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/*
* 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)
/*
* The reinterpret_cast<Type1*>([pointer to Type2]) expressions - where
* sizeof(Type1) > sizeof(Type2) - cause the following warning on ARM with GCC:
* increases required alignment of target type.
*
* An implicit or an extra static_cast<void*> bypasses the warning.
* For more info see the following bugzilla entries:
* - https://bugs.webkit.org/show_bug.cgi?id=38045
* - http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43976
*/
#if (CPU(ARM) || CPU(MIPS)) && COMPILER(GCC)
template<typename Type>
bool isPointerTypeAlignmentOkay(Type* ptr)
{
return !(reinterpret_cast<intptr_t>(ptr) % __alignof__(Type));
}
template<typename TypePtr>
TypePtr reinterpret_cast_ptr(void* ptr)
{
ASSERT(isPointerTypeAlignmentOkay(reinterpret_cast<TypePtr>(ptr)));
return reinterpret_cast<TypePtr>(ptr);
}
template<typename TypePtr>
TypePtr reinterpret_cast_ptr(const void* ptr)
{
ASSERT(isPointerTypeAlignmentOkay(reinterpret_cast<TypePtr>(ptr)));
return reinterpret_cast<TypePtr>(ptr);
}
#else
#define reinterpret_cast_ptr reinterpret_cast
#endif
namespace WTF {
/*
* C++'s idea of a reinterpret_cast lacks sufficient cojones.
*/
template<typename TO, typename FROM>
inline 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;
}
// Macro that returns a compile time constant with the length of an array, but gives an error if passed a non-array.
template<typename T, size_t Size> char (&ArrayLengthHelperFunction(T (&)[Size]))[Size];
#define WTF_ARRAY_LENGTH(array) sizeof(::WTF::ArrayLengthHelperFunction(array))
// Efficient implementation that takes advantage of powers of two.
template<size_t divisor> inline size_t roundUpToMultipleOf(size_t x)
{
COMPILE_ASSERT(divisor && !(divisor & (divisor - 1)), divisor_is_a_power_of_two);
size_t remainderMask = divisor - 1;
return (x + remainderMask) & ~remainderMask;
}
// Binary search algorithm, calls extractKey on pre-sorted elements in array,
// compares result with key (KeyTypes should be comparable with '--', '<', '>').
// Optimized for cases where the array contains the key, checked by assertions.
template<typename ArrayType, typename KeyType, KeyType(*extractKey)(ArrayType*)>
inline ArrayType* binarySearch(ArrayType* array, size_t size, KeyType key)
{
// The array must contain at least one element (pre-condition, array does conatin key).
// If the array only contains one element, no need to do the comparison.
while (size > 1) {
// Pick an element to check, half way through the array, and read the value.
int pos = (size - 1) >> 1;
KeyType val = extractKey(&array[pos]);
// If the key matches, success!
if (val == key)
return &array[pos];
// The item we are looking for is smaller than the item being check; reduce the value of 'size',
// chopping off the right hand half of the array.
else if (key < val)
size = pos;
// Discard all values in the left hand half of the array, up to and including the item at pos.
else {
size -= (pos + 1);
array += (pos + 1);
}
// 'size' should never reach zero.
ASSERT(size);
}
// If we reach this point we've chopped down to one element, no need to check it matches
ASSERT(size == 1);
ASSERT(key == extractKey(&array[0]));
return &array[0];
}
} // namespace WTF
using WTF::binarySearch;
using WTF::bitwise_cast;
#endif // WTF_StdLibExtras_h
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