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decuslib20-03
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decus/20-0078/maint/tdiid.rno
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00010 .sp 1;.nonum;.lm 9;.ps 50,72
00020 .ts 1,9,17,25,33,41,49,57,65
00030 .pg;.nm appendix D
00040 .ax SIMULA FOR DEC SYSTEM 10#############TD, COMPILER
00050 .nm 1
00060 .st 780302################6###########################Claes Wihlborg
00070 .pg;.lm 9;.p -8,0,10;II.D####DETAILS OF THE HIDDEN/PROTECTED IMPLEMENTATION
00080 .s 2;The implementation details are described below as SIMULA
00090 algorithms approximating the actual assembly code and data structures.
00100 .s;The current implementation of HIDDEN/PROTECTED has the following main properties:
00110 .s;- Whether or not an entity is visible, is entirely decided by ZQU.INVISIBLE.
00120 .s;- The flag ZQU.INVISIBLE is only changed at entry/exit of class/prefixed block.
00130 .s;- Thus, the visibility of an element is not dependent on the access method,
00140 only from where access is made.
00150 .nf;.br;_;
00010 .s;BEGIN
00020 .S; CLASS zqu(idno,no,hid,prot,next);
00030 INTEGER idno; COMMENT identifier number;
00040 BOOLEAN no,hid,prot; COMMENT not hidden protected;
00050 REF(zqu) next;
00060 BEGIN
00070 BOOLEAN invisible,match,virtual__match;
00080 END zqu ;
00090 .s
00100 CLASS zhe;
00110 BEGIN
00120 REF(zqu) declarations;
00130 END zhe;
00140 .s
00150 zhe CLASS zhb;
00160 COMMENT ZHB is used for classes, procedures,
00170 connections and prefixed blocks;
00180 BEGIN
00190 REF(zhb) prefix; COMMENT to this class or block;
00200 REF(zqu) hspec; COMMENT HIDDEN specifications;
00210 END zhb ;
00220 .s
00230 PROCEDURE error(message);VALUE message;TEXT message;;
00240 .s
00250 .s
00260 BEGIN COMMENT pass 1;
00270 .s
00280 CLASS level(head);
00290 REF(zhe) head;
00300 BEGIN
00310 REF(level) environment;
00320 REF(zqu) pspec; COMMENT protected specifications;
00330 environment:-c__level;
00340 END level;
00350 .s
00360 REF(level) c__level;
00370 .s
00380 PROCEDURE class__entry(idno);
00390 INTEGER idno ;
00400 BEGIN
00410 normal__declaration(idno);
00420 c__level:-NEW level(NEW zhb);
00430 END class__entry;
00440 .s
00450 PROCEDURE class__exit;
00460 INSPECT c__level DO BEGIN
00470 IF pspec=/=NONE THEN BEGIN
00480 REF(zqu) pzqu;
00490 IF pspec.no THEN BEGIN
00500 pzqu:-head.declarations;
00510 WHILE pzqu=/=NONE DO BEGIN
00520 pzqu.prot:=pzqu.invisible:=TRUE;
00530 pzqu:-pzqu.next;
00540 END;
00550 WHILE pspec=/=NONE DO BEGIN
00560 BOOLEAN found;
00570 pzqu:-head.declarations;
00580 WHILE pzqu=/=NONE AND NOT found DO
00590 IF pzqu.idno=pspec.idno
00600 THEN found:=TRUE
00610 ELSE pzqu:-pzqu.next;
00620 IF found THEN
00630 pzqu.prot:=pzqu.invisible:=FALSE
00640 ELSE error(
00650 "Attribute XXXX not found.");
00660 pspec:-pspec.next;
00670 END;
00680 END ELSE
00690 WHILE pspec=/=NONE DO BEGIN
00700 BOOLEAN found;
00710 pzqu:-head.declarations;
00720 WHILE pzqu=/=NONE AND NOT found DO
00730 IF pzqu.idno=pspec.idno
00740 THEN found:=TRUE
00750 ELSE pzqu:-pzqu.next;
00760 IF found THEN
00770 pzqu.prot:=pzqu.invisible:=TRUE
00780 ELSE error(
00790 "Attribute XXXX not found.");
00800 pspec:-pspec.next;
00810 END;
00820 END;
00830 c__level:-environment;
00840 END class__exit;
00850 .s
00860 PROCEDURE normal__declaration(idno);
00870 INTEGER idno;
00880 c__level.head.declarations:-
00890 NEW zqu(idno,FALSE,FALSE,FALSE,
00900 c__level.head.declarations);
00910 .s
00920 PROCEDURE hidden__protected__specification
00930 (idno,no,hid,prot);
00940 INTEGER idno;
00950 BOOLEAN no,hid,prot;
