154 lines
3.4 KiB
C
154 lines
3.4 KiB
C
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// Copyright (c) 1993-1999 Microsoft Corporation
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#include "y1.h"
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/*
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* yclsur.1c
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*
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* Modified to make debug code conditionally compile.
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* 28-Aug-81
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* Bob Denny
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*/
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void
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closure( int i)
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{
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/* generate the closure of state i */
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int work, k;
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SSIZE_T ch, c;
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register struct wset *u, *v;
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SSIZE_T *pi;
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SSIZE_T **s, **t;
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struct item *q;
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register struct item *p;
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++zzclose;
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/* first, copy kernel of state i to wsets */
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cwp = wsets;
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ITMLOOP(i,p,q)
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{
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cwp->pitem = p->pitem;
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cwp->flag = 1; /* this item must get closed */
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SETLOOP(k) cwp->ws.lset[k] = p->look->lset[k];
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WSBUMP(cwp);
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}
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/* now, go through the loop, closing each item */
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work = 1;
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while( work )
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{
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work = 0;
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WSLOOP(wsets,u)
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{
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if( u->flag == 0 ) continue;
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c = *(u->pitem); /* dot is before c */
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if( c < NTBASE )
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{
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u->flag = 0;
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continue; /* only interesting case is where . is before nonterminal */
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}
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/* compute the lookahead */
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aryfil( clset.lset, tbitset, 0 );
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/* find items involving c */
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WSLOOP(u,v)
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{
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if( v->flag == 1 && *(pi=v->pitem) == c )
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{
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v->flag = 0;
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if( nolook ) continue;
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while( (ch= *++pi)>0 )
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{
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if( ch < NTBASE )
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{
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/* terminal symbol */
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SETBIT( clset.lset, ch );
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break;
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}
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/* nonterminal symbol */
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setunion( clset.lset, pfirst[ch-NTBASE]->lset );
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if( !pempty[ch-NTBASE] ) break;
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}
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if( ch<=0 ) setunion( clset.lset, v->ws.lset );
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}
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}
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/* now loop over productions derived from c */
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c -= NTBASE; /* c is now nonterminal number */
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t = pres[c+1];
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for( s=pres[c]; s<t; ++s )
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{
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/* put these items into the closure */
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WSLOOP(wsets,v)
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{
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/* is the item there */
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if( v->pitem == *s )
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{
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/* yes, it is there */
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if( nolook ) goto nexts;
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if( setunion( v->ws.lset, clset.lset ) ) v->flag = work = 1;
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goto nexts;
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}
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}
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/* not there; make a new entry */
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if( cwp-wsets+1 >= WSETSIZE ) error( "working set overflow" );
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cwp->pitem = *s;
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cwp->flag = 1;
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if( !nolook )
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{
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work = 1;
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SETLOOP(k) cwp->ws.lset[k] = clset.lset[k];
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}
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WSBUMP(cwp);
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nexts:
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;
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}
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}
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}
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/* have computed closure; flags are reset; return */
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if( cwp > zzcwp ) zzcwp = cwp;
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#ifdef debug
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if( foutput!=NULL )
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{
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fprintf( foutput, "\nState %d, nolook = %d\n", i, nolook );
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WSLOOP(wsets,u)
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{
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if( u->flag ) fprintf( foutput, "flag set!\n");
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u->flag = 0;
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fprintf( foutput, "\t%s", writem(u->pitem));
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prlook( &u->ws );
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fprintf( foutput, "\n" );
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}
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}
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#endif
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}
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