path: root/libc/misc/ftw/ftw.c

/* File tree walker functions.
   Copyright (C) 1996-2001, 2002, 2003 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Ulrich Drepper <drepper@cygnus.com>, 1996.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.  */

#define _GNU_SOURCE
#include <features.h>

/* If Large file support is enabled, transparently remap
 * things to use the 64-bit interfaces */
#ifdef __UCLIBC_HAS_LFS__
#if defined _FILE_OFFSET_BITS && _FILE_OFFSET_BITS != 64 
#undef _FILE_OFFSET_BITS
#define	_FILE_OFFSET_BITS   64
#endif
#ifndef __USE_LARGEFILE64
# define __USE_LARGEFILE64  1
#endif
#ifndef __USE_FILE_OFFSET64
# define __USE_FILE_OFFSET64  1
#endif
#endif

#include <alloca.h>
#include <errno.h>
#include <ftw.h>
#include <limits.h>
#include <search.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/param.h>
#include <sys/stat.h>
#include <assert.h>
#include <dirent.h>

/* We define PATH_MAX if the system does not provide a definition.
   This does not artificially limit any operation.  PATH_MAX is simply
   used as a guesstimate for the expected maximal path length.
   Buffers will be enlarged if necessary.  */
#ifndef PATH_MAX
# define PATH_MAX 1024
#endif

struct dir_data
{
    DIR *stream;
    char *content;
};

struct known_object
{
    dev_t dev;
    ino_t ino;
};

struct ftw_data
{
    /* Array with pointers to open directory streams.  */
    struct dir_data **dirstreams;
    size_t actdir;
    size_t maxdir;

    /* Buffer containing name of currently processed object.  */
    char *dirbuf;
    size_t dirbufsize;

    /* Passed as fourth argument to `nftw' callback.  The `base' member
       tracks the content of the `dirbuf'.  */
    struct FTW ftw;

    /* Flags passed to `nftw' function.  0 for `ftw'.  */
    int flags;

    /* Conversion array for flag values.  It is the identity mapping for
       `nftw' calls, otherwise it maps the values to those known by
       `ftw'.  */
    const int *cvt_arr;

    /* Callback function.  We always use the `nftw' form.  */
    __nftw_func_t func;

    /* Device of starting point.  Needed for FTW_MOUNT.  */
    dev_t dev;

    /* Data structure for keeping fingerprints of already processed
       object.  This is needed when not using FTW_PHYS.  */
    void *known_objects;
};


/* Internally we use the FTW_* constants used for `nftw'.  When invoked
   as `ftw', map each flag to the subset of values used by `ftw'.  */
static const int nftw_arr[] =
{
    FTW_F, FTW_D, FTW_DNR, FTW_NS, FTW_SL, FTW_DP, FTW_SLN
};

static const int ftw_arr[] =
{
    FTW_F, FTW_D, FTW_DNR, FTW_NS, FTW_F, FTW_D, FTW_NS
};

/* Forward declarations of local functions.  */
static int ftw_dir (struct ftw_data *data, struct stat *st) internal_function;


static int
object_compare (const void *p1, const void *p2)
{
    /* We don't need a sophisticated and useful comparison.  We are only
       interested in equality.  However, we must be careful not to
       accidentally compare `holes' in the structure.  */
    const struct known_object *kp1 = p1, *kp2 = p2;
    int cmp1;
    cmp1 = (kp1->ino > kp2->ino) - (kp1->ino < kp2->ino);
    if (cmp1 != 0)
	return cmp1;
    return (kp1->dev > kp2->dev) - (kp1->dev < kp2->dev);
}


static inline int
add_object (struct ftw_data *data, struct stat *st)
{
    struct known_object *newp = malloc (sizeof (struct known_object));
    if (newp == NULL)
	return -1;
    newp->dev = st->st_dev;
    newp->ino = st->st_ino;
    return tsearch (newp, &data->known_objects, object_compare) ? 0 : -1;
}


static inline int
find_object (struct ftw_data *data, struct stat *st)
{
    struct known_object obj;
    obj.dev = st->st_dev;
    obj.ino = st->st_ino;
    return tfind (&obj, &data->known_objects, object_compare) != NULL;
}


