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 "OwnPtr.h"
  25 #include "RefPtr.h"
  26 #include "TypeTraits.h"
  27 #include <utility>
  28 #include <memory>
  29
  30 using std::pair;
  31
  32 namespace WTF {
  33
  34     template<bool isPod, typename T>
  35     struct VectorTraitsBase;
  36
  37     template<typename T>
  38     struct VectorTraitsBase<false, T>
  39     {
  40         static const bool needsDestruction = true;
  41         static const bool needsInitialization = true;
  42         static const bool canInitializeWithMemset = false;
  43         static const bool canMoveWithMemcpy = false;
  44         static const bool canCopyWithMemcpy = false;
  45         static const bool canFillWithMemset = false;
  46         static const bool canCompareWithMemcmp = false;
  47     };
  48
  49     template<typename T>
  50     struct VectorTraitsBase<true, T>
  51     {
  52         static const bool needsDestruction = false;
  53         static const bool needsInitialization = false;
  54         static const bool canInitializeWithMemset = false;
  55         static const bool canMoveWithMemcpy = true;
  56         static const bool canCopyWithMemcpy = true;
  57         static const bool canFillWithMemset = sizeof(T) == sizeof(char);
  58         static const bool canCompareWithMemcmp = true;
  59     };
  60
  61     template<typename T>
  62     struct VectorTraits : VectorTraitsBase<IsPod<T>::value, T> { };
  63
  64     struct SimpleClassVectorTraits : VectorTraitsBase<false, void>
  65     {
  66         static const bool canInitializeWithMemset = true;
  67         static const bool canMoveWithMemcpy = true;
  68         static const bool canCompareWithMemcmp = true;
  69     };
  70
  71     // we know OwnPtr and RefPtr are simple enough that initializing to 0 and moving with memcpy
  72     // (and then not destructing the original) will totally work
  73     template<typename P>
  74     struct VectorTraits<RefPtr<P> > : SimpleClassVectorTraits { };
  75
  76     template<typename P>
  77     struct VectorTraits<OwnPtr<P> > : SimpleClassVectorTraits { };
  78
  79     template<typename First, typename Second>
  80     struct VectorTraits<pair<First, Second> >
  81     {
  82         typedef VectorTraits<First> FirstTraits;
  83         typedef VectorTraits<Second> SecondTraits;
  84
  85         static const bool needsDestruction = FirstTraits::needsDestruction || SecondTraits::needsDestruction;
  86         static const bool needsInitialization = FirstTraits::needsInitialization || SecondTraits::needsInitialization;
  87         static const bool canInitializeWithMemset = FirstTraits::canInitializeWithMemset && SecondTraits::canInitializeWithMemset;
  88         static const bool canMoveWithMemcpy = FirstTraits::canMoveWithMemcpy && SecondTraits::canMoveWithMemcpy;
  89         static const bool canCopyWithMemcpy = FirstTraits::canCopyWithMemcpy && SecondTraits::canCopyWithMemcpy;
  90         static const bool canFillWithMemset = false;
  91         static const bool canCompareWithMemcmp = FirstTraits::canCompareWithMemcmp && SecondTraits::canCompareWithMemcmp;
  92     };
  93
  94 } // namespace WTF
  95
  96 using WTF::VectorTraits;
  97 using WTF::SimpleClassVectorTraits;
  98
  99 #endif // WTF_VectorTraits_h