tblcmp.c

Flex词法/语法分析器源码

	if ( usemecs )
		{
		/* Set up doubly-linked meta-equivalence classes; these
		 * are sets of equivalence classes which all have identical
		 * transitions out of TEMPLATES.
		 */

		tecbck[1] = NIL;

		for ( i = 2; i <= numecs; ++i )
			{
			tecbck[i] = i - 1;
			tecfwd[i - 1] = i;
			}

		tecfwd[numecs] = NIL;
		}
	}


/* mkdeftbl - make the default, "jam" table entries */

void mkdeftbl()
	{
	int i;

	jamstate = lastdfa + 1;

	++tblend; /* room for transition on end-of-buffer character */

	while ( tblend + numecs >= current_max_xpairs )
		expand_nxt_chk();

	/* Add in default end-of-buffer transition. */
	nxt[tblend] = end_of_buffer_state;
	chk[tblend] = jamstate;

	for ( i = 1; i <= numecs; ++i )
		{
		nxt[tblend + i] = 0;
		chk[tblend + i] = jamstate;
		}

	jambase = tblend;

	base[jamstate] = jambase;
	def[jamstate] = 0;

	tblend += numecs;
	++numtemps;
	}


/* mkentry - create base/def and nxt/chk entries for transition array
 *
 * synopsis
 *   int state[numchars + 1], numchars, statenum, deflink, totaltrans;
 *   mkentry( state, numchars, statenum, deflink, totaltrans );
 *
 * "state" is a transition array "numchars" characters in size, "statenum"
 * is the offset to be used into the base/def tables, and "deflink" is the
 * entry to put in the "def" table entry.  If "deflink" is equal to
 * "JAMSTATE", then no attempt will be made to fit zero entries of "state"
 * (i.e., jam entries) into the table.  It is assumed that by linking to
 * "JAMSTATE" they will be taken care of.  In any case, entries in "state"
 * marking transitions to "SAME_TRANS" are treated as though they will be
 * taken care of by whereever "deflink" points.  "totaltrans" is the total
 * number of transitions out of the state.  If it is below a certain threshold,
 * the tables are searched for an interior spot that will accommodate the
 * state array.
 */

void mkentry( state, numchars, statenum, deflink, totaltrans )
register int *state;
int numchars, statenum, deflink, totaltrans;
	{
	register int minec, maxec, i, baseaddr;
	int tblbase, tbllast;

	if ( totaltrans == 0 )
		{ /* there are no out-transitions */
		if ( deflink == JAMSTATE )
			base[statenum] = JAMSTATE;
		else
			base[statenum] = 0;

		def[statenum] = deflink;
		return;
		}

	for ( minec = 1; minec <= numchars; ++minec )
		{
		if ( state[minec] != SAME_TRANS )
			if ( state[minec] != 0 || deflink != JAMSTATE )
				break;
		}

	if ( totaltrans == 1 )
		{
		/* There's only one out-transition.  Save it for later to fill
		 * in holes in the tables.
		 */
		stack1( statenum, minec, state[minec], deflink );
		return;
		}

	for ( maxec = numchars; maxec > 0; --maxec )
		{
		if ( state[maxec] != SAME_TRANS )
			if ( state[maxec] != 0 || deflink != JAMSTATE )
				break;
		}

	/* Whether we try to fit the state table in the middle of the table
	 * entries we have already generated, or if we just take the state
	 * table at the end of the nxt/chk tables, we must make sure that we
	 * have a valid base address (i.e., non-negative).  Note that
	 * negative base addresses dangerous at run-time (because indexing
	 * the nxt array with one and a low-valued character will access
	 * memory before the start of the array.
	 */

