env(1): unbreak build of 2_2 release branch under HEAD

[dragonfly.git] / usr.bin / make / dir.c

/*-
 * Copyright (c) 1988, 1989, 1990, 1993
 *      The Regents of the University of California.  All rights reserved.
 * Copyright (c) 1988, 1989 by Adam de Boor
 * Copyright (c) 1989 by Berkeley Softworks
 * All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Adam de Boor.
 *
 * 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.
 *
 * @(#)dir.c    8.2 (Berkeley) 1/2/94
 * $FreeBSD: src/usr.bin/make/dir.c,v 1.47 2005/02/04 07:50:59 harti Exp $
 * $DragonFly: src/usr.bin/make/dir.c,v 1.44 2005/11/05 15:35:10 swildner Exp $
 */

/*-
 * dir.c --
 *      Directory searching using wildcards and/or normal names...
 *      Used both for source wildcarding in the Makefile and for finding
 *      implicit sources.
 *
 * The interface for this module is:
 *      Dir_Init        Initialize the module.
 *
 *      Dir_HasWildcards Returns true if the name given it needs to
 *                      be wildcard-expanded.
 *
 *      Path_Expand     Given a pattern and a path, return a Lst of names
 *                      which match the pattern on the search path.
 *
 *      Path_FindFile   Searches for a file on a given search path.
 *                      If it exists, the entire path is returned.
 *                      Otherwise NULL is returned.
 *
 *      Dir_MTime       Return the modification time of a node. The file
 *                      is searched for along the default search path.
 *                      The path and mtime fields of the node are filled in.
 *
 *      Path_AddDir     Add a directory to a search path.
 *
 *      Dir_MakeFlags   Given a search path and a command flag, create
 *                      a string with each of the directories in the path
 *                      preceded by the command flag and all of them
 *                      separated by a space.
 *
 *      Dir_Destroy     Destroy an element of a search path. Frees up all
 *                      things that can be freed for the element as long
 *                      as the element is no longer referenced by any other
 *                      search path.
 *
 *      Dir_ClearPath   Resets a search path to the empty list.
 *
 * For debugging:
 *      Dir_PrintDirectories    Print stats about the directory cache.
 */

#include <sys/types.h>
#include <sys/stat.h>
#include <dirent.h>
#include <err.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "arch.h"
#include "dir.h"
#include "globals.h"
#include "GNode.h"
#include "hash.h"
#include "lst.h"
#include "make.h"
#include "str.h"
#include "targ.h"
#include "util.h"

/*
 *      A search path consists of a list of Dir structures. A Dir structure
 *      has in it the name of the directory and a hash table of all the files
 *      in the directory. This is used to cut down on the number of system
 *      calls necessary to find implicit dependents and their like. Since
 *      these searches are made before any actions are taken, we need not
 *      worry about the directory changing due to creation commands. If this
 *      hampers the style of some makefiles, they must be changed.
 *
 *      A list of all previously-read directories is kept in the
 *      openDirectories list. This list is checked first before a directory
 *      is opened.
 *
 *      The need for the caching of whole directories is brought about by
 *      the multi-level transformation code in suff.c, which tends to search
 *      for far more files than regular make does. In the initial
 *      implementation, the amount of time spent performing "stat" calls was
 *      truly astronomical. The problem with hashing at the start is,
 *      of course, that pmake doesn't then detect changes to these directories
 *      during the course of the make. Three possibilities suggest themselves:
 *
 *          1) just use stat to test for a file's existence. As mentioned
 *             above, this is very inefficient due to the number of checks
 *             engendered by the multi-level transformation code.
 *          2) use readdir() and company to search the directories, keeping
 *             them open between checks. I have tried this and while it
 *             didn't slow down the process too much, it could severely
 *             affect the amount of parallelism available as each directory
 *             open would take another file descriptor out of play for
 *             handling I/O for another job. Given that it is only recently
 *             that UNIX OS's have taken to allowing more than 20 or 32
 *             file descriptors for a process, this doesn't seem acceptable
 *             to me.
 *          3) record the mtime of the directory in the Dir structure and
 *             verify the directory hasn't changed since the contents were
 *             hashed. This will catch the creation or deletion of files,
 *             but not the updating of files. However, since it is the
 *             creation and deletion that is the problem, this could be
 *             a good thing to do. Unfortunately, if the directory (say ".")
 *             were fairly large and changed fairly frequently, the constant
 *             rehashing could seriously degrade performance. It might be
 *             good in such cases to keep track of the number of rehashes
 *             and if the number goes over a (small) limit, resort to using
 *             stat in its place.
 *
 *      An additional thing to consider is that pmake is used primarily
 *      to create C programs and until recently pcc-based compilers refused
 *      to allow you to specify where the resulting object file should be
 *      placed. This forced all objects to be created in the current
 *      directory. This isn't meant as a full excuse, just an explanation of
 *      some of the reasons for the caching used here.
 *
 *      One more note: the location of a target's file is only performed
 *      on the downward traversal of the graph and then only for terminal
 *      nodes in the graph. This could be construed as wrong in some cases,
 *      but prevents inadvertent modification of files when the "installed"
 *      directory for a file is provided in the search path.
 *
 *      Another data structure maintained by this module is an mtime
 *      cache used when the searching of cached directories fails to find
 *      a file. In the past, Path_FindFile would simply perform an access()
 *      call in such a case to determine if the file could be found using
 *      just the name given. When this hit, however, all that was gained
 *      was the knowledge that the file existed. Given that an access() is
 *      essentially a stat() without the copyout() call, and that the same
 *      filesystem overhead would have to be incurred in Dir_MTime, it made
 *      sense to replace the access() with a stat() and record the mtime
 *      in a cache for when Dir_MTime was actually called.
 */

