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128 lines
4.6 KiB
Plaintext
128 lines
4.6 KiB
Plaintext
;
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; File: BTScanPriv.a
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;
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; Contains: BTree scanner's private equates
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;
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; Written by: Dave Feldman
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;
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; Copyright: © 1989-1990 by Apple Computer, Inc., all rights reserved.
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;
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; Change History (most recent first):
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;
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; <3> 8/20/90 gbm (dnf and gbm, really) Change the name of LastTime to
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; LastGoodNode for clarity. Also improve explanation of the
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; Physical Scanner
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; <2> 2/26/90 dnf Add NoMoreReads bit, LastTime bit, cpGoodNodeCount
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; <1.2> 9/7/89 dnf Added CatPosition record
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; <1.1> 7/31/89 dnf Change ForceRead to FirstTime
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; <1.0> 5/30/89 dnf Integrate CatSearch, FileID's and Desktop Database Mgr into one
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; ptch
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;
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; To Do:
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;
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; State record on A6 stack while PScan is in progress
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PSR RECORD 0, Increment
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fcbPtr ds.l 1 ; ptr(FCB) for catalog file under search
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btcbPtr ds.l 1 ; BTCB for catalog file under search
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curNodePtr ds.l 1 ; points to current node in read buffer
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readBufPtr ds.l 1 ; the read buffer
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readBufLen ds.l 1 ; length in bytes of read buffer
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goodCount ds.l 1 ; # of good nodes we've seen so far
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maxNodes ds.l 1 ; # of allocated nodes in tree (calc from btcb)
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buf1stNode ds.l 1 ; node # of 1st node in read buffer
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bufCount ds.l 1 ; # nodes in read buffer
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curNode ds.l 1 ; node # of current node
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curRec ds.w 1 ; record in current node (index)
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flags ds.b 1 ; see flag bits
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align 2 ; make size of state record even
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size equ *-PSR
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ENDR
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; The Physical Scanner
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;
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; The btree physical scanner scans any ROM-btree-manager-like btree and returns
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; each of the records found in the leaf nodes to the caller.
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;
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; BTIPScan is required before any records are read. It converts a catPosition
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; record into an internal state record to use while reading.
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;
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; BTGetPhys delivers the next record
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;
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; BTEndScan converts the internal state record back into a catPosition record
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; that can be used to continue the search from the current position.
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;
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; The btree parser state machine uses a node and record index field to keep
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; track of its position in the btree. Each time BTGetPhys needs a record, the record
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; index is incremented and validated. If the index is off the end of the current
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; node, the node number is incremented and validated (forced into the read buffer).
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;
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; There are several exceptions. To allow a catPosition to specify the beginning
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; of a btree, the record index is not incremented for the first record fetched
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; on a scan. To compensate for this BTEndScan increments the record index when
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; converting its state record into a catPosition.
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;
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; Optimizations:
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; There are two optimizations in the btree scanner
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;
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; 1) Even after a timer has expired, always use up the nodes already
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; in the read buffer. The NoMoreReads bit tells ValidateNode about this
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;
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; 2) Count the number of valid nodes of all types (header, map, index, leaf)
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; and end the search when the count equals the number of allocated nodes
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; indicated by the btree header.
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; ValidateNode counts all valid non-leaf nodes
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; ValidateRecord counts leaf nodes as it increments the current
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; node counter.
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;
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; flag bits
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; These three bits control the corner cases of the ValidateNode
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;
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; FirstTime Forces a read without trying to see if any nodes are already
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; in the buffer. Tells BTGetPhys not to increment the record
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; index.
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; NoMoreReads Indicates that the caller would not like to take any more disk hits
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; Nodes that are in the buffer (conceivably quite a few) are still
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; parsed and returned
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; LastGoodNode Indicates that the last valid node (determined by counting valid
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; nodes and comparing against the free space listed in the btree
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; header) was seen in the previous call to ValidateNode. If this
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; is set on entrance to ValidateNode we know to return an eofErr.
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;
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FirstTime equ 7
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NoMoreReads equ 6
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LastGoodNode equ 5
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; the catalog position record
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CatPosition record 0, increment
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cpWriteCount ds.l 1 ; catalog state for this position <dnf 1.2>
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cpNodeNumber ds.l 1 ; node number of record <dnf 1.2>
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cpRecNumber ds.w 1 ; record # within node <dnf 1.2>
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cpGoodNodeCount ds.l 1 ; # of good nodes we've seen
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cpResrv ds.b 2
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size equ *-CatPosition
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endr
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; HIOParam block
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HIOP RECORD 0, Increment
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qLink ds.l 1;
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qType ds.w 1;
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ioTrap ds.w 1;
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ioCmdAddr ds.l 1;
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ioCompletion ds.l 1;
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ioResult ds.w 1;
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ioNamePtr ds.l 1;
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ioVRefNum ds.w 1 ; integer
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ioRefNum ds.w 1 ; integer
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ioVersNum ds.b 1 ; SignedByte
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ioPermssn ds.b 1 ; signedByte
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ioMisc ds.l 1 ; ptr
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ioBuffer ds.l 1 ; ptr
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ioReqCount ds.l 1 ; longint
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ioActCount ds.l 1 ; longint
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ioPosMode ds.w 1 ; integer
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ioPosOffset ds.l 1 ; longint
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size equ *-HIOP
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ENDR
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