	/* Find the first transition of state that we need to worry about. */
	if ( totaltrans * 100 <= numchars * INTERIOR_FIT_PERCENTAGE )
		{
		/* Attempt to squeeze it into the middle of the tables. */
		baseaddr = firstfree;

		while ( baseaddr < minec )
			{
			/* Using baseaddr would result in a negative base
			 * address below; find the next free slot.
			 */
			for ( ++baseaddr; chk[baseaddr] != 0; ++baseaddr )
				;
			}

		while ( baseaddr + maxec - minec + 1 >= current_max_xpairs )
			expand_nxt_chk();

		for ( i = minec; i <= maxec; ++i )
			if ( state[i] != SAME_TRANS &&
			     (state[i] != 0 || deflink != JAMSTATE) &&
			     chk[baseaddr + i - minec] != 0 )
				{ /* baseaddr unsuitable - find another */
				for ( ++baseaddr;
				      baseaddr < current_max_xpairs &&
				      chk[baseaddr] != 0; ++baseaddr )
					;

				while ( baseaddr + maxec - minec + 1 >=
					current_max_xpairs )
					expand_nxt_chk();

				/* Reset the loop counter so we'll start all
				 * over again next time it's incremented.
				 */

				i = minec - 1;
				}
		}

	else
		{
		/* Ensure that the base address we eventually generate is
		 * non-negative.
		 */
		baseaddr = MAX( tblend + 1, minec );
		}

	tblbase = baseaddr - minec;
	tbllast = tblbase + maxec;

	while ( tbllast + 1 >= current_max_xpairs )
		expand_nxt_chk();

	base[statenum] = tblbase;
	def[statenum] = deflink;

	for ( i = minec; i <= maxec; ++i )
		if ( state[i] != SAME_TRANS )
			if ( state[i] != 0 || deflink != JAMSTATE )
				{
				nxt[tblbase + i] = state[i];
				chk[tblbase + i] = statenum;
				}

	if ( baseaddr == firstfree )
		/* Find next free slot in tables. */
		for ( ++firstfree; chk[firstfree] != 0; ++firstfree )
			;

	tblend = MAX( tblend, tbllast );
	}


/* mk1tbl - create table entries for a state (or state fragment) which
 *            has only one out-transition
 */

void mk1tbl( state, sym, onenxt, onedef )
int state, sym, onenxt, onedef;
	{
	if ( firstfree < sym )
		firstfree = sym;

	while ( chk[firstfree] != 0 )
		if ( ++firstfree >= current_max_xpairs )
			expand_nxt_chk();

	base[state] = firstfree - sym;
	def[state] = onedef;
	chk[firstfree] = state;
	nxt[firstfree] = onenxt;

	if ( firstfree > tblend )
		{
		tblend = firstfree++;

		if ( firstfree >= current_max_xpairs )
			expand_nxt_chk();
		}
	}


/* mkprot - create new proto entry */

void mkprot( state, statenum, comstate )
int state[], statenum, comstate;
	{
	int i, slot, tblbase;

	if ( ++numprots >= MSP || numecs * numprots >= PROT_SAVE_SIZE )
		{
		/* Gotta make room for the new proto by dropping last entry in
		 * the queue.
		 */
		slot = lastprot;
		lastprot = protprev[lastprot];
		protnext[lastprot] = NIL;
		}

	else
		slot = numprots;

	protnext[slot] = firstprot;

	if ( firstprot != NIL )
		protprev[firstprot] = slot;

	firstprot = slot;
	prottbl[slot] = statenum;
	protcomst[slot] = comstate;

	/* Copy state into save area so it can be compared with rapidly. */
	tblbase = numecs * (slot - 1);

	for ( i = 1; i <= numecs; ++i )
		protsave[tblbase + i] = state[i];
	}


/* mktemplate - create a template entry based on a state, and connect the state
 *              to it
 */

void mktemplate( state, statenum, comstate )
int state[], statenum, comstate;
	{
	int i, numdiff, tmpbase, tmp[CSIZE + 1];
	Char transset[CSIZE + 1];
	int tsptr;

	++numtemps;

	tsptr = 0;

	/* Calculate where we will temporarily store the transition table
	 * of the template in the tnxt[] array.  The final transition table
	 * gets created by cmptmps().
	 */

	tmpbase = numtemps * numecs;

	if ( tmpbase + numecs >= current_max_template_xpairs )
		{
		current_max_template_xpairs += MAX_TEMPLATE_XPAIRS_INCREMENT;

