Type ASSEMBLE
Source Lines : 905
Fixes Applied : 2
Most Recent Version : Tuesday, December 12, 1978
Last Fix ID : [HRC004DS]
Module
DMSDIO (DISKIO)
Function
TO READ ONE OR MORE 800-BYTE RECORDS (BLOCKS) FROM
DISK, OR TO READ ONE 200-BYTE RECORD (SUB-BLOCK) FROM
DISK.
Attributes
NUCLEUS RESIDENT, REENTRANT
Operation
DMSDIOR DETERMINES WHETHER OR NOT THE CALLING PROGRAM
WISHES TO READ A 800-BYTE RECORD. IF IT DOES NOT,
DMSDIOR CHECKS TO SEE IF
THE BYTE COUNT EXCEEDS 800 BYTES, IMPLYING MORE THAN
ONE 800-BYTE RECORD TO BE READ. IF SO, FREE STORAGE
IS OBTAINED, AND CHAINED CCW'S ARE USED INSOFAR AS
PRACTICAL TO READ AS MANY RECORDS AS POSSIBLE WITH
ONE IO TO THE DISK. IF NOT MORE THAN 800, NO FREE
STORAGE IS NECESSARY AS A STANDARD CCW PACKAGE (IN
DIOSECT) IS USED. IN ANY EVENT, WHETHER OR NOT
REPEATED IO'S ARE NECESSARY, THE DATA IS READ INTO
THE DESIGNATED BUFFER, FREE STORAGE IS RETURNED IF
NECESSARY, AND RETURN IS MADE TO THE CALLER. IF THE
BYTE COUNT EXCEEDS 800, IT NEED NOT NECESSARILY BE AN
EXACT MULTIPLE OF 800.
IF THE CALLING PROGRAM WISHES TO READ A 200-BYTE
RECORD (SUB-BLOCK),
DMSDIOR CALLS THE DMSFREE TO OBTAIN AN 800-BYTE
BUFFER. IT THEN READS THE 800-BYTE BLOCK CONTAINING
THE DESIRED SUB-BLOCK INTO THE BUFFER.
NEXT, DMSDIOR EXTRACTS THE DESIRED SUB-BLOCK FROM THE
800-BYTE BUFFER AND MOVES IT TO THE 200-BYTE BUFFER
THE 200-BYTE
BUFFER SPECIFIED IN THE PARAMETER LIST. IT THEN
CALLS THE DMSFRET TO RELEASE THE 800-BYTE BUFFER, THE
ENTIRE BLOCK WAS READ INTO AND RETURNS TO THE CALLING
PROGRAM. SUB-BLOCKS ARE RESERVED FOR FIRST CHAIN
LINK AREAS AND SHOULD NOT BE USED FOR OTHER PURPOSES.
NOTE:
IF THE 200-BYTE BLOCK IS THE FIRST 200 BYTES OF AN
800 BYTE BUFFER, DMSDIOR READS 200 BYTES DIRECTLY
INTO THE DESIGNATED
STORAGE AREA INSTEAD OF OBTAINING FREE STORAGE AND
MOVING THE 200 BYTES LATER.
Calls to Other Routines
DMSLAD, DMSFREE, DMSFRET