Initial revision
diff --git a/Parser/pgen.c b/Parser/pgen.c
new file mode 100644
index 0000000..34d9b71
--- /dev/null
+++ b/Parser/pgen.c
@@ -0,0 +1,729 @@
+/* Parser generator */
+
+/* For a description, see the comments at end of this file */
+
+#include <stdio.h>
+#include "assert.h"
+
+#include "PROTO.h"
+#include "malloc.h"
+#include "token.h"
+#include "node.h"
+#include "grammar.h"
+#include "metagrammar.h"
+#include "pgen.h"
+
+extern int debugging;
+
+
+/* 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;
+
+static int
+addnfastate(nf)
+ nfa *nf;
+{
+ nfastate *st;
+
+ RESIZE(nf->nf_state, nfastate, nf->nf_nstates + 1);
+ if (nf->nf_state == NULL)
+ fatal("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(nf, from, to, lbl)
+ nfa *nf;
+ int from, to, lbl;
+{
+ nfastate *st;
+ nfaarc *ar;
+
+ st = &nf->nf_state[from];
+ RESIZE(st->st_arc, nfaarc, st->st_narcs + 1);
+ if (st->st_arc == NULL)
+ fatal("out of mem");
+ ar = &st->st_arc[st->st_narcs++];
+ ar->ar_label = lbl;
+ ar->ar_arrow = to;
+}
+
+static nfa *
+newnfa(name)
+ char *name;
+{
+ nfa *nf;
+ static type = NT_OFFSET; /* All types will be disjunct */
+
+ nf = NEW(nfa, 1);
+ if (nf == NULL)
+ fatal("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;
+
+static nfagrammar *
+newnfagrammar()
+{
+ nfagrammar *gr;
+
+ gr = NEW(nfagrammar, 1);
+ if (gr == NULL)
+ fatal("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(gr, name)
+ nfagrammar *gr;
+ char *name;
+{
+ nfa *nf;
+
+ nf = newnfa(name);
+ RESIZE(gr->gr_nfa, nfa *, gr->gr_nnfas + 1);
+ if (gr->gr_nfa == NULL)
+ fatal("out of mem");
+ gr->gr_nfa[gr->gr_nnfas++] = nf;
+ addlabel(&gr->gr_ll, NAME, nf->nf_name);
+ return nf;
+}
+
+#ifdef DEBUG
+
+static char REQNFMT[] = "metacompile: less than %d children\n";
+
+#define REQN(i, count) \
+ if (i < count) { \
+ fprintf(stderr, REQNFMT, count); \
+ abort(); \
+ } else
+
+#else
+#define REQN(i, count) /* empty */
+#endif
+
+static nfagrammar *
+metacompile(n)
+ node *n;
+{
+ nfagrammar *gr;
+ int i;
+
+ 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
+compile_rule(gr, n)
+ 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
+compile_rhs(ll, nf, n, pa, pb)
+ labellist *ll;
+ nfa *nf;
+ node *n;
+ int *pa, *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
+compile_alt(ll, nf, n, pa, pb)
+ labellist *ll;
+ nfa *nf;
+ node *n;
+ int *pa, *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++) {
+ if (n->n_type == COMMA) { /* XXX Temporary */
+ REQN(i, 1);
+ --i;
+ n++;
+ }
+ REQ(n, ITEM);
+ compile_item(ll, nf, n, &a, &b);
+ addnfaarc(nf, *pb, a, EMPTY);
+ *pb = b;
+ }
+}
+
+static
+compile_item(ll, nf, n, pa, pb)
+ labellist *ll;
+ nfa *nf;
+ node *n;
+ int *pa, *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
+compile_atom(ll, nf, n, pa, pb)
+ labellist *ll;
+ nfa *nf;
+ node *n;
+ int *pa, *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(ll, nf, istate)
+ 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,
+ labelrepr(&ll->ll_label[ar->ar_label]));
+ ar++;
+ }
+ printf("\n");
+}
+
+static void
+dumpnfa(ll, nf)
+ 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 int
+addclosure(ss, nf, istate)
+ 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;
+ 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;
+
+static
+makedfa(gr, nf, d)
+ 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 = NEW(ss_state, 1);
+ if (xx_state == NULL)
+ fatal("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) {
+ 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 */
+ RESIZE(yy->ss_arc, ss_arc, yy->ss_narcs + 1);
+ if (yy->ss_arc == NULL)
+ fatal("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;
+ }
+ }
+ RESIZE(xx_state, ss_state, xx_nstates + 1);
+ if (xx_state == NULL)
+ fatal("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 (debugging)
+ printssdfa(xx_nstates, xx_state, nbits, &gr->gr_ll,
+ "before minimizing");
+
+ simplify(xx_nstates, xx_state);
+
+ if (debugging)
+ printssdfa(xx_nstates, xx_state, nbits, &gr->gr_ll,
+ "after minimizing");
+
+ convert(d, xx_nstates, xx_state);
+
+ /* XXX cleanup */
+}
+
+static
+printssdfa(xx_nstates, xx_state, nbits, ll, msg)
+ 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,
+ 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 behaviour, try S: x a b+ | y a b+.)
+*/
+
+static int
+samestate(s1, s2)
+ ss_state *s1, *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(xx_nstates, xx_state, from, to)
+ int xx_nstates;
+ ss_state *xx_state;
+ int from, to;
+{
+ int i, j;
+
+ if (debugging)
+ 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
+simplify(xx_nstates, xx_state)
+ int xx_nstates;
+ ss_state *xx_state;
+{
+ int changes;
+ int i, j, k;
+
+ 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
+convert(d, xx_nstates, xx_state)
+ 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(gr)
+ 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 (debugging) {
+ 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(n)
+ node *n;
+{
+ nfagrammar *gr;
+ grammar *g;
+
+ gr = metacompile(n);
+ g = maketables(gr);
+ translatelabels(g);
+ addfirstsets(g);
+ return g;
+}
+
+
+/*
+
+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)
+
+*/