| /* Parser generator */ | |
| /* For a description, see the comments at end of this file */ | |
| #include "Python.h" | |
| #include "pgenheaders.h" | |
| #include "token.h" | |
| #include "node.h" | |
| #include "grammar.h" | |
| #include "metagrammar.h" | |
| #include "pgen.h" | |
| extern int Py_DebugFlag; | |
| extern int Py_IgnoreEnvironmentFlag; /* needed by Py_GETENV */ | |
| /* PART ONE -- CONSTRUCT NFA -- Cf. Algorithm 3.2 from [Aho&Ullman 77] */ | |
| typedef struct _nfaarc { | |
| int ar_label; | |
| int ar_arrow; | |
| } nfaarc; | |
| typedef struct _nfastate { | |
| int st_narcs; | |
| nfaarc *st_arc; | |
| } nfastate; | |
| typedef struct _nfa { | |
| int nf_type; | |
| char *nf_name; | |
| int nf_nstates; | |
| nfastate *nf_state; | |
| int nf_start, nf_finish; | |
| } nfa; | |
| /* Forward */ | |
| static void compile_rhs(labellist *ll, | |
| nfa *nf, node *n, int *pa, int *pb); | |
| static void compile_alt(labellist *ll, | |
| nfa *nf, node *n, int *pa, int *pb); | |
| static void compile_item(labellist *ll, | |
| nfa *nf, node *n, int *pa, int *pb); | |
| static void compile_atom(labellist *ll, | |
| nfa *nf, node *n, int *pa, int *pb); | |
| static int | |
| addnfastate(nfa *nf) | |
| { | |
| nfastate *st; | |
| nf->nf_state = (nfastate *)PyObject_REALLOC(nf->nf_state, | |
| sizeof(nfastate) * (nf->nf_nstates + 1)); | |
| if (nf->nf_state == NULL) | |
| Py_FatalError("out of mem"); | |
| st = &nf->nf_state[nf->nf_nstates++]; | |
| st->st_narcs = 0; | |
| st->st_arc = NULL; | |
| return st - nf->nf_state; | |
| } | |
| static void | |
| addnfaarc(nfa *nf, int from, int to, int lbl) | |
| { | |
| nfastate *st; | |
| nfaarc *ar; | |
| st = &nf->nf_state[from]; | |
| st->st_arc = (nfaarc *)PyObject_REALLOC(st->st_arc, | |
| sizeof(nfaarc) * (st->st_narcs + 1)); | |
| if (st->st_arc == NULL) | |
| Py_FatalError("out of mem"); | |
| ar = &st->st_arc[st->st_narcs++]; | |
| ar->ar_label = lbl; | |
| ar->ar_arrow = to; | |
| } | |
| static nfa * | |
| newnfa(char *name) | |
| { | |
| nfa *nf; | |
| static int type = NT_OFFSET; /* All types will be disjunct */ | |
| nf = (nfa *)PyObject_MALLOC(sizeof(nfa)); | |
| if (nf == NULL) | |
| Py_FatalError("no mem for new nfa"); | |
| nf->nf_type = type++; | |
| nf->nf_name = name; /* XXX strdup(name) ??? */ | |
| nf->nf_nstates = 0; | |
| nf->nf_state = NULL; | |
| nf->nf_start = nf->nf_finish = -1; | |
| return nf; | |
| } | |
| typedef struct _nfagrammar { | |
| int gr_nnfas; | |
| nfa **gr_nfa; | |
| labellist gr_ll; | |
| } nfagrammar; | |
| /* Forward */ | |
| static void compile_rule(nfagrammar *gr, node *n); | |
| static nfagrammar * | |
| newnfagrammar(void) | |
| { | |
| nfagrammar *gr; | |
| gr = (nfagrammar *)PyObject_MALLOC(sizeof(nfagrammar)); | |
| if (gr == NULL) | |
| Py_FatalError("no mem for new nfa grammar"); | |
| gr->gr_nnfas = 0; | |
| gr->gr_nfa = NULL; | |
| gr->gr_ll.ll_nlabels = 0; | |