00960 BEGIN
00970 IF hid THEN
00980 (c__level.head QUA zhb).hspec:-
00990 NEW zqu(idno,no,TRUE,FALSE,
01000 (c__level.head QUA zhb).hspec);
01010 IF prot THEN c__level.pspec:-NEW zqu
01020 (idno,no,FALSE,TRUE,c__level.pspec);
01030 END hidden__protected__specification;
01040 .s
01050 END pass 1 ;
01060 .s
01070 .s
01080 .s
01090 .s
01100 .s
01110 BEGIN COMMENT pass 2;
01120 .s
01130 CLASS level(pzhe);
01140 REF(zhe) pzhe;
01150 BEGIN
01160 REF(level) environment;
01170 REF(display__stack) sobj;
01180 environment:-c__level;
01190 END level;
01200 .s
01210 REF(level) c__level;
01220 .s
01230 CLASS display__stack(idno,pzqu);
01240 COMMENT Here all redeclarations are saved;
01250 INTEGER idno;
01260 REF(zqu) pzqu;
01270 BEGIN
01280 REF(display__stack) prev;
01290 prev:-c__level.sobj;
01300 END display__stack;
01310 .s
01320 REF(zqu) ARRAY display__array[1:3072];
01330 COMMENT Contains declared items;
01340 .s
01350 PROCEDURE hide(pzhb);
01360 REF(zhb) pzhb;
01370 INSPECT pzhb DO BEGIN
01380 REF(zqu) phid,pzqu;
01390 hide(prefix);
01400 unprotect(THIS zhb);
01410 IF hspec=/=NONE THEN BEGIN
01420 WHILE pzhb=/=NONE DO BEGIN
01430 pzqu:-pzhb.declarations;
01440 WHILE pzqu=/=NONE DO BEGIN
01450 IF NOT pzqu.invisible THEN BEGIN
01460 BOOLEAN found;
01470 phid:-hspec;
01480 WHILE phid=/=NONE AND NOT found DO
01490 IF pzqu.idno=phid.idno
01500 THEN found:=TRUE
01510 ELSE phid:-phid.next;
01520 IF hspec.no THEN BEGIN
01530 IF NOT found THEN BEGIN
01540 IF pzqu.match THEN
01550 pzqu.match:=FALSE
01560 ELSE BEGIN
01570 IF pzqu.prot THEN
01580 pzqu.invisible:=TRUE;
01590 IF NOT pzqu.virtual__match THEN BEGIN
01600 INTEGER idno;
01610 REF(zhb) rzh;
01620 REF(zqu) rzq;
01630 idno:=pzqu.idno;
01640 rzh:-pzhb.prefix;
01650 WHILE rzh=/=NONE DO BEGIN
01660 rzq:-rzh.declarations;
01670 WHILE rzq=/=NONE DO BEGIN
01680 IF idno=rzq.idno AND NOT
01690 rzq.invisible
01700 THEN rzq.match:=TRUE;
01710 rzq:-rzq.next;
01720 END;
01730 rzh:-rzh.prefix;
01740 END;
01750 END;
01760 END;
01770 END;
01780 END ELSE
01790 IF found AND NOT phid.match THEN BEGIN
01800 IF pzqu.prot THEN
01810 pzqu.invisible:=TRUE;
01820 IF NOT pzqu.virtual__match THEN
01830 phid.match:=TRUE;
01840 END;
01850 END;
01860 pzqu:-pzqu.next;
01870 END;
01880 pzhb:-pzhb.prefix;
01890 END;
01900 phid:-hspec;
01910 WHILE phid=/=NONE DO BEGIN
01920 phid.match:=FALSE;
01930 phid:-phid.next;
01940 END;
01950 END;
01960 END hide;
01970 .s
01980 PROCEDURE check__hidden(pzhb);
01990 REF(zhb) pzhb;
02000 INSPECT pzhb DO
02010 IF hspec=/=NONE THEN BEGIN
02020 REF(zqu) pzqu,phid;
02030 WHILE pzhb=/=NONE DO BEGIN
02040 pzqu:-pzhb.declarations;
02050 WHILE pzqu=/=NONE DO BEGIN
02060 IF NOT pzqu.invisible THEN BEGIN
02070 BOOLEAN found;
02080 phid:-hspec;
02090 WHILE phid=/=NONE AND NOT found DO
02100 IF phid.idno=pzqu.idno
02110 THEN found:=TRUE
02120 ELSE phid:-phid.next;
02130 IF found AND NOT phid.match THEN BEGIN
02140 phid.match:=TRUE;
02150 IF NOT(pzqu.prot OR phid.no) THEN
02160 error("Attribute HIDDEN"
02170 " but not PROTECTED");
02180 END;
02190 END;
02200 pzqu:-pzqu.next;
02210 END;
02220 pzhb:-pzhb.prefix;
02230 END;
02240 phid:-hspec;
02250 WHILE phid=/=NONE DO BEGIN
02260 IF NOT phid.match THEN
02270 error("No attribute XXXX visible");
02280 phid.match:=FALSE;
02290 phid:-phid.next;
02300 END;
02310 END hidden check;
02320 .s
02330 PROCEDURE unprotect(pzhb);
02340 REF(zhb) pzhb;
02350 BEGIN
02360 REF(zqu) pzqu;
02370 pzqu:-pzhb.declarations;
02380 WHILE pzqu=/=NONE DO BEGIN
02390 pzqu.invisible:=false;
02400 pzqu:-pzqu.next
02410 END
02420 END unprotect;
02430 .s
