common/misc/fts.c

	fts.c revision da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968
/***********************************************************************
*                                                                      *
*               This software is part of the ast package               *
*           Copyright (c) 1985-2007 AT&T Knowledge Ventures            *
*                      and is licensed under the                       *
*                  Common Public License, Version 1.0                  *
*                      by AT&T Knowledge Ventures                      *
*                                                                      *
*                A copy of the License is available at                 *
*            http://www.opensource.org/licenses/cpl1.0.txt             *
*         (with md5 checksum 059e8cd6165cb4c31e351f2b69388fd9)         *
*                                                                      *
*              Information and Software Systems Research               *
*                            AT&T Research                             *
*                           Florham Park NJ                            *
*                                                                      *
*                 Glenn Fowler <gsf@research.att.com>                  *
*                  David Korn <dgk@research.att.com>                   *
*                   Phong Vo <kpv@research.att.com>                    *
*                                                                      *
***********************************************************************/
#pragma prototyped
/*
 * Phong Vo
 * Glenn Fowler
 * AT&T Research
 *
 * fts implementation unwound from the kpv ftwalk() of 1988-10-30
 */

#include <ast.h>
#include <ast_dir.h>
#include <error.h>
#include <fs3d.h>

struct Ftsent;

typedef int (*Compar_f)(struct Ftsent* const*, struct Ftsent* const*);
typedef int (*Stat_f)(const char*, struct stat*);

#define _FTS_PRIVATE_ \
    FTSENT*     parent;         /* top parent       */ \
    FTSENT*     todo;           /* todo list        */ \
    FTSENT*     top;            /* top element      */ \
    FTSENT*     root;                          \
    FTSENT*     bot;            /* bottom element   */ \
    FTSENT*     free;           /* free element     */ \
    FTSENT*     diroot;                        \
    FTSENT*     curdir;                        \
    FTSENT*     current;        /* current element  */ \
    FTSENT*     previous;       /* previous current */ \
    FTSENT*     dotdot;                        \
    FTSENT*     link;           /* real current fts_link*/ \
    FTSENT*     pwd;            /* pwd parent       */ \
    DIR*        dir;            /* current dir stream   */ \
    Compar_f    comparf;        /* node comparison func */ \
    int     baselen;        /* current strlen(base) */ \
    int     cd;         /* chdir status     */ \
    int     cpname;                        \
    int     flags;          /* fts_open() flags */ \
    int     homesize;       /* sizeof(home)     */ \
    int     nd;                        \
    unsigned char   children;                      \
    unsigned char   fs3d;                          \
    unsigned char   nostat;                        \
    unsigned char   state;          /* fts_read() state */ \
    char*       base;           /* basename in path */ \
    char*       name;                          \
    char*       path;           /* path workspace   */ \
    char*       home;           /* home/path buffer */ \
    char*       endbase;        /* space to build paths */ \
    char*       endbuf;         /* space to build paths */ \
    char*       pad;

/*
 * NOTE: <ftwalk.h> relies on status and statb being the first two elements
 */

#define _FTSENT_PRIVATE_ \
    short       status;         /* internal status  */ \
    struct stat statb;          /* fts_statp data   */ \
    int     nd;         /* popdir() count   */ \
    FTSENT*     left;           /* left child       */ \
    FTSENT*     right;          /* right child      */ \
    FTSENT*     pwd;            /* pwd parent       */ \
    FTSENT*     stack;          /* getlist() stack  */ \
    FTS*        fts;            /* for fts verification */ \
    long        nlink;          /* FTS_D link count */ \
    unsigned char   must;           /* must stat        */ \
    unsigned char   type;           /* DT_* type        */ \
    unsigned char   symlink;        /* originally a symlink */ \
    char        name[sizeof(int)];  /* fts_name data    */

#include <fts.h>

#ifndef ENOSYS
#define ENOSYS      EINVAL
#endif


#if MAXNAMLEN > 16
#define MINNAME     32
#else
#define MINNAME     16
#endif

#define drop(p,f)   (((f)->fts_namelen < MINNAME) ? ((f)->fts_link = (p)->free, (p)->free = (f)) : (free(f), (p)->free))

#define ACCESS(p,f) ((p)->cd==0?(f)->fts_name:(f)->fts_path)
#define PATH(f,p,l) ((!((f)->flags&FTS_SEEDOTDIR)&&(l)>0&&(p)[0]=='.'&&(p)[1]=='/')?((p)+2):(p))
#define SAME(one,two)   ((one)->st_ino==(two)->st_ino&&(one)->st_dev==(two)->st_dev)
#define SKIPLINK(p,f)   ((f)->fts_parent->nlink == 0)

