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Atari Mega Archive 1
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flexs237.zoo
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dfa.c
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1990-06-28
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/* dfa - DFA construction routines */
/*-
* Copyright (c) 1990 The Regents of the University of California.
* All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Vern Paxson.
*
* The United States Government has rights in this work pursuant
* to contract no. DE-AC03-76SF00098 between the United States
* Department of Energy and the University of California.
*
* Redistribution and use in source and binary forms are permitted provided
* that: (1) source distributions retain this entire copyright notice and
* comment, and (2) distributions including binaries display the following
* acknowledgement: ``This product includes software developed by the
* University of California, Berkeley and its contributors'' in the
* documentation or other materials provided with the distribution and in
* all advertising materials mentioning features or use of this software.
* Neither the name of the University nor the names of its contributors may
* be used to endorse or promote products derived from this software without
* specific prior written permission.
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
*/
#ifndef lint
static char rcsid[] =
"@(#) $Header: /usr/fsys/odin/a/vern/flex/RCS/dfa.c,v 2.7 90/06/27 23:48:15 vern Exp $ (LBL)";
#endif
#include "flexdef.h"
/* declare functions that have forward references */
void dump_associated_rules PROTO((FILE*, int));
void dump_transitions PROTO((FILE*, int[]));
void sympartition PROTO((int[], int, int[], int[]));
int symfollowset PROTO((int[], int, int, int[]));
/* check_for_backtracking - check a DFA state for backtracking
*
* synopsis
* int ds, state[numecs];
* check_for_backtracking( ds, state );
*
* ds is the number of the state to check and state[] is its out-transitions,
* indexed by equivalence class, and state_rules[] is the set of rules
* associated with this state
*/
void check_for_backtracking( ds, state )
int ds;
int state[];
{
if ( (reject && ! dfaacc[ds].dfaacc_set) || ! dfaacc[ds].dfaacc_state )
{ /* state is non-accepting */
++num_backtracking;
if ( backtrack_report )
{
fprintf( backtrack_file, "State #%d is non-accepting -\n", ds );
/* identify the state */
dump_associated_rules( backtrack_file, ds );
/* now identify it further using the out- and jam-transitions */
dump_transitions( backtrack_file, state );
putc( '\n', backtrack_file );
}
}
}
/* check_trailing_context - check to see if NFA state set constitutes
* "dangerous" trailing context
*
* synopsis
* int nfa_states[num_states+1], num_states;
* int accset[nacc+1], nacc;
* check_trailing_context( nfa_states, num_states, accset, nacc );
*
* NOTES
* Trailing context is "dangerous" if both the head and the trailing
* part are of variable size \and/ there's a DFA state which contains
* both an accepting state for the head part of the rule and NFA states
* which occur after the beginning of the trailing context.
* When such a rule is matched, it's impossible to tell if having been
* in the DFA state indicates the beginning of the trailing context
* or further-along scanning of the pattern. In these cases, a warning
* message is issued.
*
* nfa_states[1 .. num_states] is the list of NFA states in the DFA.
* accset[1 .. nacc] is the list of accepting numbers for the DFA state.
*/
void check_trailing_context( nfa_states, num_states, accset, nacc )
int *nfa_states, num_states;
int *accset;
register int nacc;
{
register int i, j;
for ( i = 1; i <= num_states; ++i )
{
int ns = nfa_states[i];
register int type = state_type[ns];
register int ar = assoc_rule[ns];
if ( type == STATE_NORMAL || rule_type[ar] != RULE_VARIABLE )
{ /* do nothing */
}
else if ( type == STATE_TRAILING_CONTEXT )
{
/* potential trouble. Scan set of accepting numbers for
* the one marking the end of the "head". We assume that
* this looping will be fairly cheap since it's rare that
* an accepting number set is large.
