path: root/usr.bin/yacc/lr0.c

/*	$OpenBSD: lr0.c,v 1.16 2014/01/13 23:14:17 millert Exp $	*/
/*	$NetBSD: lr0.c,v 1.4 1996/03/19 03:21:35 jtc Exp $	*/

/*
 * Copyright (c) 1989 The Regents of the University of California.
 * All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Robert Paul Corbett.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. 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 BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include "defs.h"

extern short *itemset;
extern short *itemsetend;
extern unsigned *ruleset;

int nstates;
core *first_state;
shifts *first_shift;
reductions *first_reduction;

short get_state(int);
core *new_state(int);

void allocate_itemsets(void);
void allocate_storage(void);
void append_states(void);
void free_storage(void);
void generate_states(void);
void initialize_states(void);
void new_itemsets(void);
void save_shifts(void);
void save_reductions(void);
void set_derives(void);
void print_derives(void);
void set_nullable(void);

static core **state_set;
static core *this_state;
static core *last_state;
static shifts *last_shift;
static reductions *last_reduction;

static int nshifts;
static short *shift_symbol;

static short *redset;
static short *shiftset;

static short **kernel_base;
static short **kernel_end;
static short *kernel_items;

void
allocate_itemsets(void)
{
    short *itemp;
    short *item_end;
    int symbol;
    int i;
    int count;
    int max;
    short *symbol_count;

    count = 0;
    symbol_count = NEW2(nsyms, short);

    item_end = ritem + nitems;
    for (itemp = ritem; itemp < item_end; itemp++)
    {
	symbol = *itemp;
	if (symbol >= 0)
	{
	    count++;
	    symbol_count[symbol]++;
	}
    }

    kernel_base = NEW2(nsyms, short *);
    kernel_items = NEW2(count, short);

    count = 0;
    max = 0;
    for (i = 0; i < nsyms; i++)
    {
	kernel_base[i] = kernel_items + count;
	count += symbol_count[i];
	if (max < symbol_count[i])
	    max = symbol_count[i];
    }

    shift_symbol = symbol_count;
    kernel_end = NEW2(nsyms, short *);
}

void
allocate_storage(void)
{
    allocate_itemsets();
    shiftset = NEW2(nsyms, short);
    redset = NEW2(nrules + 1, short);
    state_set = NEW2(nitems, core *);
}

void
append_states(void)
{
    int i;
    int j;
    int symbol;

#ifdef	TRACE
    fprintf(stderr, "Entering append_states()\n");
#endif
    for (i = 1; i < nshifts; i++)
    {
	symbol = shift_symbol[i];
	j = i;
	while (j > 0 && shift_symbol[j - 1] > symbol)
	{
	    shift_symbol[j] = shift_symbol[j - 1];
	    j--;
	}
	shift_symbol[j] = symbol;
    }

    for (i = 0; i < nshifts; i++)
    {
	symbol = shift_symbol[i];
	shiftset[i] = get_state(symbol);
    }
}

void
free_storage(void)
{
    free(shift_symbol);
    free(redset);
    free(shiftset);
    free(kernel_base);
    free(kernel_end);
    free(kernel_items);
    free(state_set);
}


void
generate_states(void)
{
    allocate_storage();
    itemset = NEW2(nitems, short);
    ruleset = NEW2(WORDSIZE(nrules), unsigned);
    set_first_derives();
    initialize_states();

    while (this_state)
    {
	closure(this_state->items, this_state->nitems);
	save_reductions();
	new_itemsets();
	append_states();

	if (nshifts > 0)
	    save_shifts();

	this_state = this_state->next;
    }

    finalize_closure();
    free_storage();
}



short
get_state(int symbol)
{
    int key;
    short *isp1;
    short *isp2;
    short *iend;
    core *sp;
    int found;
    int n;

#ifdef	TRACE
    fprintf(stderr, "Entering get_state(%d)\n", symbol);
#endif

    isp1 = kernel_base[symbol];
    iend = kernel_end[symbol];
    n = iend - isp1;

    key = *isp1;
    assert(0 <= key && key < nitems);
    sp = state_set[key];
    if (sp)
    {
	found = 0;
	while (!found)
	{
	    if (sp->nitems == n)
	    {
		found = 1;
		isp1 = kernel_base[symbol];
		isp2 = sp->items;

		while (found && isp1 < iend)
		{
		    if (*isp1++ != *isp2++)
			found = 0;
		}
	    }

	    if (!found)
	    {
		if (sp->link)
		{
		    sp = sp->link;
		}
		else
		{
		    sp = sp->link = new_state(symbol);
		    found = 1;
		}
	    }
	}
    }
    else
    {
	state_set[key] = sp = new_state(symbol);
    }

    return (sp->number);
}


void
initialize_states(void)
{
    int i;
    short *start_derives;
    core *p;

    start_derives = derives[start_symbol];
    for (i = 0; start_derives[i] >= 0; ++i)
	continue;

    p = (core *) malloc(sizeof(core) + i*sizeof(short));
    if (p == 0) no_space();

    p->next = 0;
    p->link = 0;
    p->number = 0;
    p->accessing_symbol = 0;
    p->nitems = i;

    for (i = 0;  start_derives[i] >= 0; ++i)
	p->items[i] = rrhs[start_derives[i]];

    first_state = last_state = this_state = p;
    nstates = 1;
}

void
new_itemsets(void)
{
    int i;
    int shiftcount;
    short *isp;
    short *ksp;
    int symbol;

    memset(kernel_end, 0, nsyms * sizeof(short *));

    shiftcount = 0;
    isp = itemset;
    while (isp < itemsetend)
    {
	i = *isp++;
	symbol = ritem[i];
	if (symbol > 0)
	{
	    ksp = kernel_end[symbol];
	    if (!ksp)
	    {
		shift_symbol[shiftcount++] = symbol;
		ksp = kernel_base[symbol];
	    }