#ifdef D_TYPE
#define ISTYPE(f,t) ((f)->type == (t))
#define TYPE(f,t)   ((f)->type = (t))
#define SKIP(p,f)   ((f)->fts_parent->must == 0 && (((f)->type == DT_UNKNOWN) ? SKIPLINK(p,f) : ((f)->type != DT_DIR && ((f)->type != DT_LNK || ((p)->flags & FTS_PHYSICAL)))))
#else
#undef  DT_UNKNOWN
#define DT_UNKNOWN  0
#undef  DT_LNK
#define DT_LNK      1
#define ISTYPE(f,t) ((t)==DT_UNKNOWN)
#define TYPE(f,d)
#define SKIP(p,f)   ((f)->fts_parent->must == 0 && SKIPLINK(p,f))
#endif

#ifndef D_FILENO
#define D_FILENO(d) (1)
#endif

/*
 * NOTE: a malicious dir rename() could change .. underfoot so we
 *   must always verify; undef verify to enable the unsafe code
 */

#define verify      1

/*
 * FTS_NOSTAT requires a dir with
 *  D_TYPE(&dirent_t)!=DT_UNKNOWN
 *      OR
 *  st_nlink>=2
 */

#define FTS_children_resume 1
#define FTS_children_return 2
#define FTS_error       3
#define FTS_popstack        4
#define FTS_popstack_resume 5
#define FTS_popstack_return 6
#define FTS_preorder        7
#define FTS_preorder_resume 8
#define FTS_preorder_return 9
#define FTS_readdir     10
#define FTS_terminal        11
#define FTS_todo        12
#define FTS_top_return      13

typedef int (*Notify_f)(FTS*, FTSENT*, void*);

typedef struct Notify_s
{
    struct Notify_s*    next;
    Notify_f        notifyf;
    void*           context;
} Notify_t;

static Notify_t*        notify;

/*
 * allocate an FTSENT node
 */

static FTSENT*
node(FTS* fts, FTSENT* parent, register char* name, register int namelen)
{
    register FTSENT*    f;
    register int        n;

    if (fts->free && namelen < MINNAME)
    {
        f = fts->free;
        fts->free = f->fts_link;
    }
    else
    {
        n = (namelen < MINNAME ? MINNAME : namelen + 1) - sizeof(int);
        if (!(f = newof(0, FTSENT, 1, n)))
        {
            fts->fts_errno = errno;
            fts->state = FTS_error;
            return 0;
        }
        f->fts = fts;
    }
    TYPE(f, DT_UNKNOWN);
    f->status = 0;
    f->symlink = 0;
    f->fts_level = (f->fts_parent = parent)->fts_level + 1;
    f->fts_link = 0;
    f->fts_pointer = 0;
    f->fts_number = 0;
    f->fts_errno = 0;
    f->fts_namelen = namelen;
    f->fts_name = f->name;
    f->fts_statp = &f->statb;
    memcpy(f->fts_name, name, namelen + 1);
    return f;
}

/*
 * compare directories by device/inode
 */

static int
statcmp(FTSENT* const* pf1, FTSENT* const* pf2)
{
    register const FTSENT*  f1 = *pf1;
    register const FTSENT*  f2 = *pf2;

    if (f1->statb.st_ino < f2->statb.st_ino)
        return -1;
    if (f1->statb.st_ino > f2->statb.st_ino)
        return 1;
    if (f1->statb.st_dev < f2->statb.st_dev)
        return -1;
    if (f1->statb.st_dev > f2->statb.st_dev)
        return 1;

    /*
     * hack for NFS where <dev,ino> may not uniquely identify objects
     */

    if (f1->statb.st_mtime < f2->statb.st_mtime)
        return -1;
    if (f1->statb.st_mtime > f2->statb.st_mtime)
        return 1;
    return 0;
}

/*
 * search trees with top-down splaying (a la Tarjan and Sleator)
 * when used for insertion sort, this implements a stable sort
 */

#define RROTATE(r)  (t = r->left, r->left = t->right, t->right = r, r = t)
#define LROTATE(r)  (t = r->right, r->right = t->left, t->left = r, r = t)

static FTSENT*
search(FTSENT* e, FTSENT* root, int(*comparf)(FTSENT* const*, FTSENT* const*), int insert)
{
    register int        cmp;
    register FTSENT*    t;
    register FTSENT*    left;
    register FTSENT*    right;
    register FTSENT*    lroot;
    register FTSENT*    rroot;

    left = right = lroot = rroot = 0;
    while (root)
    {
        if (!(cmp = (*comparf)(&e, &root)) && !insert)
            break;
        if (cmp < 0)
        {
            /*
             * this is the left zig-zig case
             */

            if (root->left && (cmp = (*comparf)(&e, &root->left)) <= 0)
            {
                RROTATE(root);
                if (!cmp && !insert)
                    break;
            }

            /*
             * stick all things > e to the right tree
             */

            if (right)
                right->left = root;
            else
                rroot = root;
            right = root;
            root = root->left;
            right->left = 0;
        }
        else
        {
            /*
             * this is the right zig-zig case
             */

            if (root->right && (cmp = (*comparf)(&e, &root->right)) >= 0)
            {
                LROTATE(root);
                if (!cmp && !insert)
                    break;
            }