| gr->gr_ll.ll_label = NULL; | |
| addlabel(&gr->gr_ll, ENDMARKER, "EMPTY"); | |
| return gr; | |
| } | |
| static nfa * | |
| addnfa(nfagrammar *gr, char *name) | |
| { | |
| nfa *nf; | |
| nf = newnfa(name); | |
| gr->gr_nfa = (nfa **)PyObject_REALLOC(gr->gr_nfa, | |
| sizeof(nfa*) * (gr->gr_nnfas + 1)); | |
| if (gr->gr_nfa == NULL) | |
| Py_FatalError("out of mem"); | |
| gr->gr_nfa[gr->gr_nnfas++] = nf; | |
| addlabel(&gr->gr_ll, NAME, nf->nf_name); | |
| return nf; | |
| } | |
| #ifdef Py_DEBUG | |
| static char REQNFMT[] = "metacompile: less than %d children\n"; | |
| #define REQN(i, count) \ | |
| if (i < count) { \ | |
| fprintf(stderr, REQNFMT, count); \ | |
| Py_FatalError("REQN"); \ | |
| } else | |
| #else | |
| #define REQN(i, count) /* empty */ | |
| #endif | |
| static nfagrammar * | |
| metacompile(node *n) | |
| { | |
| nfagrammar *gr; | |
| int i; | |
| if (Py_DebugFlag) | |
| printf("Compiling (meta-) parse tree into NFA grammar\n"); | |
| gr = newnfagrammar(); | |
| REQ(n, MSTART); | |
| i = n->n_nchildren - 1; /* Last child is ENDMARKER */ | |
| n = n->n_child; | |
| for (; --i >= 0; n++) { | |
| if (n->n_type != NEWLINE) | |
| compile_rule(gr, n); | |
| } | |
| return gr; | |
| } | |
| static void | |
| compile_rule(nfagrammar *gr, node *n) | |
| { | |
| nfa *nf; | |
| REQ(n, RULE); | |
| REQN(n->n_nchildren, 4); | |
| n = n->n_child; | |
| REQ(n, NAME); | |
| nf = addnfa(gr, n->n_str); | |
| n++; | |
| REQ(n, COLON); | |
| n++; | |
| REQ(n, RHS); | |
| compile_rhs(&gr->gr_ll, nf, n, &nf->nf_start, &nf->nf_finish); | |
| n++; | |
| REQ(n, NEWLINE); | |
| } | |
| static void | |
| compile_rhs(labellist *ll, nfa *nf, node *n, int *pa, int *pb) | |
| { | |
| int i; | |
| int a, b; | |
| REQ(n, RHS); | |
| i = n->n_nchildren; | |
| REQN(i, 1); | |
| n = n->n_child; | |
| REQ(n, ALT); | |
| compile_alt(ll, nf, n, pa, pb); | |
| if (--i <= 0) | |
| return; | |
| n++; | |
| a = *pa; | |
| b = *pb; | |
| *pa = addnfastate(nf); | |
| *pb = addnfastate(nf); | |
| addnfaarc(nf, *pa, a, EMPTY); | |
| addnfaarc(nf, b, *pb, EMPTY); | |
| for (; --i >= 0; n++) { | |
| REQ(n, VBAR); | |
| REQN(i, 1); | |
| --i; | |
| n++; | |
| REQ(n, ALT); | |
| compile_alt(ll, nf, n, &a, &b); | |
| addnfaarc(nf, *pa, a, EMPTY); | |
| addnfaarc(nf, b, *pb, EMPTY); | |
| } | |
| } | |
| static void | |
| compile_alt(labellist *ll, nfa *nf, node *n, int *pa, int *pb) | |
| { | |
| int i; | |
| int a, b; | |
| REQ(n, ALT); | |
| i = n->n_nchildren; | |
| REQN(i, 1); | |
| n = n->n_child; | |
| REQ(n, ITEM); | |
| compile_item(ll, nf, n, pa, pb); | |
| --i; | |
| n++; | |
| for (; --i >= 0; n++) { | |
| REQ(n, ITEM); | |
| compile_item(ll, nf, n, &a, &b); | |
| addnfaarc(nf, *pb, a, EMPTY); | |
| *pb = b; | |
| } | |
| } | |
| static void | |
| compile_item(labellist *ll, nfa *nf, node *n, int *pa, int *pb) | |
| { | |
| int i; | |
| int a, b; | |
| REQ(n, ITEM); | |
| i = n->n_nchildren; | |
