automata.c

本工具提供一个词法分析器和语法分析器的集成开发环境

/* Automata conversion functions for DLG
 *
 * SOFTWARE RIGHTS
 *
 * We reserve no LEGAL rights to the Purdue Compiler Construction Tool
 * Set (PCCTS) -- PCCTS is in the public domain.  An individual or
 * company may do whatever they wish with source code distributed with
 * PCCTS or the code generated by PCCTS, including the incorporation of
 * PCCTS, or its output, into commerical software.
 *
 * We encourage users to develop software with PCCTS.  However, we do ask
 * that credit is given to us for developing PCCTS.  By "credit",
 * we mean that if you incorporate our source code into one of your
 * programs (commercial product, research project, or otherwise) that you
 * acknowledge this fact somewhere in the documentation, research report,
 * etc...  If you like PCCTS and have developed a nice tool with the
 * output, please mention that you developed it using PCCTS.  In
 * addition, we ask that this header remain intact in our source code.
 * As long as these guidelines are kept, we expect to continue enhancing
 * this system and expect to make other tools available as they are
 * completed.
 *
 * DLG 1.33
 * Will Cohen
 * With mods by Terence Parr; AHPCRC, University of Minnesota
 * 1989-1998
 */

#include <stdio.h>
#include "dlg.h"
#ifdef MEMCHK
#include "trax.h"
#else
#ifdef __STDC__
#include <stdlib.h>
#else
#include <malloc.h>
#endif /* __STDC__ */
#endif

#define hash_list struct _hash_list_
hash_list{
	hash_list *next;	/* next thing in list */
	dfa_node *node;
 };

int	dfa_allocated = 0;	/* keeps track of number of dfa nodes */
dfa_node	**dfa_array;	/* root of binary tree that stores dfa array */
dfa_node	*dfa_model_node;
hash_list 	*dfa_hash[HASH_SIZE];	/* used to quickly find */
					/* desired dfa node */

void
make_dfa_model_node(width)
int width;
{
	register int i;
	dfa_model_node = (dfa_node*) malloc(sizeof(dfa_node)
			 + sizeof(int)*width);
	dfa_model_node->node_no = -1; /* impossible value for real dfa node */
	dfa_model_node->dfa_set = 0;
	dfa_model_node->alternatives = FALSE;
	dfa_model_node->done = FALSE;
	dfa_model_node->nfa_states = empty;
	for(i = 0; i<width; i++){
		dfa_model_node->trans[i] = NIL_INDEX;
	}
}


/* adds a new nfa to the binary tree and returns a pointer to it */
dfa_node *new_dfa_node(nfa_states)
set nfa_states;
{
	register int j;
	register dfa_node *t;
	static int dfa_size=0;	/* elements dfa_array[] can hold */

	++dfa_allocated;
	if (dfa_size<=dfa_allocated){
		/* need to redo array */
		if (!dfa_array){
			/* need some to do inital allocation */
			dfa_size=dfa_allocated+DFA_MIN;
			dfa_array=(dfa_node **) malloc(sizeof(dfa_node*)*
				dfa_size);
		}else{
			/* need more space */
			dfa_size=2*(dfa_allocated+1);
			dfa_array=(dfa_node **) realloc(dfa_array,
				sizeof(dfa_node*)*dfa_size);
		}
	}
	/* fill out entry in array */
	t = (dfa_node*) malloc(sizeof(nfa_node)+sizeof(int)*class_no);
	*t = *dfa_model_node;
	for (j=0; j<class_no; ++j)
		t->trans[j] = NIL_INDEX;
	t->node_no = dfa_allocated;
	t->nfa_states = set_dup(nfa_states);
	dfa_array[dfa_allocated] = t;
	return t;
}


/* past a pointer to the start start of the nfa graph
 * nfa_to_dfa convers this graph to dfa.  The function returns
 * a pointer to the first dfa state.
 * NOTE:  The function that prints out the table will have to figure out how
 * to find the other dfa states given the first dfa_state and the number of dfa
 * nodes allocated
 */
dfa_node **nfa_to_dfa(start)
nfa_node *start;
{
	register dfa_node *d_state, *trans_d_state;
	register int a;
	set t;
	int last_done;
	unsigned *nfa_list;
	unsigned *reach_list;

	reach_list = (unsigned *) malloc((2+nfa_allocated)*sizeof(unsigned));
	if (!start) return NULL;
	t = set_of(NFA_NO(start));
	_set_pdq(t,reach_list);
	closure(&t,reach_list);
	/* Make t a dfa state */
	d_state = dfastate(t);
	last_done = DFA_NO(d_state);
	
