xref: /csrg-svn/usr.bin/indent/parse.c (revision 24456)

/*
 * Copyright (c) 1980 Regents of the University of California.
 * All rights reserved.  The Berkeley software License Agreement
 * specifies the terms and conditions for redistribution.
 */

#ifndef lint
static char sccsid[] = "@(#)parse.c	5.2 (Berkeley) 08/28/85";
#endif not lint

/*-
 *
 *			  Copyright (C) 1976
 *				by the
 *			  Board of Trustees
 *				of the
 *			University of Illinois
 *
 *			 All rights reserved
 *
 *
 * FILE NAME:
 *	parse.c
 *
 * PURPOSE:
 *	Contains the routines which keep track of the parse stack.
 *
 * GLOBALS:
 *	ps.p_stack =	The parse stack, set by both routines
 *	ps.il =		Stack of indentation levels, set by parse
 *	ps.cstk =		Stack of case statement indentation levels, set by parse
 *	ps.tos =		Pointer to top of stack, set by both routines.
 *
 * FUNCTIONS:
 *	parse
 *	reduce
 */
/*-
 * Copyright (C) 1976 by the Board of Trustees of the University of Illinois
 *
 * All rights reserved
 *
 *
 * NAME: parse
 *
 * FUNCTION: Parse is given one input which is a "maxi token" just scanned
 * from input.  Maxi tokens are signifigant constructs such as else, {,
 * do, if (...), etc.  Parse works with reduce to maintain a parse stack
 * of these constructs.  Parse is responsible for the "shift" portion of
 * the parse algorithm, and reduce handles the "reduce" portion.
 *
 * HISTORY: initial coding 	November 1976	D A Willcox of CAC
 *
 */

#include "./indent_globs.h";
#include "./indent_codes.h";




parse(tk)
    int         tk;		/* the code for the construct scanned */
{
    int         i;

#ifdef debug
    printf("%2d - %s\n", tk, token);
#endif
    while (ps.p_stack[ps.tos] == ifhead && tk != elselit) {
	/* true if we have an if without an else */
	ps.p_stack[ps.tos] = stmt;	/* apply the if(..) stmt ::= stmt
				 * reduction */
	reduce();		/* see if this allows any reduction */
    }


    switch (tk) {		/* go on and figure out what to do with
				 * the input */

	case decl: 		/* scanned a declaration word */
	    ps.search_brace = btype_2;
	    /* indicate that following brace should be on same line */
	    if (ps.p_stack[ps.tos] != decl) {	/* only put one declaration onto
					 * stack */
		break_comma = true;	/* while in declaration, newline
					 * should be forced after comma */
		ps.p_stack[++ps.tos] = decl;
		ps.il[ps.tos] = ps.i_l_follow;

		if (ps.ljust_decl) {	/* only do if we want left
					 * justified declarations */
		    ps.ind_level = 0;
		    for (i = ps.tos - 1; i > 0; --i)
			if (ps.p_stack[i] == decl)
			    ++ps.ind_level;	/* indentation is number
						 * of declaration levels
						 * deep we are */
		    ps.i_l_follow = ps.ind_level;
		}
	    }
	    break;

	case ifstmt: 		/* scanned if (...) */
	    if (ps.p_stack[ps.tos] == elsehead && ps.else_if)	/* "else if ..." */
		ps.i_l_follow = ps.il[ps.tos];
	case dolit: 		/* 'do' */
	case forstmt: 		/* for (...) */
	    ps.p_stack[++ps.tos] = tk;
	    ps.il[ps.tos] = ps.ind_level = ps.i_l_follow;
	    ++ps.i_l_follow;	/* subsequent statements should be
				 * indented 1 */
	    ps.search_brace = btype_2;
	    break;

	case lbrace: 		/* scanned { */
	    break_comma = false;/* don't break comma in an initial list */
	    if (ps.p_stack[ps.tos] == stmt || ps.p_stack[ps.tos] == decl
		    || ps.p_stack[ps.tos] == stmtl)
		++ps.i_l_follow;	/* it is a random, isolated stmt group or
				 * a declaration */
	    else {
		if (s_code == e_code) {
		    /* only do this if there is nothing on the line */
		    --ps.ind_level;
		    /* it is a group as part of a while, for, etc. */
		    if (ps.p_stack[ps.tos] == swstmt && ps.case_indent)
			--ps.ind_level;
		    /*
		     * for a switch, brace should be two levels out from
		     * the code
		     */
		}
	    }

	    ps.p_stack[++ps.tos] = lbrace;
	    ps.il[ps.tos] = ps.ind_level;
	    ps.p_stack[++ps.tos] = stmt;
	    /* allow null stmt between braces */
	    ps.il[ps.tos] = ps.i_l_follow;
	    break;

	case whilestmt: 	/* scanned while (...) */
	    if (ps.p_stack[ps.tos] == dohead) {
		/* it is matched with do stmt */
		ps.ind_level = ps.i_l_follow = ps.il[ps.tos];
		ps.p_stack[++ps.tos] = whilestmt;
		ps.il[ps.tos] = ps.ind_level = ps.i_l_follow;
	    }
	    else {		/* it is a while loop */
		ps.p_stack[++ps.tos] = whilestmt;
		ps.il[ps.tos] = ps.i_l_follow;
		++ps.i_l_follow;
		ps.search_brace = btype_2;
	    }

	    break;

