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 Error API
 Usage Example
------------------------------------------------------------------------------
 Usage Example

     .  This example demonstrates how to handle a retriable error by
        producing, launching, and destroying an Error object.

        The first function is a CA-Clipper-callable interface function which
        calls a second C routine to actually open the file.

        The isolated C function opens the file, retrying the operation as many
        times as the CA-Clipper Error Handler indicates.  The example uses
        the function _fsExtOpen() to perform the low-level file I/O (See The
        File System API Reference chapter in this guide for more
        information).

        /***
        *   FILEOPEN()
        *
        *   CA-Clipper-callable function that attempts to open a file
        *   for reading and writing using FileOpener() and returns the
        *   file handle.  The first parameter is the name of the file to
        *   open and the second is a logical value indicating if the
        *   file should be opened shared (default is false).  If the
        *   filename is passed by reference it will be changed to the
        *   fully qualified name of the file if the open is successful,
        *   or the name that was attempted if unsuccessful.
        *
        *   Note: the subsystem code is set in this function since the
        *   lower-level function FileOpener() is designed to be called
        *   from many different routines.
        */

        #include "extend.api"

        CLIPPER FILEOPEN()
        {

           BYTEP fpFileName;
           FHANDLE hFile = FS_ERROR;
           USHORT uiFlags = FO_READWRITE
           ERRORP pError;


           if ( ISCHAR( 1 ) )
           {
              fpFileName = _parc( 1 );
              uiFlags |= ( ISLOG( 2 ) && _parl( 2 ) )
                ? FO_SHARED : FO_EXCLUSIVE;

              pError = _errNew()

              _errPutSubCode( pError, 1111 ); // subCode determined by
                                              // caller

              hFile = FileOpener( fpFileName, uiFlags, pError );

              if ( ISBYREF( 1 ) )
                 _storc( fpFileName, 1 );

           {


           _retni( hFile );
        }


        /***
        *   FileOpener()
        *
        *   Attempts to open a file whose name is passed as an argument
        *   along with the open mode flags and a pointer to an allocated
        *   Error object.  A default extension of ".TXT" will be assumed
        *   if the filename does not include an extension.
        *
        *   The function will generate an error if the open fails and
        *   will continue to retry for as long as the Error Handler
        *   returns E_RETRY.
        *
        *   The return value will be a valid file handle if successful,
        *   otherwise FS_ERROR is returned.
        */

        #include "error.api"
        #include "error.ch"
        #include "filesys.api"

        FHANDLE FileOpener( BYTEP fpFileName, USHORT uiFlags,
                            ERRORP pError )
        {

           FHANDLE hHandle;
           BOOL    retry;

           _errPutSeverity( pError, ES_ERROR );   // we determine the
                                                  // severity

           _errPutFlags( pError, EF_CANRETRY );   // and the allowable
                                                  // action
           _errPutGenCode( pError, EG_OPEN );     // open error

           // will be modified by _fsExtOpen() to the opened filename
           _errPutFileName( pError, fpFileName )


           do
           {
              hHandle = _fsExtOpen( fpFileName, ".TXT", uiFlags,
                 NULL, pError );

              retry = FALSE;

              if (hHandle == FS_ERROR)
              {
                 retry = ( _errLaunch( pError) == E_RETRY );
              }

           } while (retry);


           fpFileName = _errGetFileName( pError );

           return (handle);
        }