Parser/parser.c - platform/external/python/cpython3 - Gitiles

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

                         All Rights Reserved

 Permission to use, copy, modify, and distribute this software and its
 documentation for any purpose and without fee is hereby granted,
 provided that the above copyright notice appear in all copies and that
 both that copyright notice and this permission notice appear in
 supporting documentation, and that the names of Stichting Mathematisch
 Centrum or CWI not be used in advertising or publicity pertaining to
 distribution of the software without specific, written prior permission.

 STICHTING MATHEMATISCH CENTRUM DISCLAIMS ALL WARRANTIES WITH REGARD TO
 THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
 FITNESS, IN NO EVENT SHALL STICHTING MATHEMATISCH CENTRUM BE LIABLE
 FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
 OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

 ******************************************************************/

 /* Parser implementation */

 /* For a description, see the comments at end of this file */

 /* XXX To do: error recovery */

 #include "pgenheaders.h"
 #include "assert.h"
 #include "token.h"
 #include "grammar.h"
 #include "node.h"
 #include "parser.h"
 #include "errcode.h"


 #ifdef DEBUG
 extern int debugging;
 #define D(x) if (!debugging); else x
 #else
 #define D(x)
 #endif


 /* STACK DATA TYPE */

 static void s_reset PROTO((stack *));

 static void
 s_reset(s)
 	stack *s;
 {
 	s->s_top = &s->s_base[MAXSTACK];
 }

 #define s_empty(s) ((s)->s_top == &(s)->s_base[MAXSTACK])

 static int s_push PROTO((stack *, dfa *, node *));

 static int
 s_push(s, d, parent)
 	register stack *s;
 	dfa *d;
 	node *parent;
 {
 	register stackentry *top;
 	if (s->s_top == s->s_base) {
 		fprintf(stderr, "s_push: parser stack overflow\n");
 		return -1;
 	}
 	top = --s->s_top;
 	top->s_dfa = d;
 	top->s_parent = parent;
 	top->s_state = 0;
 	return 0;
 }

 #ifdef DEBUG

 static void s_pop PROTO((stack *));

 static void
 s_pop(s)
 	register stack *s;
 {
 	if (s_empty(s))
 		fatal("s_pop: parser stack underflow -- FATAL");
 	s->s_top++;
 }

 #else /* !DEBUG */

 #define s_pop(s) (s)->s_top++

 #endif


 /* PARSER CREATION */

 parser_state *
 newparser(g, start)
 	grammar *g;
 	int start;
 {
 	parser_state *ps;

 	if (!g->g_accel)
 		addaccelerators(g);
 	ps = NEW(parser_state, 1);
 	if (ps == NULL)
 		return NULL;
 	ps->p_grammar = g;
 	ps->p_tree = newtree(start);
 	if (ps->p_tree == NULL) {
 		DEL(ps);
 		return NULL;
 	}
 	s_reset(&ps->p_stack);
 	(void) s_push(&ps->p_stack, finddfa(g, start), ps->p_tree);
 	return ps;
 }

 void
 delparser(ps)
 	parser_state *ps;
 {
 	/* NB If you want to save the parse tree,
 	   you must set p_tree to NULL before calling delparser! */
 	freetree(ps->p_tree);
 	DEL(ps);
 }


 /* PARSER STACK OPERATIONS */

 static int shift PROTO((stack *, int, char *, int, int));

 static int
 shift(s, type, str, newstate, lineno)
 	register stack *s;
 	int type;
 	char *str;
 	int newstate;
 	int lineno;
 {
 	assert(!s_empty(s));
 	if (addchild(s->s_top->s_parent, type, str, lineno) == NULL) {
 		fprintf(stderr, "shift: no mem in addchild\n");
 		return -1;
 	}
 	s->s_top->s_state = newstate;
 	return 0;
 }

 static int push PROTO((stack *, int, dfa *, int, int));

 static int
 push(s, type, d, newstate, lineno)
 	register stack *s;
 	int type;
 	dfa *d;
 	int newstate;
 	int lineno;
 {
 	register node *n;
 	n = s->s_top->s_parent;
 	assert(!s_empty(s));
 	if (addchild(n, type, (char *)NULL, lineno) == NULL) {
 		fprintf(stderr, "push: no mem in addchild\n");
 		return -1;
 	}
 	s->s_top->s_state = newstate;
 	return s_push(s, d, CHILD(n, NCH(n)-1));
 }