            /*
             * stick all things <= e to the left tree
             */

            if (left)
                left->right = root;
            else
                lroot = root;
            left = root;
            root = root->right;
            left->right = 0;
        }
    }
    if (!root)
        root = e;
    else
    {
        if (right)
            right->left = root->right;
        else
            rroot = root->right;
        if (left)
            left->right = root->left;
        else
            lroot = root->left;
    }
    root->left = lroot;
    root->right = rroot;
    return root;
}

/*
 * delete the root element from the tree
 */

static FTSENT*
deleteroot(register FTSENT* root)
{
    register FTSENT*    t;
    register FTSENT*    left;
    register FTSENT*    right;

    right = root->right;
    if (!(left = root->left))
        root = right;
    else
    {
        while (left->right)
            LROTATE(left);
        left->right = right;
        root = left;
    }
    return root;
}

/*
 * generate ordered fts_link list from binary tree at root
 * FTSENT.stack instead of recursion to avoid blowing the real
 * stack on big directories
 */

static void
getlist(register FTSENT** top, register FTSENT** bot, register FTSENT* root)
{
    register FTSENT*    stack = 0;

    for (;;)
    {
        if (root->left)
        {
            root->stack = stack;
            stack = root;
            root = root->left;
        }
        else
        {
            for (;;)
            {
                if (*top)
                    *bot = (*bot)->fts_link = root;
                else
                    *bot = *top = root;
                if (root->right)
                {
                    root = root->right;
                    break;
                }
                if (!(root = stack))
                    return;
                stack = stack->stack;
            }
        }
    }
}

/*
 * set directory when curdir is lost in space
 */

static int
setdir(register char* home, register char* path)
{
    register int    cdrv;

    if (path[0] == '/')
        cdrv = pathcd(path, NiL);
    else
    {
        /*
         * note that path and home are in the same buffer
         */

        path[-1] = '/';
        cdrv = pathcd(home, NiL);
        path[-1] = 0;
    }
    if (cdrv < 0)
        pathcd(home, NiL);
    return cdrv;
}

/*
 * set to parent dir
 */

static int
setpdir(register char* home, register char* path, register char* base)
{
    register int    c;
    register int    cdrv;

    if (base > path)
    {
        c = base[0];
        base[0] = 0;
        cdrv = setdir(home, path);
        base[0] = c;
    }
    else
        cdrv = pathcd(home, NiL);
    return cdrv;
}

/*
 * pop a set of directories
 */
static int
popdirs(FTS* fts)
{
    register FTSENT*f;
    register char*  s;
    register char*  e;
#ifndef verify
    register int    verify;
#endif
    struct stat sb;
    char        buf[PATH_MAX];

    if (!(f = fts->curdir) || f->fts_level < 0)
        return -1;
    e = buf + sizeof(buf) - 4;
#ifndef verify
    verify = 0;
#endif
    while (fts->nd > 0)
    {
        for (s = buf; s < e && fts->nd > 0; fts->nd--)
        {
            if (fts->pwd)
            {
#ifndef verify
                verify |= fts->pwd->symlink;
#endif
                fts->pwd = fts->pwd->pwd;
            }
            *s++ = '.';
            *s++ = '.';
            *s++ = '/';
        }
        *s = 0;
        if (chdir(buf))
            return -1;
    }
    return (verify && (stat(".", &sb) < 0 || !SAME(&sb, f->fts_statp))) ? -1 : 0;
}

/*
 * initialize st from path and fts_info from st
 */

static int
info(FTS* fts, register FTSENT* f, const char* path, struct stat* sp, int flags)
{
    if (path)
    {
#ifdef S_ISLNK
        if (!f->symlink && (ISTYPE(f, DT_UNKNOWN) || ISTYPE(f, DT_LNK)))
        {
            if (lstat(path, sp) < 0)
                goto bad;
        }
        else
#endif
            if (stat(path, sp) < 0)
                goto bad;
    }
#ifdef S_ISLNK
 again:
#endif
    if (S_ISDIR(sp->st_mode))
    {
        if ((flags & FTS_NOSTAT) && !fts->fs3d)
        {
            f->fts_parent->nlink--;
#ifdef D_TYPE
            f->must = 0;
            if ((f->nlink = sp->st_nlink) < 2)
                f->nlink = 2;
#else
            if ((f->nlink = sp->st_nlink) >= 2)
                f->must = 1;
            else
                f->must = 2;
#endif
        }
        else
            f->must = 2;
        TYPE(f, DT_DIR);
        f->fts_info = FTS_D;
    }
#ifdef S_ISLNK
    else if (S_ISLNK((sp)->st_mode))
    {
        struct stat sb;

        f->symlink = 1;
        if (!(flags & FTS_PHYSICAL) && stat(path, &sb) >= 0)
        {
            *sp = sb;
            flags = FTS_PHYSICAL;
            goto again;
        }
        TYPE(f, DT_LNK);
        f->fts_info = FTS_SL;
    }
#endif
    else
    {
        TYPE(f, DT_REG);
        f->fts_info = FTS_F;
    }
    return 0;
 bad:
    TYPE(f, DT_UNKNOWN);
    f->fts_info = FTS_NS;
    return -1;
}

