2.11BSD/ingres/source/equel/parser.c

# define	MAXDEPTH	150

/*
**  PARSER FOR YACC OUTPUT
**
**  This is the same as the yacc parser found in the UNIX system
**  library "/lib/liby.a".  There have been two kinds of
**  modifications. 1) The coding style has been altered to conform
**  to the INGRES standard.  2) The changes marked by comments.
**
**	History:
**		6/16/78 -- (marc) modified to call yyerror 
**			appropriately
**		76 -- (rick) modified for quel parser
**
*/

extern int	yyval;		/* defined in the table file */
extern int	yylval;		/* defined in the table file */
extern int	*yypv;		/* defined in the table file */


/* -------- the next line is an INGRES customization -------- */
int	yypflag		= 1;	/* zero for no actions performed */
int	yydebug		= 0;	/* 1 for debugging */
int	yyv[MAXDEPTH];		/* where the values are stored */
int	yystate		= 0;	/* current parser state */
int	yychar		= -1;	/* current input token number */
int	yynerrs		= 0;	/* number of errors */
int	yyerrflag	= 0;	/* error recovery flag */


yyparse()
{
	extern int	yygo[], yypgo[], yyr1[], yyr2[], yyact[], yypact[];
	/* INGRES customization to make 'ps', 'p', and 'n' register variables */
	int		s[MAXDEPTH];
	register int	*ps, *p;
	register int	n;
	int		ac;

	yystate = 0;
	yychar = -1;
	yynerrs = 0;
	yyerrflag = 0;
	ps = &s[0] - 1;
	yypv = &yyv[0] - 1;

stack:		/* put a state and value onto the stack */
	if (yydebug)
		printf("state %d value %d char %d\n", yystate, yyval, yychar);
	*++ps = yystate;
	*++yypv = yyval;

newstate:	/* set ap to point to the parsing actions for the new state */

	p = &yyact[yypact[yystate + 1]];

actn:		/* get the next action, and perform it */
	n = (ac = *p++) & 07777;	/* n is the "address" of the action */

	switch (ac >> 12)	/* switch on operation */
	{

	  case 1:	/* skip on test */
		if (yychar < 0)
		{
			yychar = yylex();
			if (yydebug)
				printf( "character %d read\n", yychar );
		}
		/* ---------- the next two lines are an INGRES customization ---------- */
		if (yychar < 0)
			return(1);
		if (n != yychar)
			p++;
		goto actn;	/* get next action */

	  case 2:		/* shift */
		yystate = n;
		yyval = yylval;
		yychar = -1;
		if (yyerrflag)
			yyerrflag--;
		goto stack;	/* stack new state */

	  case 3:		/* reduce */
		if (yydebug)
			printf("reduce %d\n", n);
		ps -= yyr2[n];
		yypv -= yyr2[n];
		yyval = yypv[1];
		/* --------  the next 2 lines are an INGRES customization -------- */
		if (yypflag && yyactr(n))
			 goto abort;
		/* consult goto table to find next state */
		for (p = &yygo[yypgo[yyr1[n]]]; *p != *ps && *p >= 0; p += 2) ;
		yystate = p[1];
		goto stack;  /* stack new state and value */

	  case 4:		/* accept */
		return(0);

	  case 0:		/* error ... attempt to resume parsing */
		switch (yyerrflag)
		{

		  case 0:		/* brand new error */
		/* ----------the next 2 lines are an INGRES customization ---------- */
			/* syntax error */
			yyerror("syntax error");
			yynerrs++;

		  case 1:
		  case 2: /* incompletely recovered error ... try again */
			yyerrflag = 3;

			/* find a state where "error" is a legal shift action */
			while (ps >= s)
			{
				/* search ps actions */
				for (p = &yyact[yypact[*ps + 1]]; (*p >> 12) == 1; p += 2)
				if (*p == 4352)
					goto found;

				/* the current ps has no shift onn "error", pop stack */

				if (yydebug)
					printf("err recov pops state %d, uncovers %d\n", ps[0], ps[-1]);
				ps--;
				yypv--;
			}

			/* there is no state on the stack with an error shift ... abort */

		abort:
			return(1);

		found:   /* we have a state with a shift on "error", resume parsing */
			yystate = p[1] & 07777;
			goto stack;

		  case 3:  /* no shift yet; clobber input char */
			if (yydebug)
				printf("err recov discards char %d\n", yychar);

			/* don't discard EOF; quit */
			if (yychar == 0)
				goto abort;
			yychar = -1;
			goto newstate;   /* try again in the same state */

		}
	}
}