OS/2 Shareware BBS: 10 Tools/10-Tools.zip/py2s152.zip/Parser/acceler.c

C/C++ Source or Header | 1999-06-27 | 5KB | 181 lines

/***********************************************************
Copyright 1991-1995 by Stichting Mathematisch Centrum, Amsterdam,
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permission.

While CWI is the initial source for this software, a modified version
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/* 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 Py_PROTO((grammar *, dfa *));
static void fixstate Py_PROTO((grammar *, state *));

void
PyGrammar_AddAccelerators(g)
    grammar *g;
{
    dfa *d;
    int i;
#ifdef Py_DEBUG
    fprintf(stderr, "Adding parser accelerators ...\n");
#endif
    d = g->g_dfa;
    for (i = g->g_ndfas; --i >= 0; d++)
        fixdfa(g, d);
    g->g_accel = 1;
#ifdef Py_DEBUG
    fprintf(stderr, "Done.\n");
#endif
}

void
PyGrammar_RemoveAccelerators(g)
    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)
                PyMem_DEL(s->s_accel);
            s->s_accel = NULL;
        }
    }
}

static void
fixdfa(g, d)
    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(g, s)
    grammar *g;
    state *s;
{
    arc *a;
    int k;
    int *accel;
    int nl = g->g_ll.ll_nlabels;
    s->s_accept = 0;
    accel = PyMem_NEW(int, nl);
    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)) {
#ifdef applec
#define MPW_881_BUG            /* Undefine if bug below is fixed */
#endif
#ifdef MPW_881_BUG
                    /* In 881 mode MPW 3.1 has a code
                       generation bug which seems to
                       set the upper bits; fix this by
                       explicitly masking them off */
                    int temp;
#endif
                    if (accel[ibit] != -1)
                        printf("XXX ambiguity!\n");
#ifdef MPW_881_BUG
                    temp = 0xFFFF &
                        (a->a_arrow | (1 << 7) |
                         ((type - NT_OFFSET) << 8));
                    accel[ibit] = temp;
#else
                    accel[ibit] = a->a_arrow | (1 << 7) |
                        ((type - NT_OFFSET) << 8);
#endif
                }
            }
        }
        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 = PyMem_NEW(int, nl-k);
        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];
    }
    PyMem_DEL(accel);
}