	do {
		/* Mark dfa state x as "done" */
		d_state->done = TRUE;
		nfa_list = set_pdq(d_state->nfa_states);
		for (a = 0; a<class_no; ++a) {
			/* Add NFA states reached by a from d_state */
			reach(nfa_list,a,reach_list);
			/* Were any states found? */
			if ((*reach_list)!=nil) {
				/* was t=empty; */
				set_free(t);
				/* yes, compute closure */
				closure(&t,reach_list);
				/* Make DFA state of it ... */
				trans_d_state = dfastate(t);
				/* And make transition x->t, labeled with a */
				d_state->trans[a] = DFA_NO(trans_d_state);
				d_state->alternatives = TRUE;
			}
		}
		free(nfa_list);
		++last_done; /* move forward in queue */
		/* And so forth until nothing isn't done */
		d_state = DFA(last_done);
	} while (last_done<=dfa_allocated);

	free(reach_list);
	set_free(t);

	/* returns pointer to the array that holds the automaton */
	return dfa_array;
}

void clear_hash()
{
	register int i;

	for(i=0; i<HASH_SIZE; ++i)
		dfa_hash[i] = 0;
}

#if HASH_STAT
fprint_hash_stats(f)
FILE *f;
{
	register hash_list *p;
	register int i,j;
	register total;

	total=0;
	for(i=0; i<HASH_SIZE; ++i){
		j=0;
		p = dfa_hash[i];
		while(p){
			++j;
			p = p->next;
		}
		total+=j;
		fprintf(f,"bin[%d] has %d\n",i,j);
	}
	fprintf(f,"total = %d\n",total);
}
#endif

/* Returns a pointer to a dfa node that has the same nfa nodes in it.
 * This may or maynot be a newly created node.
 */
dfa_node *dfastate(nfa_states)
set nfa_states;		/* list of nfa states it could be */
{
	register hash_list *p;
	int bin;

	/* hash using set and see if it exists */
	bin = set_hash(nfa_states,HASH_SIZE);
	p = dfa_hash[bin];
	while(p && !set_equ(nfa_states,(p->node)->nfa_states)){
		p = p->next;
	}
	if(!p){
		/* next state to add to hash table */
		p = (hash_list*)malloc(sizeof(hash_list));
		p->node = new_dfa_node(nfa_states);
		p->next = dfa_hash[bin];
		dfa_hash[bin] = p;
	}
	return (p->node);
}


/* this reach assumes the closure has been done already on set */
int reach(nfa_list,a,reach_list)
unsigned *nfa_list;
register int a;
unsigned *reach_list;
{
	register unsigned *e;
	register nfa_node *node;
	int t=0;

	e = nfa_list;
	if (e){
		while (*e != nil){
			node = NFA(*e);
			if (set_el(a,node->label)){
				t=1;
				*reach_list=NFA_NO(node->trans[0]);
				++reach_list;
			}
			++e;
		}
	}
	*reach_list=nil;
	return t;
}

/* finds all the nodes that can be reached by epsilon transitions
   from the set of a nodes and returns puts them back in set b */
set closure(b,reach_list)
set *b;
unsigned *reach_list;
{
	register nfa_node *node,*n;	/* current node being examined */
	register unsigned *e;

	++operation_no;
#if 0
	t = e = set_pdq(*b);
#else
	e=reach_list;
#endif
	while (*e != nil){
		node = NFA(*e);
		set_orel(NFA_NO(node),b);
		/* mark it done */
		node->nfa_set = operation_no;
		if ((n=node->trans[0]) != NIL_INDEX && set_nil(node->label) &&
		  (n->nfa_set != operation_no)){
			/* put in b */
			set_orel(NFA_NO(n),b);
			close1(n,operation_no,b);
		}
		if ((n=node->trans[1]) != NIL_INDEX &&
		  (n->nfa_set != operation_no)){
			/* put in b */
			set_orel(NFA_NO(node->trans[1]),b);
			close1(n,operation_no,b);
		}
		++e;
	}
#if 0
	free(t);
#endif
	return *b;
}

void close1(node,o,b)
nfa_node *node;
int o;	/* marker to avoid cycles */
set *b;
{
	register nfa_node *n;	/* current node being examined */

	/* mark it done */
	node->nfa_set = o;
	if ((n=node->trans[0]) != NIL_INDEX && set_nil(node->label) &&
	  (n->nfa_set != o)){
		/* put in b */
		set_orel(NFA_NO(n),b);
		close1(n,o,b);
	}
	if ((n=node->trans[1]) != NIL_INDEX &&
	  (n->nfa_set != o)){
		/* put in b */
		set_orel(NFA_NO(node->trans[1]),b);
		close1(n,o,b);
	}
}