		++num_reallocs;

		tnxt = reallocate_integer_array( tnxt,
			current_max_template_xpairs );
		}

	for ( i = 1; i <= numecs; ++i )
		if ( state[i] == 0 )
			tnxt[tmpbase + i] = 0;
		else
			{
			transset[tsptr++] = i;
			tnxt[tmpbase + i] = comstate;
			}

	if ( usemecs )
		mkeccl( transset, tsptr, tecfwd, tecbck, numecs, 0 );

	mkprot( tnxt + tmpbase, -numtemps, comstate );

	/* We rely on the fact that mkprot adds things to the beginning
	 * of the proto queue.
	 */

	numdiff = tbldiff( state, firstprot, tmp );
	mkentry( tmp, numecs, statenum, -numtemps, numdiff );
	}


/* mv2front - move proto queue element to front of queue */

void mv2front( qelm )
int qelm;
	{
	if ( firstprot != qelm )
		{
		if ( qelm == lastprot )
			lastprot = protprev[lastprot];

		protnext[protprev[qelm]] = protnext[qelm];

		if ( protnext[qelm] != NIL )
			protprev[protnext[qelm]] = protprev[qelm];

		protprev[qelm] = NIL;
		protnext[qelm] = firstprot;
		protprev[firstprot] = qelm;
		firstprot = qelm;
		}
	}


/* place_state - place a state into full speed transition table
 *
 * State is the statenum'th state.  It is indexed by equivalence class and
 * gives the number of the state to enter for a given equivalence class.
 * Transnum is the number of out-transitions for the state.
 */

void place_state( state, statenum, transnum )
int *state, statenum, transnum;
	{
	register int i;
	register int *state_ptr;
	int position = find_table_space( state, transnum );

	/* "base" is the table of start positions. */
	base[statenum] = position;

	/* Put in action number marker; this non-zero number makes sure that
	 * find_table_space() knows that this position in chk/nxt is taken
	 * and should not be used for another accepting number in another
	 * state.
	 */
	chk[position - 1] = 1;

	/* Put in end-of-buffer marker; this is for the same purposes as
	 * above.
	 */
	chk[position] = 1;

	/* Place the state into chk and nxt. */
	state_ptr = &state[1];

	for ( i = 1; i <= numecs; ++i, ++state_ptr )
		if ( *state_ptr != 0 )
			{
			chk[position + i] = i;
			nxt[position + i] = *state_ptr;
			}

	if ( position + numecs > tblend )
		tblend = position + numecs;
	}


/* stack1 - save states with only one out-transition to be processed later
 *
 * If there's room for another state on the "one-transition" stack, the
 * state is pushed onto it, to be processed later by mk1tbl.  If there's
 * no room, we process the sucker right now.
 */

void stack1( statenum, sym, nextstate, deflink )
int statenum, sym, nextstate, deflink;
	{
	if ( onesp >= ONE_STACK_SIZE - 1 )
		mk1tbl( statenum, sym, nextstate, deflink );

	else
		{
		++onesp;
		onestate[onesp] = statenum;
		onesym[onesp] = sym;
		onenext[onesp] = nextstate;
		onedef[onesp] = deflink;
		}
	}


/* tbldiff - compute differences between two state tables
 *
 * "state" is the state array which is to be extracted from the pr'th
 * proto.  "pr" is both the number of the proto we are extracting from
 * and an index into the save area where we can find the proto's complete
 * state table.  Each entry in "state" which differs from the corresponding
 * entry of "pr" will appear in "ext".
 *
 * Entries which are the same in both "state" and "pr" will be marked
 * as transitions to "SAME_TRANS" in "ext".  The total number of differences
 * between "state" and "pr" is returned as function value.  Note that this
 * number is "numecs" minus the number of "SAME_TRANS" entries in "ext".
 */

int tbldiff( state, pr, ext )
int state[], pr, ext[];
	{
	register int i, *sp = state, *ep = ext, *protp;
	register int numdiff = 0;

	protp = &protsave[numecs * (pr - 1)];

	for ( i = numecs; i > 0; --i )
		{
		if ( *++protp == *++sp )
			*++ep = SAME_TRANS;
		else
			{
			*++ep = *sp;
			++numdiff;
			}
		}

	return numdiff;
	}