typedef struct Dir {
        char    *name;          /* Name of directory */
        int     refCount;       /* No. of paths with this directory */
        int     hits;           /* No. of times a file has been found here */
        Hash_Table files;       /* Hash table of files in directory */
        TAILQ_ENTRY(Dir) link;  /* allDirs link */
} Dir;

/*
 * A path is a list of pointers to directories. These directories are
 * reference counted so a directory can be on more than one path.
 */
struct PathElement {
        struct Dir      *dir;   /* pointer to the directory */
        TAILQ_ENTRY(PathElement) link;  /* path link */
};

/* main search path */
struct Path                     dirSearchPath;

/* the list of all open directories */
static TAILQ_HEAD(, Dir)        openDirectories;

/*
 * Variables for gathering statistics on the efficiency of the hashing
 * mechanism.
 */
static int hits;        /* Found in directory cache */
static int misses;      /* Sad, but not evil misses */
static int nearmisses;  /* Found under search path */
static int bigmisses;   /* Sought by itself */

static Dir *dot;            /* contents of current directory */

/* Results of doing a last-resort stat in Path_FindFile --
 * if we have to go to the system to find the file, we might as well
 * have its mtime on record.
 * XXX: If this is done way early, there's a chance other rules will
 * have already updated the file, in which case we'll update it again.
 * Generally, there won't be two rules to update a single file, so this
 * should be ok, but...
 */
static Hash_Table mtimes;

/**
 * initialize things for this module
 *      add the "." directory
 *      add curdir if it is not the same as objdir
 */
void
Dir_Init(void)
{

        Hash_InitTable(&mtimes, 0);
        TAILQ_INIT(&dirSearchPath);
        TAILQ_INIT(&openDirectories);
}

/**
 * add the "." directory
 * add curdir if it is not the same as objdir
 */
void
Dir_CurObj(const char curdir[], const char objdir[])
{

        dot = Path_AddDir(NULL, ".");
        if (dot == NULL)
                err(1, "cannot open current directory");

        /*
         * We always need to have dot around, so we increment its
         * reference count to make sure it's not destroyed.
         */
        dot->refCount += 1;

        if (strcmp(objdir, curdir) != 0)
                Path_AddDir(&dirSearchPath, curdir);
}

/*-
 *-----------------------------------------------------------------------
 * Dir_HasWildcards  --
 *      See if the given name has any wildcard characters in it.
 *
 * Results:
 *      returns true if the word should be expanded, false otherwise
 *
 * Side Effects:
 *      none
 *-----------------------------------------------------------------------
 */
bool
Dir_HasWildcards(const char *name)
{
        const char *cp;
        int wild = 0, brace = 0, bracket = 0;

        for (cp = name; *cp; cp++) {
                switch (*cp) {
                case '{':
                        brace++;
                        wild = 1;
                        break;
                case '}':
                        brace--;
                        break;
                case '[':
                        bracket++;
                        wild = 1;
                        break;
                case ']':
                        bracket--;
                        break;
                case '?':
                case '*':
                        wild = 1;
                        break;
                default:
                        break;
                }
        }
        return (wild && bracket == 0 && brace == 0);
}

