//----------------------------------------------------------------------------//
//                                                                            //
// ozz-animation is hosted at http://github.com/guillaumeblanc/ozz-animation  //
// and distributed under the MIT License (MIT).                               //
//                                                                            //
// Copyright (c) Guillaume Blanc                                              //
//                                                                            //
// Permission is hereby granted, free of charge, to any person obtaining a    //
// copy of this software and associated documentation files (the "Software"), //
// to deal in the Software without restriction, including without limitation  //
// the rights to use, copy, modify, merge, publish, distribute, sublicense,   //
// and/or sell copies of the Software, and to permit persons to whom the      //
// Software is furnished to do so, subject to the following conditions:       //
//                                                                            //
// The above copyright notice and this permission notice shall be included in //
// all copies or substantial portions of the Software.                        //
//                                                                            //
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR //
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,   //
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL    //
// THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER //
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING    //
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER        //
// DEALINGS IN THE SOFTWARE.                                                  //
//                                                                            //
//----------------------------------------------------------------------------//

#ifndef OZZ_OZZ_BASE_ENDIANNESS_H_
#define OZZ_OZZ_BASE_ENDIANNESS_H_

// Declares endianness modes and functions to swap data from a mode to another.

#include <cstddef>

#include "platform.h"

namespace ozz {

// Declares supported endianness.
enum Endianness {
  kBigEndian,
  kLittleEndian,
};

// Get the native endianness of the targeted processor.
// This function does not rely on a pre-processor definition as no standard
// definition exists. It is rather implemented as a portable runtime function.
inline Endianness GetNativeEndianness() {
  const union {
    uint16_t s;
    uint8_t c[2];
  } u = {1};  // Initializes u.s -> then read u.c.
  return Endianness(u.c[0]);
}

// Declare the endian swapper struct that is aimed to be specialized (template
// meaning) for every type sizes.
// The swapper provides two functions:
// - void Swap(_Ty* _ty, size_t _count) swaps the array _ty of _count
// elements in-place.
// - _Ty Swap(_Ty _ty) returns a swapped copy of _ty.
// It can be used directly if _Ty is known or through EndianSwap function.
// The default value of template attribute _size enables automatic
// specialization selection.
template <typename _Ty, size_t _size = sizeof(_Ty)>
struct EndianSwapper;

// Internal macro used to swap two bytes.
#define OZZ_BYTE_SWAP(_a, _b) \
  do {                        \
    const char temp = _a;     \
    _a = _b;                  \
    _b = temp;                \
  } while (0)

// EndianSwapper specialization for 1 byte types.
template <typename _Ty>
struct EndianSwapper<_Ty, 1> {
  OZZ_INLINE static void Swap(_Ty* _ty, size_t _count) {
    (void)_ty;
    (void)_count;
  }
  OZZ_INLINE static _Ty Swap(_Ty _ty) { return _ty; }
};

// EndianSwapper specialization for 2 bytes types.
template <typename _Ty>
struct EndianSwapper<_Ty, 2> {
  OZZ_INLINE static void Swap(_Ty* _ty, size_t _count) {
    char* alias = reinterpret_cast<char*>(_ty);
    for (size_t i = 0; i < _count * 2; i += 2) {
      OZZ_BYTE_SWAP(alias[i + 0], alias[i + 1]);
    }
  }
  OZZ_INLINE static _Ty Swap(_Ty _ty) {  // Pass by copy to swap _ty in-place.
    char* alias = reinterpret_cast<char*>(&_ty);
    OZZ_BYTE_SWAP(alias[0], alias[1]);
    return _ty;
  }
};

// EndianSwapper specialization for 4 bytes types.
template <typename _Ty>
struct EndianSwapper<_Ty, 4> {
  OZZ_INLINE static void Swap(_Ty* _ty, size_t _count) {
    char* alias = reinterpret_cast<char*>(_ty);
    for (size_t i = 0; i < _count * 4; i += 4) {
      OZZ_BYTE_SWAP(alias[i + 0], alias[i + 3]);
      OZZ_BYTE_SWAP(alias[i + 1], alias[i + 2]);
    }
  }
  OZZ_INLINE static _Ty Swap(_Ty _ty) {  // Pass by copy to swap _ty in-place.
    char* alias = reinterpret_cast<char*>(&_ty);
    OZZ_BYTE_SWAP(alias[0], alias[3]);
    OZZ_BYTE_SWAP(alias[1], alias[2]);
    return _ty;
  }
};

// EndianSwapper specialization for 8 bytes types.
template <typename _Ty>
struct EndianSwapper<_Ty, 8> {
  OZZ_INLINE static void Swap(_Ty* _ty, size_t _count) {
    char* alias = reinterpret_cast<char*>(_ty);
    for (size_t i = 0; i < _count * 8; i += 8) {
      OZZ_BYTE_SWAP(alias[i + 0], alias[i + 7]);
      OZZ_BYTE_SWAP(alias[i + 1], alias[i + 6]);
      OZZ_BYTE_SWAP(alias[i + 2], alias[i + 5]);
      OZZ_BYTE_SWAP(alias[i + 3], alias[i + 4]);
    }
  }
  OZZ_INLINE static _Ty Swap(_Ty _ty) {  // Pass by copy to swap _ty in-place.
    char* alias = reinterpret_cast<char*>(&_ty);
    OZZ_BYTE_SWAP(alias[0], alias[7]);
    OZZ_BYTE_SWAP(alias[1], alias[6]);
    OZZ_BYTE_SWAP(alias[2], alias[5]);
    OZZ_BYTE_SWAP(alias[3], alias[4]);
    return _ty;
  }
};

// OZZ_BYTE_SWAP is not useful anymore.
#undef OZZ_BYTE_SWAP

// Helper function that swaps _count elements of the array _ty in place.
template <typename _Ty>
OZZ_INLINE void EndianSwap(_Ty* _ty, size_t _count) {
  EndianSwapper<_Ty>::Swap(_ty, _count);
}

// Helper function that swaps _ty in place.
template <typename _Ty>
OZZ_INLINE _Ty EndianSwap(_Ty _ty) {
  return EndianSwapper<_Ty>::Swap(_ty);
}
}  // namespace ozz
#endif  // OZZ_OZZ_BASE_ENDIANNESS_H_