 /* PARSER PROPER */

 static int classify PROTO((grammar *, int, char *));

 static int
 classify(g, type, str)
 	grammar *g;
 	register int type;
 	char *str;
 {
 	register int n = g->g_ll.ll_nlabels;

 	if (type == NAME) {
 		register char *s = str;
 		register label *l = g->g_ll.ll_label;
 		register int i;
 		for (i = n; i > 0; i--, l++) {
 			if (l->lb_type == NAME && l->lb_str != NULL &&
 					l->lb_str[0] == s[0] &&
 					strcmp(l->lb_str, s) == 0) {
 				D(printf("It's a keyword\n"));
 				return n - i;
 			}
 		}
 	}

 	{
 		register label *l = g->g_ll.ll_label;
 		register int i;
 		for (i = n; i > 0; i--, l++) {
 			if (l->lb_type == type && l->lb_str == NULL) {
 				D(printf("It's a token we know\n"));
 				return n - i;
 			}
 		}
 	}

 	D(printf("Illegal token\n"));
 	return -1;
 }

 int
 addtoken(ps, type, str, lineno)
 	register parser_state *ps;
 	register int type;
 	char *str;
 	int lineno;
 {
 	register int ilabel;

 	D(printf("Token %s/'%s' ... ", tok_name[type], str));

 	/* Find out which label this token is */
 	ilabel = classify(ps->p_grammar, type, str);
 	if (ilabel < 0)
 		return E_SYNTAX;

 	/* Loop until the token is shifted or an error occurred */
 	for (;;) {
 		/* Fetch the current dfa and state */
 		register dfa *d = ps->p_stack.s_top->s_dfa;
 		register state *s = &d->d_state[ps->p_stack.s_top->s_state];

 		D(printf(" DFA '%s', state %d:",
 			d->d_name, ps->p_stack.s_top->s_state));

 		/* Check accelerator */
 		if (s->s_lower <= ilabel && ilabel < s->s_upper) {
 			register int x = s->s_accel[ilabel - s->s_lower];
 			if (x != -1) {
 				if (x & (1<<7)) {
 					/* Push non-terminal */
 					int nt = (x >> 8) + NT_OFFSET;
 					int arrow = x & ((1<<7)-1);
 					dfa *d1 = finddfa(ps->p_grammar, nt);
 					if (push(&ps->p_stack, nt, d1,
 						arrow, lineno) < 0) {
 						D(printf(" MemError: push.\n"));
 						return E_NOMEM;
 					}
 					D(printf(" Push ...\n"));
 					continue;
 				}

 				/* Shift the token */
 				if (shift(&ps->p_stack, type, str,
 						x, lineno) < 0) {
 					D(printf(" MemError: shift.\n"));
 					return E_NOMEM;
 				}
 				D(printf(" Shift.\n"));
 				/* Pop while we are in an accept-only state */
 				while (s = &d->d_state
 						[ps->p_stack.s_top->s_state],
 					s->s_accept && s->s_narcs == 1) {
 					D(printf("  Direct pop.\n"));
 					s_pop(&ps->p_stack);
 					if (s_empty(&ps->p_stack)) {
 						D(printf("  ACCEPT.\n"));
 						return E_DONE;
 					}
 					d = ps->p_stack.s_top->s_dfa;
 				}
 				return E_OK;
 			}
 		}

 		if (s->s_accept) {
 			/* Pop this dfa and try again */
 			s_pop(&ps->p_stack);
 			D(printf(" Pop ...\n"));
 			if (s_empty(&ps->p_stack)) {
 				D(printf(" Error: bottom of stack.\n"));
 				return E_SYNTAX;
 			}
 			continue;
 		}

 		/* Stuck, report syntax error */
 		D(printf(" Error.\n"));
 		return E_SYNTAX;
 	}
 }


 #ifdef DEBUG

 /* DEBUG OUTPUT */

 void
 dumptree(g, n)
 	grammar *g;
 	node *n;
 {
 	int i;

 	if (n == NULL)
 		printf("NIL");
 	else {
 		label l;
 		l.lb_type = TYPE(n);
 		l.lb_str = STR(n);
 		printf("%s", labelrepr(&l));
 		if (ISNONTERMINAL(TYPE(n))) {
 			printf("(");
 			for (i = 0; i < NCH(n); i++) {
 				if (i > 0)
 					printf(",");
 				dumptree(g, CHILD(n, i));
 			}
 			printf(")");
 		}
 	}
 }

 void
 showtree(g, n)
 	grammar *g;
 	node *n;
 {
 	int i;