/*-
 *-----------------------------------------------------------------------
 * DirMatchFiles --
 *      Given a pattern and a Dir structure, see if any files
 *      match the pattern and add their names to the 'expansions' list if
 *      any do. This is incomplete -- it doesn't take care of patterns like
 *      src / *src / *.c properly (just *.c on any of the directories), but it
 *      will do for now.
 *
 * Results:
 *      Always returns 0
 *
 * Side Effects:
 *      File names are added to the expansions lst. The directory will be
 *      fully hashed when this is done.
 *-----------------------------------------------------------------------
 */
static int
DirMatchFiles(const char *pattern, const Dir *p, Lst *expansions)
{
        Hash_Search search;     /* Index into the directory's table */
        Hash_Entry *entry;      /* Current entry in the table */
        bool isDot;             /* true if the directory being searched is . */

        isDot = (*p->name == '.' && p->name[1] == '\0');

        for (entry = Hash_EnumFirst(&p->files, &search);
            entry != NULL;
            entry = Hash_EnumNext(&search)) {
                /*
                 * See if the file matches the given pattern. Note we follow
                 * the UNIX convention that dot files will only be found if
                 * the pattern begins with a dot (note also that as a side
                 * effect of the hashing scheme, .* won't match . or ..
                 * since they aren't hashed).
                 */
                if (Str_Match(entry->name, pattern) &&
                    ((entry->name[0] != '.') ||
                    (pattern[0] == '.'))) {
                        Lst_AtEnd(expansions, (isDot ? estrdup(entry->name) :
                            str_concat(p->name, '/', entry->name)));
                }
        }
        return (0);
}

/*-
 *-----------------------------------------------------------------------
 * DirExpandCurly --
 *      Expand curly braces like the C shell. Does this recursively.
 *      Note the special case: if after the piece of the curly brace is
 *      done there are no wildcard characters in the result, the result is
 *      placed on the list WITHOUT CHECKING FOR ITS EXISTENCE.  The
 *      given arguments are the entire word to expand, the first curly
 *      brace in the word, the search path, and the list to store the
 *      expansions in.
 *
 * Results:
 *      None.
 *
 * Side Effects:
 *      The given list is filled with the expansions...
 *
 *-----------------------------------------------------------------------
 */
static void
DirExpandCurly(const char *word, const char *brace, struct Path *path,
    Lst *expansions)
{
        const char *end;        /* Character after the closing brace */
        const char *cp;         /* Current position in brace clause */
        const char *start;      /* Start of current piece of brace clause */
        int bracelevel; /* Number of braces we've seen. If we see a right brace
                         * when this is 0, we've hit the end of the clause. */
        char *file;     /* Current expansion */
        int otherLen;   /* The length of the other pieces of the expansion
                         * (chars before and after the clause in 'word') */
        char *cp2;      /* Pointer for checking for wildcards in
                         * expansion before calling Dir_Expand */

        start = brace + 1;

        /*
         * Find the end of the brace clause first, being wary of nested brace
         * clauses.
         */
        for (end = start, bracelevel = 0; *end != '\0'; end++) {
                if (*end == '{')
                        bracelevel++;
                else if ((*end == '}') && (bracelevel-- == 0))
                        break;
        }
        if (*end == '\0') {
                Error("Unterminated {} clause \"%s\"", start);
                return;
        } else
                end++;

        otherLen = brace - word + strlen(end);

        for (cp = start; cp < end; cp++) {
                /*
                 * Find the end of this piece of the clause.
                 */
                bracelevel = 0;
                while (*cp != ',') {
                        if (*cp == '{')
                                bracelevel++;
                        else if ((*cp == '}') && (bracelevel-- <= 0))
                                break;
                        cp++;
                }
                /*
                 * Allocate room for the combination and install the
                 * three pieces.
                 */
                file = emalloc(otherLen + cp - start + 1);
                if (brace != word)
                        strncpy(file, word, brace - word);
                if (cp != start)
                        strncpy(&file[brace - word], start, cp - start);
                strcpy(&file[(brace - word) + (cp - start)], end);

