xref: /src/usr.bin/indent/parse.c

/*	$NetBSD: parse.c,v 1.16 2021/03/09 18:21:01 rillig Exp $	*/

/*-
 * SPDX-License-Identifier: BSD-4-Clause
 *
 * Copyright (c) 1985 Sun Microsystems, Inc.
 * Copyright (c) 1980, 1993
 *	The Regents of the University of California.  All rights reserved.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#if 0
#ifndef lint
static char sccsid[] = "@(#)parse.c	8.1 (Berkeley) 6/6/93";
#endif /* not lint */
#endif

#include <sys/cdefs.h>
#ifndef lint
#if defined(__NetBSD__)
__RCSID("$FreeBSD$");
#else
__FBSDID("$FreeBSD: head/usr.bin/indent/parse.c 337651 2018-08-11 19:20:06Z pstef $");
#endif
#endif

#include <err.h>
#include <stdio.h>

#include "indent.h"

static void reduce(void);

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

#ifdef debug
    printf("parse token: '%s' \"%s\"\n", token_type_name(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 = opt.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 (opt.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 && opt.else_if) /* "else if ..." */
		/*
		 * Note that the stack pointer here is decremented, effectively
		 * reducing "else if" to "if". This saves a lot of stack space
		 * in case of a long "if-else-if ... else-if" sequence.
		 */
		ps.i_l_follow = ps.il[ps.tos--];
	/* the rest is the same as for dolit and forstmt */
	/* FALLTHROUGH */
    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 = opt.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 && opt.case_indent >= 1)
		    --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 = opt.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 = opt.btype_2 | opt.else_if;
	}
	break;

    case rbrace:		/* scanned a } */
	/* stack should have <lbrace> <stmt> or <lbrace> <stmtl> */
	if (ps.tos > 0 && 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, "Statement 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 + opt.case_indent;	/* cases should be one
							 * level down from
							 * switch */
	ps.i_l_follow += opt.case_indent + 1;	/* statements should be two
						 * levels in */
	ps.search_brace = opt.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 */

    if (ps.tos >= STACKSIZE - 1)
	errx(1, "Parser stack overflow");

    reduce();			/* see if any reduction can be done */

#ifdef debug
    printf("parse stack:");
    for (i = 1; i <= ps.tos; ++i)
	printf(" ('%s' at %d)", token_type_name(ps.p_stack[i]), ps.il[i]);
    if (ps.tos == 0)
        printf(" empty");
    printf("\n");
#endif
}

/*----------------------------------------------*\
|   REDUCTION PHASE				 |
\*----------------------------------------------*/

/*
 * Try to combine the statement on the top of the parse stack with the symbol
 * directly below it, replacing these two symbols with a single symbol.
 */
static int
reduce_stmt(void)
{
    switch (ps.p_stack[ps.tos - 1]) {

    case stmt:		/* stmt stmt */
    case stmtl:		/* stmtl stmt */
	ps.p_stack[--ps.tos] = stmtl;
	return true;

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

    case ifstmt:	/* if (<expr>) <stmt> */
	ps.p_stack[--ps.tos] = ifhead;
	int i = ps.tos - 1;
	while (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
	 */
	return true;

    case swstmt:	/* switch (<expr>) <stmt> */
	case_ind = ps.cstk[ps.tos - 1];
	/* FALLTHROUGH */
    case decl:		/* finish of a declaration */
    case elsehead:	/* if (<expr>) <stmt> else <stmt> */
    case forstmt:	/* for (<...>) <stmt> */
    case whilestmt:	/* while (<expr>) <stmt> */
	ps.p_stack[--ps.tos] = stmt;
	ps.i_l_follow = ps.il[ps.tos];
	return true;

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

/*
 * Repeatedly try to reduce the top two symbols on the parse stack to a
 * single symbol, until no more reductions are possible.
 *
 * On each reduction, ps.i_l_follow (the indentation for the following line)
 * is set to the indentation level associated with the old TOS.
 */
static void
reduce(void)
{
again:
    if (ps.p_stack[ps.tos] == stmt) {
	if (reduce_stmt())
	    goto again;
    } else if (ps.p_stack[ps.tos] == whilestmt) {
	if (ps.p_stack[ps.tos - 1] == dohead) {
	    ps.tos -= 2;
	    goto again;
	}
    }
}