cpl_vsil.cpp

用于读取TAB、MIF、SHP文件的类

 * Analog of the POSIX fseek() call.
 *
 * @param fp file handle opened with VSIFOpenL(). 
 * @param nOffset offset in bytes.
 * @param nWhence one of SEEK_SET, SEEK_CUR or SEEK_END.
 *
 * @return 0 on success or -1 one failure.
 */

int VSIFSeekL( FILE * fp, vsi_l_offset nOffset, int nWhence )

{
    VSIVirtualHandle *poFileHandle = (VSIVirtualHandle *) fp;
    
    return poFileHandle->Seek( nOffset, nWhence );
}

/************************************************************************/
/*                             VSIFTellL()                              */
/************************************************************************/

/**
 * \brief Tell current file offset.
 *
 * Returns the current file read/write offset in bytes from the beginning of
 * the file. 
 *
 * This method goes through the VSIFileHandler virtualization and may
 * work on unusual filesystems such as in memory.
 *
 * Analog of the POSIX ftell() call.
 *
 * @param fp file handle opened with VSIFOpenL(). 
 *
 * @return file offset in bytes.
 */

vsi_l_offset VSIFTellL( FILE * fp )

{
    VSIVirtualHandle *poFileHandle = (VSIVirtualHandle *) fp;
    
    return poFileHandle->Tell();
}

/************************************************************************/
/*                             VSIRewindL()                             */
/************************************************************************/

void VSIRewindL( FILE * fp )

{
    VSIFSeekL( fp, 0, SEEK_SET );
}

/************************************************************************/
/*                             VSIFFlushL()                             */
/************************************************************************/

/**
 * \brief Flush pending writes to disk.
 *
 * For files in write or update mode and on filesystem types where it is
 * applicable, all pending output on the file is flushed to the physical disk.
 *
 * This method goes through the VSIFileHandler virtualization and may
 * work on unusual filesystems such as in memory.
 *
 * Analog of the POSIX fflush() call.
 *
 * @param fp file handle opened with VSIFOpenL(). 
 *
 * @return 0 on success or -1 on error.
 */

int VSIFFlushL( FILE * fp )

{
    VSIVirtualHandle *poFileHandle = (VSIVirtualHandle *) fp;
    
    return poFileHandle->Flush();
}

/************************************************************************/
/*                             VSIFReadL()                              */
/************************************************************************/

/**
 * \brief Read bytes from file.
 *
 * Reads nCount objects of nSize bytes from the indicated file at the
 * current offset into the indicated buffer.
 *
 * This method goes through the VSIFileHandler virtualization and may
 * work on unusual filesystems such as in memory.
 *
 * Analog of the POSIX fread() call.
 *
 * @param pBuffer the buffer into which the data should be read (at least
 * nCount * nSize bytes in size. 
 * @param nSize size of objects to read in bytes.
 * @param nCount number of objects to read.
 * @param fp file handle opened with VSIFOpenL(). 
 *
 * @return number of objects successfully read. 
 */

size_t VSIFReadL( void * pBuffer, size_t nSize, size_t nCount, FILE * fp )

{
    VSIVirtualHandle *poFileHandle = (VSIVirtualHandle *) fp;
    
    return poFileHandle->Read( pBuffer, nSize, nCount );
}

/************************************************************************/
/*                             VSIFWriteL()                             */
/************************************************************************/

/**
 * \brief Write bytes to file.
 *
 * Writess nCount objects of nSize bytes to the indicated file at the
 * current offset into the indicated buffer.
 *
 * This method goes through the VSIFileHandler virtualization and may
 * work on unusual filesystems such as in memory.
 *
 * Analog of the POSIX fwrite() call.
 *
 * @param pBuffer the buffer from which the data should be written (at least
 * nCount * nSize bytes in size. 
 * @param nSize size of objects to read in bytes.
 * @param nCount number of objects to read.
 * @param fp file handle opened with VSIFOpenL(). 
 *
 * @return number of objects successfully written.
 */

size_t VSIFWriteL( const void *pBuffer, size_t nSize, size_t nCount, FILE *fp )

{
    VSIVirtualHandle *poFileHandle = (VSIVirtualHandle *) fp;
    
    return poFileHandle->Write( pBuffer, nSize, nCount );
}

/************************************************************************/
/*                              VSIFEofL()                              */
/************************************************************************/

/**
 * \brief Test for end of file.
 *
 * Returns TRUE (non-zero) if the file read/write offset is currently at the
 * end of the file. 
 *
 * This method goes through the VSIFileHandler virtualization and may
 * work on unusual filesystems such as in memory.
 *
 * Analog of the POSIX feof() call.
 *
 * @param fp file handle opened with VSIFOpenL(). 
 *
 * @return TRUE if at EOF else FALSE.
 */

int VSIFEofL( FILE * fp )

{
    VSIVirtualHandle *poFileHandle = (VSIVirtualHandle *) fp;
    
    return poFileHandle->Eof();
}

/************************************************************************/
/* ==================================================================== */
/*                           VSIFileManager()                           */
/* ==================================================================== */
/************************************************************************/

/*
** Notes on Multithreading:
**
** The VSIFileManager maintains a list of file type handlers (mem, large
** file, etc).  It should be thread safe as long as all the handlers are
** instantiated before multiple threads begin to operate. 
**/

/************************************************************************/
/*                           VSIFileManager()                           */
/************************************************************************/

VSIFileManager::VSIFileManager()

{
    poDefaultHandler = NULL;
}

/************************************************************************/
/*                          ~VSIFileManager()                           */
/************************************************************************/

VSIFileManager::~VSIFileManager()
{
    std::map<std::string,VSIFilesystemHandler*>::const_iterator iter;

    for( iter = oHandlers.begin();
         iter != oHandlers.end();
         iter++ )
    {
        delete iter->second;
    }

    delete poDefaultHandler;
}


/************************************************************************/
/*                                Get()                                 */
/************************************************************************/

static VSIFileManager *poManager = NULL;

VSIFileManager *VSIFileManager::Get()

{
    
    if( poManager == NULL )
    {
        poManager = new VSIFileManager;
        VSIInstallLargeFileHandler();
        VSIInstallMemFileHandler();
    }
    
    return poManager;
}

/************************************************************************/
/*                             GetHandler()                             */
/************************************************************************/

VSIFilesystemHandler *VSIFileManager::GetHandler( const char *pszPath )

{
    VSIFileManager *poThis = Get();
    std::map<std::string,VSIFilesystemHandler*>::const_iterator iter;

    for( iter = poThis->oHandlers.begin();
         iter != poThis->oHandlers.end();
         iter++ )
    {
        if( strncmp(pszPath,iter->first.c_str(),iter->first.size()) == 0 )
            return iter->second;
    }
    
    return poThis->poDefaultHandler;
}

/************************************************************************/
/*                           InstallHandler()                           */
/************************************************************************/

void VSIFileManager::InstallHandler( std::string osPrefix,
                                     VSIFilesystemHandler *poHandler )

{
    if( osPrefix == "" )
        Get()->poDefaultHandler = poHandler;
    else
        Get()->oHandlers[osPrefix] = poHandler;
}

/************************************************************************/
/*                       VSICleanupFileManager()                        */
/************************************************************************/

void VSICleanupFileManager()

{
    if( poManager )
    {
        delete poManager;
        poManager = NULL;
    }
}