 	if (n == NULL)
 		return;
 	if (ISNONTERMINAL(TYPE(n))) {
 		for (i = 0; i < NCH(n); i++)
 			showtree(g, CHILD(n, i));
 	}
 	else if (ISTERMINAL(TYPE(n))) {
 		printf("%s", tok_name[TYPE(n)]);
 		if (TYPE(n) == NUMBER || TYPE(n) == NAME)
 			printf("(%s)", STR(n));
 		printf(" ");
 	}
 	else
 		printf("? ");
 }

 void
 printtree(ps)
 	parser_state *ps;
 {
 	if (debugging) {
 		printf("Parse tree:\n");
 		dumptree(ps->p_grammar, ps->p_tree);
 		printf("\n");
 		printf("Tokens:\n");
 		showtree(ps->p_grammar, ps->p_tree);
 		printf("\n");
 	}
 	printf("Listing:\n");
 	listtree(ps->p_tree);
 	printf("\n");
 }

 #endif /* DEBUG */

 /*

 Description
 -----------

 The parser's interface is different than usual: the function addtoken()
 must be called for each token in the input.  This makes it possible to
 turn it into an incremental parsing system later.  The parsing system
 constructs a parse tree as it goes.

 A parsing rule is represented as a Deterministic Finite-state Automaton
 (DFA).  A node in a DFA represents a state of the parser; an arc represents
 a transition.  Transitions are either labeled with terminal symbols or
 with non-terminals.  When the parser decides to follow an arc labeled
 with a non-terminal, it is invoked recursively with the DFA representing
 the parsing rule for that as its initial state; when that DFA accepts,
 the parser that invoked it continues.  The parse tree constructed by the
 recursively called parser is inserted as a child in the current parse tree.

 The DFA's can be constructed automatically from a more conventional
 language description.  An extended LL(1) grammar (ELL(1)) is suitable.
 Certain restrictions make the parser's life easier: rules that can produce
 the empty string should be outlawed (there are other ways to put loops
 or optional parts in the language).  To avoid the need to construct
 FIRST sets, we can require that all but the last alternative of a rule
 (really: arc going out of a DFA's state) must begin with a terminal
 symbol.

 As an example, consider this grammar:

 expr:	term (OP term)*
 term:	CONSTANT | '(' expr ')'

 The DFA corresponding to the rule for expr is:

 ------->.---term-->.------->
 	^          |
 	|          |
 	\----OP----/

 The parse tree generated for the input a+b is:

 (expr: (term: (NAME: a)), (OP: +), (term: (NAME: b)))

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

	All Rights Reserved

	Permission to use, copy, modify, and distribute this software and its
	documentation for any purpose and without fee is hereby granted,
	provided that the above copyright notice appear in all copies and that
	both that copyright notice and this permission notice appear in
	supporting documentation, and that the names of Stichting Mathematisch
	Centrum or CWI not be used in advertising or publicity pertaining to
	distribution of the software without specific, written prior permission.

	STICHTING MATHEMATISCH CENTRUM DISCLAIMS ALL WARRANTIES WITH REGARD TO
	THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
	FITNESS, IN NO EVENT SHALL STICHTING MATHEMATISCH CENTRUM BE LIABLE
	FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
	WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
	ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
	OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

	******************************************************************/

	/* Parser implementation */

	/* For a description, see the comments at end of this file */

	/* XXX To do: error recovery */

	#include "pgenheaders.h"
	#include "assert.h"
	#include "token.h"
	#include "grammar.h"
	#include "node.h"
	#include "parser.h"
	#include "errcode.h"


	#ifdef DEBUG
	extern int debugging;
	#define D(x) if (!debugging); else x
	#else
	#define D(x)
	#endif


	/* STACK DATA TYPE */

	static void s_reset PROTO((stack *));

	static void
	s_reset(s)
	stack *s;
	{
	s->s_top = &s->s_base[MAXSTACK];
	}

	#define s_empty(s) ((s)->s_top == &(s)->s_base[MAXSTACK])

	static int s_push PROTO((stack , dfa , node *));

	static int
	s_push(s, d, parent)
	register stack *s;
	dfa *d;
	node *parent;
	{
	register stackentry *top;
	if (s->s_top == s->s_base) {
	fprintf(stderr, "s_push: parser stack overflow\n");
	return -1;
	}
	top = --s->s_top;
	top->s_dfa = d;
	top->s_parent = parent;
	top->s_state = 0;
	return 0;
	}

