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Access to data

Following fortran subroutine accesses DSPACK data. It expects a structure of constants POINT_C_T to exist, copies it's contents into it's own structure and uses it to create 10 entries of structure point_t.

Example of access to data - point_fill.f file

subroutine fill_points(ierr)
* 
*   ********************************************************************
*   *                                                                  *
*$$ *   subroutine fill_points  put some random data into 10 points    *
*   *                                                                  *
*   ********************************************************************
* 
      structure /V3/                                    
         real  x               
         real  y               
         real  z               
      end structure
      structure /point_t/                               
         record/V3/  pos             
         record/V3/  d               
         integer  flags(2)        
         integer  next           
      end structure
      record/point_t/ point(1)
      pointer ( point_p,point )

      structure/POINT_C_T/
         real A
         real B
         real C
         real D
      end structure
      record/POINT_C_T/ PC(2)

      data ivdsn_point/0/
      data ivdsn_const/0/

* Get constants into PC

      call dsget('POINT_C_T',ivdsn_const,2,nent,PC,ierr)
      if( nent.eq.0 ) return

* Tell DSPACK that right now we want pointers (remember what it was before)

      mode_old = ids_pnt_conv(1)

* Make 10 points

      point_p = idsput_ds('point_t',ivdsn_point,10)
      if( point_p.eq.0 ) then
         write(*,*)'Cannot make points'
         go to 995
      endif

* Build two link-lists of points:
* (1 3 5 7 9) and (2 4 6 8 10)

      z0 = 0.0
      do i=1,9,2
         point(i).pos.z = z0
         point(i).pos.y = PC(1).A*point(i).pos.z + PC(1).B
         point(i).pos.x = PC(1).C*point(i).pos.z + PC(1).D

         point(i).d.z = 0.01
         point(i).d.y = 0.01*point(i).pos.y
         point(i).d.x = 0.01*point(i).pos.x

         point(i).flags(1) = 1
         point(i).flags(2) = 2

         point(i).next = loc(point(i+2))
         z0 = z0 + 1.0
      enddo
      point(9).next = 0

      z0 = 0.0
      do i=2,10,2
         point(i).pos.z = z0
         point(i).pos.y = PC(2).A*point(i).pos.z + PC(2).B
         point(i).pos.x = PC(2).C*point(i).pos.z + PC(2).D

         point(i).d.z = 0.01
         point(i).d.y = 0.01*point(i).pos.y
         point(i).d.x = 0.01*point(i).pos.x

         point(i).flags(1) = 1
         point(i).flags(2) = 2

         point(i).next = loc(point(i+2))
         z0 = z0 + 1.0
      enddo
      point(10).next = 0

* Tell DSPACK that we have finished with point_t

      call ds_update('point_t',ivdsn_point,ierr)

* Reset pointer/index flag to what it was before

 995  continue
      idum = ids_pnt_conv(mode_old)

      end

Structure of constants POINT_C_T is defined and initialized in another object description file which should be used now instead of dspack_tut_2.d.

Object initialization - dspack_tut_4.d

* 
*   ********************************************************************
*   *                                                                  *
*$$ *   dspack_tut_4.d  DSPACK tutorial - example 2                    *
*   *                                                                  *
*   ********************************************************************
*

DEFINE point_t S 1                  ! define structure point_t, section 1
                V3 pos              ! position
                V3 d                ! position errors
               .INT4  flags(2)
                point_t *next       ! pointer to the next hit on track
END DEFINE -CLASS point -TYPE 0

DEFINE vertex_t S 1                 ! define structure point_t, section 1
                V3 pos              ! position
                V3 d                ! position errors
               .INT4 n_tracks       ! number of tracks
               .INT4  flags(2)
                track_t *tracks     ! pointer to tracks
END DEFINE

DEFINE POINT_C_T R 2                ! define point constants, section 2
               "Y slope"     A
               "Y intercept" B
               "X slope"     C
               "X intercept" D
END DEFINE

INIT POINT_C_T(1)    CREATE   2        ! Initialize two entries
      A = 0.01
      B = 1.0
      C = 0.02
      D = 0.5
END INIT

INIT POINT_C_T(2)
      A = 0.03
      B = 3.0
      C = {POINT_C_T(1).C}
      D = 2.5
END INIT

This file defines POINT_C_T as well as point_t and vertex_t and then proceeds to initialize POINT_C_T. Note how POINT_C_T(2).C is initialized in terms of another object. The definition of point_t has changed - it contains keywords setting a class of an object. Before this file is used we have to establish a new class of objects called point.