| REQN(i, 1); | |
| n = n->n_child; | |
| if (n->n_type == LSQB) { | |
| REQN(i, 3); | |
| n++; | |
| REQ(n, RHS); | |
| *pa = addnfastate(nf); | |
| *pb = addnfastate(nf); | |
| addnfaarc(nf, *pa, *pb, EMPTY); | |
| compile_rhs(ll, nf, n, &a, &b); | |
| addnfaarc(nf, *pa, a, EMPTY); | |
| addnfaarc(nf, b, *pb, EMPTY); | |
| REQN(i, 1); | |
| n++; | |
| REQ(n, RSQB); | |
| } | |
| else { | |
| compile_atom(ll, nf, n, pa, pb); | |
| if (--i <= 0) | |
| return; | |
| n++; | |
| addnfaarc(nf, *pb, *pa, EMPTY); | |
| if (n->n_type == STAR) | |
| *pb = *pa; | |
| else | |
| REQ(n, PLUS); | |
| } | |
| } | |
| static void | |
| compile_atom(labellist *ll, nfa *nf, node *n, int *pa, int *pb) | |
| { | |
| int i; | |
| REQ(n, ATOM); | |
| i = n->n_nchildren; | |
| REQN(i, 1); | |
| n = n->n_child; | |
| if (n->n_type == LPAR) { | |
| REQN(i, 3); | |
| n++; | |
| REQ(n, RHS); | |
| compile_rhs(ll, nf, n, pa, pb); | |
| n++; | |
| REQ(n, RPAR); | |
| } | |
| else if (n->n_type == NAME || n->n_type == STRING) { | |
| *pa = addnfastate(nf); | |
| *pb = addnfastate(nf); | |
| addnfaarc(nf, *pa, *pb, addlabel(ll, n->n_type, n->n_str)); | |
| } | |
| else | |
| REQ(n, NAME); | |
| } | |
| static void | |
| dumpstate(labellist *ll, nfa *nf, int istate) | |
| { | |
| nfastate *st; | |
| int i; | |
| nfaarc *ar; | |
| printf("%c%2d%c", | |
| istate == nf->nf_start ? '*' : ' ', | |
| istate, | |
| istate == nf->nf_finish ? '.' : ' '); | |
| st = &nf->nf_state[istate]; | |
| ar = st->st_arc; | |
| for (i = 0; i < st->st_narcs; i++) { | |
| if (i > 0) | |
| printf("\n "); | |
| printf("-> %2d %s", ar->ar_arrow, | |
| PyGrammar_LabelRepr(&ll->ll_label[ar->ar_label])); | |
| ar++; | |
| } | |
| printf("\n"); | |
| } | |
| static void | |
| dumpnfa(labellist *ll, nfa *nf) | |
| { | |
| int i; | |
| printf("NFA '%s' has %d states; start %d, finish %d\n", | |
| nf->nf_name, nf->nf_nstates, nf->nf_start, nf->nf_finish); | |
| for (i = 0; i < nf->nf_nstates; i++) | |
| dumpstate(ll, nf, i); | |
| } | |
| /* PART TWO -- CONSTRUCT DFA -- Algorithm 3.1 from [Aho&Ullman 77] */ | |
| static void | |
| addclosure(bitset ss, nfa *nf, int istate) | |
| { | |
| if (addbit(ss, istate)) { | |
| nfastate *st = &nf->nf_state[istate]; | |
| nfaarc *ar = st->st_arc; | |
| int i; | |
| for (i = st->st_narcs; --i >= 0; ) { | |
| if (ar->ar_label == EMPTY) | |
| addclosure(ss, nf, ar->ar_arrow); | |
| ar++; | |
| } | |
| } | |
| } | |
| typedef struct _ss_arc { | |
| bitset sa_bitset; | |
| int sa_arrow; | |
| int sa_label; | |
| } ss_arc; | |
| typedef struct _ss_state { | |
| bitset ss_ss; | |
| int ss_narcs; | |
| struct _ss_arc *ss_arc; | |
| int ss_deleted; | |
| int ss_finish; | |
| int ss_rename; | |
| } ss_state; | |
| typedef struct _ss_dfa { | |
| int sd_nstates; | |
| ss_state *sd_state; | |
| } ss_dfa; | |
| /* Forward */ | |
| static void printssdfa(int xx_nstates, ss_state *xx_state, int nbits, | |
