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BTrees.Mod
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BTrees.Mod
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(* OBERON System 3, Release 2.3.
Copyright 1999 ETH Zürich Institute for Computer Systems,
ETH Center, CH-8092 Zürich. e-mail: [email protected].
This module may be used under the conditions of the general Oberon
System 3 license contract. The full text can be downloaded from
"ftp://ftp.inf.ethz.ch/pub/software/Oberon/System3/license.txt;A"
Under the license terms stated it is in particular (a) prohibited to modify
the interface of this module in any way that disagrees with the style
or content of the system and (b) requested to provide all conversions
of the source code to another platform with the name OBERON. *)
MODULE BTrees; (** portable *) (* ejz, *)
IMPORT Files;
(** BTrees is a utility module that manages b-trees with string (64 characters) or longint keys. Each key is linked to
a longint value (org) which normaly is an offset to where the data for that key is stored. *)
CONST
Done* = 0; NotFound* = 1; EntryChanged* = 2; (** res codes *)
Tag = 2425;
PageSize = 2*1024;
BoolSize = 1;
IntSize = 2;
LIntSize = 4;
LInt = 0;
LIntKeySize = LIntSize;
LIntPageN = (PageSize-BoolSize-LIntSize-IntSize-LIntSize) DIV (2*(LIntKeySize+2*LIntSize));
LIntPageSize = LIntSize+BoolSize+IntSize+LIntSize+2*LIntPageN*(LIntKeySize+2*LIntSize);
Str = 1;
StrKeySize* = 64; (** The maximum length of a string key. *)
StrPageN = (PageSize-BoolSize-LIntSize-IntSize-LIntSize) DIV (2*(StrKeySize+2*LIntSize));
StrPageSize = LIntSize+BoolSize+IntSize+LIntSize+2*StrPageN*(StrKeySize+2*LIntSize);
TYPE
Page = POINTER TO PageDesc;
PageDesc = RECORD
org: LONGINT; (* pos of this page *)
p0: LONGINT; (* pos of left page *)
m: INTEGER; (* number of entries *)
dirty: BOOLEAN; (* page changed *)
discard: BOOLEAN; (* TRUE: page is deleted *)
next: Page (* next page in cache *)
END;
Tree* = POINTER TO TreeDesc; (** handle to a b-tree index *)
TreeDesc = RECORD
F: Files.File; (* index file *)
cache: Page; (* list of cached pages *)
org: LONGINT; (* pos of btree header *)
root: LONGINT; (* pos of root page *)
free: LONGINT; (* pos of first free page *)
class: INTEGER; (* 0: LInt, 1: Str *)
noCache: INTEGER; (* number of pages in cache *)
maxCache: INTEGER (* max. number of pages in cache *)
END;
Entry = RECORD
org: LONGINT; (* pos of data for key *)
p: LONGINT (* pos of right page *)
END;
LIntEntry = RECORD (Entry)
key: LONGINT
END;
LIntPage = POINTER TO LIntPageDesc;
LIntPageDesc = RECORD (PageDesc)
e: ARRAY 2*LIntPageN OF LIntEntry
END;
EnumLIntProc* = PROCEDURE (key, org: LONGINT; VAR cont: BOOLEAN); (** enumerator for longin keys *)
StrEntry = RECORD (Entry)
key: ARRAY StrKeySize OF CHAR
END;
StrPage = POINTER TO StrPageDesc;
