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