static inline int
__attribute ((always_inline))
open_dir_stream (struct ftw_data *data, struct dir_data *dirp)
{
    int result = 0;

    if (data->dirstreams[data->actdir] != NULL)
    {
	/* Oh, oh.  We must close this stream.  Get all remaining
	   entries and store them as a list in the `content' member of
	   the `struct dir_data' variable.  */
	size_t bufsize = 1024;
	char *buf = malloc (bufsize);

	if (buf == NULL)
	    result = -1;
	else
	{
	    DIR *st = data->dirstreams[data->actdir]->stream;
	    struct dirent *d;
	    size_t actsize = 0;

	    while ((d = readdir (st)) != NULL)
	    {
		size_t this_len = _D_EXACT_NAMLEN (d);
		if (actsize + this_len + 2 >= bufsize)
		{
		    char *newp;
		    bufsize += MAX (1024, 2 * this_len);
		    newp = (char *) realloc (buf, bufsize);
		    if (newp == NULL)
		    {
			/* No more memory.  */
			int save_err = errno;
			free (buf);
			__set_errno (save_err);
			result = -1;
			break;
		    }
		    buf = newp;
		}

		*((char *) mempcpy (buf + actsize, d->d_name, this_len))
		    = '\0';
		actsize += this_len + 1;
	    }

	    /* Terminate the list with an additional NUL byte.  */
	    buf[actsize++] = '\0';

	    /* Shrink the buffer to what we actually need.  */
	    data->dirstreams[data->actdir]->content = realloc (buf, actsize);
	    if (data->dirstreams[data->actdir]->content == NULL)
	    {
		int save_err = errno;
		free (buf);
		__set_errno (save_err);
		result = -1;
	    }
	    else
	    {
		closedir (st);
		data->dirstreams[data->actdir]->stream = NULL;
		data->dirstreams[data->actdir] = NULL;
	    }
	}
    }

    /* Open the new stream.  */
    if (result == 0)
    {
	const char *name = ((data->flags & FTW_CHDIR)
		? data->dirbuf + data->ftw.base: data->dirbuf);
	assert (data->dirstreams[data->actdir] == NULL);

	dirp->stream = opendir (name);
	if (dirp->stream == NULL)
	    result = -1;
	else
	{
	    dirp->content = NULL;
	    data->dirstreams[data->actdir] = dirp;

	    if (++data->actdir == data->maxdir)
		data->actdir = 0;
	}
    }

    return result;
}


static int
internal_function
process_entry (struct ftw_data *data, struct dir_data *dir, const char *name, size_t namlen)
{
    struct stat st;
    int result = 0;
    int flag = 0;
    size_t new_buflen;

    if (name[0] == '.' && (name[1] == '\0'
		|| (name[1] == '.' && name[2] == '\0')))
	/* Don't process the "." and ".." entries.  */
	return 0;

    new_buflen = data->ftw.base + namlen + 2;
    if (data->dirbufsize < new_buflen)
    {
	/* Enlarge the buffer.  */
	char *newp;

	data->dirbufsize = 2 * new_buflen;
	newp = (char *) realloc (data->dirbuf, data->dirbufsize);
	if (newp == NULL)
	    return -1;
	data->dirbuf = newp;
    }

    *((char *) mempcpy (data->dirbuf + data->ftw.base, name, namlen)) = '\0';

    if ((data->flags & FTW_CHDIR) == 0)
	name = data->dirbuf;

    if (((data->flags & FTW_PHYS)
		? lstat (name, &st)
		: stat (name, &st)) < 0)
    {
	if (errno != EACCES && errno != ENOENT)
	    result = -1;
	else if (!(data->flags & FTW_PHYS)
		&& lstat (name, &st) == 0
		&& S_ISLNK (st.st_mode))
	    flag = FTW_SLN;
	else
	    flag = FTW_NS;
    }
    else
    {
	if (S_ISDIR (st.st_mode))
	    flag = FTW_D;
	else if (S_ISLNK (st.st_mode))
	    flag = FTW_SL;
	else
	    flag = FTW_F;
    }

    if (result == 0
	    && (flag == FTW_NS
		|| !(data->flags & FTW_MOUNT) || st.st_dev == data->dev))
    {
	if (flag == FTW_D)
	{
	    if ((data->flags & FTW_PHYS)
		    || (!find_object (data, &st)
			/* Remember the object.  */
			&& (result = add_object (data, &st)) == 0))
	    {
		result = ftw_dir (data, &st);