| labellist *ll, char *msg); | |
| static void simplify(int xx_nstates, ss_state *xx_state); | |
| static void convert(dfa *d, int xx_nstates, ss_state *xx_state); | |
| static void | |
| makedfa(nfagrammar *gr, nfa *nf, dfa *d) | |
| { | |
| int nbits = nf->nf_nstates; | |
| bitset ss; | |
| int xx_nstates; | |
| ss_state *xx_state, *yy; | |
| ss_arc *zz; | |
| int istate, jstate, iarc, jarc, ibit; | |
| nfastate *st; | |
| nfaarc *ar; | |
| ss = newbitset(nbits); | |
| addclosure(ss, nf, nf->nf_start); | |
| xx_state = (ss_state *)PyObject_MALLOC(sizeof(ss_state)); | |
| if (xx_state == NULL) | |
| Py_FatalError("no mem for xx_state in makedfa"); | |
| xx_nstates = 1; | |
| yy = &xx_state[0]; | |
| yy->ss_ss = ss; | |
| yy->ss_narcs = 0; | |
| yy->ss_arc = NULL; | |
| yy->ss_deleted = 0; | |
| yy->ss_finish = testbit(ss, nf->nf_finish); | |
| if (yy->ss_finish) | |
| printf("Error: nonterminal '%s' may produce empty.\n", | |
| nf->nf_name); | |
| /* This algorithm is from a book written before | |
| the invention of structured programming... */ | |
| /* For each unmarked state... */ | |
| for (istate = 0; istate < xx_nstates; ++istate) { | |
| size_t size; | |
| yy = &xx_state[istate]; | |
| ss = yy->ss_ss; | |
| /* For all its states... */ | |
| for (ibit = 0; ibit < nf->nf_nstates; ++ibit) { | |
| if (!testbit(ss, ibit)) | |
| continue; | |
| st = &nf->nf_state[ibit]; | |
| /* For all non-empty arcs from this state... */ | |
| for (iarc = 0; iarc < st->st_narcs; iarc++) { | |
| ar = &st->st_arc[iarc]; | |
| if (ar->ar_label == EMPTY) | |
| continue; | |
| /* Look up in list of arcs from this state */ | |
| for (jarc = 0; jarc < yy->ss_narcs; ++jarc) { | |
| zz = &yy->ss_arc[jarc]; | |
| if (ar->ar_label == zz->sa_label) | |
| goto found; | |
| } | |
| /* Add new arc for this state */ | |
| size = sizeof(ss_arc) * (yy->ss_narcs + 1); | |
| yy->ss_arc = (ss_arc *)PyObject_REALLOC( | |
| yy->ss_arc, size); | |
| if (yy->ss_arc == NULL) | |
| Py_FatalError("out of mem"); | |
| zz = &yy->ss_arc[yy->ss_narcs++]; | |
| zz->sa_label = ar->ar_label; | |
| zz->sa_bitset = newbitset(nbits); | |
| zz->sa_arrow = -1; | |
| found: ; | |
| /* Add destination */ | |
| addclosure(zz->sa_bitset, nf, ar->ar_arrow); | |
| } | |
| } | |
| /* Now look up all the arrow states */ | |
| for (jarc = 0; jarc < xx_state[istate].ss_narcs; jarc++) { | |
| zz = &xx_state[istate].ss_arc[jarc]; | |
| for (jstate = 0; jstate < xx_nstates; jstate++) { | |
| if (samebitset(zz->sa_bitset, | |
| xx_state[jstate].ss_ss, nbits)) { | |
| zz->sa_arrow = jstate; | |
| goto done; | |
| } | |
| } | |
| size = sizeof(ss_state) * (xx_nstates + 1); | |
| xx_state = (ss_state *)PyObject_REALLOC(xx_state, | |
| size); | |
| if (xx_state == NULL) | |
| Py_FatalError("out of mem"); | |
| zz->sa_arrow = xx_nstates; | |
| yy = &xx_state[xx_nstates++]; | |
| yy->ss_ss = zz->sa_bitset; | |
| yy->ss_narcs = 0; | |
| yy->ss_arc = NULL; | |