/*
 * get top list of elements to process
 */

static FTSENT*
toplist(FTS* fts, register char* const* pathnames)
{
    register char*      path;
    register struct stat*   sb;
    register FTSENT*    f;
    register FTSENT*    root;
    int         physical;
    int         metaphysical;
    char*           s;
    FTSENT*         top;
    FTSENT*         bot;
    struct stat     st;

    if (fts->flags & FTS_NOSEEDOTDIR)
        fts->flags &= ~FTS_SEEDOTDIR;
    physical = (fts->flags & FTS_PHYSICAL);
    metaphysical = (fts->flags & (FTS_META|FTS_PHYSICAL)) == (FTS_META|FTS_PHYSICAL);
    top = bot = root = 0;
    while (path = *pathnames++)
    {
        /*
         * make elements
         */

        if (!(f = node(fts, fts->parent, path, strlen(path))))
            break;
        path = f->fts_name;
        if (!physical)
            f->fts_namelen = (fts->flags & FTS_SEEDOTDIR) ? strlen(path) : (pathcanon(path, 0) - path);
        else if (*path != '.')
        {
            f->fts_namelen = strlen(path);
            fts->flags |= FTS_SEEDOTDIR;
        }
        else
        {
            if (fts->flags & FTS_NOSEEDOTDIR)
            {
                fts->flags &= ~FTS_SEEDOTDIR;
                s = path;
                while (*s++ == '.' && *s++ == '/')
                {
                    while (*s == '/')
                        s++;
                    if (!*s)
                        break;
                    path = f->fts_name;
                    while (*path++ = *s++);
                    path = f->fts_name;
                }
            }
            else
                fts->flags |= FTS_SEEDOTDIR;
            for (s = path + strlen(path); s > path && *(s - 1) == '/'; s--);
            *s = 0;
            f->fts_namelen = s - path;
        }
        sb = f->fts_statp;
        if (!*path)
        {
            errno = ENOENT;
            f->fts_info = FTS_NS;
        }
        else
            info(fts, f, path, sb, fts->flags);
#ifdef S_ISLNK

        /*
         * don't let any standards committee get
         * away with calling your idea a hack
         */

        if (metaphysical && f->fts_info == FTS_SL && stat(path, &st) >= 0)
        {
            *sb = st;
            info(fts, f, NiL, sb, 0);
        }
#endif
        if (fts->comparf)
            root = search(f, root, fts->comparf, 1);
        else if (bot)
        {
            bot->fts_link = f;
            bot = f;
        }
        else
            top = bot = f;
    }
    if (fts->comparf)
        getlist(&top, &bot, root);
    return top;
}

/*
 * resize the path buffer
 * note that free() is not used because we may need to chdir(fts->home)
 * if there isn't enough space to continue
 */

static int
resize(register FTS* fts, int inc)
{
    register char*  old;
    register char*  newp;
    register int    n_old;

    /*
     * add space for "/." used in testing FTS_DNX
     */

    n_old = fts->homesize;
    fts->homesize = ((fts->homesize + inc + 4) / PATH_MAX + 1) * PATH_MAX;
    if (!(newp = newof(0, char, fts->homesize, 0)))
    {
        fts->fts_errno = errno;
        fts->state = FTS_error;
        return -1;
    }
    old = fts->home;
    fts->home = newp;
    memcpy(newp, old, n_old);
    if (fts->endbuf)
        fts->endbuf = newp + fts->homesize - 4;
    if (fts->path)
        fts->path = newp + (fts->path - old);
    if (fts->base)
        fts->base = newp + (fts->base - old);
    free(old);
    return 0;
}

/*
 * open a new fts stream on pathnames
 */

FTS*
fts_open(char* const* pathnames, int flags, int (*comparf)(FTSENT* const*, FTSENT* const*))
{
    register FTS*   fts;

    if (!(fts = newof(0, FTS, 1, sizeof(FTSENT))))
        return 0;
    fts->flags = flags;
    fts->cd = (flags & FTS_NOCHDIR) ? 1 : -1;
    fts->comparf = comparf;
    fts->fs3d = fs3d(FS3D_TEST);

    /*
     * set up the path work buffer
     */

    fts->homesize = 2 * PATH_MAX;
    for (;;)
    {
        if (!(fts->home = newof(fts->home, char, fts->homesize, 0)))
        {
            free(fts);
            return 0;
        }
        if (fts->cd > 0 || getcwd(fts->home, fts->homesize))
            break;
        if (errno == ERANGE)
            fts->homesize += PATH_MAX;
        else
            fts->cd = 1;
    }
    fts->endbuf = fts->home + fts->homesize - 4;

