wtf/VectorTraits.h

   1 /*
   2  * Copyright (C) 2006, 2007, 2008 Apple Inc. All rights reserved.
   3  *
   4  * This library is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU Library General Public
   6  * License as published by the Free Software Foundation; either
   7  * version 2 of the License, or (at your option) any later version.
   8  *
   9  * This library is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * Library General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU Library General Public License
  15  * along with this library; see the file COPYING.LIB.  If not, write to
  16  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  17  * Boston, MA 02110-1301, USA.
  18  *
  19  */
  20
  21 #ifndef WTF_VectorTraits_h
  22 #define WTF_VectorTraits_h
  23
  24 #include "RefPtr.h"
  25 #include <utility>
  26 #include <memory>
  27
  28 using std::pair;
  29
  30 namespace WTF {
  31
  32     template <typename T> struct IsPod           { static const bool value = false; };
  33     template <> struct IsPod<bool>               { static const bool value = true; };
  34     template <> struct IsPod<char>               { static const bool value = true; };
  35     template <> struct IsPod<signed char>        { static const bool value = true; };
  36     template <> struct IsPod<unsigned char>      { static const bool value = true; };
  37     template <> struct IsPod<short>              { static const bool value = true; };
  38     template <> struct IsPod<unsigned short>     { static const bool value = true; };
  39     template <> struct IsPod<int>                { static const bool value = true; };
  40     template <> struct IsPod<unsigned int>       { static const bool value = true; };
  41     template <> struct IsPod<long>               { static const bool value = true; };
  42     template <> struct IsPod<unsigned long>      { static const bool value = true; };
  43     template <> struct IsPod<long long>          { static const bool value = true; };
  44     template <> struct IsPod<unsigned long long> { static const bool value = true; };
  45     template <> struct IsPod<float>              { static const bool value = true; };
  46     template <> struct IsPod<double>             { static const bool value = true; };
  47     template <> struct IsPod<long double>        { static const bool value = true; };
  48     template <typename P> struct IsPod<P *>      { static const bool value = true; };
  49
  50     template<bool isPod, typename T>
  51     class VectorTraitsBase;
  52
  53     template<typename T>
  54     struct VectorTraitsBase<false, T>
  55     {
  56         static const bool needsDestruction = true;
  57         static const bool needsInitialization = true;
  58         static const bool canInitializeWithMemset = false;
  59         static const bool canMoveWithMemcpy = false;
  60         static const bool canCopyWithMemcpy = false;
  61         static const bool canFillWithMemset = false;
  62         static const bool canCompareWithMemcmp = false;
  63     };
  64
  65     template<typename T>
  66     struct VectorTraitsBase<true, T>
  67     {
  68         static const bool needsDestruction = false;
  69         static const bool needsInitialization = false;
  70         static const bool canInitializeWithMemset = false;
  71         static const bool canMoveWithMemcpy = true;
  72         static const bool canCopyWithMemcpy = true;
  73         static const bool canFillWithMemset = sizeof(T) == sizeof(char);
  74         static const bool canCompareWithMemcmp = true;
  75     };
  76
  77     template<typename T>
  78     struct VectorTraits : VectorTraitsBase<IsPod<T>::value, T> { };
  79
  80     struct SimpleClassVectorTraits
  81     {
  82         static const bool needsDestruction = true;
  83         static const bool needsInitialization = true;
  84         static const bool canInitializeWithMemset = true;
  85         static const bool canMoveWithMemcpy = true;
  86         static const bool canCopyWithMemcpy = false;
  87         static const bool canFillWithMemset = false;
  88         static const bool canCompareWithMemcmp = true;
  89     };
  90
  91     // we know RefPtr is simple enough that initializing to 0 and moving with memcpy
  92     // (and then not destructing the original) will totally work
  93     template<typename P>
  94     struct VectorTraits<RefPtr<P> > : SimpleClassVectorTraits { };
  95
  96     template<typename P>
  97     struct VectorTraits<std::auto_ptr<P> > : SimpleClassVectorTraits { };
  98
  99     template<typename First, typename Second>
 100     struct VectorTraits<pair<First, Second> >
 101     {
 102         typedef VectorTraits<First> FirstTraits;
 103         typedef VectorTraits<Second> SecondTraits;
 104
 105         static const bool needsDestruction = FirstTraits::needsDestruction || SecondTraits::needsDestruction;
 106         static const bool needsInitialization = FirstTraits::needsInitialization || SecondTraits::needsInitialization;
 107         static const bool canInitializeWithMemset = FirstTraits::canInitializeWithMemset && SecondTraits::canInitializeWithMemset;
 108         static const bool canMoveWithMemcpy = FirstTraits::canMoveWithMemcpy && SecondTraits::canMoveWithMemcpy;
 109         static const bool canCopyWithMemcpy = FirstTraits::canCopyWithMemcpy && SecondTraits::canCopyWithMemcpy;
 110         static const bool canFillWithMemset = false;
 111         static const bool canCompareWithMemcmp = FirstTraits::canCompareWithMemcmp && SecondTraits::canCompareWithMemcmp;
 112     };
 113
 114 } // namespace WTF
 115
 116 using WTF::VectorTraits;
 117 using WTF::SimpleClassVectorTraits;
 118
 119 #endif // WTF_VectorTraits_h