StrPageDesc = RECORD (PageDesc)
e: ARRAY 2*StrPageN OF StrEntry
END;
EnumStrProc* = PROCEDURE (IN key: ARRAY OF CHAR; org: LONGINT; VAR cont: BOOLEAN); (** enumerator for string keys *)
VAR
MINStrKey*, MAXStrKey*: ARRAY StrKeySize OF CHAR; (** first and last string key *)
(* Allocate space for a new page. *)
PROCEDURE AllocSpace(T: Tree; size: LONGINT): LONGINT;
VAR
R: Files.Rider;
pos: LONGINT;
BEGIN
IF T.free > T.org THEN
pos := T.free; Files.Set(R, T.F, pos);
Files.ReadLInt(R, T.free) (* next free *)
ELSE
pos := Files.Length(T.F); Files.Set(R, T.F, pos);
WHILE size > 0 DO
Files.WriteChar(R, 0X); DEC(size)
END
END;
RETURN pos
END AllocSpace;
PROCEDURE ToFree(T: Tree; P: Page);
VAR R: Files.Rider;
BEGIN
Files.Set(R, T.F, P.org); Files.WriteLInt(R, T.free);
Files.Set(R, T.F, T.org);
Files.WriteInt(R, Tag); Files.WriteInt(R, T.class);
Files.WriteInt(R, T.maxCache);
T.free := P.org; Files.WriteLInt(R, T.free)
END ToFree;
(* Force write back of a page. *)
PROCEDURE WriteLIntPage(T: Tree; p: LIntPage);
VAR
R: Files.Rider;
i: LONGINT;
BEGIN
ASSERT(p.org <= Files.Length(T.F));
Files.Set(R, T.F, p.org);
Files.WriteLInt(R, p.org);
Files.WriteInt(R, p.m);
Files.WriteBool(R, p.discard);
Files.WriteLInt(R, p.p0);
FOR i := 0 TO p.m-1 DO
Files.WriteLInt(R, p.e[i].key);
Files.WriteLInt(R, p.e[i].org);
Files.WriteLInt(R, p.e[i].p)
END;
p.dirty := FALSE
END WriteLIntPage;
(* Allocate a new (memory) page. *)
PROCEDURE NewLIntPage(T: Tree): LIntPage;
VAR
p0, pm, pp: Page;
p: LIntPage;
BEGIN
NEW(p); INC(T.noCache);
IF T.noCache > T.maxCache THEN
pp := NIL; pm := NIL; p0 := T.cache;
WHILE p0 # NIL DO
pp := pm; pm := p0; p0 := p0.next
END;
IF pm.dirty THEN
WriteLIntPage(T, pm(LIntPage))
END;
IF pp # NIL THEN
pp.next := pm.next
ELSE
T.cache := pm.next
END;
T.noCache := T.maxCache
END;
p.next := T.cache; T.cache := p;
p.m := 0; p.p0 := -1; p.org := -1;
p.dirty := TRUE; p.discard := FALSE;
RETURN p
END NewLIntPage;
(* Read page at offset org. *)
PROCEDURE ReadLIntPage(T: Tree; org: LONGINT; VAR p: LIntPage);
VAR
R: Files.Rider;
p0: Page;
i: LONGINT;
BEGIN
IF org < 0 THEN
p := NIL; RETURN
END;
p0 := T.cache;
WHILE (p0 # NIL) & (p0.org # org) DO
p0 := p0.next
END;
IF p0 = NIL THEN
p := NewLIntPage(T);
Files.Set(R, T.F, org);
Files.ReadLInt(R, p.org); ASSERT(p.org = org);
Files.ReadInt(R, p.m);
Files.ReadBool(R, p.discard); ASSERT(~p.discard);
Files.ReadLInt(R, p.p0);
FOR i := 0 TO p.m-1 DO
Files.ReadLInt(R, p.e[i].key);
Files.ReadLInt(R, p.e[i].org);
Files.ReadLInt(R, p.e[i].p)
END;
p.dirty := FALSE
ELSE
p := p0(LIntPage);
IF (p.next = NIL) & (p # T.cache) THEN
p0 := T.cache;
WHILE p0.next # p DO
p0 := p0.next
END;
p0.next := NIL;
p.next := T.cache; T.cache := p
END
END
END ReadLIntPage;
(** Search for key in T. If the key could be found res = Done else res = NotFound. *)
