*DECK MDRPTR
USETEXT NIPDEF
USETEXT DRHDR 
USETEXT FREETAB 
PROC MDRPTR(RINGFP,RINGBP,PTR); 
STARTIMS; 
 #
*1DC  MDRPTR
* 
*     1. PROC NAME           AUTHOR              DATE 
*        MDRPTR              C. BITTNER          82/07/01 
* 
*     2. FUNCTIONAL DESCRIPTION 
*        UPDATE DATA RING POINTERS
* 
*     3. METHOD USED
*        UPDATE BACK POINTER OF NEXT ENTRY AND FORWARD
*        POINTER OF PREVIOUS ENTRY (IF MOVED) 
*        BY CALLING MCHKPTR.
* 
*     4. ENTRY PARAMETERS 
*        RINGFP - FORWARD RING POINTER
*        RINGBP - BACKWARD RING POINTER 
*        PTR - CURRENT BUFFER LOCATION
* 
*     5. EXIT PARAMETERS
*        NONE 
* 
*     6. COMDECKS CALLED AND SYMPL TEXTS USED 
*        NIPDEF     DRHDR     FREETAB     OSIZE 
* 
*     7. ROUTINES AND OVERLAYS CALLED 
*        MCHKPTR - UPDATE PTR IF MOVED
*        XTRACE - TRACE PROCEDURE CALL
* 
*     8. DAYFILE MESSAGES AND OTHER IMPORTANT INFORMATION 
*        THIS PROCEDURE IS CALLED BY MAJPTR.
*        W A R N I N G - THE TOTAL SIZE OF ALL GARBAGE COLLECTION 
*                        ROUTINES (MAJPTR,MCHKPTR,MGBGCLT AND 
*                        MDRPTR) CANNOT EXCEED THE PRIMARY
*                        AND SECONDARY
*CALL OSIZE 
 #
STOPIMS;
  
# 
      INPUT PARAMETERS
# 
      ITEM RINGFP;           # RING FORWARD POINTER                    #
      ITEM RINGBP;           # RING BACK POINTER                       #
      ITEM PTR;              # NEW POINTER OF RING ENTRY               #
  
# 
      EXTERNAL REFERENCES 
# 
 XREF 
   BEGIN
   PROC MCHKPTR;             # UPDATE PTR IF MOVED                     #
   PROC XTRACE;              # TRACE PROCEDURE CALL                    #
   END
  
      BEGIN 
  
      CONTROL IFEQ DEBUG,1; 
        XTRACE("MDRPT");
      CONTROL FI; 
  
      P<DRHDRWD> = 0; 
      MCHG = RINGFP;         # NEXT RING ENTRY                         #
      IF MCHG NQ 0
      THEN
        BEGIN 
        MCHKPTR;  # UPDATE POINTER IF MOVED                            #
        BACKPTR[MCHG] = PTR;  # UPDATE BACK POINTER OF NEXT ENTRY      #
        MCHG = RINGBP;  # PREVIOUS RING ENTRY                          #
        MCHKPTR;  # CHECK WHETHER PREVIOUS RING ENTRY MOVED            #
        NEXTPTR[MCHG] = PTR;  # UPDATE NEXT PTR OF PREV. ENTRY         #
        END 
  
      RETURN; 
      END 
TERM