                /*
                 * See if the result has any wildcards in it. If we find one,
                 * call Dir_Expand right away, telling it to place the result
                 * on our list of expansions.
                 */
                for (cp2 = file; *cp2 != '\0'; cp2++) {
                        switch (*cp2) {
                        case '*':
                        case '?':
                        case '{':
                        case '[':
                                Path_Expand(file, path, expansions);
                                goto next;
                        default:
                                break;
                        }
                }
                if (*cp2 == '\0') {
                        /*
                         * Hit the end w/o finding any wildcards, so stick
                         * the expansion on the end of the list.
                         */
                        Lst_AtEnd(expansions, file);
                } else {
                next:
                        free(file);
                }
                start = cp + 1;
        }
}

/*-
 *-----------------------------------------------------------------------
 * DirExpandInt --
 *      Internal expand routine. Passes through the directories in the
 *      path one by one, calling DirMatchFiles for each. NOTE: This still
 *      doesn't handle patterns in directories...  Works given a word to
 *      expand, a path to look in, and a list to store expansions in.
 *
 * Results:
 *      None.
 *
 * Side Effects:
 *      Things are added to the expansions list.
 *
 *-----------------------------------------------------------------------
 */
static void
DirExpandInt(const char *word, const struct Path *path, Lst *expansions)
{
        struct PathElement *pe;

        TAILQ_FOREACH(pe, path, link)
                DirMatchFiles(word, pe->dir, expansions);
}

/*-
 *-----------------------------------------------------------------------
 * Dir_Expand  --
 *      Expand the given word into a list of words by globbing it looking
 *      in the directories on the given search path.
 *
 * Results:
 *      A list of words consisting of the files which exist along the search
 *      path matching the given pattern is placed in expansions.
 *
 * Side Effects:
 *      Directories may be opened. Who knows?
 *-----------------------------------------------------------------------
 */
void
Path_Expand(char *word, struct Path *path, Lst *expansions)
{
        LstNode *ln;
        char *cp;

        DEBUGF(DIR, ("expanding \"%s\"...", word));

        cp = strchr(word, '{');
        if (cp != NULL)
                DirExpandCurly(word, cp, path, expansions);
        else {
                cp = strchr(word, '/');
                if (cp != NULL) {
                        /*
                         * The thing has a directory component -- find the
                         * first wildcard in the string.
                         */
                        for (cp = word; *cp != '\0'; cp++) {
                                if (*cp == '?' || *cp == '[' ||
                                    *cp == '*' || *cp == '{') {
                                        break;
                                }
                        }
                        if (*cp == '{') {
                                /*
                                 * This one will be fun.
                                 */
                                DirExpandCurly(word, cp, path, expansions);
                                return;
                        } else if (*cp != '\0') {
                                /*
                                 * Back up to the start of the component
                                 */
                                char *dirpath;

                                while (cp > word && *cp != '/')
                                        cp--;
                                if (cp != word) {
                                        char sc;

                                        /*
                                         * If the glob isn't in the first
                                         * component, try and find all the
                                         * components up to the one with a
                                         * wildcard.
                                         */
                                        sc = cp[1];
                                        cp[1] = '\0';
                                        dirpath = Path_FindFile(word, path);
                                        cp[1] = sc;
                                        /*
                                         * dirpath is null if can't find the
                                         * leading component
                                         * XXX: Path_FindFile won't find internal
                                         * components. i.e. if the path contains
                                         * ../Etc/Object and we're looking for
                                         * Etc, * it won't be found. Ah well.
                                         * Probably not important.
                                         */
                                        if (dirpath != NULL) {
                                                char *dp =
                                                    &dirpath[strlen(dirpath)
                                                    - 1];
                                                struct Path tp =
                                                    TAILQ_HEAD_INITIALIZER(tp);

                                                if (*dp == '/')
                                                        *dp = '\0';
                                                Path_AddDir(&tp, dirpath);
                                                DirExpandInt(cp + 1, &tp,
                                                    expansions);
                                                Path_Clear(&tp);
                                        }
                                } else {
                                        /*
                                         * Start the search from the local
                                         * directory
                                         */
                                        DirExpandInt(word, path, expansions);
                                }
                        } else {
                                /*
                                 * Return the file -- this should never happen.
                                 */
                                DirExpandInt(word, path, expansions);
                        }
                } else {
                        /*
                         * First the files in dot
                         */
                        DirMatchFiles(word, dot, expansions);

                        /*
                         * Then the files in every other directory on the path.
                         */
                        DirExpandInt(word, path, expansions);
                }
        }
        if (DEBUG(DIR)) {
                LST_FOREACH(ln, expansions)
                        DEBUGF(DIR, ("%s ", (const char *)Lst_Datum(ln)));
                DEBUGF(DIR, ("\n"));
        }
}

