Source/platform/SharedBuffer.cpp - chromium/blink - Git at Google

 /*
  * Copyright (C) 2006, 2008 Apple Inc. All rights reserved.
  * Copyright (C) Research In Motion Limited 2009-2010. 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 COMPUTER, 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 COMPUTER, 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.
  */

 #include "config.h"
 #include "platform/SharedBuffer.h"

 #include "platform/PurgeableBuffer.h"
 #include "wtf/PassOwnPtr.h"
 #include "wtf/unicode/Unicode.h"
 #include "wtf/unicode/UTF8.h"

 #undef SHARED_BUFFER_STATS

 #ifdef SHARED_BUFFER_STATS
 #include "wtf/DataLog.h"
 #include "wtf/MainThread.h"
 #endif

 using namespace std;

 namespace WebCore {

 static const unsigned segmentSize = 0x1000;
 static const unsigned segmentPositionMask = 0x0FFF;

 static inline unsigned segmentIndex(unsigned position)
 {
     return position / segmentSize;
 }

 static inline unsigned offsetInSegment(unsigned position)
 {
     return position & segmentPositionMask;
 }

 static inline char* allocateSegment()
 {
     return static_cast<char*>(fastMalloc(segmentSize));
 }

 static inline void freeSegment(char* p)
 {
     fastFree(p);
 }

 #ifdef SHARED_BUFFER_STATS

 static Mutex& statsMutex()
 {
     DEFINE_STATIC_LOCAL(Mutex, mutex, ());
     return mutex;
 }

 static HashSet<SharedBuffer*>& liveBuffers()
 {
     DEFINE_STATIC_LOCAL(HashSet<SharedBuffer*>, buffers, ());
     return buffers;
 }

 static bool sizeComparator(SharedBuffer* a, SharedBuffer* b)
 {
     return a->size() > b->size();
 }

 static CString snippetForBuffer(SharedBuffer* sharedBuffer)
 {
     const unsigned kMaxSnippetLength = 64;
     char* snippet = 0;
     unsigned snippetLength = std::min(sharedBuffer->size(), kMaxSnippetLength);
     CString result = CString::newUninitialized(snippetLength, snippet);

     const char* segment;
     unsigned offset = 0;
     while (unsigned segmentLength = sharedBuffer->getSomeData(segment, offset)) {
         unsigned length = std::min(segmentLength, snippetLength - offset);
         memcpy(snippet + offset, segment, length);
         offset += segmentLength;
         if (offset >= snippetLength)
             break;
     }

     for (unsigned i = 0; i < snippetLength; ++i) {
         if (!isASCIIPrintable(snippet[i]))
             snippet[i] = '?';
     }

     return result;
 }

 static void printStats(void*)
 {
     MutexLocker locker(statsMutex());
     Vector<SharedBuffer*> buffers;
     for (HashSet<SharedBuffer*>::const_iterator iter = liveBuffers().begin(); iter != liveBuffers().end(); ++iter)
         buffers.append(*iter);
     std::sort(buffers.begin(), buffers.end(), sizeComparator);

     dataLogF("---- Shared Buffer Stats ----\n");
     for (size_t i = 0; i < buffers.size() && i < 64; ++i) {
         CString snippet = snippetForBuffer(buffers[i]);
         dataLogF("Buffer size=%8u %s\n", buffers[i]->size(), snippet.data());
     }
 }

 static void didCreateSharedBuffer(SharedBuffer* buffer)
 {
     MutexLocker locker(statsMutex());
     liveBuffers().add(buffer);

     callOnMainThread(printStats, 0);
 }

 static void willDestroySharedBuffer(SharedBuffer* buffer)
 {
     MutexLocker locker(statsMutex());
     liveBuffers().remove(buffer);
 }

 #endif

 SharedBuffer::SharedBuffer()
     : m_size(0)
 {
 #ifdef SHARED_BUFFER_STATS
     didCreateSharedBuffer(this);
 #endif
 }

 SharedBuffer::SharedBuffer(size_t size)
     : m_size(size)
     , m_buffer(size)
 {
 #ifdef SHARED_BUFFER_STATS
     didCreateSharedBuffer(this);
 #endif
 }

