

  template<typename T> auto array(T array, unsigned size) -> serializer& {
    for(unsigned n = 0; n < size; n++) operator()(array[n]);
    return *this;
  }

  template<typename T> auto operator()(T& value, typename std::enable_if<has_serialize<T>::value>::type* = 0) -> serializer& { value.serialize(*this); return *this; }
  template<typename T> auto operator()(T& value, typename std::enable_if<std::is_integral<T>::value>::type* = 0) -> serializer& { return integer(value); }
  template<typename T> auto operator()(T& value, typename std::enable_if<std::is_floating_point<T>::value>::type* = 0) -> serializer& { return floatingpoint(value); }
  template<typename T> auto operator()(T& value, typename std::enable_if<std::is_array<T>::value>::type* = 0) -> serializer& { return array(value); }
  template<typename T> auto operator()(T& value, unsigned size, typename std::enable_if<std::is_pointer<T>::value>::type* = 0) -> serializer& { return array(value, size); }

  auto operator=(const serializer& s) -> serializer& {
    if(_data) delete[] _data;

    _mode = s._mode;
    _data = new uint8_t[s._capacity];
    _size = s._size;
    _capacity = s._capacity;

    memcpy(_data, s._data, s._capacity);
    return *this;
  }

  auto operator=(serializer&& s) -> serializer& {
    if(_data) delete[] _data;

    _mode = s._mode;
    _data = s._data;
    _size = s._size;
    _capacity = s._capacity;

    s._data = nullptr;
    return *this;
  }

  serializer() = default;
  serializer(const serializer& s) { operator=(s); }
  serializer(serializer&& s) { operator=(move(s)); }

  serializer(unsigned capacity) {
    _mode = Save;
    _data = new uint8_t[capacity]();
    _size = 0;
    _capacity = capacity;
  }

  serializer(const uint8_t* data, unsigned capacity) {
    _mode = Load;
    _data = new uint8_t[capacity];
    _size = 0;
    _capacity = capacity;
    memcpy(_data, data, capacity);
  }

  ~serializer() {
    if(_data) delete[] _data;
  }

private:
  mode_t _mode = Size;
  uint8_t* _data = nullptr;
  unsigned _size = 0;
  unsigned _capacity = 0;
};

};

#endif