/**
 * Path_FindFile
 *      Find the file with the given name along the given search path.
 *
 * Results:
 *      The path to the file or NULL. This path is guaranteed to be in a
 *      different part of memory than name and so may be safely free'd.
 *
 * Side Effects:
 *      If the file is found in a directory which is not on the path
 *      already (either 'name' is absolute or it is a relative path
 *      [ dir1/.../dirn/file ] which exists below one of the directories
 *      already on the search path), its directory is added to the end
 *      of the path on the assumption that there will be more files in
 *      that directory later on. Sometimes this is true. Sometimes not.
 */
char *
Path_FindFile(char *name, struct Path *path)
{
        char *p1;               /* pointer into p->name */
        char *p2;               /* pointer into name */
        char *file;             /* the current filename to check */
        const struct PathElement *pe;   /* current path member */
        char *cp;               /* final component of the name */
        bool hasSlash;  /* true if 'name' contains a / */
        struct stat stb;        /* Buffer for stat, if necessary */
        Hash_Entry *entry;      /* Entry for mtimes table */

        /*
         * Find the final component of the name and note whether it has a
         * slash in it (the name, I mean)
         */
        cp = strrchr(name, '/');
        if (cp != NULL) {
                hasSlash = true;
                cp += 1;
        } else {
                hasSlash = false;
                cp = name;
        }

        DEBUGF(DIR, ("Searching for %s...", name));
        /*
         * No matter what, we always look for the file in the current directory
         * before anywhere else and we *do not* add the ./ to it if it exists.
         * This is so there are no conflicts between what the user specifies
         * (fish.c) and what pmake finds (./fish.c).
         */
        if ((!hasSlash || (cp - name == 2 && *name == '.')) &&
            (Hash_FindEntry(&dot->files, cp) != NULL)) {
                DEBUGF(DIR, ("in '.'\n"));
                hits += 1;
                dot->hits += 1;
                return (estrdup(name));
        }

        /*
         * We look through all the directories on the path seeking one which
         * contains the final component of the given name and whose final
         * component(s) match the name's initial component(s). If such a beast
         * is found, we concatenate the directory name and the final component
         * and return the resulting string. If we don't find any such thing,
         * we go on to phase two...
         */
        TAILQ_FOREACH(pe, path, link) {
                DEBUGF(DIR, ("%s...", pe->dir->name));
                if (Hash_FindEntry(&pe->dir->files, cp) != NULL) {
                        DEBUGF(DIR, ("here..."));
                        if (hasSlash) {
                                /*
                                 * If the name had a slash, its initial
                                 * components and p's final components must
                                 * match. This is false if a mismatch is
                                 * encountered before all of the initial
                                 * components have been checked (p2 > name at
                                 * the end of the loop), or we matched only
                                 * part of one of the components of p
                                 * along with all the rest of them (*p1 != '/').
                                 */
                                p1 = pe->dir->name + strlen(pe->dir->name) - 1;
                                p2 = cp - 2;
                                while (p2 >= name && p1 >= pe->dir->name &&
                                    *p1 == *p2) {
                                        p1 -= 1; p2 -= 1;
                                }
                                if (p2 >= name || (p1 >= pe->dir->name &&
                                    *p1 != '/')) {
                                        DEBUGF(DIR, ("component mismatch -- "
                                            "continuing..."));
                                        continue;
                                }
                        }
                        file = str_concat(pe->dir->name, '/', cp);
                        DEBUGF(DIR, ("returning %s\n", file));
                        pe->dir->hits += 1;
                        hits += 1;
                        return (file);
                } else if (hasSlash) {
                        /*
                         * If the file has a leading path component and that
                         * component exactly matches the entire name of the
                         * current search directory, we assume the file
                         * doesn't exist and return NULL.
                         */
                        for (p1 = pe->dir->name, p2 = name; *p1 && *p1 == *p2;
                            p1++, p2++)
                                continue;
                        if (*p1 == '\0' && p2 == cp - 1) {
                                if (*cp == '\0' || ISDOT(cp) || ISDOTDOT(cp)) {
                                        DEBUGF(DIR, ("returning %s\n", name));
                                        return (estrdup(name));
                                } else {
                                        DEBUGF(DIR, ("must be here but isn't --"
                                            " returning NULL\n"));
                                        return (NULL);
                                }
                        }
                }
        }