*/
for ( j = 1; j <= nacc; ++j )
if ( accset[j] & YY_TRAILING_HEAD_MASK )
{
fprintf( stderr,
"%s: Dangerous trailing context in rule at line %d\n",
program_name, rule_linenum[ar] );
return;
}
}
}
}
/* dump_associated_rules - list the rules associated with a DFA state
*
* synopisis
* int ds;
* FILE *file;
* dump_associated_rules( file, ds );
*
* goes through the set of NFA states associated with the DFA and
* extracts the first MAX_ASSOC_RULES unique rules, sorts them,
* and writes a report to the given file
*/
void dump_associated_rules( file, ds )
FILE *file;
int ds;
{
register int i, j;
register int num_associated_rules = 0;
int rule_set[MAX_ASSOC_RULES + 1];
int *dset = dss[ds];
int size = dfasiz[ds];
for ( i = 1; i <= size; ++i )
{
register rule_num = rule_linenum[assoc_rule[dset[i]]];
for ( j = 1; j <= num_associated_rules; ++j )
if ( rule_num == rule_set[j] )
break;
if ( j > num_associated_rules )
{ /* new rule */
if ( num_associated_rules < MAX_ASSOC_RULES )
rule_set[++num_associated_rules] = rule_num;
}
}
bubble( rule_set, num_associated_rules );
fprintf( file, " associated rule line numbers:" );
for ( i = 1; i <= num_associated_rules; ++i )
{
if ( i % 8 == 1 )
putc( '\n', file );
fprintf( file, "\t%d", rule_set[i] );
}
putc( '\n', file );
}
/* dump_transitions - list the transitions associated with a DFA state
*
* synopisis
* int state[numecs];
* FILE *file;
* dump_transitions( file, state );
*
* goes through the set of out-transitions and lists them in human-readable
* form (i.e., not as equivalence classes); also lists jam transitions
* (i.e., all those which are not out-transitions, plus EOF). The dump
* is done to the given file.
*/
void dump_transitions( file, state )
FILE *file;
int state[];
{
register int i, ec;
int out_char_set[CSIZE];
for ( i = 0; i < csize; ++i )
{
ec = abs( ecgroup[i] );
out_char_set[i] = state[ec];
}
fprintf( file, " out-transitions: " );
list_character_set( file, out_char_set );
/* now invert the members of the set to get the jam transitions */
for ( i = 0; i < csize; ++i )
out_char_set[i] = ! out_char_set[i];
fprintf( file, "\n jam-transitions: EOF " );
list_character_set( file, out_char_set );
putc( '\n', file );
}
/* epsclosure - construct the epsilon closure of a set of ndfa states
*
* synopsis
* int t[current_max_dfa_size], numstates, accset[num_rules + 1], nacc;
* int hashval;
* int *epsclosure();
* t = epsclosure( t, &numstates, accset, &nacc, &hashval );
*
* NOTES
* the epsilon closure is the set of all states reachable by an arbitrary
* number of epsilon transitions which themselves do not have epsilon
* transitions going out, unioned with the set of states which have non-null
* accepting numbers. t is an array of size numstates of nfa state numbers.
* Upon return, t holds the epsilon closure and numstates is updated. accset
* holds a list of the accepting numbers, and the size of accset is given
* by nacc. t may be subjected to reallocation if it is not large enough
* to hold the epsilon closure.
*
* hashval is the hash value for the dfa corresponding to the state set
*/
int *epsclosure( t, ns_addr, accset, nacc_addr, hv_addr )
int *t, *ns_addr, accset[], *nacc_addr, *hv_addr;
{
register int stkpos, ns, tsp;
int numstates = *ns_addr, nacc, hashval, transsym, nfaccnum;
int stkend, nstate;
static int did_stk_init = false, *stk;
#define MARK_STATE(state) \
trans1[state] = trans1[state] - MARKER_DIFFERENCE;
#define IS_MARKED(state) (trans1[state] < 0)
#define UNMARK_STATE(state) \
trans1[state] = trans1[state] + MARKER_DIFFERENCE;
#define