/* $OpenBSD: lr0.c,v 1.18 2014/03/13 01:18:22 tedu 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, *item_end;
        int i, count, max, symbol;
        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, j, 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 n, found, key;
        short *isp1, *isp2, *iend;
        core *sp;

#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 = malloc(sizeof(core) + i * sizeof(short));
        if (p == NULL)
                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, shiftcount;
        short *isp, *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, *isp2, *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, *sp2, *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, *rp1, *rp2;
        int item, 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, 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 == NULL)
                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();
}