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Var_Subst is actually two distinct functions folded into one:
split the function specific to for.c out, and give them more sensible
arguments at the same time.

This makes .for loop handling more efficient, as we have some heuristic
to evaluate the size of the buffer needed...

/*	$OpenBSD: for.c,v 1.13 1999/12/16 17:27:18 espie Exp $	*/
/*	$NetBSD: for.c,v 1.4 1996/11/06 17:59:05 christos Exp $	*/

/*
 * Copyright (c) 1999 Marc Espie.
 *
 * Extensive code modifications for the OpenBSD project.
 *
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE OPENBSD PROJECT 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 OPENBSD
 * PROJECT 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.
 */

/*
 * Copyright (c) 1992, The Regents of the University of California.
 * 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.
 */

/*-
 * for.c --
 *	Functions to handle loops in a makefile.
 *
 * Interface:
 *	For_Eval 	Evaluate the .for in the passed line
 *	For_Accumulate	Add lines to an accumulating loop
 *	For_Run		Run accumulated loop
 *
 */

#include    <ctype.h>
#include    <assert.h>
#include    <stddef.h>
#include    "make.h"
#include    "buf.h"

#ifndef lint
#if 0
static char sccsid[] = "@(#)for.c	8.1 (Berkeley) 6/6/93";
#else
static char rcsid[] = "$OpenBSD: for.c,v 1.13 1999/12/16 17:27:18 espie Exp $";
#endif
#endif /* not lint */

/*
 * For statements are of the form:
 *
 * .for <variable> in <varlist>
 * ...
 * .endfor
 *
 * The trick is to look for the matching .end inside .for loops.
 * To do that, we keep track of the nesting level of .for loops
 * and matching .endfor statements, accumulating all statements between
 * the initial .for loop and the matching .endfor,
 * then we evaluate the .for loop for each variable in the varlist.
 */

/* State of a for loop.  */
struct For_ {
    char		*text;		/* unexpanded text       	*/
    char		*var;		/* Index name		 	*/
    Lst  		lst;		/* List of items	 	*/
    size_t		guess;		/* Estimated expansion size	*/
    BUFFER		buf;		/* Accumulating text	 	*/
    unsigned long	lineno;		/* Line number at start of loop */
    unsigned long	level;		/* Nesting level		*/
};

static int ForExec __P((ClientData, ClientData));
static void build_words_list __P((Lst, const char *));

/* Cut a string into words, stuff that into list.  */
static void
build_words_list(lst, s)
    Lst lst;
    const char *s;
{
    const char *wrd;

    for (;;) {
	for (; *s != '\0' && isspace(*s); s++)
	    continue;
	if (*s == '\0')
	    break;
	for (wrd = s; *s != '\0' && !isspace(*s); s++)
	    continue;
    	/* note that we fill the list backward, since 
     	 * Parse_FromString stacks strings.  */
	Lst_AtFront(lst, (ClientData)interval_dup(wrd, s));
    }
}

/*
 *-----------------------------------------------------------------------
 * For_Eval --
 *	Evaluate the for loop in the passed line. The line
 *	looks like this:
 *	    .for <variable> in <varlist>
 *
 * Results:
 *	Loop structure, to accumulate further lines.
 *	NULL if this was not a for loop after all.
 *-----------------------------------------------------------------------
 */

For *
For_Eval(line)
    char    	    *line;    /* Line to parse */
{
    char 	*ptr = line;
    char	*wrd;
    char 	*sub;
    char	*endVar;
    For 	*arg;

    for (ptr++; *ptr && isspace(*ptr); ptr++)
	continue;
    /* If we are not in a for loop quickly determine if the statement is
     * a for.  */
    if (ptr[0] != 'f' || ptr[1] != 'o' || ptr[2] != 'r' ||
	!isspace(ptr[3]))
	return NULL;
    ptr += 4;

    while (*ptr && isspace(*ptr))
	ptr++;

    /* We found a for loop, and now we are going to parse it.  */

    /* Grab the variable.  */
    for (wrd = ptr; *ptr && !isspace(*ptr); ptr++)
	continue;
    if (ptr - wrd == 0) {
	Parse_Error(PARSE_FATAL, "missing variable in for");
	return 0;
    }
    endVar = ptr++;

    while (*ptr && isspace(*ptr))
	ptr++;

