text: /*
   * Copyright (C) 2005, 2006, 2008 Apple Inc. All rights reserved.
   *
   * This library is free software; you can redistribute it and/or
   * modify it under the terms of the GNU Library General Public
   * License as published by the Free Software Foundation; either
   * version 2 of the License, or (at your option) any later version.
   *
   * This library is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * Library General Public License for more details.
   *
   * You should have received a copy of the GNU Library General Public License
   * along with this library; see the file COPYING.LIB.  If not, write to
   * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
   * Boston, MA 02110-1301, USA.
   *
   */
  
  #ifndef SKY_ENGINE_WTF_HASHFUNCTIONS_H_
  #define SKY_ENGINE_WTF_HASHFUNCTIONS_H_
  
  #include <stdint.h>
  #include "flutter/sky/engine/wtf/OwnPtr.h"
  #include "flutter/sky/engine/wtf/RefPtr.h"
  #include "flutter/sky/engine/wtf/StdLibExtras.h"
  
  namespace WTF {
  
      template<size_t size> struct IntTypes;
      template<> struct IntTypes<1> { typedef int8_t SignedType; typedef uint8_t UnsignedType; };
      template<> struct IntTypes<2> { typedef int16_t SignedType; typedef uint16_t UnsignedType; };
      template<> struct IntTypes<4> { typedef int32_t SignedType; typedef uint32_t UnsignedType; };
      template<> struct IntTypes<8> { typedef int64_t SignedType; typedef uint64_t UnsignedType; };
  
      // integer hash function
  
      // Thomas Wang's 32 Bit Mix Function: http://www.cris.com/~Ttwang/tech/inthash.htm
      inline unsigned intHash(uint8_t key8)
      {
          unsigned key = key8;
          key += ~(key << 15);
          key ^= (key >> 10);
          key += (key << 3);
          key ^= (key >> 6);
          key += ~(key << 11);
          key ^= (key >> 16);
          return key;
      }
  
      // Thomas Wang's 32 Bit Mix Function: http://www.cris.com/~Ttwang/tech/inthash.htm
      inline unsigned intHash(uint16_t key16)
      {
          unsigned key = key16;
          key += ~(key << 15);
          key ^= (key >> 10);
          key += (key << 3);
          key ^= (key >> 6);
          key += ~(key << 11);
          key ^= (key >> 16);
          return key;
      }
  
      // Thomas Wang's 32 Bit Mix Function: http://www.cris.com/~Ttwang/tech/inthash.htm
      inline unsigned intHash(uint32_t key)
      {
          key += ~(key << 15);
          key ^= (key >> 10);
          key += (key << 3);
          key ^= (key >> 6);
          key += ~(key << 11);
          key ^= (key >> 16);
          return key;
      }
  
      // Thomas Wang's 64 bit Mix Function: http://www.cris.com/~Ttwang/tech/inthash.htm
      inline unsigned intHash(uint64_t key)
      {
          key += ~(key << 32);
          key ^= (key >> 22);
          key += ~(key << 13);
          key ^= (key >> 8);
          key += (key << 3);
          key ^= (key >> 15);
          key += ~(key << 27);
          key ^= (key >> 31);
          return static_cast<unsigned>(key);
      }
  
      // Compound integer hash method: http://opendatastructures.org/versions/edition-0.1d/ods-java/node33.html#SECTION00832000000000000000
      inline unsigned pairIntHash(unsigned key1, unsigned key2)
      {
          unsigned shortRandom1 = 277951225; // A random 32-bit value.
          unsigned shortRandom2 = 95187966; // A random 32-bit value.
          uint64_t longRandom = 19248658165952622LL; // A random 64-bit value.
  
          uint64_t product = longRandom * (shortRandom1 * key1 + shortRandom2 * key2);
          unsigned highBits = static_cast<unsigned>(product >> (sizeof(uint64_t) - sizeof(unsigned)));
          return highBits;
      }
  
      template<typename T> struct IntHash {
          static unsigned hash(T key) { return intHash(static_cast<typename IntTypes<sizeof(T)>::UnsignedType>(key)); }
          static bool equal(T a, T b) { return a == b; }
          static const bool safeToCompareToEmptyOrDeleted = true;
      };
  
      template<typename T> struct FloatHash {
          typedef typename IntTypes<sizeof(T)>::UnsignedType Bits;
          static unsigned hash(T key)
          {
              return intHash(bitwise_cast<Bits>(key));
          }
          static bool equal(T a, T b)
          {
              return bitwise_cast<Bits>(a) == bitwise_cast<Bits>(b);
          }
          static const bool safeToCompareToEmptyOrDeleted = true;
      };
  