        /*
         * We didn't find the file on any existing members of the directory.
         * If the name doesn't contain a slash, that means it doesn't exist.
         * If it *does* contain a slash, however, there is still hope: it
         * could be in a subdirectory of one of the members of the search
         * path. (eg. /usr/include and sys/types.h. The above search would
         * fail to turn up types.h in /usr/include, but it *is* in
         * /usr/include/sys/types.h) If we find such a beast, we assume there
         * will be more (what else can we assume?) and add all but the last
         * component of the resulting name onto the search path (at the
         * end). This phase is only performed if the file is *not* absolute.
         */
        if (!hasSlash) {
                DEBUGF(DIR, ("failed.\n"));
                misses += 1;
                return (NULL);
        }

        if (*name != '/') {
                bool    checkedDot = false;

                DEBUGF(DIR, ("failed. Trying subdirectories..."));
                TAILQ_FOREACH(pe, path, link) {
                        if (pe->dir != dot) {
                                file = str_concat(pe->dir->name, '/', name);
                        } else {
                                /*
                                 * Checking in dot -- DON'T put a leading ./
                                 * on the thing.
                                 */
                                file = estrdup(name);
                                checkedDot = true;
                        }
                        DEBUGF(DIR, ("checking %s...", file));

                        if (stat(file, &stb) == 0) {
                                DEBUGF(DIR, ("got it.\n"));

                                /*
                                 * We've found another directory to search. We
                                 * know there's a slash in 'file' because we put
                                 * one there. We nuke it after finding it and
                                 * call Path_AddDir to add this new directory
                                 * onto the existing search path. Once that's
                                 * done, we restore the slash and triumphantly
                                 * return the file name, knowing that should a
                                 * file in this directory every be referenced
                                 * again in such a manner, we will find it
                                 * without having to do numerous numbers of
                                 * access calls. Hurrah!
                                 */
                                cp = strrchr(file, '/');
                                *cp = '\0';
                                Path_AddDir(path, file);
                                *cp = '/';

                                /*
                                 * Save the modification time so if
                                 * it's needed, we don't have to fetch it again.
                                 */
                                DEBUGF(DIR, ("Caching %s for %s\n",
                                    Targ_FmtTime(stb.st_mtime), file));
                                entry = Hash_CreateEntry(&mtimes, file, NULL);
                                Hash_SetValue(entry,
                                    (void *)(long)stb.st_mtime);
                                nearmisses += 1;
                                return (file);
                        } else {
                                free(file);
                        }
                }

                DEBUGF(DIR, ("failed. "));

                if (checkedDot) {
                        /*
                         * Already checked by the given name, since . was in
                         * the path, so no point in proceeding...
                         */
                        DEBUGF(DIR, ("Checked . already, returning NULL\n"));
                        return (NULL);
                }
        }

        /*
         * Didn't find it that way, either. Sigh. Phase 3. Add its directory
         * onto the search path in any case, just in case, then look for the
         * thing in the hash table. If we find it, grand. We return a new
         * copy of the name. Otherwise we sadly return a NULL pointer. Sigh.
         * Note that if the directory holding the file doesn't exist, this will
         * do an extra search of the final directory on the path. Unless
         * something weird happens, this search won't succeed and life will
         * be groovy.
         *
         * Sigh. We cannot add the directory onto the search path because
         * of this amusing case:
         * $(INSTALLDIR)/$(FILE): $(FILE)
         *
         * $(FILE) exists in $(INSTALLDIR) but not in the current one.
         * When searching for $(FILE), we will find it in $(INSTALLDIR)
         * b/c we added it here. This is not good...
         */
#ifdef notdef
        cp[-1] = '\0';
        Path_AddDir(path, name);
        cp[-1] = '/';

        bigmisses += 1;
        pe = TAILQ_LAST(path, Path);
        if (pe == NULL)
                return (NULL);

        if (Hash_FindEntry(&pe->dir->files, cp) != NULL) {
                return (estrdup(name));

        return (NULL);
#else /* !notdef */
        DEBUGF(DIR, ("Looking for \"%s\"...", name));

        bigmisses += 1;
        entry = Hash_FindEntry(&mtimes, name);
        if (entry != NULL) {
                DEBUGF(DIR, ("got it (in mtime cache)\n"));
                return (estrdup(name));
        } else if (stat(name, &stb) == 0) {
                entry = Hash_CreateEntry(&mtimes, name, NULL);
                DEBUGF(DIR, ("Caching %s for %s\n",
                    Targ_FmtTime(stb.st_mtime), name));
                Hash_SetValue(entry, (void *)(long)stb.st_mtime);
                return (estrdup(name));
        } else {
                DEBUGF(DIR, ("failed. Returning NULL\n"));
                return (NULL);
        }
#endif /* notdef */
}