	#ifdef DEBUG

	static void s_pop PROTO((stack *));

	static void
	s_pop(s)
	register stack *s;
	{
	if (s_empty(s))
	fatal("s_pop: parser stack underflow -- FATAL");
	s->s_top++;
	}

	#else /* !DEBUG */

	#define s_pop(s) (s)->s_top++

	#endif


	/* PARSER CREATION */

	parser_state *
	newparser(g, start)
	grammar *g;
	int start;
	{
	parser_state *ps;

	if (!g->g_accel)
	addaccelerators(g);
	ps = NEW(parser_state, 1);
	if (ps == NULL)
	return NULL;
	ps->p_grammar = g;
	ps->p_tree = newtree(start);
	if (ps->p_tree == NULL) {
	DEL(ps);
	return NULL;
	}
	s_reset(&ps->p_stack);
	(void) s_push(&ps->p_stack, finddfa(g, start), ps->p_tree);
	return ps;
	}

	void
	delparser(ps)
	parser_state *ps;
	{
	/* NB If you want to save the parse tree,
	you must set p_tree to NULL before calling delparser! */
	freetree(ps->p_tree);
	DEL(ps);
	}


	/* PARSER STACK OPERATIONS */

	static int shift PROTO((stack , int, char , int, int));

	static int
	shift(s, type, str, newstate, lineno)
	register stack *s;
	int type;
	char *str;
	int newstate;
	int lineno;
	{
	assert(!s_empty(s));
	if (addchild(s->s_top->s_parent, type, str, lineno) == NULL) {
	fprintf(stderr, "shift: no mem in addchild\n");
	return -1;
	}
	s->s_top->s_state = newstate;
	return 0;
	}

	static int push PROTO((stack , int, dfa , int, int));

	static int
	push(s, type, d, newstate, lineno)
	register stack *s;
	int type;
	dfa *d;
	int newstate;
	int lineno;
	{
	register node *n;
	n = s->s_top->s_parent;
	assert(!s_empty(s));
	if (addchild(n, type, (char *)NULL, lineno) == NULL) {
	fprintf(stderr, "push: no mem in addchild\n");
	return -1;
	}
	s->s_top->s_state = newstate;
	return s_push(s, d, CHILD(n, NCH(n)-1));
	}


	/* PARSER PROPER */

	static int classify PROTO((grammar , int, char ));

	static int
	classify(g, type, str)
	grammar *g;
	register int type;
	char *str;
	{
	register int n = g->g_ll.ll_nlabels;

	if (type == NAME) {
	register char *s = str;
	register label *l = g->g_ll.ll_label;
	register int i;
	for (i = n; i > 0; i--, l++) {
	if (l->lb_type == NAME && l->lb_str != NULL &&
	l->lb_str[0] == s[0] &&
	strcmp(l->lb_str, s) == 0) {
	D(printf("It's a keyword\n"));
	return n - i;
	}
	}
	}

	{
	register label *l = g->g_ll.ll_label;
	register int i;
	for (i = n; i > 0; i--, l++) {
	if (l->lb_type == type && l->lb_str == NULL) {
	D(printf("It's a token we know\n"));
	return n - i;
	}
	}
	}

	D(printf("Illegal token\n"));
	return -1;
	}

	int
	addtoken(ps, type, str, lineno)
	register parser_state *ps;
	register int type;
	char *str;
	int lineno;
	{
	register int ilabel;

	D(printf("Token %s/'%s' ... ", tok_name[type], str));

	/* Find out which label this token is */
	ilabel = classify(ps->p_grammar, type, str);
	if (ilabel < 0)
	return E_SYNTAX;

	/* Loop until the token is shifted or an error occurred */
	for (;;) {
	/* Fetch the current dfa and state */
	register dfa *d = ps->p_stack.s_top->s_dfa;
	register state *s = &d->d_state[ps->p_stack.s_top->s_state];

	D(printf(" DFA '%s', state %d:",
	d->d_name, ps->p_stack.s_top->s_state));

	/* Check accelerator */
	if (s->s_lower <= ilabel && ilabel < s->s_upper) {
	register int x = s->s_accel[ilabel - s->s_lower];
	if (x != -1) {
	if (x & (1<<7)) {
	/* Push non-terminal */
	int nt = (x >> 8) + NT_OFFSET;
	int arrow = x & ((1<<7)-1);
	dfa *d1 = finddfa(ps->p_grammar, nt);
	if (push(&ps->p_stack, nt, d1,
	arrow, lineno) < 0) {
	D(printf(" MemError: push.\n"));
	return E_NOMEM;
	}
	D(printf(" Push ...\n"));
	continue;
	}

