Application: gvSIG desktop

/* $Id: lt_ioStreamInf.h 3539 2006-01-09 12:23:20Z nacho $ */

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

//                                                                         //

// This code is Copyright (c) 2004 LizardTech, Inc, 1008 Western Avenue,   //

// Suite 200, Seattle, WA 98104.  Unauthorized use or distribution         //

// prohibited.  Access to and use of this code is permitted only under     //

// license from LizardTech, Inc.  Portions of the code are protected by    //

// US and foreign patents and other filings. All Rights Reserved.          //

//                                                                         //

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

/* PUBLIC */

#ifndef LT_STREAMINF_H

#define LT_STREAMINF_H

#include "lt_lib_io.h"

LT_BEGIN_NAMESPACE( LizardTech )

/**

 * Abstract definition of a stream.

 *

 * This class is intentionally very sparse, and completely abstract to 

 * facilitate COM usage.  The semantics of the LTIOStreamInf class are

 * very similar to the unix stdio model.

 */

class LTIOStreamInf

{

public:

   // The following is a pure virtual destructor with an empty definition.

   // It might look broken to you, but this is a well-known practice and

   // is explicitly allowed by the standard for very good, technical reasons.

   // (Do a google search for "pure virtual destructor" for details.)

#if defined(LT_COMPILER_GNU) || defined(LT_COMPILER_SUN)

   // gcc doesn't allow the declaration to be in the class body,

   // so we put the member function "definition" in lt_ioStreamInf.cpp

   virtual ~LTIOStreamInf() =0;

#else

   virtual ~LTIOStreamInf() =0 {}

#endif

   /** 

    * @name Status accessors

    */

   //@{

        /**

    * Test for end-of-stream

    *

    * Returns true after the first read operation that attempts to 

    * read past the end of the stream. It returns false if the current 

    * position is not end of stream.

    *

         *        @retval  true     end of stream  

    * @retval  false    otherwise

         */

        virtual bool isEOF() =0;

        /**

    * Test for stream openness.

    *

         *        @retval  true     The stream is open

    * @retval  false    otherwise

         */

        virtual bool isOpen() =0;

   //@}

   /** 

    * @name Opening and closing

    */

   //@{

        /**

         *        Opens the stream.

    *

    * Opening a stream puts it in a state that allows data access based on cached

         *        initialization parameters. 

    *

         * @retval  LT_STS_IOStreamUninitialized  The stream has not been initialized with enough

         *                                                    information to open the stream

         *        @retval  LT_STS_IOStreamInvalidState   The stream is already open

         *        @retval  LT_STS_Success                On success.

         *        @retval  LT_STS_Failure                Failure.

    * @retval  other                         Implementations may return other codes

         */

        virtual LT_STATUS open() =0;

        /**

         *        Closes the stream.

    *

         *        Puts the stream in a state that does not allow data access.  May

         *        free up resources, but only in such a way that doesn't inhibit

         *        successful future calls to open()

    *

         *        @retval  LT_STS_Success                On success, or if the stream is already closed.

         *        @retval  LT_STS_Failure                Otherwise.

         */

        virtual LT_STATUS close() =0;

   //@}

   /** 

    * @name Data access

    */

   //@{

        /**

         * Retrieve the specified number of bytes from the data source and

         *        place them in pDest.

         *        

         *        @param   pDest         buffer in which to store read data

         *        @param   numBytes      number of bytes to read from stream

    *

         *        @retval numBytes        The number of bytes actually read

         */

   virtual lt_uint32 read( lt_uint8 *pDest, lt_uint32 numBytes ) = 0;

        /**

         * Store the specified number of bytes in the data source.  

    *

         *        @param   pSrc        buffer from which to store data

         *        @param   numBytes    number of bytes to write to stream

    *

         *        @retval  numBytes    number of bytes actually written

         */

   virtual lt_uint32 write( const lt_uint8 *pSrc, lt_uint32 numBytes ) = 0;

   //@}

   /** 

    * @name Positioning

    */

   //@{

        /**

         *        Moves the data access position to origin + offset

    * 

         *        @param   offset   number of bytes from origin at which to the next read or write will take place

         *        @param   origin   place in stream from which to seek

    *

         *        @retval  LT_STS_IOStreamUnsupported    The stream is not seekable

         *        @retval  LT_STS_IOStreamInvalidArgs    The offset and origin do not specify a valid location in the stream

         *        @retval  LT_STS_Success                On success

         *        @retval  LT_STS_Failure                Otherwise

    * @retval  other                         Implementations may return other codes

         */

   virtual LT_STATUS seek( lt_int64 offset, LTIOSeekDir origin ) =0;

        /**

         *        Returns the current data access position as an offset from the start of the data

    *

         *        @retval  postion     Number of bytes from the start of the data  

         *        @retval  -1          On error.  

    * @retval  other       Implementations may return other codes

         */

   virtual lt_int64 tell() =0;

   //@}

   /** 

    * @name Other operations

    */

   //@{

        /**

    * @brief   Clone the stream

    *

    * Create new stream of the same type with the same initialization parameters.  

         *        The transmission of these parameters is the responsibility of the derived type.

         *        The new stream should initially return false for isOpen().

         *        

         *        @retval  NULL  the stream could not be duplicated; valid LTIOStreamInf* otherwise.

        */

        virtual LTIOStreamInf* duplicate() =0;

        /**

    * @brief   Get status code of last error event.

    *

    * read(), write(), tell(), and duplicate() do not explicitly return status codes

    * in the event of an error.  When an error has occurred, this function returns

    * the appropriate status code.  Note calling this function after a successful

    * I/O operation will return an undefined value. 

         *        

         *        @retval  status  the error code

        */

        virtual LT_STATUS getLastError() const =0;

        /**

    * @brief   Get a URI describing the stream object.

    *

    * This function returns a UTF-8, null-terminated string which is a

    * URI describing the origin of the stream object -- for example,

    * "file://foo.txt" or "lt_memstream:".  This string is only intended

    * for diagnostic purposes, i.e. it may not be valid to pass it

    * to the ctor in an attempt to reopen the stream. 

         *        

         *        @retval  uri  the uri string

        */

        virtual const char* getID() const =0;

   //@}

};

LT_END_NAMESPACE( LizardTech )

#endif        // LT_STREAMINF_H