 SharedBuffer::SharedBuffer(const char* data, int size)
     : m_size(0)
 {
     // FIXME: Use unsigned consistently, and check for invalid casts when calling into SharedBuffer from other code.
     if (size < 0)
         CRASH();

     append(data, size);

 #ifdef SHARED_BUFFER_STATS
     didCreateSharedBuffer(this);
 #endif
 }

 SharedBuffer::SharedBuffer(const unsigned char* data, int size)
     : m_size(0)
 {
     // FIXME: Use unsigned consistently, and check for invalid casts when calling into SharedBuffer from other code.
     if (size < 0)
         CRASH();

     append(reinterpret_cast<const char*>(data), size);

 #ifdef SHARED_BUFFER_STATS
     didCreateSharedBuffer(this);
 #endif
 }

 SharedBuffer::~SharedBuffer()
 {
     clear();

 #ifdef SHARED_BUFFER_STATS
     willDestroySharedBuffer(this);
 #endif
 }

 PassRefPtr<SharedBuffer> SharedBuffer::adoptVector(Vector<char>& vector)
 {
     RefPtr<SharedBuffer> buffer = create();
     buffer->m_buffer.swap(vector);
     buffer->m_size = buffer->m_buffer.size();
     return buffer.release();
 }

 PassRefPtr<SharedBuffer> SharedBuffer::adoptPurgeableBuffer(PassOwnPtr<PurgeableBuffer> purgeableBuffer)
 {
     ASSERT(!purgeableBuffer->isPurgeable());
     RefPtr<SharedBuffer> buffer = create();
     buffer->m_purgeableBuffer = purgeableBuffer;
     return buffer.release();
 }

 unsigned SharedBuffer::size() const
 {
     if (m_purgeableBuffer)
         return m_purgeableBuffer->size();

     return m_size;
 }

 void SharedBuffer::createPurgeableBuffer() const
 {
     if (m_purgeableBuffer)
         return;

     m_purgeableBuffer = PurgeableBuffer::create(buffer().data(), m_size);
 }

 const char* SharedBuffer::data() const
 {
     if (m_purgeableBuffer)
         return m_purgeableBuffer->data();

     return this->buffer().data();
 }

 void SharedBuffer::moveTo(Vector<char>& result)
 {
     ASSERT(result.isEmpty());
     if (m_purgeableBuffer) {
         result.reserveCapacity(m_purgeableBuffer->size());
         result.append(m_purgeableBuffer->data(), m_purgeableBuffer->size());
         clear();
         return;
     }

     unsigned bufferSize = m_buffer.size();
     if (m_size == bufferSize) {
         m_buffer.swap(result);
         clear();
         return;
     }

     result.reserveCapacity(m_size);

     const char* segment = 0;
     unsigned position = 0;
     while (unsigned segmentSize = getSomeData(segment, position)) {
         result.append(segment, segmentSize);
         position += segmentSize;
     }
     ASSERT(result.size() == m_size);
     clear();
     return;
 }

 void SharedBuffer::append(SharedBuffer* data)
 {
     const char* segment;
     size_t position = 0;
     while (size_t length = data->getSomeData(segment, position)) {
         append(segment, length);
         position += length;
     }
 }

 void SharedBuffer::append(const char* data, unsigned length)
 {
     ASSERT(!m_purgeableBuffer);
     if (!length)
         return;

     unsigned positionInSegment = offsetInSegment(m_size - m_buffer.size());
     m_size += length;

     if (m_size <= segmentSize) {
         // No need to use segments for small resource data
         if (m_buffer.isEmpty())
             m_buffer.reserveInitialCapacity(length);
         m_buffer.append(data, length);
         return;
     }

     char* segment;
     if (!positionInSegment) {
         segment = allocateSegment();
         m_segments.append(segment);
     } else
         segment = m_segments.last() + positionInSegment;

     unsigned segmentFreeSpace = segmentSize - positionInSegment;
     unsigned bytesToCopy = min(length, segmentFreeSpace);

     for (;;) {
         memcpy(segment, data, bytesToCopy);
         if (static_cast<unsigned>(length) == bytesToCopy)
             break;