      // pointer identity hash function
  
      template<typename T> struct PtrHash {
          static unsigned hash(T key)
          {
              return IntHash<uintptr_t>::hash(reinterpret_cast<uintptr_t>(key));
          }
          static bool equal(T a, T b) { return a == b; }
          static bool equal(std::nullptr_t, T b) { return b == 0; }
          static bool equal(T a, std::nullptr_t) { return a == 0; }
          static const bool safeToCompareToEmptyOrDeleted = true;
      };
      template<typename P> struct PtrHash<RefPtr<P> > : PtrHash<P*> {
          using PtrHash<P*>::hash;
          static unsigned hash(const RefPtr<P>& key) { return hash(key.get()); }
          static unsigned hash(const PassRefPtr<P>& key) { return hash(key.get()); }
          using PtrHash<P*>::equal;
          static bool equal(const RefPtr<P>& a, const RefPtr<P>& b) { return a == b; }
          static bool equal(P* a, const RefPtr<P>& b) { return a == b; }
          static bool equal(const RefPtr<P>& a, P* b) { return a == b; }
          static bool equal(const RefPtr<P>& a, const PassRefPtr<P>& b) { return a == b; }
      };
      template<typename P> struct PtrHash<RawPtr<P> > : PtrHash<P*> {
          using PtrHash<P*>::hash;
          static unsigned hash(const RawPtr<P>& key) { return hash(key.get()); }
          using PtrHash<P*>::equal;
          static bool equal(const RawPtr<P>& a, const RawPtr<P>& b) { return a == b; }
          static bool equal(P* a, const RawPtr<P>& b) { return a == b; }
          static bool equal(const RawPtr<P>& a, P* b) { return a == b; }
      };
      template<typename P> struct PtrHash<OwnPtr<P> > : PtrHash<P*> {
          using PtrHash<P*>::hash;
          static unsigned hash(const OwnPtr<P>& key) { return hash(key.get()); }
          static unsigned hash(const PassOwnPtr<P>& key) { return hash(key.get()); }
  
          static bool equal(const OwnPtr<P>& a, const OwnPtr<P>& b)
          {
              return a.get() == b.get();
          }
          static bool equal(const OwnPtr<P>& a, P* b) { return a == b; }
          static bool equal(const OwnPtr<P>& a, const PassOwnPtr<P>& b)
          {
              return a.get() == b.get();
          }
      };
  
      // default hash function for each type
  
      template<typename T> struct DefaultHash;
  
      template<typename T, typename U> struct PairHash {
          static unsigned hash(const std::pair<T, U>& p)
          {
              return pairIntHash(DefaultHash<T>::Hash::hash(p.first), DefaultHash<U>::Hash::hash(p.second));
          }
          static bool equal(const std::pair<T, U>& a, const std::pair<T, U>& b)
          {
              return DefaultHash<T>::Hash::equal(a.first, b.first) && DefaultHash<U>::Hash::equal(a.second, b.second);
          }
          static const bool safeToCompareToEmptyOrDeleted = DefaultHash<T>::Hash::safeToCompareToEmptyOrDeleted
                                                              && DefaultHash<U>::Hash::safeToCompareToEmptyOrDeleted;
      };
  
      template<typename T, typename U> struct IntPairHash {
          static unsigned hash(const std::pair<T, U>& p) { return pairIntHash(p.first, p.second); }
          static bool equal(const std::pair<T, U>& a, const std::pair<T, U>& b) { return PairHash<T, T>::equal(a, b); }
          static const bool safeToCompareToEmptyOrDeleted = PairHash<T, U>::safeToCompareToEmptyOrDeleted;
      };
  