PROCEDURE SearchLInt*(T: Tree; key: LONGINT; VAR org: LONGINT; VAR res: INTEGER);
VAR
i, L, R: LONGINT;
a: LIntPage;
BEGIN
ASSERT(T.class = LInt);
ReadLIntPage(T, T.root, a);
LOOP
L := 0; R := a.m;
WHILE L < R DO
i := (L+R) DIV 2;
IF key <= a.e[i].key THEN
R := i
ELSE
L := i+1
END
END;
IF (R < a.m) & (a.e[R].key = key) THEN
res := Done; org := a.e[R].org;
RETURN
END;
IF R = 0 THEN
ReadLIntPage(T, a.p0, a)
ELSE
ReadLIntPage(T, a.e[R-1].p, a)
END;
IF a = NIL THEN
res := NotFound; org := -1;
RETURN
END
END
END SearchLInt;
PROCEDURE insertLInt(T: Tree; key, org: LONGINT; a: LIntPage; VAR h: BOOLEAN; VAR v: LIntEntry; VAR res: INTEGER);
VAR
i, L, R: LONGINT;
b: LIntPage;
u: LIntEntry;
BEGIN
L := 0; R := a.m;
WHILE L < R DO
i := (L+R) DIV 2;
IF key <= a.e[i].key THEN
R := i
ELSE
L := i+1
END
END;
IF (R < a.m) & (a.e[R].key = key) THEN
res := EntryChanged;
a.dirty := TRUE; a.e[R].org := org
ELSE
IF R = 0 THEN
ReadLIntPage(T, a.p0, b)
ELSE
ReadLIntPage(T, a.e[R-1].p, b)
END;
IF b = NIL THEN
res := Done;
u.p := -1; h := TRUE;
u.key := key; u.org := org
ELSE
insertLInt(T, key, org, b, h, u, res)
END;
IF h THEN
ReadLIntPage(T, a.org, a); (* ensure a is still cached *)
a.dirty := TRUE;
IF a.m < 2*LIntPageN THEN
h := FALSE; i := a.m;
WHILE i > R DO
DEC(i); a.e[i+1] := a.e[i]
END;
a.e[R] := u; INC(a.m)
ELSE
b := NewLIntPage(T);
b.dirty := TRUE; b.org := AllocSpace(T, LIntPageSize);
IF R < LIntPageN THEN
i := LIntPageN-1; v := a.e[i];
WHILE i > R DO
DEC(i); a.e[i+1] := a.e[i]
END;
a.e[R] := u;
i := 0;
WHILE i < LIntPageN DO
b.e[i] := a.e[i+LIntPageN]; INC(i)
END
ELSE
DEC(R, LIntPageN);
i := 0;
IF R = 0 THEN
v := u
ELSE
v := a.e[LIntPageN];
WHILE i < R-1 DO
b.e[i] := a.e[i+LIntPageN+1]; INC(i)
END;
b.e[i] := u; INC(i)
END;
WHILE i < LIntPageN DO
b.e[i] := a.e[i+LIntPageN]; INC(i)
END
END;
a.m := LIntPageN; b.m := LIntPageN;
b.p0 := v.p; v.p := b.org
END
END
END
END insertLInt;
(** Insert a new key into T. If a new key was inserted, res = Done else res = EntryChanged. *)
PROCEDURE InsertLInt*(T: Tree; key, org: LONGINT; VAR res: INTEGER);
VAR
u: LIntEntry;
r, q: LIntPage;
h: BOOLEAN;
BEGIN
ASSERT(T.class = LInt);
h := FALSE; u.p := -1;
ReadLIntPage(T, T.root, r);
insertLInt(T, key, org, r, h, u, res);
IF h THEN
ReadLIntPage(T, T.root, q);
q.dirty := TRUE; q.org := AllocSpace(T, LIntPageSize);
r := NewLIntPage(T);
r.m := 1; r.dirty := TRUE;
r.org := T.root; r.p0 := q.org;
r.e[0] := u
END
END InsertLInt;
PROCEDURE underflowLInt(T: Tree; c, a: LIntPage; s: LONGINT; VAR h: BOOLEAN);
VAR
b: LIntPage;
i, k: LONGINT;
BEGIN
IF s < c.m THEN
ReadLIntPage(T, c.e[s].p, b); k := (b.m-LIntPageN+1) DIV 2;
ReadLIntPage(T, a.org, a); (* ensure a is still cached *)
ReadLIntPage(T, c.org, c); (* ensure c is still cached *)
a.dirty := TRUE; c.dirty := TRUE;