	/* Shift the token */
	if (shift(&ps->p_stack, type, str,
	x, lineno) < 0) {
	D(printf(" MemError: shift.\n"));
	return E_NOMEM;
	}
	D(printf(" Shift.\n"));
	/* Pop while we are in an accept-only state */
	while (s = &d->d_state
	[ps->p_stack.s_top->s_state],
	s->s_accept && s->s_narcs == 1) {
	D(printf(" Direct pop.\n"));
	s_pop(&ps->p_stack);
	if (s_empty(&ps->p_stack)) {
	D(printf(" ACCEPT.\n"));
	return E_DONE;
	}
	d = ps->p_stack.s_top->s_dfa;
	}
	return E_OK;
	}
	}

	if (s->s_accept) {
	/* Pop this dfa and try again */
	s_pop(&ps->p_stack);
	D(printf(" Pop ...\n"));
	if (s_empty(&ps->p_stack)) {
	D(printf(" Error: bottom of stack.\n"));
	return E_SYNTAX;
	}
	continue;
	}

	/* Stuck, report syntax error */
	D(printf(" Error.\n"));
	return E_SYNTAX;
	}
	}


	#ifdef DEBUG

	/* DEBUG OUTPUT */

	void
	dumptree(g, n)
	grammar *g;
	node *n;
	{
	int i;

	if (n == NULL)
	printf("NIL");
	else {
	label l;
	l.lb_type = TYPE(n);
	l.lb_str = STR(n);
	printf("%s", labelrepr(&l));
	if (ISNONTERMINAL(TYPE(n))) {
	printf("(");
	for (i = 0; i < NCH(n); i++) {
	if (i > 0)
	printf(",");
	dumptree(g, CHILD(n, i));
	}
	printf(")");
	}
	}
	}

	void
	showtree(g, n)
	grammar *g;
	node *n;
	{
	int i;

	if (n == NULL)
	return;
	if (ISNONTERMINAL(TYPE(n))) {
	for (i = 0; i < NCH(n); i++)
	showtree(g, CHILD(n, i));
	}
	else if (ISTERMINAL(TYPE(n))) {
	printf("%s", tok_name[TYPE(n)]);
	if (TYPE(n) == NUMBER \|\| TYPE(n) == NAME)
	printf("(%s)", STR(n));
	printf(" ");
	}
	else
	printf("? ");
	}

	void
	printtree(ps)
	parser_state *ps;
	{
	if (debugging) {
	printf("Parse tree:\n");
	dumptree(ps->p_grammar, ps->p_tree);
	printf("\n");
	printf("Tokens:\n");
	showtree(ps->p_grammar, ps->p_tree);
	printf("\n");
	}
	printf("Listing:\n");
	listtree(ps->p_tree);
	printf("\n");
	}

	#endif /* DEBUG */

	/*

	Description
	-----------

	The parser's interface is different than usual: the function addtoken()
	must be called for each token in the input. This makes it possible to
	turn it into an incremental parsing system later. The parsing system
	constructs a parse tree as it goes.

	A parsing rule is represented as a Deterministic Finite-state Automaton
	(DFA). A node in a DFA represents a state of the parser; an arc represents
	a transition. Transitions are either labeled with terminal symbols or
	with non-terminals. When the parser decides to follow an arc labeled
	with a non-terminal, it is invoked recursively with the DFA representing
	the parsing rule for that as its initial state; when that DFA accepts,
	the parser that invoked it continues. The parse tree constructed by the
	recursively called parser is inserted as a child in the current parse tree.

	The DFA's can be constructed automatically from a more conventional
	language description. An extended LL(1) grammar (ELL(1)) is suitable.
	Certain restrictions make the parser's life easier: rules that can produce
	the empty string should be outlawed (there are other ways to put loops
	or optional parts in the language). To avoid the need to construct
	FIRST sets, we can require that all but the last alternative of a rule
	(really: arc going out of a DFA's state) must begin with a terminal
	symbol.

	As an example, consider this grammar:

	expr: term (OP term)*
	term: CONSTANT \| '(' expr ')'

	The DFA corresponding to the rule for expr is:

	------->.---term-->.------->
	^ \|
	\| \|
	\----OP----/

	The parse tree generated for the input a+b is:

	(expr: (term: (NAME: a)), (OP: +), (term: (NAME: b)))

	*/