	case elselit: 		/* scanned an else */

	    if (ps.p_stack[ps.tos] != ifhead)
		diag(1,"Unmatched 'else'");
	    else {
		ps.ind_level = ps.il[ps.tos];		/* indentation for else should be same as for if */
		ps.i_l_follow = ps.ind_level + 1;	/* everything following should be in 1 level */
		ps.p_stack[ps.tos] = elsehead;
		/* remember if with else */
		ps.search_brace = btype_2;
	    }

	    break;

	case rbrace: 		/* scanned a } */
	    /* stack should have <lbrace> <stmt> or <lbrace> <stmtl> */
	    if (ps.p_stack[ps.tos - 1] == lbrace) {
		ps.ind_level = ps.i_l_follow = ps.il[--ps.tos];
		ps.p_stack[ps.tos] = stmt;
	    }
	    else
		diag(1,"Stmt nesting error.");
	    break;

	case swstmt: 		/* had switch (...) */
	    ps.p_stack[++ps.tos] = swstmt;
	    ps.cstk[ps.tos] = case_ind;
	    /* save current case indent level */
	    ps.il[ps.tos] = ps.i_l_follow;
	    case_ind = ps.i_l_follow + ps.case_indent;	/* cases should be one
							 * level down from
							 * switch */
	    ps.i_l_follow + = ps.case_indent + 1;	/* statements should be
						 * two levels in */
	    ps.search_brace = btype_2;
	    break;

	case semicolon: 	/* this indicates a simple stmt */
	    break_comma = false;/* turn off flag to break after commas in
				 * a declaration */
	    ps.p_stack[++ps.tos] = stmt;
	    ps.il[ps.tos] = ps.ind_level;
	    break;

	default: 		/* this is an error */
	    diag(1,"Unknown code to parser");
	    return;


    }				/* end of switch */

    reduce();			/* see if any reduction can be done */
#ifdef debug
    for (i = 1; i <= ps.tos; ++i)
	printf("(%d %d)", ps.p_stack[i], ps.il[i]);
    printf("\n");
#endif
    return;
}
/*
 * Copyright (C) 1976 by the Board of Trustees of the University of Illinois
 *
 * All rights reserved
 *
 *
 * NAME: reduce
 *
 * FUNCTION: Implements the reduce part of the parsing algorithm
 *
 * ALGORITHM: The following reductions are done.  Reductions are repeated
 * until no more are possible.
 *
 * Old TOS		New TOS <stmt> <stmt>	<stmtl> <stmtl> <stmt>	<stmtl> do
 * <stmt>	"dostmt" if <stmt>	"ifstmt" switch <stmt>	<stmt>
 * decl <stmt>	<stmt> "ifelse" <stmt>	<stmt> for <stmt>	<stmt>
 * while <stmt>	<stmt> "dostmt" while	<stmt>
 *
 * On each reduction, ps.i_l_follow (the indentation for the following line) is
 * set to the indentation level associated with the old TOS.
 *
 * PARAMETERS: None
 *
 * RETURNS: Nothing
 *
 * GLOBALS: ps.cstk ps.i_l_follow = ps.il ps.p_stack = ps.tos =
 *
 * CALLS: None
 *
 * CALLED BY: parse 
 *
 * HISTORY: initial coding 	November 1976	D A Willcox of CAC
 *
 */
/*----------------------------------------------*\
 * |   REDUCTION PHASE
\*----------------------------------------------*/
reduce() {

    register int i;

    for (;;) {			/* keep looping until there is nothing
				 * left to reduce */

	switch (ps.p_stack[ps.tos]) {

	    case stmt:
		switch (ps.p_stack[ps.tos - 1]) {

		    case stmt:
		    case stmtl:
			/* stmtl stmt or stmt stmt */
			ps.p_stack[--ps.tos] = stmtl;
			break;

		    case dolit: /* <do> <stmt> */
			ps.p_stack[--ps.tos] = dohead;
			ps.i_l_follow = ps.il[ps.tos];
			break;

		    case ifstmt:
			/* <if> <stmt> */
			ps.p_stack[--ps.tos] = ifhead;
			for (i = ps.tos - 1;
				(
				    ps.p_stack[i] != stmt
				    &&
				    ps.p_stack[i] != stmtl
				    &&
				    ps.p_stack[i] != lbrace
				);
				--i);
			ps.i_l_follow = ps.il[i];
			/*
			 * for the time being, we will assume that there
			 * is no else on this if, and set the indentation
			 * level accordingly. If an else is scanned, it
			 * will be fixed up later
			 */
			break;

		    case swstmt:
			/* <switch> <stmt> */
			case_ind = ps.cstk[ps.tos - 1];

		    case decl: 	/* finish of a declaration */
		    case elsehead:
			/* <<if> <stmt> else> <stmt> */
		    case forstmt:
			/* <for> <stmt> */
		    case whilestmt:
			/* <while> <stmt> */
			ps.p_stack[--ps.tos] = stmt;
			ps.i_l_follow = ps.il[ps.tos];
			break;

		    default: 	/* <anything else> <stmt> */
			return;

		}		/* end of section for <stmt> on top of
				 * stack */
		break;

	    case whilestmt: 	/* while (...) on top */
		if (ps.p_stack[ps.tos - 1] == dohead) {
		    /* it is termination of a do while */
		    ps.p_stack[--ps.tos] = stmt;
		    break;
		}
		else
		    return;

	    default: 		/* anything else on top */
		return;

	}
    }
}