ToC path:

mco_class_save

Save an entire class to an external file.

Prototype

 
    MCO_RET	mco_class_save( /*IN*/ uint2 class_code,
                  /*IN*/ void * stream_handle,
                  /*IN*/ mco_stream_write output_stream_writer,
                  /*IN*/ mco_db_h db);

Arguments

class_code	Integer class code (from generated header file)
stream_handle	Handle to the output stream
output_stream_writer	Handler function called by the runtime to format output
db	The database handle

Description

This function is used to stream the entire contents of a database class to permanent storage. Used together with mco_class_load() an application can save and optionally load class data. Note that a transaction is opened implicitly for this operation – no transaction handle is required.

The mco_class_save() / mco_class_load() combination is compatible with mco_db_save() / mco_db_load(). That means that the application can save the entire database image with mco_db_save() and later load (or reload) the content of a particular class from the full image. Or it's possible to save the content of only one class with mco_class_save() and then use this image to create a database with the mco_db_load().

See the control structure stream writer for further details.

Return Codes

MCO_S_OK	The database was closed successfully
MCO_E_NOINSTANCE	The specified database is not opened
MCO_E_WRITE_STREAM	Error writing to output stream

Example

 
    Application snippet:
        
     
    const char * dbname = "SimpleDb";
     
    /* Stream writer with prototype mco_stream_write */
    mco_size_sig_t file_writer( void *stream_handle /* FILE *  */, const void *from, mco_size_t nbytes )
    {
        FILE *f = (FILE *)stream_handle;
        mco_size_sig_t nbs;
        nbs = fwrite( from, 1, nbytes, f );
        return nbs;
    }
     
    int main(int argc, char* argv[])
    {
        mco_db_h db;
        MCO_RET rc;
        FILE * fbak;
        uint2 my_class_code = 1;
        ...
         
        if( (rc = mco_runtime_start()) != MCO_S_OK)
            exit(-1);
             
        rc = mco_db_open_dev( dbname, simpledb_get_dictionary(), &dev, 1, &db_params );
        if ( MCO_S_OK != rc )
        {
            rc = mco_db_connect(dbname, &db);
            ...
             
            /* Backup database */
            fbak = fopen( "myclass.bak", "wb" );
            if ( fbak == 0 ) 
            {
                printf( "\n\t Can't open output file for streaming\n");
            }
            else 
            { 
                rc = mco_class_save( my_class_code, (void *)fbak, file_writer, db );
        
                fclose( fbak );
                sample_rc_check( "\t Save class", rc );
            }
            ...
        }
    }

Files

Header file:

mco.h

Source file:

mcosericmn.c

Library:

libmcoseri.a