a.e[LIntPageN-1] := c.e[s]; a.e[LIntPageN-1].p := b.p0;
IF k > 0 THEN
i := 0;
WHILE i < k-1 DO
a.e[i+LIntPageN] := b.e[i]; INC(i)
END;
c.e[s] := b.e[k-1]; b.p0 := c.e[s].p;
c.e[s].p := b.org; b.m := b.m-SHORT(k);
b.dirty := TRUE; i := 0;
WHILE i < b.m DO
b.e[i] := b.e[i+k]; INC(i)
END;
a.m := LIntPageN-1+SHORT(k); h := FALSE
ELSE
i := 0;
WHILE i < LIntPageN DO
a.e[i+LIntPageN] := b.e[i]; INC(i)
END;
i := s; DEC(c.m);
WHILE i < c.m DO
c.e[i] := c.e[i+1]; INC(i)
END;
a.m := 2*LIntPageN; h := c.m < LIntPageN
END
ELSE
DEC(s);
IF s = 0 THEN
ReadLIntPage(T, c.p0, b)
ELSE
ReadLIntPage(T, c.e[s-1].p, b)
END;
ReadLIntPage(T, a.org, a); (* ensure a is still cached *)
ReadLIntPage(T, c.org, c); (* ensure c is still cached *)
k := (b.m-LIntPageN+1) DIV 2; b.dirty := TRUE;
IF k > 0 THEN
a.dirty := TRUE; c.dirty := TRUE;
i := LIntPageN-1;
WHILE i > 0 DO
DEC(i); a.e[i+k] := a.e[i]
END;
i := k-1; a.e[i] := c.e[s]; a.e[i].p := a.p0;
b.m := b.m-SHORT(k);
WHILE i > 0 DO
DEC(i); a.e[i] := b.e[i+b.m+1]
END;
c.e[s] := b.e[b.m]; a.p0 := c.e[s].p;
c.e[s].p := a.org; a.m := LIntPageN-1+SHORT(k); h := FALSE
ELSE
c.dirty := TRUE;
c.e[s].p := a.p0; b.e[LIntPageN] := c.e[s]; i := 0;
WHILE i < LIntPageN-1 DO
b.e[i+LIntPageN+1] := a.e[i]; INC(i)
END;
b.m := 2*LIntPageN; DEC(c.m); h := c.m < LIntPageN
END
END
END underflowLInt;
PROCEDURE deleteLInt(T: Tree; key: LONGINT; a: LIntPage; VAR h: BOOLEAN; VAR res: INTEGER);
VAR
i, L, R: LONGINT;
q: LIntPage;
PROCEDURE del(p: LIntPage; VAR h: BOOLEAN);
VAR
k: LONGINT;
q: LIntPage;
BEGIN
k := p.m-1; ReadLIntPage(T, p.e[k].p, q);
IF q # NIL THEN
del(q, h);
IF h THEN underflowLInt(T, p, q, p.m, h) END
ELSE
p.dirty := TRUE; a.dirty := TRUE;
p.e[k].p := a.e[R].p; a.e[R] := p.e[k];
DEC(p.m); h := p.m < LIntPageN
END
END del;
BEGIN
L := 0; R := a.m;
WHILE L < R DO
i := (L+R) DIV 2;
IF key <= a.e[i].key THEN
R := i
ELSE
L := i+1
END
END ;
IF R = 0 THEN
ReadLIntPage(T, a.p0, q)
ELSE
ReadLIntPage(T, a.e[R-1].p, q)
END;
IF (R < a.m) & (a.e[R].key = key) THEN
res := Done;
IF q = NIL THEN
a.dirty := TRUE;
DEC(a.m); h := a.m < LIntPageN; i := R;
WHILE i < a.m DO
a.e[i] := a.e[i+1]; INC(i)
END
ELSE
del(q, h);
IF h THEN underflowLInt(T, a, q, R, h) END
END
ELSIF q # NIL THEN
deleteLInt(T, key, q, h, res);
IF h THEN underflowLInt(T, a, q, R, h) END
END
END deleteLInt;
(** Delete key from T. If key was deleted res = Done else res = NotFound. *)
PROCEDURE DeleteLInt*(T: Tree; key: LONGINT; VAR res: INTEGER);
VAR
p: Page;
r, r0: LIntPage;
h: BOOLEAN;
BEGIN
ASSERT(T.class = LInt); res := NotFound;
ReadLIntPage(T, T.root, r);
deleteLInt(T, key, r, h, res);
IF (res = Done) & h THEN
ReadLIntPage(T, T.root, r);
IF r.m = 0 THEN
IF r.p0 >= 0 THEN
p := T.cache;
WHILE p # NIL DO
IF p.dirty THEN
WriteLIntPage(T, p(LIntPage))
END;
p := p.next
END;
ReadLIntPage(T, r.p0, r0);