    /* Grab the `in'.  */
    if (ptr[0] != 'i' || ptr[1] != 'n' ||
	!isspace(ptr[2])) {
	Parse_Error(PARSE_FATAL, "missing `in' in for");
	printf("%s\n", ptr);
	return NULL;
    }
    ptr += 3;

    /* .for loop is go, collate what we need.  */
    arg = emalloc(sizeof(*arg));
    arg->var = interval_dup(wrd, endVar);

    /* Make a list with the remaining words.  */
    sub = Var_Subst(ptr, VAR_GLOBAL, FALSE);
    if (DEBUG(FOR))
	(void)fprintf(stderr, "For: Iterator %s List %s\n", arg->var, sub);

    arg->lst = Lst_Init(FALSE);
    build_words_list(arg->lst, sub);
    free(sub);
    arg->lineno = Parse_Getlineno();
    arg->level = 1;
    Buf_Init(&arg->buf, 0);

    return arg;
}


/*-
 *-----------------------------------------------------------------------
 * For_Accumulate --
 *	Accumulate lines in a for loop, until we find the matching endfor.
 *
 * Results:
 *	TRUE: keep accumulating lines.
 *	FALSE: We found the matching .endfor
 *
 * Side Effects:
 *	Accumulate lines in arg.
 *-----------------------------------------------------------------------
 */
Boolean
For_Accumulate(arg, line)
    For		    *arg;
    const char      *line;    /* Line to parse */
{
    const char	    *ptr = line;

    assert(arg->level > 0);

    if (*ptr == '.') {

	for (ptr++; *ptr && isspace(*ptr); ptr++)
	    continue;

	if (strncmp(ptr, "endfor", 6) == 0 &&
	    (isspace(ptr[6]) || !ptr[6])) {
	    if (DEBUG(FOR))
		(void)fprintf(stderr, "For: end for %lu\n", arg->level);
	    /* If matching endfor, don't add line to buffer.  */
	    if (--arg->level == 0)
		return FALSE;
	}
	else if (strncmp(ptr, "for", 3) == 0 &&
		 isspace(ptr[3])) {
	    arg->level++;
	    if (DEBUG(FOR))
		(void)fprintf(stderr, "For: new loop %lu\n", arg->level);
	}
    }
    Buf_AddString(&arg->buf, line);
    Buf_AddChar(&arg->buf, '\n');
    return TRUE;
}


#define GUESS_EXPANSION 32
/*-
 *-----------------------------------------------------------------------
 * ForExec --
 *	Expand the for loop for this index and push it in the Makefile
 *-----------------------------------------------------------------------
 */
static int
ForExec(namep, argp)
    ClientData namep;
    ClientData argp;
{
    char *name = (char *)namep;
    For *arg = (For *)argp;

    Buf_Init(&arg->buf, arg->guess);
    Var_Set(arg->var, name, VAR_GLOBAL);
    if (DEBUG(FOR))
	(void)fprintf(stderr, "--- %s = %s\n", arg->var, name);
    Var_SubstVar(&arg->buf, arg->text, arg->var, VAR_GLOBAL);
    if (Buf_Size(&arg->buf) >= arg->guess)
    	arg->guess = Buf_Size(&arg->buf) + GUESS_EXPANSION;
    
    Parse_FromString(Buf_Retrieve(&arg->buf), arg->lineno);
    Var_Delete(arg->var, VAR_GLOBAL);
    return 0;
}


/*-
 *-----------------------------------------------------------------------
 * For_Run --
 *	Run the for loop, pushing expanded lines for reparse
 *-----------------------------------------------------------------------
 */

void
For_Run(arg)
    For *arg;
{
    arg->text = Buf_Retrieve(&arg->buf);
    arg->guess = Buf_Size(&arg->buf) + GUESS_EXPANSION;

    Lst_ForEach(arg->lst, ForExec, (ClientData)arg);
    free(arg->var);
    free(arg->text);
    Lst_Destroy(arg->lst, (void (*) __P((ClientData)))free);
    free(arg);
}