| yy->ss_deleted = 0; | |
| yy->ss_finish = testbit(yy->ss_ss, nf->nf_finish); | |
| done: ; | |
| } | |
| } | |
| if (Py_DebugFlag) | |
| printssdfa(xx_nstates, xx_state, nbits, &gr->gr_ll, | |
| "before minimizing"); | |
| simplify(xx_nstates, xx_state); | |
| if (Py_DebugFlag) | |
| printssdfa(xx_nstates, xx_state, nbits, &gr->gr_ll, | |
| "after minimizing"); | |
| convert(d, xx_nstates, xx_state); | |
| /* XXX cleanup */ | |
| PyObject_FREE(xx_state); | |
| } | |
| static void | |
| printssdfa(int xx_nstates, ss_state *xx_state, int nbits, | |
| labellist *ll, char *msg) | |
| { | |
| int i, ibit, iarc; | |
| ss_state *yy; | |
| ss_arc *zz; | |
| printf("Subset DFA %s\n", msg); | |
| for (i = 0; i < xx_nstates; i++) { | |
| yy = &xx_state[i]; | |
| if (yy->ss_deleted) | |
| continue; | |
| printf(" Subset %d", i); | |
| if (yy->ss_finish) | |
| printf(" (finish)"); | |
| printf(" { "); | |
| for (ibit = 0; ibit < nbits; ibit++) { | |
| if (testbit(yy->ss_ss, ibit)) | |
| printf("%d ", ibit); | |
| } | |
| printf("}\n"); | |
| for (iarc = 0; iarc < yy->ss_narcs; iarc++) { | |
| zz = &yy->ss_arc[iarc]; | |
| printf(" Arc to state %d, label %s\n", | |
| zz->sa_arrow, | |
| PyGrammar_LabelRepr( | |
| &ll->ll_label[zz->sa_label])); | |
| } | |
| } | |
| } | |
| /* PART THREE -- SIMPLIFY DFA */ | |
| /* Simplify the DFA by repeatedly eliminating states that are | |
| equivalent to another oner. This is NOT Algorithm 3.3 from | |
| [Aho&Ullman 77]. It does not always finds the minimal DFA, | |
| but it does usually make a much smaller one... (For an example | |
| of sub-optimal behavior, try S: x a b+ | y a b+.) | |
| */ | |
| static int | |
| samestate(ss_state *s1, ss_state *s2) | |
| { | |
| int i; | |
| if (s1->ss_narcs != s2->ss_narcs || s1->ss_finish != s2->ss_finish) | |
| return 0; | |
| for (i = 0; i < s1->ss_narcs; i++) { | |
| if (s1->ss_arc[i].sa_arrow != s2->ss_arc[i].sa_arrow || | |
| s1->ss_arc[i].sa_label != s2->ss_arc[i].sa_label) | |
| return 0; | |
| } | |
| return 1; | |
| } | |
| static void | |
| renamestates(int xx_nstates, ss_state *xx_state, int from, int to) | |
| { | |
| int i, j; | |
| if (Py_DebugFlag) | |
| printf("Rename state %d to %d.\n", from, to); | |
| for (i = 0; i < xx_nstates; i++) { | |
| if (xx_state[i].ss_deleted) | |
| continue; | |
| for (j = 0; j < xx_state[i].ss_narcs; j++) { | |
| if (xx_state[i].ss_arc[j].sa_arrow == from) | |
| xx_state[i].ss_arc[j].sa_arrow = to; | |
| } | |
| } | |
| } | |
| static void | |
| simplify(int xx_nstates, ss_state *xx_state) | |
| { | |
| int changes; | |
| int i, j; | |
| do { | |
| changes = 0; | |
| for (i = 1; i < xx_nstates; i++) { | |
| if (xx_state[i].ss_deleted) | |
| continue; | |
| for (j = 0; j < i; j++) { | |
| if (xx_state[j].ss_deleted) | |
| continue; | |
| if (samestate(&xx_state[i], &xx_state[j])) { | |
| xx_state[i].ss_deleted++; | |
| renamestates(xx_nstates, xx_state, | |
| i, j); | |
