// Copyright (c) 2015-2016 The Khronos Group Inc.

//

// Licensed under the Apache License, Version 2.0 (the "License");

// you may not use this file except in compliance with the License.

// You may obtain a copy of the License at

//

//     http://www.apache.org/licenses/LICENSE-2.0

//

// Unless required by applicable law or agreed to in writing, software

// distributed under the License is distributed on an "AS IS" BASIS,

// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

// See the License for the specific language governing permissions and

// limitations under the License.

#include "source/spirv_endian.h"

#include <cstring>

enum {

  I32_ENDIAN_LITTLE = 0x03020100ul,

  I32_ENDIAN_BIG = 0x00010203ul,

};

// This constant value allows the detection of the host machine's endianness.

// Accessing it through the "value" member is valid due to C++11 section 3.10

// paragraph 10.

static const union {

  unsigned char bytes[4];

  uint32_t value;

} o32_host_order = {{0, 1, 2, 3}};

#define I32_ENDIAN_HOST (o32_host_order.value)

uint32_t spvFixWord(const uint32_t word, const spv_endianness_t endian) {

  if ((SPV_ENDIANNESS_LITTLE == endian && I32_ENDIAN_HOST == I32_ENDIAN_BIG) ||

      (SPV_ENDIANNESS_BIG == endian && I32_ENDIAN_HOST == I32_ENDIAN_LITTLE)) {

    return (word & 0x000000ff) << 24 | (word & 0x0000ff00) << 8 |

           (word & 0x00ff0000) >> 8 | (word & 0xff000000) >> 24;

  }

  return word;

}

uint64_t spvFixDoubleWord(const uint32_t low, const uint32_t high,

                          const spv_endianness_t endian) {

  return (uint64_t(spvFixWord(high, endian)) << 32) | spvFixWord(low, endian);

}

spv_result_t spvBinaryEndianness(spv_const_binary binary,

                                 spv_endianness_t* pEndian) {

  if (!binary->code || !binary->wordCount) return SPV_ERROR_INVALID_BINARY;

  if (!pEndian) return SPV_ERROR_INVALID_POINTER;

  uint8_t bytes[4];

  memcpy(bytes, binary->code, sizeof(uint32_t));

  if (0x03 == bytes[0] && 0x02 == bytes[1] && 0x23 == bytes[2] &&

      0x07 == bytes[3]) {

    *pEndian = SPV_ENDIANNESS_LITTLE;

    return SPV_SUCCESS;

  }

  if (0x07 == bytes[0] && 0x23 == bytes[1] && 0x02 == bytes[2] &&

      0x03 == bytes[3]) {

    *pEndian = SPV_ENDIANNESS_BIG;

    return SPV_SUCCESS;

  }

  return SPV_ERROR_INVALID_BINARY;

}

bool spvIsHostEndian(spv_endianness_t endian) {

  return ((SPV_ENDIANNESS_LITTLE == endian) &&

          (I32_ENDIAN_LITTLE == I32_ENDIAN_HOST)) ||

         ((SPV_ENDIANNESS_BIG == endian) &&

          (I32_ENDIAN_BIG == I32_ENDIAN_HOST));

}