         length -= bytesToCopy;
         data += bytesToCopy;
         segment = allocateSegment();
         m_segments.append(segment);
         bytesToCopy = min(length, segmentSize);
     }
 }

 void SharedBuffer::append(const Vector<char>& data)
 {
     append(data.data(), data.size());
 }

 void SharedBuffer::clear()
 {
     for (unsigned i = 0; i < m_segments.size(); ++i)
         freeSegment(m_segments[i]);

     m_segments.clear();
     m_size = 0;

     m_buffer.clear();
     m_purgeableBuffer.clear();
 }

 PassRefPtr<SharedBuffer> SharedBuffer::copy() const
 {
     RefPtr<SharedBuffer> clone(adoptRef(new SharedBuffer));
     if (m_purgeableBuffer) {
         clone->append(data(), size());
         return clone.release();
     }

     clone->m_size = m_size;
     clone->m_buffer.reserveCapacity(m_size);
     clone->m_buffer.append(m_buffer.data(), m_buffer.size());
     if (!m_segments.isEmpty()) {
         const char* segment = 0;
         unsigned position = m_buffer.size();
         while (unsigned segmentSize = getSomeData(segment, position)) {
             clone->m_buffer.append(segment, segmentSize);
             position += segmentSize;
         }
         ASSERT(position == clone->size());
     }
     return clone.release();
 }

 PassOwnPtr<PurgeableBuffer> SharedBuffer::releasePurgeableBuffer()
 {
     ASSERT(hasOneRef());
     return m_purgeableBuffer.release();
 }

 const Vector<char>& SharedBuffer::buffer() const
 {
     unsigned bufferSize = m_buffer.size();
     if (m_size > bufferSize) {
         m_buffer.resize(m_size);
         char* destination = m_buffer.data() + bufferSize;
         unsigned bytesLeft = m_size - bufferSize;
         for (unsigned i = 0; i < m_segments.size(); ++i) {
             unsigned bytesToCopy = min(bytesLeft, segmentSize);
             memcpy(destination, m_segments[i], bytesToCopy);
             destination += bytesToCopy;
             bytesLeft -= bytesToCopy;
             freeSegment(m_segments[i]);
         }
         m_segments.clear();
     }
     return m_buffer;
 }

 unsigned SharedBuffer::getSomeData(const char*& someData, unsigned position) const
 {
     unsigned totalSize = size();
     if (position >= totalSize) {
         someData = 0;
         return 0;
     }

     if (m_purgeableBuffer) {
         ASSERT_WITH_SECURITY_IMPLICATION(position < size());
         someData = data() + position;
         return totalSize - position;
     }

     ASSERT_WITH_SECURITY_IMPLICATION(position < m_size);
     unsigned consecutiveSize = m_buffer.size();
     if (position < consecutiveSize) {
         someData = m_buffer.data() + position;
         return consecutiveSize - position;
     }

     position -= consecutiveSize;
     unsigned segments = m_segments.size();
     unsigned maxSegmentedSize = segments * segmentSize;
     unsigned segment = segmentIndex(position);
     if (segment < segments) {
         unsigned bytesLeft = totalSize - consecutiveSize;
         unsigned segmentedSize = min(maxSegmentedSize, bytesLeft);

         unsigned positionInSegment = offsetInSegment(position);
         someData = m_segments[segment] + positionInSegment;
         return segment == segments - 1 ? segmentedSize - position : segmentSize - positionInSegment;
     }
     ASSERT_NOT_REACHED();
     return 0;
 }

 PassRefPtr<ArrayBuffer> SharedBuffer::getAsArrayBuffer() const
 {
     RefPtr<ArrayBuffer> arrayBuffer = ArrayBuffer::createUninitialized(static_cast<unsigned>(size()), 1);

     const char* segment = 0;
     unsigned position = 0;
     while (unsigned segmentSize = getSomeData(segment, position)) {
         memcpy(static_cast<char*>(arrayBuffer->data()) + position, segment, segmentSize);
         position += segmentSize;
     }

     if (position != arrayBuffer->byteLength()) {
         ASSERT_NOT_REACHED();
         // Don't return the incomplete ArrayBuffer.
         return 0;
     }

     return arrayBuffer;
 }

 } // namespace WebCore
	/*
	* Copyright (C) 2006, 2008 Apple Inc. All rights reserved.
	* Copyright (C) Research In Motion Limited 2009-2010. 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 COMPUTER, 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 COMPUTER, 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.
	*/