	    *ksp++ = i + 1;
	    kernel_end[symbol] = ksp;
	}
    }

    nshifts = shiftcount;
}



core *
new_state(int symbol)
{
    int n;
    core *p;
    short *isp1;
    short *isp2;
    short *iend;

#ifdef	TRACE
    fprintf(stderr, "Entering new_state(%d)\n", symbol);
#endif

    if (nstates >= MAXSHORT)
	fatal("too many states");

    isp1 = kernel_base[symbol];
    iend = kernel_end[symbol];
    n = iend - isp1;

    p = allocate(sizeof(core) + (n - 1) * sizeof(short));
    p->accessing_symbol = symbol;
    p->number = nstates;
    p->nitems = n;

    isp2 = p->items;
    while (isp1 < iend)
	*isp2++ = *isp1++;

    last_state->next = p;
    last_state = p;

    nstates++;

    return (p);
}


void
save_shifts(void)
{
    shifts *p;
    short *sp1;
    short *sp2;
    short *send;

    p = allocate(sizeof(shifts) + (nshifts - 1) * sizeof(short));

    p->number = this_state->number;
    p->nshifts = nshifts;

    sp1 = shiftset;
    sp2 = p->shift;
    send = shiftset + nshifts;

    while (sp1 < send)
	*sp2++ = *sp1++;

    if (last_shift)
    {
	last_shift->next = p;
	last_shift = p;
    }
    else
    {
	first_shift = p;
	last_shift = p;
    }
}


void
save_reductions(void)
{
    short *isp;
    short *rp1;
    short *rp2;
    int item;
    int count;
    reductions *p;
    short *rend;

    count = 0;
    for (isp = itemset; isp < itemsetend; isp++)
    {
	item = ritem[*isp];
	if (item < 0)
	{
	    redset[count++] = -item;
	}
    }

    if (count)
    {
	p = allocate(sizeof(reductions) + (count - 1) * sizeof(short));

	p->number = this_state->number;
	p->nreds = count;

	rp1 = redset;
	rp2 = p->rules;
	rend = rp1 + count;

	while (rp1 < rend)
	    *rp2++ = *rp1++;

	if (last_reduction)
	{
	    last_reduction->next = p;
	    last_reduction = p;
	}
	else
	{
	    first_reduction = p;
	    last_reduction = p;
	}
    }
}

void
set_derives(void)
{
    int i, k;
    int lhs;
    short *rules;

    derives = NEW2(nsyms, short *);
    rules = NEW2(nvars + nrules, short);

    k = 0;
    for (lhs = start_symbol; lhs < nsyms; lhs++)
    {
	derives[lhs] = rules + k;
	for (i = 0; i < nrules; i++)
	{
	    if (rlhs[i] == lhs)
	    {
		rules[k] = i;
		k++;
	    }
	}
	rules[k] = -1;
	k++;
    }

#ifdef	DEBUG
    print_derives();
#endif
}

void
free_derives(void)
{
    free(derives[start_symbol]);
    free(derives);
}

#ifdef	DEBUG
void
print_derives(void)
{
    int i;
    short *sp;

    printf("\nDERIVES\n\n");

    for (i = start_symbol; i < nsyms; i++)
    {
	printf("%s derives ", symbol_name[i]);
	for (sp = derives[i]; *sp >= 0; sp++)
	{
	    printf("  %d", *sp);
	}
	putchar('\n');
    }

    putchar('\n');
}
#endif

void
set_nullable(void)
{
    int i, j;
    int empty;
    int done;

    nullable = calloc(1, nsyms);
    if (nullable == 0) no_space();

    done = 0;
    while (!done)
    {
	done = 1;
	for (i = 1; i < nitems; i++)
	{
	    empty = 1;
	    while ((j = ritem[i]) >= 0)
	    {
		if (!nullable[j])
		    empty = 0;
		++i;
	    }
	    if (empty)
	    {
		j = rlhs[-j];
		if (!nullable[j])
		{
		    nullable[j] = 1;
		    done = 0;
		}
	    }
	}
    }

#ifdef DEBUG
    for (i = 0; i < nsyms; i++)
    {
	if (nullable[i])
	    printf("%s is nullable\n", symbol_name[i]);
	else
	    printf("%s is not nullable\n", symbol_name[i]);
    }
#endif
}

void
free_nullable(void)
{
    free(nullable);
}

void
lr0(void)
{
    set_derives();
    set_nullable();
    generate_states();
}