wxWidgets/interface/buffer.h

/////////////////////////////////////////////////////////////////////////////
// Name:        buffer.h
// Purpose:     interface of wxMemoryBuffer
// Author:      wxWidgets team
// RCS-ID:      $Id$
// Licence:     wxWindows license
/////////////////////////////////////////////////////////////////////////////

/**
    @class wxMemoryBuffer
    @wxheader{buffer.h}

    A @b wxMemoryBuffer is a useful data structure for storing arbitrary sized
    blocks of memory. wxMemoryBuffer guarantees deletion of the memory block when
    the object is destroyed.

    @library{wxbase}
    @category{data}
*/
class wxMemoryBuffer
{
public:
    /**
        Copy constructor, refcounting is used for performance, but wxMemoryBuffer
        is not a copy-on-write structure so changes made to one buffer effect all
        copies made from it.

        @see @ref overview_refcount
    */
    wxMemoryBuffer(const wxMemoryBuffer& src);

    /**
        Create a new buffer.

        @param size
            size of the new buffer.
    */
    wxMemoryBuffer(size_t size);

    /**
        Append a single byte to the buffer.

        @param data
            New byte to append to the buffer.
    */
    void AppendByte(char data);

    /**
        Ensure that the buffer is big enough and return a pointer to the start
        of the empty space in the buffer. This pointer can be used to directly
        write data into the buffer, this new data will be appended to the
        existing data.

        @param sizeNeeded
            Amount of extra space required in the buffer for
            the append operation
    */
    void* GetAppendBuf(size_t sizeNeeded);

    /**
        Returns the size of the buffer.
    */
    size_t GetBufSize() const;

    /**
        Return a pointer to the data in the buffer.
    */
    void* GetData() const;

    /**
        Returns the length of the valid data in the buffer.
    */
    size_t GetDataLen() const;

    /**
        Ensure the buffer is big enough and return a pointer to the
        buffer which can be used to directly write into the buffer
        up to @a sizeNeeded bytes.
    */
    void* GetWriteBuf(size_t sizeNeeded);

    /**
        Ensures the buffer has at least @a size bytes available.
    */
    void SetBufSize(size_t size);

    /**
        Sets the length of the data stored in the buffer.
        Mainly useful for truncating existing data.

        @param size
            New length of the valid data in the buffer. This is
            distinct from the allocated size
    */
    void SetDataLen(size_t size);

    /**
        Update the length after completing a direct append, which
        you must have used GetAppendBuf() to initialise.

        @param sizeUsed
            This is the amount of new data that has been
            appended.
    */
    void UngetAppendBuf(size_t sizeUsed);

    /**
        Update the buffer after completing a direct write, which
        you must have used GetWriteBuf() to initialise.

        @param sizeUsed
            The amount of data written in to buffer
            by the direct write
    */
    void UngetWriteBuf(size_t sizeUsed);
};