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/*
* Copyright (C) 2011 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 RefCountedArray_h
#define RefCountedArray_h
#include <wtf/FastMalloc.h>
#include <wtf/StdLibExtras.h>
#include <wtf/Vector.h>
// This implements a reference counted array for POD** values, which is optimized for:
// - An empty array only uses one word.
// - A copy of the array only uses one word (i.e. assignment means aliasing).
// - The vector can't grow beyond 2^32-1 elements.
// - In all other regards this has similar space usage to a Vector.
//
// ** This could be modified to support non-POD values quite easily. It just
// hasn't been, so far, because there has been no need. Moreover, even now,
// it's used for things that aren't quite POD according to the official
// defintion, such as JSC::Instruction.
namespace WTF {
template<typename T>
class RefCountedArray {
public:
RefCountedArray()
: m_data(0)
{
}
RefCountedArray(const RefCountedArray& other)
: m_data(other.m_data)
{
if (m_data)
Header::fromPayload(m_data)->refCount++;
}
explicit RefCountedArray(const Vector<T>& other)
{
if (other.isEmpty()) {
m_data = 0;
return;
}
m_data = (static_cast<Header*>(fastMalloc(Header::size() + sizeof(T) * other.size())))->payload();
Header::fromPayload(m_data)->refCount = 1;
Header::fromPayload(m_data)->length = other.size();
ASSERT(Header::fromPayload(m_data)->length == other.size());
memcpy(m_data, other.begin(), sizeof(T) * other.size());
}
RefCountedArray& operator=(const RefCountedArray& other)
{
T* oldData = m_data;
m_data = other.m_data;
if (m_data)
Header::fromPayload(m_data)->refCount++;
if (!oldData)
return *this;
if (--Header::fromPayload(oldData)->refCount)
return *this;
fastFree(Header::fromPayload(oldData));
return *this;
}
~RefCountedArray()
{
if (!m_data)
return;
if (--Header::fromPayload(m_data)->refCount)
return;
fastFree(Header::fromPayload(m_data));
}
size_t size() const
{
if (!m_data)
return 0;
return Header::fromPayload(m_data)->length;
}
T* data() { return m_data; }
T* begin() { return m_data; }
T* end()
{
if (!m_data)
return 0;
return m_data + Header::fromPayload(m_data)->length;
}
const T* data() const { return m_data; }
const T* begin() const { return m_data; }
const T* end() const { return const_cast<RefCountedArray*>(this)->end(); }
T& at(size_t i)
{
ASSERT(i < size());
return begin()[i];
}
const T& at(size_t i) const
{
ASSERT(i < size());
return begin()[i];
}
T& operator[](size_t i) { return at(i); }
const T& operator[](size_t i) const { return at(i); }
private:
struct Header {
unsigned refCount;
unsigned length;
static size_t size()
{
return (sizeof(Header) + 7) & ~7;
}
T* payload()
{
char* result = reinterpret_cast<char*>(this) + size();
ASSERT(!(bitwise_cast<uintptr_t>(result) & 7));
return reinterpret_cast<T*>(result);
}
static Header* fromPayload(T* payload)
{
return reinterpret_cast_ptr<Header*>(reinterpret_cast<char*>(payload) - size());
}
};
T* m_data;
};
} // namespace WTF
using WTF::RefCountedArray;
#endif // RefCountedArray_h
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