	#include "config.h"
	#include "platform/SharedBuffer.h"

	#include "platform/PurgeableBuffer.h"
	#include "wtf/PassOwnPtr.h"
	#include "wtf/unicode/Unicode.h"
	#include "wtf/unicode/UTF8.h"

	#undef SHARED_BUFFER_STATS

	#ifdef SHARED_BUFFER_STATS
	#include "wtf/DataLog.h"
	#include "wtf/MainThread.h"
	#endif

	using namespace std;

	namespace WebCore {

	static const unsigned segmentSize = 0x1000;
	static const unsigned segmentPositionMask = 0x0FFF;

	static inline unsigned segmentIndex(unsigned position)
	{
	return position / segmentSize;
	}

	static inline unsigned offsetInSegment(unsigned position)
	{
	return position & segmentPositionMask;
	}

	static inline char* allocateSegment()
	{
	return static_cast<char*>(fastMalloc(segmentSize));
	}

	static inline void freeSegment(char* p)
	{
	fastFree(p);
	}

	#ifdef SHARED_BUFFER_STATS

	static Mutex& statsMutex()
	{
	DEFINE_STATIC_LOCAL(Mutex, mutex, ());
	return mutex;
	}

	static HashSet<SharedBuffer*>& liveBuffers()
	{
	DEFINE_STATIC_LOCAL(HashSet<SharedBuffer*>, buffers, ());
	return buffers;
	}

	static bool sizeComparator(SharedBuffer* a, SharedBuffer* b)
	{
	return a->size() > b->size();
	}

	static CString snippetForBuffer(SharedBuffer* sharedBuffer)
	{
	const unsigned kMaxSnippetLength = 64;
	char* snippet = 0;
	unsigned snippetLength = std::min(sharedBuffer->size(), kMaxSnippetLength);
	CString result = CString::newUninitialized(snippetLength, snippet);

	const char* segment;
	unsigned offset = 0;
	while (unsigned segmentLength = sharedBuffer->getSomeData(segment, offset)) {
	unsigned length = std::min(segmentLength, snippetLength - offset);
	memcpy(snippet + offset, segment, length);
	offset += segmentLength;
	if (offset >= snippetLength)
	break;
	}

	for (unsigned i = 0; i < snippetLength; ++i) {
	if (!isASCIIPrintable(snippet[i]))
	snippet[i] = '?';
	}

	return result;
	}

	static void printStats(void*)
	{
	MutexLocker locker(statsMutex());
	Vector<SharedBuffer*> buffers;
	for (HashSet<SharedBuffer*>::const_iterator iter = liveBuffers().begin(); iter != liveBuffers().end(); ++iter)
	buffers.append(*iter);
	std::sort(buffers.begin(), buffers.end(), sizeComparator);

	dataLogF("---- Shared Buffer Stats ----\n");
	for (size_t i = 0; i < buffers.size() && i < 64; ++i) {
	CString snippet = snippetForBuffer(buffers[i]);
	dataLogF("Buffer size=%8u %s\n", buffers[i]->size(), snippet.data());
	}
	}

	static void didCreateSharedBuffer(SharedBuffer* buffer)
	{
	MutexLocker locker(statsMutex());
	liveBuffers().add(buffer);

	callOnMainThread(printStats, 0);
	}

	static void willDestroySharedBuffer(SharedBuffer* buffer)
	{
	MutexLocker locker(statsMutex());
	liveBuffers().remove(buffer);
	}

	#endif

	SharedBuffer::SharedBuffer()
	: m_size(0)
	{
	#ifdef SHARED_BUFFER_STATS
	didCreateSharedBuffer(this);
	#endif
	}

	SharedBuffer::SharedBuffer(size_t size)
	: m_size(size)
	, m_buffer(size)
	{
	#ifdef SHARED_BUFFER_STATS
	didCreateSharedBuffer(this);
	#endif
	}

