File DBStorageExtTuple.mesa
Copyright © 1985 by Xerox Corporation. All rights reserved.
Last edited by MBrown on August 12, 1980 3:51 PM
Willie-Sue, February 15, 1985 11:17:02 am PST
DIRECTORY
DBStorageVec USING[VecHeader];
DBStorageExtTuple:
CEDAR
DEFINITIONS =
BEGIN
This interface defines the external (secondary storage) representation of tuples.
TupleBody:
TYPE =
MACHINE
DEPENDENT
RECORD[
header: DBStorageVec.VecHeader,
TupleBody is stored in a vec, so prefix is a VecHeader
groupOffset:
CARDINAL,
offset from TupleBody of 1st GroupEntry
fields:
ARRAY[0..0)
OF
CARDINAL
words for tuple fields (fixed length), uninterpreted at this level
];--TupleBody
This is the layout of the "body" of a tuple, consisting of the fixed-length
representations of the fields, plus the variable-length representation of pointers
to the groups of which this tuple is head. This is limited in length to the maximum
vec length; tuple bodies do not cross page boundaries. Variable-length fields are
represented by a fixed-length portion, at a fixed offset in the tuple body, and a
variable-length portion, which lies outside of the tuple body (maybe on another
page).
SizeOfNullTuple: CARDINAL = SIZE[TupleBody];
END.--DBStorageExtTuple
CHANGE LOG
Created by MBrown on August 12, 1980 3:52 PM
Changed by Willie-Sue on February 15, 1985
made Cedar, added tioga formatting