StdLibExtras.h   [plain text]

/*
 * Copyright (C) 2008 Apple Inc. All Rights Reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
 */

#ifndef WTF_StdLibExtras_h
#define WTF_StdLibExtras_h

#include <wtf/Assertions.h>

// Use these to declare and define a static local variable (static T;) so that
//  it is leaked so that its destructors are not called at exit. Using this
//  macro also allows workarounds a compiler bug present in Apple's version of GCC 4.0.1.
#ifndef DEFINE_STATIC_LOCAL
#if COMPILER(GCC) && defined(__APPLE_CC__) && __GNUC__ == 4 && __GNUC_MINOR__ == 0 && __GNUC_PATCHLEVEL__ == 1
#define DEFINE_STATIC_LOCAL(type, name, arguments) \
    static type* name##Ptr = new type arguments; \
    type& name = *name##Ptr
#else
#define DEFINE_STATIC_LOCAL(type, name, arguments) \
    static type& name = *new type arguments
#endif
#endif

// OBJECT_OFFSETOF: Like the C++ offsetof macro, but you can use it with classes.
// The magic number 0x4000 is insignificant. We use it to avoid using NULL, since
// NULL can cause compiler problems, especially in cases of multiple inheritance.
#define OBJECT_OFFSETOF(class, field) (reinterpret_cast<ptrdiff_t>(&(reinterpret_cast<class*>(0x4000)->field)) - 0x4000)

// STRINGIZE: Can convert any value to quoted string, even expandable macros
#define STRINGIZE(exp) #exp
#define STRINGIZE_VALUE_OF(exp) STRINGIZE(exp)

namespace WTF {

    /*
     * C++'s idea of a reinterpret_cast lacks sufficient cojones.
     */
    template<typename TO, typename FROM>
    TO bitwise_cast(FROM from)
    {
        COMPILE_ASSERT(sizeof(TO) == sizeof(FROM), WTF_bitwise_cast_sizeof_casted_types_is_equal);
        union {
            FROM from;
            TO to;
        } u;
        u.from = from;
        return u.to;
    }

    // Returns a count of the number of bits set in 'bits'.
    inline size_t bitCount(unsigned bits)
    {
        bits = bits - ((bits >> 1) & 0x55555555);
        bits = (bits & 0x33333333) + ((bits >> 2) & 0x33333333);
        return (((bits + (bits >> 4)) & 0xF0F0F0F) * 0x1010101) >> 24;
    }

} // namespace WTF

#endif