	SharedBuffer::SharedBuffer(const char* data, int size)
	: m_size(0)
	{
	// FIXME: Use unsigned consistently, and check for invalid casts when calling into SharedBuffer from other code.
	if (size < 0)
	CRASH();

	append(data, size);

	#ifdef SHARED_BUFFER_STATS
	didCreateSharedBuffer(this);
	#endif
	}

	SharedBuffer::SharedBuffer(const unsigned char* data, int size)
	: m_size(0)
	{
	// FIXME: Use unsigned consistently, and check for invalid casts when calling into SharedBuffer from other code.
	if (size < 0)
	CRASH();

	append(reinterpret_cast<const char*>(data), size);

	#ifdef SHARED_BUFFER_STATS
	didCreateSharedBuffer(this);
	#endif
	}

	SharedBuffer::~SharedBuffer()
	{
	clear();

	#ifdef SHARED_BUFFER_STATS
	willDestroySharedBuffer(this);
	#endif
	}

	PassRefPtr<SharedBuffer> SharedBuffer::adoptVector(Vector<char>& vector)
	{
	RefPtr<SharedBuffer> buffer = create();
	buffer->m_buffer.swap(vector);
	buffer->m_size = buffer->m_buffer.size();
	return buffer.release();
	}

	PassRefPtr<SharedBuffer> SharedBuffer::adoptPurgeableBuffer(PassOwnPtr<PurgeableBuffer> purgeableBuffer)
	{
	ASSERT(!purgeableBuffer->isPurgeable());
	RefPtr<SharedBuffer> buffer = create();
	buffer->m_purgeableBuffer = purgeableBuffer;
	return buffer.release();
	}

	unsigned SharedBuffer::size() const
	{
	if (m_purgeableBuffer)
	return m_purgeableBuffer->size();

	return m_size;
	}

	void SharedBuffer::createPurgeableBuffer() const
	{
	if (m_purgeableBuffer)
	return;

	m_purgeableBuffer = PurgeableBuffer::create(buffer().data(), m_size);
	}

	const char* SharedBuffer::data() const
	{
	if (m_purgeableBuffer)
	return m_purgeableBuffer->data();

	return this->buffer().data();
	}

	void SharedBuffer::moveTo(Vector<char>& result)
	{
	ASSERT(result.isEmpty());
	if (m_purgeableBuffer) {
	result.reserveCapacity(m_purgeableBuffer->size());
	result.append(m_purgeableBuffer->data(), m_purgeableBuffer->size());
	clear();
	return;
	}

	unsigned bufferSize = m_buffer.size();
	if (m_size == bufferSize) {
	m_buffer.swap(result);
	clear();
	return;
	}

	result.reserveCapacity(m_size);

	const char* segment = 0;
	unsigned position = 0;
	while (unsigned segmentSize = getSomeData(segment, position)) {
	result.append(segment, segmentSize);
	position += segmentSize;
	}
	ASSERT(result.size() == m_size);
	clear();
	return;
	}

	void SharedBuffer::append(SharedBuffer* data)
	{
	const char* segment;
	size_t position = 0;
	while (size_t length = data->getSomeData(segment, position)) {
	append(segment, length);
	position += length;
	}
	}

	void SharedBuffer::append(const char* data, unsigned length)
	{
	ASSERT(!m_purgeableBuffer);
	if (!length)
	return;

	unsigned positionInSegment = offsetInSegment(m_size - m_buffer.size());
	m_size += length;

	if (m_size <= segmentSize) {
	// No need to use segments for small resource data
	if (m_buffer.isEmpty())
	m_buffer.reserveInitialCapacity(length);
	m_buffer.append(data, length);
	return;
	}

	char* segment;
	if (!positionInSegment) {
	segment = allocateSegment();
	m_segments.append(segment);
	} else
	segment = m_segments.last() + positionInSegment;

	unsigned segmentFreeSpace = segmentSize - positionInSegment;
	unsigned bytesToCopy = min(length, segmentFreeSpace);

	for (;;) {
	memcpy(segment, data, bytesToCopy);
	if (static_cast<unsigned>(length) == bytesToCopy)
	break;

