/* Copyright 2013 Google Inc. All Rights Reserved.

   Distributed under MIT license.

   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT

*/

/* Helpers common across multiple parts of woff2 */

#include <algorithm>

#include "./woff2_common.h"

#include "./port.h"

namespace woff2 {

uint32_t ComputeULongSum(const uint8_t* buf, size_t size) {

  uint32_t checksum = 0;

  size_t aligned_size = size & ~3;

  for (size_t i = 0; i < aligned_size; i += 4) {

#if defined(WOFF_LITTLE_ENDIAN)

    uint32_t v = *reinterpret_cast<const uint32_t*>(buf + i);

    checksum += (((v & 0xFF) << 24) | ((v & 0xFF00) << 8) |

      ((v & 0xFF0000) >> 8) | ((v & 0xFF000000) >> 24));

#elif defined(WOFF_BIG_ENDIAN)

    checksum += *reinterpret_cast<const uint32_t*>(buf + i);

#else

    checksum += (buf[i] << 24) | (buf[i + 1] << 16) |

      (buf[i + 2] << 8) | buf[i + 3];

#endif

  }

  // treat size not aligned on 4 as if it were padded to 4 with 0's

  if (size != aligned_size) {

    uint32_t v = 0;

    for (size_t i = aligned_size; i < size; ++i) {

      v |= buf[i] << (24 - 8 * (i & 3));

    }

    checksum += v;

  }

  return checksum;

}

size_t CollectionHeaderSize(uint32_t header_version, uint32_t num_fonts) {

  size_t size = 0;

  if (header_version == 0x00020000) {

    size += 12;  // ulDsig{Tag,Length,Offset}

  }

  if (header_version == 0x00010000 || header_version == 0x00020000) {

    size += 12   // TTCTag, Version, numFonts

      + 4 * num_fonts;  // OffsetTable[numFonts]

  }

  return size;

}

} // namespace woff2