12.3.42 SP_get_stream_user_data()


     #include <sicstus/sicstus.h>
        SP_stream *stream,
        void const *user_class,
        void **puser_data);

Get the user data of a user defined stream of a particular class.


An arbitrary stream. It is legal, and often useful, to call SP_get_stream_user_data() on a stream even if it is not known whether the stream is in fact a user defined stream of a particular class.
On success, *puser_data will be set to the user_data value used when the stream was created.

Return Value

On success, *puser_data is assigned and SPIO_S_NOERR or some other success code is returned.

On failure, e.g. if the stream was not created with this user_class, an error code is returned.


This function is used in order to recognize streams of a particular type (or class). At the same time as it verifies the type of stream it also returns the user_data which gives the caller a handle to the internal state of the user defined stream.

The following sample illustrates how all streams of a particular class can be found and closed. This function mimics the behavior of the SP_FCLOSE_OPTION_USER_STREAMS option to SP_fclose, see cpg-ref-SP_fclose.

     spio_t_error_code close_streams(void const *user_class, int force)
       spio_t_error_code ecode = SPIO_E_ERROR;
       SP_stream *stream;
       SP_stream *next_stream;
       void *user_data;
       spio_t_bits fclose_options = 0;
       if (force) fclose_options |= SP_FCLOSE_OPTION_FORCE;
       stream = NULL;           /* means start of list of stream */
           /* Note: We need to do this before closing stream */
           ecode = SP_next_stream(stream, &next_stream);
           if (SPIO_FAILED(ecode)) goto barf;
           if (stream != NULL)
               if (SPIO_SUCCEEDED(SP_get_stream_user_data(stream, user_class, &user_data)))
                   /* This is the right class of stream, close it */
                   ecode = SP_fclose(stream, fclose_options);
                   if (SPIO_FAILED(ecode))
                       if (!force) goto barf; /* ignore error if force */
           stream = next_stream;
       while (stream != NULL);
       return SPIO_S_NOERR;
       return ecode;

See Also

cpg-ref-SP_create_stream. Defining a New Stream.

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