/* 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);
}