    /*
     * initialize the tippity-top
     */

    fts->parent = (FTSENT*)(fts + 1);
    fts->parent->fts_info = FTS_D;
    memcpy(fts->parent->fts_accpath = fts->parent->fts_path = fts->parent->fts_name = fts->parent->name, ".", 2);
    fts->parent->fts_level = -1;
    fts->parent->fts_statp = &fts->parent->statb;
    fts->parent->must = 2;
    fts->parent->type = DT_UNKNOWN;
    fts->path = fts->home + strlen(fts->home) + 1;

    /*
     * make the list of top elements
     */

    if (!pathnames || (flags & FTS_ONEPATH) || !*pathnames)
    {
        char*   v[2];

        v[0] = pathnames && (flags & FTS_ONEPATH) ? (char*)pathnames : ".";
        v[1] = 0;
        fts->todo = toplist(fts, v);
    }
    else
        fts->todo = toplist(fts, pathnames);
    if (!fts->todo || fts->todo->fts_info == FTS_NS && !fts->todo->fts_link)
    {
        fts_close(fts);
        return 0;
    }
    return fts;
}

/*
 * return the next FTS entry
 */

FTSENT*
fts_read(register FTS* fts)
{
    register char*      s;
    register int        n;
    register FTSENT*    f;
    struct dirent*      d;
    int         i;
    FTSENT*         t;
    Notify_t*       p;
#ifdef verify
    struct stat     sb;
#endif

    for (;;) switch (fts->state)
    {

    case FTS_top_return:

        f = fts->todo;
        t = 0;
        while (f)
            if (f->status == FTS_SKIP)
            {
                if (t)
                {
                    t->fts_link = f->fts_link;
                    drop(fts, f);
                    f = t->fts_link;
                }
                else
                {
                    fts->todo = f->fts_link;
                    drop(fts, f);
                    f = fts->todo;
                }
            }
            else
            {
                t = f;
                f = f->fts_link;
            }
        /*FALLTHROUGH*/

    case 0:

        if (!(f = fts->todo))
            return 0;
        /*FALLTHROUGH*/

    case FTS_todo:

        /*
         * process the top object on the stack
         */

        fts->root = fts->top = fts->bot = 0;

        /*
         * initialize the top level
         */

        if (f->fts_level == 0)
        {
            fts->parent->fts_number = f->fts_number;
            fts->parent->fts_pointer = f->fts_pointer;
            fts->parent->fts_statp = f->fts_statp;
            fts->parent->statb = *f->fts_statp;
            f->fts_parent = fts->parent;
            fts->diroot = 0;
            if (fts->cd == 0)
                pathcd(fts->home, NiL);
            else if (fts->cd < 0)
                fts->cd = 0;
            fts->pwd = f->fts_parent;
            fts->curdir = fts->cd ? 0 : f->fts_parent;
            *(fts->base = fts->path) = 0;
        }

        /*
         * chdir to parent if asked for
         */

        if (fts->cd < 0)
        {
            fts->cd = setdir(fts->home, fts->path);
            fts->pwd = f->fts_parent;
            fts->curdir = fts->cd ? 0 : f->fts_parent;
        }

        /*
         * add object's name to the path
         */

        if ((fts->baselen = f->fts_namelen) >= (fts->endbuf - fts->base) && resize(fts, fts->baselen))
            return 0;
        memcpy(fts->base, f->name, fts->baselen + 1);
        fts->name = fts->cd ? fts->path : fts->base;
        /*FALLTHROUGH*/

    case FTS_preorder:

        /*
         * check for cycle and open dir
         */

        if (f->fts_info == FTS_D)
        {
            if ((fts->diroot = search(f, fts->diroot, statcmp, 0)) != f || f->fts_level > 0 && (t = f) && statcmp(&t, &f->fts_parent) == 0)
            {
                f->fts_info = FTS_DC;
                f->fts_cycle = fts->diroot;
            }
            else if (!(fts->flags & FTS_TOP) && (!(fts->flags & FTS_XDEV) || f->statb.st_dev == f->fts_parent->statb.st_dev))
            {
                /*
                 * buffer is known to be large enough here!
                 */

                if (fts->base[fts->baselen - 1] != '/')
                    memcpy(fts->base + fts->baselen, "/.", 3);
                if (!(fts->dir = opendir(fts->name)))
                    f->fts_info = FTS_DNX;
                fts->base[fts->baselen] = 0;
                if (!fts->dir && !(fts->dir = opendir(fts->name)))
                    f->fts_info = FTS_DNR;
            }
        }
        f->nd = f->fts_info & ~FTS_DNX;
        if (f->nd || !(fts->flags & FTS_NOPREORDER))
        {
            fts->current = f;
            fts->link = f->fts_link;
            f->fts_link = 0;
            f->fts_path = PATH(fts, fts->path, f->fts_level);
            f->fts_pathlen = (fts->base - f->fts_path) + fts->baselen;
            f->fts_accpath = ACCESS(fts, f);
            fts->state = FTS_preorder_return;
            goto note;
        }
        /*FALLTHROUGH*/

    case FTS_preorder_resume:

        /*
         * prune
         */

        if (!fts->dir || f->nd || f->status == FTS_SKIP)
        {
            if (fts->dir)
            {
                closedir(fts->dir);
                fts->dir = 0;
            }
            fts->state = FTS_popstack;
            continue;
        }

        /*
         * FTS_D or FTS_DNX, about to read children
         */

        if (fts->cd == 0)
        {
            if ((fts->cd = chdir(fts->name)) < 0)
                pathcd(fts->home, NiL);
            else if (fts->pwd != f)
            {
                f->pwd = fts->pwd;
                fts->pwd = f;
            }
            fts->curdir = fts->cd < 0 ? 0 : f;
        }
        fts->nostat = fts->children > 1 || f->fts_info == FTS_DNX;
        fts->cpname = fts->cd && !fts->nostat || !fts->children && !fts->comparf;
        fts->dotdot = 0;
        fts->endbase = fts->base + fts->baselen;
        if (fts->endbase[-1] != '/')
            *fts->endbase++ = '/';
        fts->current = f;
        /*FALLTHROUGH*/

    case FTS_readdir:

        while (d = readdir(fts->dir))
        {
            s = d->d_name;
            if (s[0] == '.')
            {
                if (s[1] == 0)
                {
                    fts->current->nlink--;
                    if (!(fts->flags & FTS_SEEDOT))
                        continue;
                    n = 1;
                }
                else if (s[1] == '.' && s[2] == 0)
                {
                    fts->current->nlink--;
                    if (fts->current->must == 1)
                        fts->current->must = 0;
                    if (!(fts->flags & FTS_SEEDOT))
                        continue;
                    n = 2;
                }
                else
                    n = 0;
            }
            else
                n = 0;

            /*
             * make a new entry
             */

            i = D_NAMLEN(d);
            if (!(f = node(fts, fts->current, s, i)))
                return 0;
            TYPE(f, D_TYPE(d));

            /*
             * check for space
             */

            if (i >= fts->endbuf - fts->endbase)
            {
                if (resize(fts, i))
                    return 0;
                fts->endbase = fts->base + fts->baselen;
                if (fts->endbase[-1] != '/')
                    fts->endbase++;
            }
            if (fts->cpname)
            {
                memcpy(fts->endbase, s, i + 1);
                if (fts->cd)
                    s = fts->path;
            }
            if (n)
            {
                /*
                 * don't recurse on . and ..
                 */

                if (n == 1)
                    f->fts_statp = fts->current->fts_statp;
                else
                {
                    if (f->fts_info != FTS_NS)
                        fts->dotdot = f;
                    if (fts->current->fts_parent->fts_level < 0)
                    {
                        f->fts_statp = &fts->current->fts_parent->statb;
                        info(fts, f, s, f->fts_statp, 0);
                    }
                    else
                        f->fts_statp = fts->current->fts_parent->fts_statp;
                }
                f->fts_info = FTS_DOT;
            }
            else if ((fts->nostat || SKIP(fts, f)) && (f->fts_info = FTS_NSOK) || info(fts, f, s, &f->statb, fts->flags))
                f->statb.st_ino = D_FILENO(d);
            if (fts->comparf)
                fts->root = search(f, fts->root, fts->comparf, 1);
            else if (fts->children || f->fts_info == FTS_D || f->fts_info == FTS_SL)
            {
                if (fts->top)
                    fts->bot = fts->bot->fts_link = f;
                else
                    fts->top = fts->bot = f;
            }
            else
            {
                /*
                 * terminal node
                 */

                f->fts_path = PATH(fts, fts->path, 1);
                f->fts_pathlen = fts->endbase - f->fts_path + f->fts_namelen;
                f->fts_accpath = ACCESS(fts, f);
                fts->previous = fts->current;
                fts->current = f;
                fts->state = FTS_terminal;
                goto note;
            }
        }

        /*
         * done with the directory
         */

        closedir(fts->dir);
        fts->dir = 0;
        if (fts->root)
            getlist(&fts->top, &fts->bot, fts->root);
        if (fts->children)
        {
            /*
             * try moving back to parent dir
             */

            fts->base[fts->baselen] = 0;
            if (fts->cd <= 0)
            {
                f = fts->current->fts_parent;
                if (fts->cd < 0
                    || f != fts->curdir
                    || !fts->dotdot
                    || !SAME(f->fts_statp, fts->dotdot->fts_statp)
                    || fts->pwd && fts->pwd->symlink
                    || (fts->cd = chdir("..")) < 0
#ifdef verify
                    || stat(".", &sb) < 0
                    || !SAME(&sb, fts->dotdot->fts_statp)
#endif
                    )
                    fts->cd = setpdir(fts->home, fts->path, fts->base);
                if (fts->pwd)
                    fts->pwd = fts->pwd->pwd;
                fts->curdir = fts->cd ? 0 : f;
            }
            f = fts->current;
            fts->link = f->fts_link;
            f->fts_link = fts->top;
            f->fts_path = PATH(fts, fts->path, f->fts_level);
            f->fts_pathlen = (fts->base - f->fts_path) + f->fts_namelen;
            f->fts_accpath = ACCESS(fts, f);
            fts->state = FTS_children_return;
            goto note;
        }
        /*FALLTHROUGH*/

    case FTS_children_resume:

        fts->base[fts->baselen] = 0;
        if (fts->top)
        {
            fts->bot->fts_link = fts->todo;
            fts->todo = fts->top;
            fts->top = 0;
        }
        /*FALLTHROUGH*/

    case FTS_popstack:

        /*
         * pop objects completely processed
         */

        fts->nd = 0;
        f = fts->current;
        /*FALLTHROUGH*/

    case FTS_popstack_resume:

        while (fts->todo && f == fts->todo)
        {
            t = f->fts_parent;
            if ((f->fts_info & FTS_DP) == FTS_D)
            {
                /*
                 * delete from <dev,ino> tree
                 */

                if (f != fts->diroot)
                    fts->diroot = search(f, fts->diroot, statcmp, 0);
                fts->diroot = deleteroot(fts->diroot);
                if (f == fts->curdir)
                {
                    fts->nd++;
                    fts->curdir = t;
                }

                /*
                 * perform post-order processing
                 */

                if (!(fts->flags & FTS_NOPOSTORDER) &&
                    f->status != FTS_SKIP &&
                    f->status != FTS_NOPOSTORDER)
                {
                    /*
                     * move to parent dir
                     */

                    if (fts->nd > 0)
                        fts->cd = popdirs(fts);
                    if (fts->cd < 0)
                        fts->cd = setpdir(fts->home, fts->path, fts->base);
                    fts->curdir = fts->cd ? 0 : t;
                    f->fts_info = FTS_DP;
                    f->fts_path = PATH(fts, fts->path, f->fts_level);
                    f->fts_pathlen = (fts->base - f->fts_path) + f->fts_namelen;
                    f->fts_accpath = ACCESS(fts, f);

                    /*
                     * re-stat to update nlink/times
                     */

                    stat(f->fts_accpath, f->fts_statp);
                    fts->link = f->fts_link;
                    f->fts_link = 0;
                    fts->state = FTS_popstack_return;
                    goto note;
                }
            }

            /*
             * reset base
             */

            if (fts->base > fts->path + t->fts_namelen)
                fts->base--;
            *fts->base = 0;
            fts->base -= t->fts_namelen;

            /*
             * try again or delete from top of stack
             */

            if (f->status == FTS_AGAIN)
            {
                f->fts_info = FTS_D;
                f->status = 0;
            }
            else
            {
                fts->todo = fts->todo->fts_link;
                drop(fts, f);
            }
            f = t;
        }

        /*
         * reset current directory
         */

        if (fts->nd > 0 && popdirs(fts) < 0)
        {
            pathcd(fts->home, NiL);
            fts->curdir = 0;
            fts->cd = -1;
        }
        if (fts->todo)
        {
            if (*fts->base)
                fts->base += f->fts_namelen;
            if (*(fts->base - 1) != '/')
                *fts->base++ = '/';
            *fts->base = 0;
            f = fts->todo;
            fts->state = FTS_todo;
            continue;
        }
        return 0;

    case FTS_children_return:

        f = fts->current;
        f->fts_link = fts->link;

        /*
         * chdir down again
         */

        i = f->fts_info != FTS_DNX;
        n = f->status == FTS_SKIP;
        if (!n && fts->cd == 0)
        {
            if ((fts->cd = chdir(fts->base)) < 0)
                pathcd(fts->home, NiL);
            else if (fts->pwd != f)
            {
                f->pwd = fts->pwd;
                fts->pwd = f;
            }
            fts->curdir = fts->cd ? 0 : f;
        }

        /*
         * prune
         */

        if (fts->base[fts->baselen - 1] != '/')
            fts->base[fts->baselen] = '/';
        for (fts->bot = 0, f = fts->top; f; )
            if (n || f->status == FTS_SKIP)
            {
                if (fts->bot)
                    fts->bot->fts_link = f->fts_link;
                else
                    fts->top = f->fts_link;
                drop(fts, f);
                f = fts->bot ? fts->bot->fts_link : fts->top;
            }
            else
            {
                if (fts->children > 1 && i)
                {
                    if (f->status == FTS_STAT)
                        info(fts, f, NiL, f->fts_statp, 0);
                    else if (f->fts_info == FTS_NSOK && !SKIP(fts, f))
                    {
                        s = f->fts_name;
                        if (fts->cd)
                        {
                            memcpy(fts->endbase, s, f->fts_namelen + 1);
                            s = fts->path;
                        }
                        info(fts, f, s, f->fts_statp, fts->flags);
                    }
                }
                fts->bot = f;
                f = f->fts_link;
            }
        fts->children = 0;
        fts->state = FTS_children_resume;
        continue;

    case FTS_popstack_return:

        f = fts->todo;
        f->fts_link = fts->link;
        f->fts_info = f->status == FTS_AGAIN ? FTS_DP : 0;
        fts->state = FTS_popstack_resume;
        continue;

    case FTS_preorder_return:

        f = fts->current;
        f->fts_link = fts->link;