      // make IntHash the default hash function for many integer types
  
      template<> struct DefaultHash<short> { typedef IntHash<unsigned> Hash; };
      template<> struct DefaultHash<unsigned short> { typedef IntHash<unsigned> Hash; };
      template<> struct DefaultHash<int> { typedef IntHash<unsigned> Hash; };
      template<> struct DefaultHash<unsigned> { typedef IntHash<unsigned> Hash; };
      template<> struct DefaultHash<long> { typedef IntHash<unsigned long> Hash; };
      template<> struct DefaultHash<unsigned long> { typedef IntHash<unsigned long> Hash; };
      template<> struct DefaultHash<long long> { typedef IntHash<unsigned long long> Hash; };
      template<> struct DefaultHash<unsigned long long> { typedef IntHash<unsigned long long> Hash; };
      template<> struct DefaultHash<wchar_t> { typedef IntHash<wchar_t> Hash; };
      template<> struct DefaultHash<float> { typedef FloatHash<float> Hash; };
      template<> struct DefaultHash<double> { typedef FloatHash<double> Hash; };
  
      // make PtrHash the default hash function for pointer types that don't specialize
  
      template<typename P> struct DefaultHash<P*> { typedef PtrHash<P*> Hash; };
      template<typename P> struct DefaultHash<RefPtr<P> > { typedef PtrHash<RefPtr<P> > Hash; };
      template<typename P> struct DefaultHash<RawPtr<P> > { typedef PtrHash<RawPtr<P> > Hash; };
      template<typename P> struct DefaultHash<OwnPtr<P> > { typedef PtrHash<OwnPtr<P> > Hash; };
  
      // make IntPairHash the default hash function for pairs of (at most) 32-bit integers.
  
      template<> struct DefaultHash<std::pair<short, short> > { typedef IntPairHash<short, short> Hash; };
      template<> struct DefaultHash<std::pair<short, unsigned short> > { typedef IntPairHash<short, unsigned short> Hash; };
      template<> struct DefaultHash<std::pair<short, int> > { typedef IntPairHash<short, int> Hash; };
      template<> struct DefaultHash<std::pair<short, unsigned> > { typedef IntPairHash<short, unsigned> Hash; };
      template<> struct DefaultHash<std::pair<unsigned short, short> > { typedef IntPairHash<unsigned short, short> Hash; };
      template<> struct DefaultHash<std::pair<unsigned short, unsigned short> > { typedef IntPairHash<unsigned short, unsigned short> Hash; };
      template<> struct DefaultHash<std::pair<unsigned short, int> > { typedef IntPairHash<unsigned short, int> Hash; };
      template<> struct DefaultHash<std::pair<unsigned short, unsigned> > { typedef IntPairHash<unsigned short, unsigned> Hash; };
      template<> struct DefaultHash<std::pair<int, short> > { typedef IntPairHash<int, short> Hash; };
      template<> struct DefaultHash<std::pair<int, unsigned short> > { typedef IntPairHash<int, unsigned short> Hash; };
      template<> struct DefaultHash<std::pair<int, int> > { typedef IntPairHash<int, int> Hash; };
      template<> struct DefaultHash<std::pair<int, unsigned> > { typedef IntPairHash<unsigned, unsigned> Hash; };
      template<> struct DefaultHash<std::pair<unsigned, short> > { typedef IntPairHash<unsigned, short> Hash; };
      template<> struct DefaultHash<std::pair<unsigned, unsigned short> > { typedef IntPairHash<unsigned, unsigned short> Hash; };
      template<> struct DefaultHash<std::pair<unsigned, int> > { typedef IntPairHash<unsigned, int> Hash; };
      template<> struct DefaultHash<std::pair<unsigned, unsigned> > { typedef IntPairHash<unsigned, unsigned> Hash; };
  
      // make PairHash the default hash function for pairs of arbitrary values.
  
      template<typename T, typename U> struct DefaultHash<std::pair<T, U> > { typedef PairHash<T, U> Hash; };
  
  } // namespace WTF
  
  using WTF::DefaultHash;
  using WTF::IntHash;
  using WTF::PtrHash;
  
  #endif  // SKY_ENGINE_WTF_HASHFUNCTIONS_H_
  