r.org := r0.org; r.dirty := TRUE; r.discard := TRUE; r.next := NIL;
WriteLIntPage(T, r); ToFree(T, r);
r0.org := T.root; r0.dirty := TRUE; r0.next := NIL;
T.cache := r0; T.noCache := 1
END
END
END
END DeleteLInt;
PROCEDURE enumerateLInt(T: Tree; p: LIntPage; min, max: LONGINT; enum: EnumLIntProc; VAR cont: BOOLEAN);
VAR
key, lkey, i: LONGINT;
q: LIntPage;
BEGIN
IF p # NIL THEN
lkey := MIN(LONGINT); i := 0;
WHILE (i < p.m) & (lkey < max) DO
key := p.e[i].key;
IF key >= min THEN
IF key > min THEN
IF i = 0 THEN
ReadLIntPage(T, p.p0, q)
ELSE
ReadLIntPage(T, p.e[i-1].p, q)
END;
enumerateLInt(T, q, min, max, enum, cont)
END;
IF cont & (key <= max) THEN
enum(key, p.e[i].org, cont)
END
END;
lkey := key; INC(i)
END;
IF cont & (lkey < max) THEN
ReadLIntPage(T, p.e[p.m-1].p, q);
enumerateLInt(T, q, min, max, enum, cont)
END
END
END enumerateLInt;
(** Enumerate all keys in T witch range from min upto max (key >= min) & (key <= max). *)
PROCEDURE EnumLInt*(T: Tree; min, max: LONGINT; enum: EnumLIntProc);
VAR
r: LIntPage;
cont: BOOLEAN;
BEGIN
ASSERT(T.class = LInt);
ReadLIntPage(T, T.root, r);
IF r.m > 0 THEN
cont := TRUE;
enumerateLInt(T, r, min, max, enum, cont)
END
END EnumLInt;
PROCEDURE minLIntKey(T: Tree; p: LIntPage; VAR key: LONGINT);
BEGIN
IF p # NIL THEN
key := p.e[0].key;
ReadLIntPage(T, p.p0, p);
minLIntKey(T, p, key)
END
END minLIntKey;
(** Searches the smallest key used in T. *)
PROCEDURE MinLIntKey*(T: Tree; VAR key: LONGINT; VAR res: INTEGER);
VAR r: LIntPage;
BEGIN
ASSERT(T.class = LInt);
ReadLIntPage(T, T.root, r);
IF r.m > 0 THEN
minLIntKey(T, r, key); res := Done
ELSE
key := MAX(LONGINT); res := NotFound
END
END MinLIntKey;
PROCEDURE maxLIntKey(T: Tree; p: LIntPage; VAR key: LONGINT);
BEGIN
IF (p # NIL) & (p.m > 0) THEN
key := p.e[p.m-1].key;
ReadLIntPage(T, p.e[p.m-1].p, p);
maxLIntKey(T, p, key)
END
END maxLIntKey;
(** Searches the biggest key used in T. *)
PROCEDURE MaxLIntKey*(T: Tree; VAR key: LONGINT; VAR res: INTEGER);
VAR r: LIntPage;
BEGIN
ASSERT(T.class = LInt);
ReadLIntPage(T, T.root, r);
IF r.m > 0 THEN
maxLIntKey(T, r, key); res := Done
ELSE
key := MIN(LONGINT); res := NotFound
END
END MaxLIntKey;
(** Create a new b-tree with longint keys. The tree is written to F starting at org.
cache gives the minumum number of keys which should fit into the page cache. *)
PROCEDURE NewLInt*(F: Files.File; org: LONGINT; cache: INTEGER): Tree;
VAR
T: Tree;
R: Files.Rider;
BEGIN
NEW(T);
T.maxCache := (cache+2*LIntPageN-1) DIV (2*LIntPageN);
IF T.maxCache < 4 THEN
T.maxCache := 4
END;
T.F := F; T.org := org;
Files.Set(R, F, org);
Files.WriteInt(R, Tag); Files.WriteInt(R, LInt);
Files.WriteInt(R, T.maxCache);
T.free := -1; Files.WriteLInt(R, T.free);
T.root := AllocSpace(T, LIntPageSize);
T.class := LInt; T.noCache := 0;
T.cache := NewLIntPage(T);
T.cache.dirty := TRUE;