02440 PROCEDURE display(pzhe);
02450 REF(zhe) pzhe;
02460 INSPECT pzhe DO BEGIN
02470 REF(zqu) pzqu;
02480 INSPECT THIS zhe WHEN zhb DO display(prefix);
02490 pzqu:-declarations;
02500 WHILE pzqu=/=NONE DO BEGIN
02510 IF NOT pzqu.invisible THEN BEGIN
02520 c__level.sobj:-NEW display__stack
02530 (pzqu.idno,display__array[pzqu.idno]);
02540 display__array[pzqu.idno]:-pzqu;
02550 END;
02560 pzqu:-pzqu.next;
02570 END;
02580 END display;
02590 .s
02600 PROCEDURE undisplay;
02610 WHILE c__level.sobj=/=NONE DO BEGIN
02620 display__array[c__level.sobj.idno]:-
02630 c__level.sobj.pzqu;
02640 c__level.sobj:-c__level.sobj.prev;
02650 END undisplay;
02660 .s
02670 PROCEDURE protect(pzhb);
02680 REF(zhb) pzhb;
02690 INSPECT pzhb DO BEGIN
02700 REF(zqu) pzqu;
02710 pzqu:-declarations;
02720 WHILE pzqu=/=NONE DO BEGIN
02730 IF pzqu.prot THEN pzqu.invisible:=TRUE;
02740 pzqu:-pzqu.next;
02750 END;
02760 protect(prefix);
02770 END protect;
02780 .s
02790 PROCEDURE class__declaration(pzhb);
02800 COMMENT Called for all new classes when a declaration
02810 segment has been read;
02820 REF(zhb) pzhb;
02830 BEGIN
02840 hide(pzhb.prefix);
02850 unprotect(pzhb);
02860 check__hidden(pzhb);
02870 protect(pzhb);
02880 END class__declaration;
02890 .s
02900 REF(zqu) PROCEDURE normal__access(idno);
02910 INTEGER idno;
02920 IF display__array[idno]==NONE
02930 THEN error("Identifier not declared")
02940 ELSE normal__access:-display__array[idno];
02950 .s
02960 REF(zqu) PROCEDURE remote__access(idno,pzhb);
02970 INTEGER idno;
02980 REF(zhb) pzhb; COMMENT Qualifying class;
02990 BEGIN
03000 REF(zqu) pzqu;
03010 BOOLEAN found;
03020 WHILE pzhb=/=NONE AND NOT found DO BEGIN
03030 pzqu:-pzhb.declarations;
03040 WHILE pzqu=/=NONE AND NOT found DO
03050 IF pzqu.idno=idno AND NOT pzqu.invisible
03060 THEN found:=TRUE
03070 ELSE pzqu:-pzqu.next;
03080 pzhb:-pzhb.prefix;
03090 END;
03100 remote__access:-pzqu;
03110 END remote__access;
03120 .s
03130 PROCEDURE class__entry(pzhb);
03140 REF(zhb) pzhb;
03150 BEGIN
03160 c__level:-NEW level(pzhb);
03170 hide(pzhb.prefix);
03180 unprotect(pzhb);
03190 display(pzhb);
03200 END class__entry;
03210 .s
03220 PROCEDURE class__exit;
03230 BEGIN
03240 undisplay;
03250 protect(c__level.pzhe QUA zhb);
03260 c__level:-c__level.environment;
03270 END class__exit;
03280 .s
03290 PROCEDURE entry__prefix__block(pzhb);
03300 REF(zhb) pzhb;
03310 BEGIN
03320 c__level:-NEW level(pzhb);
03330 hide(pzhb.prefix);
03340 display(pzhb);
03350 END entry__prefix__block;
03360 .s
03370 PROCEDURE exit__prefix__block;
03380 BEGIN
03390 undisplay;
03400 protect((c__level.pzhe QUA zhb).prefix);
03410 c__level:-c__level.environment;
03420 END exit__prefix__block;
03430 .s
03440 PROCEDURE entry__connection(pzhb);
03450 REF(zhb) pzhb;
03460 BEGIN
03470 c__level:-NEW level(pzhb);
03480 display(pzhb.prefix);
03490 END entry__connection__block;
03500 .s
03510 PROCEDURE exit__connection;
03520 BEGIN
03530 undisplay;
03540 c__level:-c__level.environment;
03550 END exit__connection__block;
03560 .s
03570 END pass 2;
03580 .s
03590 END Declaration handling: DECsystem-10;
00010 .f;.s
00020 COMMENT
00030 The algorithms above show only the logic of the implementation. In reality
00040 they are more complicated due to some lists being merged together and some
00050 pointers being substituted with the relation
00060 "placed in the immediately following
00070 memory location". As these details only would clutter up the description they
00080 are not given here. For the same reason, a lot of details which are irrelevant
00090 here are missing.
00100 ;