4.3BSD-Reno/src/pgrm/yacc/lr0.c
/*
* 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 are permitted provided
* that: (1) source distributions retain this entire copyright notice and
* comment, and (2) distributions including binaries display the following
* acknowledgement: ``This product includes software developed by the
* University of California, Berkeley and its contributors'' in the
* documentation or other materials provided with the distribution and in
* all advertising materials mentioning features or use of this software.
* 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 ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
*/
#ifndef lint
static char sccsid[] = "@(#)lr0.c 5.2 (Berkeley) 6/1/90";
#endif /* not lint */
#include "defs.h"
extern short *itemset;
extern short *itemsetend;
extern unsigned *ruleset;
int nstates;
core *first_state;
shifts *first_shift;
reductions *first_reduction;
int get_state();
core *new_state();
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;
static core **state_table;
allocate_itemsets()
{
register short *itemp;
register short *item_end;
register int symbol;
register int i;
register int count;
register int max;
register 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 *);
}
allocate_storage()
{
allocate_itemsets();
shiftset = NEW2(nsyms, short);
redset = NEW2(nrules + 1, short);
state_table = NEW2(nitems, core *);
}
append_states()
{
register int i;
register int j;
register 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);
}
}
free_storage()
{
FREE(shift_symbol);
FREE(redset);
FREE(shiftset);
FREE(kernel_base);
FREE(kernel_end);
FREE(kernel_items);
FREE(state_table);
}
generate_states()
{
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();
}
int
get_state(symbol)
int symbol;
{
register int key;
register short *isp1;
register short *isp2;
register short *iend;
register core *sp;
register int found;
int n;
#ifdef TRACE
fprintf(stderr, "Entering get_state, symbol = %d\n", symbol);
#endif
isp1 = kernel_base[symbol];
iend = kernel_end[symbol];
n = iend - isp1;
key = *isp1;
assert(0 <= key && key < nitems);
sp = state_table[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_table[key] = sp = new_state(symbol);
}
return (sp->number);
}
initialize_states()
{
register int i;
register short *start_derives;
register 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;
}
new_itemsets()
{
register int i;
register int shiftcount;
register short *isp;
register short *ksp;
register int symbol;
for (i = 0; i < nsyms; i++)
kernel_end[i] = 0;
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(symbol)
int symbol;
{
register int n;
register core *p;
register short *isp1;
register short *isp2;
register short *iend;
#ifdef TRACE
fprintf(stderr, "Entering new_state, symbol = %d\n", symbol);
#endif
if (nstates >= MAXSHORT)
fatal("too many states");
isp1 = kernel_base[symbol];
iend = kernel_end[symbol];
n = iend - isp1;
p = (core *) allocate((unsigned) (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);
}
/* show_cores is used for debugging */
show_cores()
{
core *p;
int i, j, k, n;
int itemno;
k = 0;
for (p = first_state; p; ++k, p = p->next)
{
if (k) printf("\n");
printf("state %d, number = %d, accessing symbol = %s\n",
k, p->number, symbol_name[p->accessing_symbol]);
n = p->nitems;
for (i = 0; i < n; ++i)
{
itemno = p->items[i];
printf("%4d ", itemno);
j = itemno;
while (ritem[j] >= 0) ++j;
printf("%s :", symbol_name[rlhs[-ritem[j]]]);
j = rrhs[-ritem[j]];
while (j < itemno)
printf(" %s", symbol_name[ritem[j++]]);
printf(" .");
while (ritem[j] >= 0)
printf(" %s", symbol_name[ritem[j++]]);
printf("\n");
fflush(stdout);
}
}
}
/* show_ritems is used for debugging */
show_ritems()
{
int i;
for (i = 0; i < nitems; ++i)
printf("ritem[%d] = %d\n", i, ritem[i]);
}
/* show_rrhs is used for debugging */
show_rrhs()
{
int i;
for (i = 0; i < nrules; ++i)
printf("rrhs[%d] = %d\n", i, rrhs[i]);
}
/* show_shifts is used for debugging */
show_shifts()
{
shifts *p;
int i, j, k;
k = 0;
for (p = first_shift; p; ++k, p = p->next)
{
if (k) printf("\n");
printf("shift %d, number = %d, nshifts = %d\n", k, p->number,
p->nshifts);
j = p->nshifts;
for (i = 0; i < j; ++i)
printf("\t%d\n", p->shift[i]);
}
}
save_shifts()
{
register shifts *p;
register short *sp1;
register short *sp2;
register short *send;
p = (shifts *) allocate((unsigned) (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;
}
}
save_reductions()
{
register short *isp;
register short *rp1;
register short *rp2;
register int item;
register int count;
register reductions *p;
short *rend;
count = 0;
for (isp = itemset; isp < itemsetend; isp++)
{
item = ritem[*isp];
if (item < 0)
{
redset[count++] = -item;
}
}
if (count)
{
p = (reductions *) allocate((unsigned) (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;
}
}
}
set_derives()
{
register int i, k;
register int lhs;
register 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
}
free_derives()
{
FREE(derives[start_symbol]);
FREE(derives);
}
#ifdef DEBUG
print_derives()
{
register int i;
register 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
set_nullable()
{
register int i, j;
register int empty;
int done;
nullable = MALLOC(nsyms);
if (nullable == 0) no_space();
for (i = 0; i < nsyms; ++i)
nullable[i] = 0;
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
}
free_nullable()
{
FREE(nullable);
}
lr0()
{
set_derives();
set_nullable();
generate_states();
}