T.cache.org := T.root;
RETURN T
END NewLInt;
(* Force write back of a page. *)
PROCEDURE WriteStrPage(T: Tree; p: StrPage);
VAR
R: Files.Rider;
i: LONGINT;
BEGIN
ASSERT(p.org <= Files.Length(T.F));
Files.Set(R, T.F, p.org);
Files.WriteLInt(R, p.org);
Files.WriteInt(R, p.m);
Files.WriteBool(R, p.discard);
Files.WriteLInt(R, p.p0);
FOR i := 0 TO p.m-1 DO
Files.WriteFixString(R, p.e[i].key, StrKeySize);
Files.WriteLInt(R, p.e[i].org);
Files.WriteLInt(R, p.e[i].p)
END;
p.dirty := FALSE
END WriteStrPage;
(* Allocate a new (memory) page. *)
PROCEDURE NewStrPage(T: Tree): StrPage;
VAR
p0, pm, pp: Page;
p: StrPage;
BEGIN
NEW(p); INC(T.noCache);
IF T.noCache > T.maxCache THEN
pp := NIL; pm := NIL; p0 := T.cache;
WHILE p0 # NIL DO
pp := pm; pm := p0; p0 := p0.next
END;
IF pm.dirty THEN
WriteStrPage(T, pm(StrPage))
END;
IF pp # NIL THEN
pp.next := pm.next
ELSE
T.cache := pm.next
END;
T.noCache := T.maxCache
END;
p.next := T.cache; T.cache := p;
p.m := 0; p.p0 := -1; p.org := -1;
p.dirty := TRUE; p.discard := FALSE;
RETURN p
END NewStrPage;
(* Read page at offset org. *)
PROCEDURE ReadStrPage(T: Tree; org: LONGINT; VAR p: StrPage);
VAR
R: Files.Rider;
p0: Page;
i: LONGINT;
BEGIN
IF org < 0 THEN
p := NIL; RETURN
END;
p0 := T.cache;
WHILE (p0 # NIL) & (p0.org # org) DO
p0 := p0.next
END;
IF p0 = NIL THEN
p := NewStrPage(T);
Files.Set(R, T.F, org);
Files.ReadLInt(R, p.org); ASSERT(p.org = org);
Files.ReadInt(R, p.m);
Files.ReadBool(R, p.discard); ASSERT(~p.discard);
Files.ReadLInt(R, p.p0);
FOR i := 0 TO p.m-1 DO
Files.ReadFixString(R, p.e[i].key, StrKeySize);
Files.ReadLInt(R, p.e[i].org);
Files.ReadLInt(R, p.e[i].p)
END;
p.dirty := FALSE
ELSE
p := p0(StrPage);
IF (p.next = NIL) & (p # T.cache) THEN
p0 := T.cache;
WHILE p0.next # p DO
p0 := p0.next
END;
p0.next := NIL;
p.next := T.cache; T.cache := p
END
END
END ReadStrPage;
(** Search for key in T. If the key could be found res = Done else res = NotFound. *)
PROCEDURE SearchStr*(T: Tree; IN key: ARRAY OF CHAR; VAR org: LONGINT; VAR res: INTEGER);
VAR
i, L, R: LONGINT;
a: StrPage;
sKey: ARRAY StrKeySize OF CHAR;
BEGIN
ASSERT(T.class = Str); sKey := key;
ReadStrPage(T, T.root, a);
LOOP
L := 0; R := a.m;
WHILE L < R DO
i := (L+R) DIV 2;
IF sKey <= a.e[i].key THEN
R := i
ELSE
L := i+1
END
END;
IF (R < a.m) & (a.e[R].key = sKey) THEN
res := Done; org := a.e[R].org;
RETURN
END;
IF R = 0 THEN
ReadStrPage(T, a.p0, a)
ELSE
ReadStrPage(T, a.e[R-1].p, a)
END;
IF a = NIL THEN
res := NotFound; org := -1;
RETURN
END
END
END SearchStr;
PROCEDURE insertStr(T: Tree; VAR key: ARRAY OF CHAR; org: LONGINT; a: StrPage; VAR h: BOOLEAN; VAR v: StrEntry; VAR res: INTEGER);
VAR
i, L, R: LONGINT;
b: StrPage;
u: StrEntry;
BEGIN
L := 0; R := a.m;
WHILE L < R DO
i := (L+R) DIV 2;
IF key <= a.e[i].key THEN
R := i
ELSE
L := i+1
END
END;
