BITMP

Prolog  

Control Block Contents  
   BITMP DSECT

Storage Layout  

Cross Reference (Contains links to field and bit definitions)  

BITMP Prolog

 NAME       : HCPBITMP
 DESCRIPTION: Bit Map Control Block
 DSECT      : BITMP
 FUNCTION   : The Bit Map Control Block contains fields that control
              access to the bits, pointers to the bits, and other
              useful stuff.
 LOCATED BY : R2 at entry to HCPBIT routines points to a full
              word that points to the BITMP.
 CREATED BY : HCPBIT
 DELETED BY : HCPBITRL
 REFERENCES : None
 SERIALIZED : Changes to the contents of bit maps need not be done
              under the control of the BITMP lock, because
              Compare-and-Swap is used to change the bits and the
              pointers to the bits.  However, if serialization is
              needed, the users of the bit maps should call the
              HCPBIT entry points AS, AX, RS, RX, SX, etc., which
              call the analogous HCPLCK entry points for control
              over the BITMP lock.

BITMP Control Block Content

BITMP DSECT

Hex   Dec Type/Val   Lng Label (dup)    Comments
---- ---- --------- ---- -------------- --------
0000    0 Structure      BITMP          Bit Map Control Block
     This portion of the BITMP is fixed length. The final size of the BITMP
     depends on how many pointers are actually stored at BITMPPTR.
          00000000       BITMPFXD       * Fixed portion of the BITMP
0000    0 Dbl-Word     8 BITMPLCK (3)   The BITMP lock
0018   24 Signed       4 BITMPMAX       The max bit number allowed
001C   28 Signed       4 BITMPPGS       How many pointers at BITMPPTR
          00000020       BITMPFSZ       *-BITMP Size of fixed portion of
                                        BITMP expressed in bytes.
0020   32 Address      4 BITMPPTR (0)   Start of variable length data.
                                        Pointers to pages of bits. The
                                        upper bound of the subscript for
                                        this array is contained in
                                        BITMPPGS.

BITMP Storage Layout

          
*** BITMP - Bit Map Control Block
*
*     +-------------------------------------------------------+
*   0 |                                                       |
*     =                       BITMPLCK                        =
*     |                                                       |
*     +---------------------------+---------------------------+
*  18 |         BITMPMAX          |         BITMPPGS          |
*     +---------------------------+---------------------------+
*
*** BITMP - Bit Map Control Block

BITMP Cross Reference

Symbol         Dspl Value
-------------- ---- -----
BITMPFSZ       001C 00000020
BITMPFXD       0000 00000000
BITMPLCK       0000
BITMPMAX       0018
BITMPPGS       001C
BITMPPTR       0020