/*-
 *-----------------------------------------------------------------------
 * Dir_MTime  --
 *      Find the modification time of the file described by gn along the
 *      search path dirSearchPath.
 *
 * Results:
 *      The modification time or 0 if it doesn't exist
 *
 * Side Effects:
 *      The modification time is placed in the node's mtime slot.
 *      If the node didn't have a path entry before, and Dir_FindFile
 *      found one for it, the full name is placed in the path slot.
 *-----------------------------------------------------------------------
 */
int
Dir_MTime(GNode *gn)
{
        char *fullName;         /* the full pathname of name */
        struct stat stb;        /* buffer for finding the mod time */
        Hash_Entry *entry;

        if (gn->type & OP_ARCHV)
                return (Arch_MTime(gn));

        else if (gn->path == NULL)
                fullName = Path_FindFile(gn->name, &dirSearchPath);
        else
                fullName = gn->path;

        if (fullName == NULL)
                fullName = estrdup(gn->name);

        entry = Hash_FindEntry(&mtimes, fullName);
        if (entry != NULL) {
                /*
                 * Only do this once -- the second time folks are checking to
                 * see if the file was actually updated, so we need to
                 * actually go to the filesystem.
                 */
                DEBUGF(DIR, ("Using cached time %s for %s\n",
                    Targ_FmtTime((time_t)(long)Hash_GetValue(entry)),
                    fullName));
                stb.st_mtime = (time_t)(long)Hash_GetValue(entry);
                Hash_DeleteEntry(&mtimes, entry);
        } else if (stat(fullName, &stb) < 0) {
                if (gn->type & OP_MEMBER) {
                        if (fullName != gn->path)
                                free(fullName);
                        return (Arch_MemMTime(gn));
                } else {
                        stb.st_mtime = 0;
                }
        }
        if (fullName && gn->path == NULL)
                gn->path = fullName;

        gn->mtime = stb.st_mtime;
        return (gn->mtime);
}

/*-
 *-----------------------------------------------------------------------
 * Path_AddDir --
 *      Add the given name to the end of the given path.
 *
 * Results:
 *      none
 *
 * Side Effects:
 *      A structure is added to the list and the directory is
 *      read and hashed.
 *-----------------------------------------------------------------------
 */
struct Dir *
Path_AddDir(struct Path *path, const char *name)
{
        Dir *d;                 /* pointer to new Path structure */
        DIR *dir;               /* for reading directory */
        struct PathElement *pe;
        struct dirent *dp;      /* entry in directory */

        /* check whether we know this directory */
        TAILQ_FOREACH(d, &openDirectories, link) {
                if (strcmp(d->name, name) == 0) {
                        /* Found it. */
                        if (path == NULL)
                                return (d);

                        /* Check whether its already on the path. */
                        TAILQ_FOREACH(pe, path, link) {
                                if (pe->dir == d)
                                        return (d);
                        }
                        /* Add it to the path */
                        d->refCount += 1;
                        pe = emalloc(sizeof(*pe));
                        pe->dir = d;
                        TAILQ_INSERT_TAIL(path, pe, link);
                        return (d);
                }
        }

        DEBUGF(DIR, ("Caching %s...", name));

        if ((dir = opendir(name)) == NULL) {
                DEBUGF(DIR, (" cannot open\n"));
                return (NULL);
        }

        d = emalloc(sizeof(*d));
        d->name = estrdup(name);
        d->hits = 0;
        d->refCount = 1;
        Hash_InitTable(&d->files, -1);

        while ((dp = readdir(dir)) != NULL) {
#if defined(sun) && defined(d_ino) /* d_ino is a sunos4 #define for d_fileno */
                /*
                 * The sun directory library doesn't check for
                 * a 0 inode (0-inode slots just take up space),
                 * so we have to do it ourselves.
                 */
                if (dp->d_fileno == 0)
                        continue;
#endif /* sun && d_ino */