		if (result == 0 && (data->flags & FTW_CHDIR))
		{
		    /* Change back to the parent directory.  */
		    int done = 0;
		    if (dir->stream != NULL)
			if (fchdir (dirfd (dir->stream)) == 0)
			    done = 1;

		    if (!done)
		    {
			if (data->ftw.base == 1)
			{
			    if (chdir ("/") < 0)
				result = -1;
			}
			else
			    if (chdir ("..") < 0)
				result = -1;
		    }
		}
	    }
	}
	else
	    result = (*data->func) (data->dirbuf, &st, data->cvt_arr[flag],
		    &data->ftw);
    }

    return result;
}

static int
internal_function
ftw_dir (struct ftw_data *data, struct stat *st)
{
    struct dir_data dir;
    struct dirent *d;
    int previous_base = data->ftw.base;
    int result;
    char *startp;

    /* Open the stream for this directory.  This might require that
       another stream has to be closed.  */
    result = open_dir_stream (data, &dir);
    if (result != 0)
    {
	if (errno == EACCES)
	    /* We cannot read the directory.  Signal this with a special flag.  */
	    result = (*data->func) (data->dirbuf, st, FTW_DNR, &data->ftw);

	return result;
    }

    /* First, report the directory (if not depth-first).  */
    if (!(data->flags & FTW_DEPTH))
    {
	result = (*data->func) (data->dirbuf, st, FTW_D, &data->ftw);
	if (result != 0)
	    return result;
    }

    /* If necessary, change to this directory.  */
    if (data->flags & FTW_CHDIR)
    {
	if (fchdir (dirfd (dir.stream)) < 0)
	{
	    int save_err = errno;
	    closedir (dir.stream);
	    __set_errno (save_err);

	    if (data->actdir-- == 0)
		data->actdir = data->maxdir - 1;
	    data->dirstreams[data->actdir] = NULL;

	    return -1;
	}
    }

    /* Next, update the `struct FTW' information.  */
    ++data->ftw.level;
    startp = strchr (data->dirbuf, '\0');
    /* There always must be a directory name.  */
    assert (startp != data->dirbuf);
    if (startp[-1] != '/')
	*startp++ = '/';
    data->ftw.base = startp - data->dirbuf;

    while (dir.stream != NULL && (d = readdir (dir.stream)) != NULL)
    {
	result = process_entry (data, &dir, d->d_name, _D_EXACT_NAMLEN (d));
	if (result != 0)
	    break;
    }

    if (dir.stream != NULL)
    {
	/* The stream is still open.  I.e., we did not need more
	   descriptors.  Simply close the stream now.  */
	int save_err = errno;

	assert (dir.content == NULL);

	closedir (dir.stream);
	__set_errno (save_err);

	if (data->actdir-- == 0)
	    data->actdir = data->maxdir - 1;
	data->dirstreams[data->actdir] = NULL;
    }
    else
    {
	int save_err;
	char *runp = dir.content;

	while (result == 0 && *runp != '\0')
	{
	    char *endp = strchr (runp, '\0');

	    result = process_entry (data, &dir, runp, endp - runp);

	    runp = endp + 1;
	}

	save_err = errno;
	free (dir.content);
	__set_errno (save_err);
    }

    /* Prepare the return, revert the `struct FTW' information.  */
    data->dirbuf[data->ftw.base - 1] = '\0';
    --data->ftw.level;
    data->ftw.base = previous_base;

    /* Finally, if we process depth-first report the directory.  */
    if (result == 0 && (data->flags & FTW_DEPTH))
	result = (*data->func) (data->dirbuf, st, FTW_DP, &data->ftw);

    return result;
}


static int
internal_function
ftw_startup (const char *dir, int is_nftw, void *func, int descriptors, int flags)
{
    struct ftw_data data;
    struct stat st;
    int result = 0;
    int save_err;
    char *cwd = NULL;
    char *cp;

