wtf/StdLibExtras.h

   1 /*
   2  * Copyright (C) 2008 Apple Inc. All Rights Reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  * 1. Redistributions of source code must retain the above copyright
   8  *    notice, this list of conditions and the following disclaimer.
   9  * 2. Redistributions in binary form must reproduce the above copyright
  10  *    notice, this list of conditions and the following disclaimer in the
  11  *    documentation and/or other materials provided with the distribution.
  12  *
  13  * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
  14  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  15  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  16  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
  17  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  18  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  19  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  20  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  21  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  23  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  24  */
  25
  26 #ifndef WTF_StdLibExtras_h
  27 #define WTF_StdLibExtras_h
  28
  29 #include <wtf/Assertions.h>
  30
  31 // Use these to declare and define a static local variable (static T;) so that
  32 //  it is leaked so that its destructors are not called at exit. Using this
  33 //  macro also allows workarounds a compiler bug present in Apple's version of GCC 4.0.1.
  34 #ifndef DEFINE_STATIC_LOCAL
  35 #if COMPILER(GCC) && defined(__APPLE_CC__) && __GNUC__ == 4 && __GNUC_MINOR__ == 0 && __GNUC_PATCHLEVEL__ == 1
  36 #define DEFINE_STATIC_LOCAL(type, name, arguments) \
  37     static type* name##Ptr = new type arguments; \
  38     type& name = *name##Ptr
  39 #else
  40 #define DEFINE_STATIC_LOCAL(type, name, arguments) \
  41     static type& name = *new type arguments
  42 #endif
  43 #endif
  44
  45 // OBJECT_OFFSETOF: Like the C++ offsetof macro, but you can use it with classes.
  46 // The magic number 0x4000 is insignificant. We use it to avoid using NULL, since
  47 // NULL can cause compiler problems, especially in cases of multiple inheritance.
  48 #define OBJECT_OFFSETOF(class, field) (reinterpret_cast<ptrdiff_t>(&(reinterpret_cast<class*>(0x4000)->field)) - 0x4000)
  49
  50 // STRINGIZE: Can convert any value to quoted string, even expandable macros
  51 #define STRINGIZE(exp) #exp
  52 #define STRINGIZE_VALUE_OF(exp) STRINGIZE(exp)
  53
  54 namespace WTF {
  55
  56     /*
  57      * C++'s idea of a reinterpret_cast lacks sufficient cojones.
  58      */
  59     template<typename TO, typename FROM>
  60     TO bitwise_cast(FROM from)
  61     {
  62         COMPILE_ASSERT(sizeof(TO) == sizeof(FROM), WTF_bitwise_cast_sizeof_casted_types_is_equal);
  63         union {
  64             FROM from;
  65             TO to;
  66         } u;
  67         u.from = from;
  68         return u.to;
  69     }
  70
  71     // Returns a count of the number of bits set in 'bits'.
  72     inline size_t bitCount(unsigned bits)
  73     {
  74         bits = bits - ((bits >> 1) & 0x55555555);
  75         bits = (bits & 0x33333333) + ((bits >> 2) & 0x33333333);
  76         return (((bits + (bits >> 4)) & 0xF0F0F0F) * 0x1010101) >> 24;
  77     }
  78
  79 } // namespace WTF
  80
  81 #endif