| changes++; | |
| break; | |
| } | |
| } | |
| } | |
| } while (changes); | |
| } | |
| /* PART FOUR -- GENERATE PARSING TABLES */ | |
| /* Convert the DFA into a grammar that can be used by our parser */ | |
| static void | |
| convert(dfa *d, int xx_nstates, ss_state *xx_state) | |
| { | |
| int i, j; | |
| ss_state *yy; | |
| ss_arc *zz; | |
| for (i = 0; i < xx_nstates; i++) { | |
| yy = &xx_state[i]; | |
| if (yy->ss_deleted) | |
| continue; | |
| yy->ss_rename = addstate(d); | |
| } | |
| for (i = 0; i < xx_nstates; i++) { | |
| yy = &xx_state[i]; | |
| if (yy->ss_deleted) | |
| continue; | |
| for (j = 0; j < yy->ss_narcs; j++) { | |
| zz = &yy->ss_arc[j]; | |
| addarc(d, yy->ss_rename, | |
| xx_state[zz->sa_arrow].ss_rename, | |
| zz->sa_label); | |
| } | |
| if (yy->ss_finish) | |
| addarc(d, yy->ss_rename, yy->ss_rename, 0); | |
| } | |
| d->d_initial = 0; | |
| } | |
| /* PART FIVE -- GLUE IT ALL TOGETHER */ | |
| static grammar * | |
| maketables(nfagrammar *gr) | |
| { | |
| int i; | |
| nfa *nf; | |
| dfa *d; | |
| grammar *g; | |
| if (gr->gr_nnfas == 0) | |
| return NULL; | |
| g = newgrammar(gr->gr_nfa[0]->nf_type); | |
| /* XXX first rule must be start rule */ | |
| g->g_ll = gr->gr_ll; | |
| for (i = 0; i < gr->gr_nnfas; i++) { | |
| nf = gr->gr_nfa[i]; | |
| if (Py_DebugFlag) { | |
| printf("Dump of NFA for '%s' ...\n", nf->nf_name); | |
| dumpnfa(&gr->gr_ll, nf); | |
| printf("Making DFA for '%s' ...\n", nf->nf_name); | |
| } | |
| d = adddfa(g, nf->nf_type, nf->nf_name); | |
| makedfa(gr, gr->gr_nfa[i], d); | |
| } | |
| return g; | |
| } | |
| grammar * | |
| pgen(node *n) | |
| { | |
| nfagrammar *gr; | |
| grammar *g; | |
| gr = metacompile(n); | |
| g = maketables(gr); | |
| translatelabels(g); | |
| addfirstsets(g); | |
| PyObject_FREE(gr); | |
| return g; | |
| } | |
| grammar * | |
| Py_pgen(node *n) | |
| { | |
| return pgen(n); | |
| } | |
| /* | |
| Description | |
| ----------- | |
| Input is a grammar in extended BNF (using * for repetition, + for | |
| at-least-once repetition, [] for optional parts, | for alternatives and | |
| () for grouping). This has already been parsed and turned into a parse | |
| tree. | |
| Each rule is considered as a regular expression in its own right. | |
| It is turned into a Non-deterministic Finite Automaton (NFA), which | |
| is then turned into a Deterministic Finite Automaton (DFA), which is then | |
| optimized to reduce the number of states. See [Aho&Ullman 77] chapter 3, | |
| or similar compiler books (this technique is more often used for lexical | |
| analyzers). | |
| The DFA's are used by the parser as parsing tables in a special way | |
| that's probably unique. Before they are usable, the FIRST sets of all | |
| non-terminals are computed. | |
| Reference | |
| --------- | |
| [Aho&Ullman 77] | |
| Aho&Ullman, Principles of Compiler Design, Addison-Wesley 1977 | |
| (first edition) | |
| */ |