IF (R < a.m) & (a.e[R].key = key) THEN
res := EntryChanged;
a.dirty := TRUE; a.e[R].org := org
ELSE
IF R = 0 THEN
ReadStrPage(T, a.p0, b)
ELSE
ReadStrPage(T, a.e[R-1].p, b)
END;
IF b = NIL THEN
res := Done;
u.p := -1; h := TRUE;
u.key := key; u.org := org
ELSE
insertStr(T, key, org, b, h, u, res)
END;
IF h THEN
ReadStrPage(T, a.org, a); (* ensure a is still cached *)
a.dirty := TRUE;
IF a.m < 2*StrPageN THEN
h := FALSE; i := a.m;
WHILE i > R DO
DEC(i); a.e[i+1] := a.e[i]
END;
a.e[R] := u; INC(a.m)
ELSE
b := NewStrPage(T);
b.dirty := TRUE; b.org := AllocSpace(T, StrPageSize);
IF R < StrPageN THEN
i := StrPageN-1; v := a.e[i];
WHILE i > R DO
DEC(i); a.e[i+1] := a.e[i]
END;
a.e[R] := u;
i := 0;
WHILE i < StrPageN DO
b.e[i] := a.e[i+StrPageN]; INC(i)
END
ELSE
DEC(R, StrPageN);
i := 0;
IF R = 0 THEN
v := u
ELSE
v := a.e[StrPageN];
WHILE i < R-1 DO
b.e[i] := a.e[i+StrPageN+1]; INC(i)
END;
b.e[i] := u; INC(i)
END;
WHILE i < StrPageN DO
b.e[i] := a.e[i+StrPageN]; INC(i)
END
END;
a.m := StrPageN; b.m := StrPageN;
b.p0 := v.p; v.p := b.org
END
END
END
END insertStr;
(** Insert a new key into T. If a new key was inserted, res = Done else res = EntryChanged. *)
PROCEDURE InsertStr*(T: Tree; IN key: ARRAY OF CHAR; org: LONGINT; VAR res: INTEGER);
VAR
u: StrEntry;
r, q: StrPage;
h: BOOLEAN;
sKey: ARRAY StrKeySize OF CHAR;
BEGIN
ASSERT(T.class = Str); sKey := key;
h := FALSE; u.p := -1;
ReadStrPage(T, T.root, r);
insertStr(T, sKey, org, r, h, u, res);
IF h THEN
ReadStrPage(T, T.root, q);
q.dirty := TRUE; q.org := AllocSpace(T, StrPageSize);
r := NewStrPage(T);
r.m := 1; r.dirty := TRUE;
r.org := T.root; r.p0 := q.org;
r.e[0] := u
END
END InsertStr;
PROCEDURE underflowStr(T: Tree; c, a: StrPage; s: LONGINT; VAR h: BOOLEAN);
VAR
b: StrPage;
i, k: LONGINT;
BEGIN
IF s < c.m THEN
ReadStrPage(T, c.e[s].p, b); k := (b.m-StrPageN+1) DIV 2;
ReadStrPage(T, a.org, a); (* ensure a is still cached *)
ReadStrPage(T, c.org, c); (* ensure c is still cached *)
a.dirty := TRUE; c.dirty := TRUE;
a.e[StrPageN-1] := c.e[s]; a.e[StrPageN-1].p := b.p0;
IF k > 0 THEN
i := 0;
WHILE i < k-1 DO
a.e[i+StrPageN] := b.e[i]; INC(i)
END;
c.e[s] := b.e[k-1]; b.p0 := c.e[s].p;
c.e[s].p := b.org; b.m := b.m-SHORT(k);
b.dirty := TRUE; i := 0;
WHILE i < b.m DO
b.e[i] := b.e[i+k]; INC(i)
END;
a.m := StrPageN-1+SHORT(k); h := FALSE
ELSE
i := 0;
WHILE i < StrPageN DO
a.e[i+StrPageN] := b.e[i]; INC(i)
END;
i := s; DEC(c.m);
WHILE i < c.m DO
c.e[i] := c.e[i+1]; INC(i)
END;
a.m := 2*StrPageN; h := c.m < StrPageN
END
ELSE
DEC(s);
IF s = 0 THEN
ReadStrPage(T, c.p0, b)
ELSE
ReadStrPage(T, c.e[s-1].p, b)
END;
ReadStrPage(T, a.org, a); (* ensure a is still cached *)
ReadStrPage(T, c.org, c); (* ensure c is still cached *)
k := (b.m-StrPageN+1) DIV 2; b.dirty := TRUE;
IF k > 0 THEN
a.dirty := TRUE; c.dirty := TRUE;
i := StrPageN-1;
