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v0.8.1
v0.8.1
https://github.com/python/cpython
Revision 222a704100fe744eb0e3bf158825a10f42285215 authored by Fred Drake on 15 February 2006, 06:56:35 UTC, committed by Fred Drake on 15 February 2006, 06:56:35 UTC
1 parent d577b6d
Tip revision: 222a704100fe744eb0e3bf158825a10f42285215 authored by Fred Drake on 15 February 2006, 06:56:35 UTC
use correct function in example (backport of trunk revision 42377)
use correct function in example (backport of trunk revision 42377)
Tip revision: 222a704
acceler.c
/* Parser accelerator module */
/* The parser as originally conceived had disappointing performance.
This module does some precomputation that speeds up the selection
of a DFA based upon a token, turning a search through an array
into a simple indexing operation. The parser now cannot work
without the accelerators installed. Note that the accelerators
are installed dynamically when the parser is initialized, they
are not part of the static data structure written on graminit.[ch]
by the parser generator. */
#include "pgenheaders.h"
#include "grammar.h"
#include "node.h"
#include "token.h"
#include "parser.h"
/* Forward references */
static void fixdfa(grammar *, dfa *);
static void fixstate(grammar *, state *);
void
PyGrammar_AddAccelerators(grammar *g)
{
dfa *d;
int i;
d = g->g_dfa;
for (i = g->g_ndfas; --i >= 0; d++)
fixdfa(g, d);
g->g_accel = 1;
}
void
PyGrammar_RemoveAccelerators(grammar *g)
{
dfa *d;
int i;
g->g_accel = 0;
d = g->g_dfa;
for (i = g->g_ndfas; --i >= 0; d++) {
state *s;
int j;
s = d->d_state;
for (j = 0; j < d->d_nstates; j++, s++) {
if (s->s_accel)
PyObject_FREE(s->s_accel);
s->s_accel = NULL;
}
}
}
static void
fixdfa(grammar *g, dfa *d)
{
state *s;
int j;
s = d->d_state;
for (j = 0; j < d->d_nstates; j++, s++)
fixstate(g, s);
}
static void
fixstate(grammar *g, state *s)
{
arc *a;
int k;
int *accel;
int nl = g->g_ll.ll_nlabels;
s->s_accept = 0;
accel = (int *) PyObject_MALLOC(nl * sizeof(int));
if (accel == NULL) {
fprintf(stderr, "no mem to build parser accelerators\n");
exit(1);
}
for (k = 0; k < nl; k++)
accel[k] = -1;
a = s->s_arc;
for (k = s->s_narcs; --k >= 0; a++) {
int lbl = a->a_lbl;
label *l = &g->g_ll.ll_label[lbl];
int type = l->lb_type;
if (a->a_arrow >= (1 << 7)) {
printf("XXX too many states!\n");
continue;
}
if (ISNONTERMINAL(type)) {
dfa *d1 = PyGrammar_FindDFA(g, type);
int ibit;
if (type - NT_OFFSET >= (1 << 7)) {
printf("XXX too high nonterminal number!\n");
continue;
}
for (ibit = 0; ibit < g->g_ll.ll_nlabels; ibit++) {
if (testbit(d1->d_first, ibit)) {
if (accel[ibit] != -1)
printf("XXX ambiguity!\n");
accel[ibit] = a->a_arrow | (1 << 7) |
((type - NT_OFFSET) << 8);
}
}
}
else if (lbl == EMPTY)
s->s_accept = 1;
else if (lbl >= 0 && lbl < nl)
accel[lbl] = a->a_arrow;
}
while (nl > 0 && accel[nl-1] == -1)
nl--;
for (k = 0; k < nl && accel[k] == -1;)
k++;
if (k < nl) {
int i;
s->s_accel = (int *) PyObject_MALLOC((nl-k) * sizeof(int));
if (s->s_accel == NULL) {
fprintf(stderr, "no mem to add parser accelerators\n");
exit(1);
}
s->s_lower = k;
s->s_upper = nl;
for (i = 0; k < nl; i++, k++)
s->s_accel[i] = accel[k];
}
PyObject_FREE(accel);
}
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