                /* Skip the '.' and '..' entries by checking
                 * for them specifically instead of assuming
                 * readdir() reuturns them in that order when
                 * first going through a directory.  This is
                 * needed for XFS over NFS filesystems since
                 * SGI does not guarantee that these are the
                 * first two entries returned from readdir().
                 */
                if (ISDOT(dp->d_name) || ISDOTDOT(dp->d_name))
                        continue;

                Hash_CreateEntry(&d->files, dp->d_name, NULL);
        }
        closedir(dir);

        if (path != NULL) {
                /* Add it to the path */
                d->refCount += 1;
                pe = emalloc(sizeof(*pe));
                pe->dir = d;
                TAILQ_INSERT_TAIL(path, pe, link);
        }

        /* Add to list of all directories */
        TAILQ_INSERT_TAIL(&openDirectories, d, link);

        DEBUGF(DIR, ("done\n"));

        return (d);
}

/**
 * Path_Duplicate
 *      Duplicate a path. Ups the reference count for the directories.
 */
void
Path_Duplicate(struct Path *dst, const struct Path *src)
{
        struct PathElement *ped, *pes;

        TAILQ_FOREACH(pes, src, link) {
                ped = emalloc(sizeof(*ped));
                ped->dir = pes->dir;
                ped->dir->refCount++;
                TAILQ_INSERT_TAIL(dst, ped, link);
        }
}

/**
 * Path_MakeFlags
 *      Make a string by taking all the directories in the given search
 *      path and preceding them by the given flag. Used by the suffix
 *      module to create variables for compilers based on suffix search
 *      paths.
 *
 * Results:
 *      The string mentioned above. Note that there is no space between
 *      the given flag and each directory. The empty string is returned if
 *      Things don't go well.
 */
char *
Path_MakeFlags(const char *flag, const struct Path *path)
{
        char *str;      /* the string which will be returned */
        char *tstr;     /* the current directory preceded by 'flag' */
        char *nstr;
        const struct PathElement *pe;

        str = estrdup("");

        TAILQ_FOREACH(pe, path, link) {
                tstr = str_concat(flag, '\0', pe->dir->name);
                nstr = str_concat(str, ' ', tstr);
                free(str);
                free(tstr);
                str = nstr;
        }

        return (str);
}

/**
 * Path_Clear
 *
 *      Destroy a path. This decrements the reference counts of all
 *      directories of this path and, if a reference count goes 0,
 *      destroys the directory object.
 */
void
Path_Clear(struct Path *path)
{
        struct PathElement *pe;

        while ((pe = TAILQ_FIRST(path)) != NULL) {
                pe->dir->refCount--;
                TAILQ_REMOVE(path, pe, link);
                if (pe->dir->refCount == 0) {
                        TAILQ_REMOVE(&openDirectories, pe->dir, link);
                        Hash_DeleteTable(&pe->dir->files);
                        free(pe->dir->name);
                        free(pe->dir);
                }
                free(pe);
        }
}

/**
 * Path_Concat
 *
 *      Concatenate two paths, adding the second to the end of the first.
 *      Make sure to avoid duplicates.
 *
 * Side Effects:
 *      Reference counts for added dirs are upped.
 */
void
Path_Concat(struct Path *path1, const struct Path *path2)
{
        struct PathElement *p1, *p2;

        TAILQ_FOREACH(p2, path2, link) {
                TAILQ_FOREACH(p1, path1, link) {
                        if (p1->dir == p2->dir)
                                break;
                }
                if (p1 == NULL) {
                        p1 = emalloc(sizeof(*p1));
                        p1->dir = p2->dir;
                        p1->dir->refCount++;
                        TAILQ_INSERT_TAIL(path1, p1, link);
                }
        }
}

/********** DEBUG INFO **********/
void
Dir_PrintDirectories(void)
{
        const Dir *d;

        printf("#*** Directory Cache:\n");
        printf("# Stats: %d hits %d misses %d near misses %d losers (%d%%)\n",
            hits, misses, nearmisses, bigmisses,
            (hits + bigmisses + nearmisses ?
            hits * 100 / (hits + bigmisses + nearmisses) : 0));
        printf("# %-20s referenced\thits\n", "directory");
        TAILQ_FOREACH(d, &openDirectories, link)
                printf("# %-20s %10d\t%4d\n", d->name, d->refCount, d->hits);
}

void
Path_Print(const struct Path *path)
{
        const struct PathElement *p;

        TAILQ_FOREACH(p, path, link)
                printf("%s ", p->dir->name);
}