tblcmp.c

C++版 词法分析、语法分析器

 *
 * synopsis
 *   mkdeftbl();
 */

void mkdeftbl()

    {
    int i;

    jamstate = lastdfa + 1;

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

    if ( 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 not only are
     * negative base addresses dangerous at run-time (because indexing the
     * next array with one and a low-valued character might generate an
     * array-out-of-bounds error message), but at compile-time negative
     * base addresses denote TEMPLATES.
     */

    /* 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 tabls */
	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 )
		;
	    }

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

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

			if ( 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;

    if ( 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
 *
 * synopsis
 *   int state, sym, onenxt, onedef;
 *   mk1tbl( state, sym, onenxt, onedef );
 */

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
 *
 * synopsis
 *   int state[], statenum, comstate;
 *   mkprot( state, statenum, comstate );
 */

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
 *
 * synopsis
 *   int state[], statenum, comstate, totaltrans;
 *   mktemplate( state, statenum, comstate, totaltrans );
 */

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
 *
 * synopsis
 *   int qelm;
 *   mv2front( qelm );
 */

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
 *
 * synopsis
 *     int *state, statenum, transnum;
 *     place_state( state, statenum, transnum );
 *
 * 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
 *
 * synopsis
 *   int statenum, sym, nextstate, deflink;
 *   stack1( statenum, sym, nextstate, deflink );
 *
 * if there's room for another state one 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
 *
 * synopsis
 *   int state[], pr, ext[];
 *   int tbldiff, numdifferences;
 *   numdifferences = tbldiff( state, pr, ext )
 *
 * "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 );
    }