Source/platform/SharedBuffer.h

/*
 * Copyright (C) 2006 Apple Computer, 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.
 */

#ifndef SharedBuffer_h
#define SharedBuffer_h

#include "platform/PlatformExport.h"
#include "wtf/ArrayBuffer.h"
#include "wtf/Forward.h"
#include "wtf/OwnPtr.h"
#include "wtf/RefCounted.h"
#include "wtf/Vector.h"
#include "wtf/text/WTFString.h"

namespace WebCore {

class PurgeableBuffer;

class PLATFORM_EXPORT SharedBuffer : public RefCounted<SharedBuffer> {
public:
    static PassRefPtr<SharedBuffer> create() { return adoptRef(new SharedBuffer); }
    static PassRefPtr<SharedBuffer> create(size_t size) { return adoptRef(new SharedBuffer(size)); }
    static PassRefPtr<SharedBuffer> create(const char* c, int i) { return adoptRef(new SharedBuffer(c, i)); }
    static PassRefPtr<SharedBuffer> create(const unsigned char* c, int i) { return adoptRef(new SharedBuffer(c, i)); }

    static PassRefPtr<SharedBuffer> adoptVector(Vector<char>& vector);

    // The buffer must be in non-purgeable state before adopted to a SharedBuffer.
    // It will stay that way until released.
    static PassRefPtr<SharedBuffer> adoptPurgeableBuffer(PassOwnPtr<PurgeableBuffer>);

    ~SharedBuffer();

    // Calling this function will force internal segmented buffers
    // to be merged into a flat buffer. Use getSomeData() whenever possible
    // for better performance.
    const char* data() const;

    void moveTo(Vector<char>&);

    unsigned size() const;

    bool isEmpty() const { return !size(); }

    void append(SharedBuffer*);
    void append(const char*, unsigned);
    void append(const Vector<char>&);

    void clear();

    PassRefPtr<SharedBuffer> copy() const;

    bool hasPurgeableBuffer() const { return m_purgeableBuffer.get(); }

    // Ensure this buffer has no other clients before calling this.
    PassOwnPtr<PurgeableBuffer> releasePurgeableBuffer();

    // Return the number of consecutive bytes after "position". "data"
    // points to the first byte.
    // Return 0 when no more data left.
    // When extracting all data with getSomeData(), the caller should
    // repeat calling it until it returns 0.
    // Usage:
    //      const char* segment;
    //      unsigned pos = 0;
    //      while (unsigned length = sharedBuffer->getSomeData(segment, pos)) {
    //          // Use the data. for example: decoder->decode(segment, length);
    //          pos += length;
    //      }
    unsigned getSomeData(const char*& data, unsigned position = 0) const;

    void createPurgeableBuffer() const;

    // Creates an ArrayBuffer and copies this SharedBuffer's contents to that
    // ArrayBuffer without merging segmented buffers into a flat buffer.
    PassRefPtr<ArrayBuffer> getAsArrayBuffer() const;

private:
    SharedBuffer();
    explicit SharedBuffer(size_t);
    SharedBuffer(const char*, int);
    SharedBuffer(const unsigned char*, int);

    // Calling this function will force internal segmented buffers
    // to be merged into a flat buffer. Use getSomeData() whenever possible
    // for better performance.
    // As well, be aware that this method does *not* return any purgeable
    // memory, which can be a source of bugs.
    const Vector<char>& buffer() const;

    unsigned m_size;
    mutable Vector<char> m_buffer;
    mutable Vector<char*> m_segments;
    mutable OwnPtr<PurgeableBuffer> m_purgeableBuffer;
};

} // namespace WebCore

#endif // SharedBuffer_h