/xbmc/lib/libPython/Python/Parser/acceler.c
C | 125 lines | 107 code | 8 blank | 10 comment | 32 complexity | f8202a7056f4db569072653b05bb114b MD5 | raw file
Possible License(s): LGPL-2.1, AGPL-1.0, GPL-2.0
- /* 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);
- }