File DBStorageTID.mesa
Copyright © 1985 by Xerox Corporation. All rights reserved.
Last edited by
MBrown on 1-Mar-81 11:21:34
Cattell on January 14, 1983 2:09 pm
Willie-Sue, February 15, 1985 11:09:04 am PST
DIRECTORY
Basics,
DBCommon,
DBEnvironment USING[InternalError],
PrincOpsUtils;
DBStorageTID:
CEDAR
DEFINITIONS
IMPORTS DBEnvironment, PrincOpsUtils
This interface contains definitions that relate to tuple IDs (TIDs).
= BEGIN
TID:
TYPE =
LONG
CARDINAL;
"Pointer" to a tuple in the database. Structure is given by the procedures
below:
DecomposeTID:
PROCEDURE[tid:
TID]
RETURNS[
--p-- DBCommon.DBPage,
--slotIndex--
CARDINAL] =
INLINE
BEGIN
Breaks a TID into the DBPage where the tuple's slot is, and the number of
the slot on that page.
slotIndex: CARDINAL;
TRUSTED
{ slotIndex ←
PrincOpsUtils.BITAND[LOOPHOLE[tid, num Basics.LongNumber].lowbits, TIDSlotMask];
LOOPHOLE[tid, num Basics.LongNumber].lowbits ←
PrincOpsUtils.BITAND[LOOPHOLE[tid, num Basics.LongNumber].lowbits, TIDLowPageMask];
};
RETURN[tid, slotIndex];
END;--DecomposeTID
ConsTID:
PROCEDURE[p: DBCommon.DBPage, slotIndex:
CARDINAL]
RETURNS[
--tid--
TID] =
INLINE
BEGIN
Makes a TID from the DBPage where the tuple's slot is, and the number of
the slot on that page.
IF slotIndex > TIDSlotMask THEN ERROR DBEnvironment.InternalError; -- BadSlotIndex
RETURN[p + slotIndex];
END;--ConsTID
NullTID: TID = 0;
Masks that define the maximum number of slots allowed per page.
Must agree with DBSegmentPrivate.BitsUnused.
DBPageIncrement: CARDINAL = 100B;
TIDSlotMask: CARDINAL = DBPageIncrement - 1; --000077B
TIDLowPageMask: CARDINAL = LAST[CARDINAL] - TIDSlotMask; --177700B
END. -- DBStorageTID
Module History
Created by MBrown on June 10, 1980 3:56 PM
Moved TID-related stuff here from DBStoragePrivateA.
Changed by MBrown on September 26, 1980 11:13 AM
Defined error code BadSlotIndex.
Changed by MBrown on December 8, 1980 1:48 PM
Defined DBPageIncrement, for use in Segment block allocator.
Changed by MBrown on 1-Mar-81 11:22:17
InlineDefs -> Inline.
Changed by Cattell on November 10, 1983 2:14 am
Inline is gone.
Changed by Willie-Sue on February 14, 1985
Made Cedar, added tioga formatting