WHILE i > 0 DO
DEC(i); a.e[i+k] := a.e[i]
END;
i := k-1; a.e[i] := c.e[s]; a.e[i].p := a.p0;
b.m := b.m-SHORT(k);
WHILE i > 0 DO
DEC(i); a.e[i] := b.e[i+b.m+1]
END;
c.e[s] := b.e[b.m]; a.p0 := c.e[s].p;
c.e[s].p := a.org; a.m := StrPageN-1+SHORT(k); h := FALSE
ELSE
c.dirty := TRUE;
c.e[s].p := a.p0; b.e[StrPageN] := c.e[s]; i := 0;
WHILE i < StrPageN-1 DO
b.e[i+StrPageN+1] := a.e[i]; INC(i)
END;
b.m := 2*StrPageN; DEC(c.m); h := c.m < StrPageN
END
END
END underflowStr;
PROCEDURE deleteStr(T: Tree; VAR key: ARRAY OF CHAR; a: StrPage; VAR h: BOOLEAN; VAR res: INTEGER);
VAR
i, L, R: LONGINT;
q: StrPage;
PROCEDURE del(p: StrPage; VAR h: BOOLEAN);
VAR
k: LONGINT;
q: StrPage;
BEGIN
k := p.m-1; ReadStrPage(T, p.e[k].p, q);
IF q # NIL THEN
del(q, h);
IF h THEN underflowStr(T, p, q, p.m, h) END
ELSE
p.dirty := TRUE; a.dirty := TRUE;
p.e[k].p := a.e[R].p; a.e[R] := p.e[k];
DEC(p.m); h := p.m < StrPageN
END
END del;
BEGIN
L := 0; R := a.m;
WHILE L < R DO
i := (L+R) DIV 2;
IF key <= a.e[i].key THEN
R := i
ELSE
L := i+1
END
END ;
IF R = 0 THEN
ReadStrPage(T, a.p0, q)
ELSE
ReadStrPage(T, a.e[R-1].p, q)
END;
IF (R < a.m) & (a.e[R].key = key) THEN
res := Done;
IF q = NIL THEN
a.dirty := TRUE;
DEC(a.m); h := a.m < StrPageN; i := R;
WHILE i < a.m DO
a.e[i] := a.e[i+1]; INC(i)
END
ELSE
del(q, h);
IF h THEN underflowStr(T, a, q, R, h) END
END
ELSIF q # NIL THEN
deleteStr(T, key, q, h, res);
IF h THEN underflowStr(T, a, q, R, h) END
END
END deleteStr;
(** Delete key from T. If key was deleted res = Done else res = NotFound. *)
PROCEDURE DeleteStr*(T: Tree; IN key: ARRAY OF CHAR; VAR res: INTEGER);
VAR
p: Page;
r, r0: StrPage;
sKey: ARRAY StrKeySize OF CHAR;
h: BOOLEAN;
BEGIN
ASSERT(T.class = Str); sKey := key; res := NotFound;
ReadStrPage(T, T.root, r);
deleteStr(T, sKey, r, h, res);
IF (res = Done) & h THEN
ReadStrPage(T, T.root, r);
IF r.m = 0 THEN
IF r.p0 >= 0 THEN
p := T.cache;
WHILE p # NIL DO
IF p.dirty THEN
WriteStrPage(T, p(StrPage))
END;
p := p.next
END;
ReadStrPage(T, r.p0, r0);
r.org := r0.org; r.dirty := TRUE; r.discard := TRUE; r.next := NIL;
WriteStrPage(T, r); ToFree(T, r);
r0.org := T.root; r0.dirty := TRUE; r0.next := NIL;
T.cache := r0; T.noCache := 1
END
END
END
END DeleteStr;
PROCEDURE enumerateStr(T: Tree; p: StrPage; IN min, max: ARRAY OF CHAR; enum: EnumStrProc; VAR cont: BOOLEAN);
VAR
key, lkey: ARRAY StrKeySize OF CHAR;
q: StrPage;
i: LONGINT;
BEGIN
IF p # NIL THEN
lkey := MINStrKey; i := 0;
WHILE (i < p.m) & (lkey < max) DO
key := p.e[i].key;
IF key >= min THEN
IF key > min THEN
IF i = 0 THEN
ReadStrPage(T, p.p0, q)
ELSE
ReadStrPage(T, p.e[i-1].p, q)
END;
enumerateStr(T, q, min, max, enum, cont)
END;
IF cont & (key <= max) THEN
enum(key, p.e[i].org, cont)
END
END;
lkey := key; INC(i)
END;
IF cont & (lkey < max) THEN
ReadStrPage(T, p.e[p.m-1].p, q);