SharedBuffer.h

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/*
 * Copyright (c) 2005 Palmsource, Inc.
 * 
 * This software is licensed as described in the file LICENSE, which
 * you should have received as part of this distribution. The terms
 * are also available at http://www.openbinder.org/license.html.
 * 
 * This software consists of voluntary contributions made by many
 * individuals. For the exact contribution history, see the revision
 * history and logs, available at http://www.openbinder.org
 */

#ifndef _SUPPORT_SHARED_BUFFER_H_
#define _SUPPORT_SHARED_BUFFER_H_

#include <support/Atom.h>
#include <support/SupportDefs.h>
#include <support/atomic.h>

#if _SUPPORTS_NAMESPACE
namespace palmos {
namespace support {
#endif



enum {

    B_BUFFER_USERS_SHIFT    = 4,        
    B_BUFFER_LENGTH_SHIFT   = 1,        


    B_STATIC_USERS          = 0x00000001,


    B_POOLED_USERS          = 0x00000002,


    B_EXTENDED_BUFFER   = 0x00000001
};

// *************************************************************************

class SSharedBuffer
{
public:

    static  SSharedBuffer*  Alloc(size_t length);
            
    inline  const void*     Data() const;

    inline  void*           Data();
    inline  size_t          Length() const;
            

    static inline   const SSharedBuffer* BufferFromData(const void *data);

            void            IncUsers() const;

            void            DecUsers() const;

    inline  int32_t         Users() const;
            

            SSharedBuffer*  Edit(size_t newLength) const;

            SSharedBuffer*  Edit() const;


    const   SSharedBuffer*  Pool() const;


            int32_t         Compare(const SSharedBuffer* other) const;


            SSharedBuffer*  BeginBuffering();
            SSharedBuffer*  EndBuffering();

            bool            Buffering() const;
            size_t          BufferSize() const;

            void            IncStrong(const void* ) const   { IncUsers(); }
            void            DecStrong(const void* ) const   { DecUsers(); }
            void            IncStrongFast() const           { IncUsers(); }
            void            DecStrongFast() const           { DecUsers(); }

            // These are used for static values.  See StaticValue.h.
    typedef void            (*inc_ref_func)();
    typedef void            (*dec_ref_func)();

private:
    inline                  SSharedBuffer() { }
    inline                  ~SSharedBuffer() { }
    
    struct  extended_info;
            extended_info*  get_extended_info() const;
            bool            unpool() const;
            void            do_delete() const;

                            SSharedBuffer(const SSharedBuffer& o);

    static  SSharedBuffer*  AllocExtended(extended_info* prototype, size_t length);
            SSharedBuffer*  Extend(size_t length) const;

            void            SetBufferSize(size_t size);
            void            SetLength(size_t len);

    /* *******************************************************
     * WARNING
     *
     * The size or layout of SSharedBuffer cannot be changed.
     * In order to do some important optimizations, some code
     * assumes this layout. For eg, see support/StaticValue.h.
     *
     * *******************************************************/

    mutable int32_t         m_users;
            size_t          m_length;
#if defined(_MSC_VER)
            char            m_data[0];
#endif
};

/*-------------------------------------------------------------*/
/*---- No user serviceable parts after this -------------------*/

inline const void* SSharedBuffer::Data() const
{
    return this+1;
}

inline void* SSharedBuffer::Data()
{
    return this+1;
}

inline const SSharedBuffer* SSharedBuffer::BufferFromData(const void *data)
{
    return ((static_cast<const SSharedBuffer *>(data)) - 1);
}

inline size_t SSharedBuffer::Length() const
{
    return m_length>>B_BUFFER_LENGTH_SHIFT;
}

inline int32_t SSharedBuffer::Users() const
{
    return m_users>>B_BUFFER_USERS_SHIFT;
}

/*-------------------------------------------------------------*/
// We need to specialize SSharedBuffer, because
// raw SSharedBuffer alread have a count of 1

template<> inline
sptr<SSharedBuffer>::sptr(SSharedBuffer* p)
{
    m_ptr = p;
}

template<> inline
sptr<SSharedBuffer>& sptr<SSharedBuffer>::operator = (SSharedBuffer* p)
{
    if (m_ptr) B_DEC_STRONG(m_ptr, this);
    m_ptr = p;
    return *this;
}


#if _SUPPORTS_NAMESPACE
} } // namespace palmos::support
#endif

#endif  /* _SUPPORT_SHARED_BUFFER_H_ */

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PalmSource, Inc. © 2005