include/o3tl/hash_combine.hxx

   1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
   2 /*
   3  * This file is part of the LibreOffice project.
   4  *
   5  * This Source Code Form is subject to the terms of the Mozilla Public
   6  * License, v. 2.0. If a copy of the MPL was not distributed with this
   7  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
   8  */
   9
  10 #pragma once
  11
  12 namespace o3tl
  13 {
  14 template <typename T, typename N>
  15 inline std::enable_if_t<(sizeof(N) == 4)> hash_combine(N& nSeed, T const* pValue, size_t nCount)
  16 {
  17     static_assert(sizeof(nSeed) == 4);
  18     for (size_t i = 0; i < nCount; ++i)
  19     {
  20         nSeed ^= std::hash<T>{}(*pValue) + 0x9E3779B9u + (nSeed << 6) + (nSeed >> 2);
  21         ++pValue;
  22     }
  23 }
  24
  25 template <typename T, typename N>
  26 inline std::enable_if_t<(sizeof(N) == 4)> hash_combine(N& nSeed, T const& nValue)
  27 {
  28     static_assert(sizeof(nSeed) == 4);
  29     nSeed ^= std::hash<T>{}(nValue) + 0x9E3779B9u + (nSeed << 6) + (nSeed >> 2);
  30 }
  31
  32 template <typename T, typename N>
  33 inline std::enable_if_t<(sizeof(N) == 8)> hash_combine(N& nSeed, T const* pValue, size_t nCount)
  34 {
  35     static_assert(sizeof(nSeed) == 8);
  36     for (size_t i = 0; i < nCount; ++i)
  37     {
  38         nSeed ^= std::hash<T>{}(*pValue) + 0x9E3779B97F4A7C15llu + (nSeed << 12) + (nSeed >> 4);
  39         ++pValue;
  40     }
  41 }
  42
  43 template <typename T, typename N>
  44 inline std::enable_if_t<(sizeof(N) == 8)> hash_combine(N& nSeed, T const& nValue)
  45 {
  46     static_assert(sizeof(nSeed) == 8);
  47     nSeed ^= std::hash<T>{}(nValue) + 0x9E3779B97F4A7C15llu + (nSeed << 12) + (nSeed >> 4);
  48 }
  49 }
  50
  51 /* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */