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

                 SUBROUTINE THREEJSORT

 THREEJSORT SORTS A FILE NUMERICALLY.  FIRST THE CONTENTS OF THE
 FILE ARE READ INTO AN ARRAY.  THEN THEY ARE SORTED USING
 THE QSORT FACILITY.  THEN THE CONTENTS ARE READ BACK OUT
 TO THE ORIGINAL FILE.  THREEJSORT IS ONLY FOR FILES CONTAINING
 THTEE INTEGER STRUCTURES (PREP).
 

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

threejsort_( 

 int *fn          /* FILE IDENTIFICATION NUMBER */

       )
{

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

 PARAMETERS:

  I - COUNTER
  NUMPROS - NUMBER OF VALUES TO BE SORTED

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

 int i;
 int numpros = 0;

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

  READ IN ALL THE VALUES FROM FILE.

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

 while ( !feof(fp[*fn]) ) {

  numpros++;
  fread( &prep3[numpros], sizeof( struct write3 ) , 1, fp[*fn]);

 }

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

 SUBTRACT ONE FROM THE VALUE COUNTER SINCE THE LAST ADDITION
 WAS FOR THE END OF FILE MARKER.

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

 
 numpros--;

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

 REWIND THE FILE

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

 fseek( fp[*fn], 0L, SEEK_SET );

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

 SORT FILES USING QSORT:

  PREP3[1] - STARTING POINT FOR SORT
  NUMPROS - NUMBER OF VALUES TO SORT
  SIZEOF() - SIZE OF VALUES BEING SORTED
  UNCOMPAREM - SORTING SUBROUTINE  

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

 qsort( &prep3[1], numpros, sizeof( struct write3 ), comparem3);

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

  PLACE SORTED VALUES BACK IN FILE.

****************************************************************/
 
 for ( i = 1; i <= numpros; i++ )
  fwrite( &prep3[i], sizeof( struct write3 ), 1, fp[*fn] );

}