parse.c

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/*-
 * 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. 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 "c.h"
 
#include <err.h>
#include <stdio.h>
#include "indent_globs.h"
#include "indent_codes.h"
#include "indent.h"
 
static void reduce(void);
 
void
parse(int tk) /* 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 ..." */
        /*
         * 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 = 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 >= 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 = btype_2;
    }
 
    break;
 
    case elselit:       /* scanned an else */
 
    if (ps.p_stack[ps.tos] != ifhead)
        diag2(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 | ps.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
        diag2(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 + 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 */
    diag2(1, "Unknown code to parser");
    return;
 
 
    }               /* end of switch */
 
    if (ps.tos >= nitems(ps.p_stack) - 1)
    errx(1, "Parser stack overflow");
 
    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;
}
 
/*
 * 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                 |
\*----------------------------------------------*/
static void
reduce(void)
{
    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];
        /* FALLTHROUGH */
        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.tos -= 2;
        break;
        }
        else
        return;
 
    default:        /* anything else on top */
        return;
 
    }
    }
}