	length -= bytesToCopy;
	data += bytesToCopy;
	segment = allocateSegment();
	m_segments.append(segment);
	bytesToCopy = min(length, segmentSize);
	}
	}

	void SharedBuffer::append(const Vector<char>& data)
	{
	append(data.data(), data.size());
	}

	void SharedBuffer::clear()
	{
	for (unsigned i = 0; i < m_segments.size(); ++i)
	freeSegment(m_segments[i]);

	m_segments.clear();
	m_size = 0;

	m_buffer.clear();
	m_purgeableBuffer.clear();
	}

	PassRefPtr<SharedBuffer> SharedBuffer::copy() const
	{
	RefPtr<SharedBuffer> clone(adoptRef(new SharedBuffer));
	if (m_purgeableBuffer) {
	clone->append(data(), size());
	return clone.release();
	}

	clone->m_size = m_size;
	clone->m_buffer.reserveCapacity(m_size);
	clone->m_buffer.append(m_buffer.data(), m_buffer.size());
	if (!m_segments.isEmpty()) {
	const char* segment = 0;
	unsigned position = m_buffer.size();
	while (unsigned segmentSize = getSomeData(segment, position)) {
	clone->m_buffer.append(segment, segmentSize);
	position += segmentSize;
	}
	ASSERT(position == clone->size());
	}
	return clone.release();
	}

	PassOwnPtr<PurgeableBuffer> SharedBuffer::releasePurgeableBuffer()
	{
	ASSERT(hasOneRef());
	return m_purgeableBuffer.release();
	}

	const Vector<char>& SharedBuffer::buffer() const
	{
	unsigned bufferSize = m_buffer.size();
	if (m_size > bufferSize) {
	m_buffer.resize(m_size);
	char* destination = m_buffer.data() + bufferSize;
	unsigned bytesLeft = m_size - bufferSize;
	for (unsigned i = 0; i < m_segments.size(); ++i) {
	unsigned bytesToCopy = min(bytesLeft, segmentSize);
	memcpy(destination, m_segments[i], bytesToCopy);
	destination += bytesToCopy;
	bytesLeft -= bytesToCopy;
	freeSegment(m_segments[i]);
	}
	m_segments.clear();
	}
	return m_buffer;
	}

	unsigned SharedBuffer::getSomeData(const char*& someData, unsigned position) const
	{
	unsigned totalSize = size();
	if (position >= totalSize) {
	someData = 0;
	return 0;
	}

	if (m_purgeableBuffer) {
	ASSERT_WITH_SECURITY_IMPLICATION(position < size());
	someData = data() + position;
	return totalSize - position;
	}

	ASSERT_WITH_SECURITY_IMPLICATION(position < m_size);
	unsigned consecutiveSize = m_buffer.size();
	if (position < consecutiveSize) {
	someData = m_buffer.data() + position;
	return consecutiveSize - position;
	}

	position -= consecutiveSize;
	unsigned segments = m_segments.size();
	unsigned maxSegmentedSize = segments * segmentSize;
	unsigned segment = segmentIndex(position);
	if (segment < segments) {
	unsigned bytesLeft = totalSize - consecutiveSize;
	unsigned segmentedSize = min(maxSegmentedSize, bytesLeft);

	unsigned positionInSegment = offsetInSegment(position);
	someData = m_segments[segment] + positionInSegment;
	return segment == segments - 1 ? segmentedSize - position : segmentSize - positionInSegment;
	}
	ASSERT_NOT_REACHED();
	return 0;
	}

	PassRefPtr<ArrayBuffer> SharedBuffer::getAsArrayBuffer() const
	{
	RefPtr<ArrayBuffer> arrayBuffer = ArrayBuffer::createUninitialized(static_cast<unsigned>(size()), 1);

	const char* segment = 0;
	unsigned position = 0;
	while (unsigned segmentSize = getSomeData(segment, position)) {
	memcpy(static_cast<char*>(arrayBuffer->data()) + position, segment, segmentSize);
	position += segmentSize;
	}

	if (position != arrayBuffer->byteLength()) {
	ASSERT_NOT_REACHED();
	// Don't return the incomplete ArrayBuffer.
	return 0;
	}

	return arrayBuffer;
	}

	} // namespace WebCore