        /*
         * follow symlink if asked to
         */

        if (f->status == FTS_FOLLOW)
        {
            f->status = 0;
            if (f->fts_info == FTS_SL || ISTYPE(f, DT_LNK) || f->fts_info == FTS_NSOK)
            {
                info(fts, f, f->fts_accpath, f->fts_statp, 0);
                if (f->fts_info != FTS_SL)
                {
                    fts->state = FTS_preorder;
                    continue;
                }
            }
        }

        /*
         * about to prune this f and already at home
         */

        if (fts->cd == 0 && f->fts_level == 0 && f->nd)
            fts->cd = -1;
        fts->state = FTS_preorder_resume;
        continue;

    case FTS_terminal:

        f = fts->current;
        if (f->status == FTS_FOLLOW)
        {
            f->status = 0;
            if (f->fts_info == FTS_SL || ISTYPE(f, DT_LNK) || f->fts_info == FTS_NSOK)
            {
                info(fts, f, f->fts_accpath, f->fts_statp, 0);
                if (f->symlink && f->fts_info != FTS_SL)
                {
                    if (!(f->fts_link = fts->top))
                        fts->bot = f;
                    fts->top = f;
                    fts->current = fts->previous;
                    fts->state = FTS_readdir;
                    continue;
                }
            }
        }
        f = f->fts_parent;
        drop(fts, fts->current);
        fts->current = f;
        fts->state = FTS_readdir;
        continue;

    case FTS_error:

        return 0;

    default:

        fts->fts_errno = EINVAL;
        fts->state = FTS_error;
        return 0;

    }
 note:
    for (p = notify; p; p = p->next)
        if ((n = (*p->notifyf)(fts, f, p->context)) > 0)
            break;
        else if (n < 0)
        {
            fts->fts_errno = EINVAL;
            fts->state = FTS_error;
            return 0;
        }
    return f;
}

/*
 * set stream or entry flags
 */

int
fts_set(register FTS* fts, register FTSENT* f, int status)
{
    if (fts || !f || f->fts->current != f)
        return -1;
    switch (status)
    {
    case FTS_AGAIN:
        break;
    case FTS_FOLLOW:
        if (!(f->fts_info & FTS_SL))
            return -1;
        break;
    case FTS_NOPOSTORDER:
        break;
    case FTS_SKIP:
        if ((f->fts_info & (FTS_D|FTS_P)) != FTS_D)
            return -1;
        break;
    default:
        return -1;
    }
    f->status = status;
    return 0;
}

/*
 * return the list of child entries
 */

FTSENT*
fts_children(register FTS* fts, int flags)
{
    register FTSENT*    f;

    switch (fts->state)
    {

    case 0:

        fts->state = FTS_top_return;
        return fts->todo;

    case FTS_preorder_return:

        fts->children = ((flags | fts->flags) & FTS_NOSTAT) ? 2 : 1;
        if (f = fts_read(fts))
            f = f->fts_link;
        return f;

    }
    return 0;
}

/*
 * return default (FTS_LOGICAL|FTS_META|FTS_PHYSICAL|FTS_SEEDOTDIR) flags
 * conditioned by astconf()
 */

int
fts_flags(void)
{
    register char*  s;

    s = astconf("PATH_RESOLVE", NiL, NiL);
    if (streq(s, "logical"))
        return FTS_LOGICAL;
    if (streq(s, "physical"))
        return FTS_PHYSICAL|FTS_SEEDOTDIR;
    return FTS_META|FTS_PHYSICAL|FTS_SEEDOTDIR;
}

/*
 * close an open fts stream
 */

int
fts_close(register FTS* fts)
{
    register FTSENT*    f;
    register FTSENT*    x;

    if (fts->dir)
        closedir(fts->dir);
    if (fts->cd == 0)
        pathcd(fts->home, NiL);
    free(fts->home);
    if (fts->state == FTS_children_return)
        fts->current->fts_link = fts->link;
    if (fts->top)
    {
        fts->bot->fts_link = fts->todo;
        fts->todo = fts->top;
    }
    for (f = fts->todo; f; f = x)
    {
        x = f->fts_link;
        free(f);
    }
    for (f = fts->free; f; f = x)
    {
        x = f->fts_link;
        free(f);
    }
    return 0;
}

/*
 * register function to be called for each fts_read() entry
 */

int
fts_notify(Notify_f notifyf, void* context)
{
    register Notify_t*  np;

    if (!(np = newof(0, Notify_t, 1, 0)))
        return -1;
    np->notifyf = notifyf;
    np->context = context;
    np->next = notify;
    notify = np;
    return 0;
}