    /* First make sure the parameters are reasonable.  */
    if (dir[0] == '\0')
    {
	__set_errno (ENOENT);
	return -1;
    }

    data.maxdir = descriptors < 1 ? 1 : descriptors;
    data.actdir = 0;
    data.dirstreams = (struct dir_data **) alloca (data.maxdir
	    * sizeof (struct dir_data *));
    memset (data.dirstreams, '\0', data.maxdir * sizeof (struct dir_data *));

    /* PATH_MAX is always defined when we get here.  */
    data.dirbufsize = MAX (2 * strlen (dir), PATH_MAX);
    data.dirbuf = (char *) malloc (data.dirbufsize);
    if (data.dirbuf == NULL)
	return -1;
    cp = stpcpy (data.dirbuf, dir);
    /* Strip trailing slashes.  */
    while (cp > data.dirbuf + 1 && cp[-1] == '/')
	--cp;
    *cp = '\0';

    data.ftw.level = 0;

    /* Find basename.  */
    while (cp > data.dirbuf && cp[-1] != '/')
	--cp;
    data.ftw.base = cp - data.dirbuf;

    data.flags = flags;

    /* This assignment might seem to be strange but it is what we want.
       The trick is that the first three arguments to the `ftw' and
       `nftw' callback functions are equal.  Therefore we can call in
       every case the callback using the format of the `nftw' version
       and get the correct result since the stack layout for a function
       call in C allows this.  */
    data.func = (__nftw_func_t) func;

    /* Since we internally use the complete set of FTW_* values we need
       to reduce the value range before calling a `ftw' callback.  */
    data.cvt_arr = is_nftw ? nftw_arr : ftw_arr;

    /* No object known so far.  */
    data.known_objects = NULL;

    /* Now go to the directory containing the initial file/directory.  */
    if (flags & FTW_CHDIR)
    {
	/* GNU extension ahead.  */
	cwd =  getcwd (NULL, 0);
	if (cwd == NULL)
	    result = -1;
	else if (data.ftw.base > 0)
	{
	    /* Change to the directory the file is in.  In data.dirbuf
	       we have a writable copy of the file name.  Just NUL
	       terminate it for now and change the directory.  */
	    if (data.ftw.base == 1)
		/* I.e., the file is in the root directory.  */
		result = chdir ("/");
	    else
	    {
		char ch = data.dirbuf[data.ftw.base - 1];
		data.dirbuf[data.ftw.base - 1] = '\0';
		result = chdir (data.dirbuf);
		data.dirbuf[data.ftw.base - 1] = ch;
	    }
	}
    }

    /* Get stat info for start directory.  */
    if (result == 0)
    {
	const char *name = ((data.flags & FTW_CHDIR)
		? data.dirbuf + data.ftw.base
		: data.dirbuf);

	if (((flags & FTW_PHYS)
		    ? lstat (name, &st)
		    : stat (name, &st)) < 0)
	{
	    if (!(flags & FTW_PHYS)
		    && errno == ENOENT
		    && lstat (name, &st) == 0
		    && S_ISLNK (st.st_mode))
		result = (*data.func) (data.dirbuf, &st, data.cvt_arr[FTW_SLN],
			&data.ftw);
	    else
		/* No need to call the callback since we cannot say anything
		   about the object.  */
		result = -1;
	}
	else
	{
	    if (S_ISDIR (st.st_mode))
	    {
		/* Remember the device of the initial directory in case
		   FTW_MOUNT is given.  */
		data.dev = st.st_dev;

		/* We know this directory now.  */
		if (!(flags & FTW_PHYS))
		    result = add_object (&data, &st);

		if (result == 0)
		    result = ftw_dir (&data, &st);
	    }
	    else
	    {
		int flag = S_ISLNK (st.st_mode) ? FTW_SL : FTW_F;

		result = (*data.func) (data.dirbuf, &st, data.cvt_arr[flag],
			&data.ftw);
	    }
	}
    }

    /* Return to the start directory (if necessary).  */
    if (cwd != NULL)
    {
	int save_err = errno;
	chdir (cwd);
	free (cwd);
	__set_errno (save_err);
    }

    /* Free all memory.  */
    save_err = errno;
    tdestroy (data.known_objects, free);
    free (data.dirbuf);
    __set_errno (save_err);

    return result;
}



/* Entry points.  */

int ftw (const char *path, __ftw_func_t func, int descriptors)
{
    return ftw_startup (path, 0, func, descriptors, 0);
}

int nftw (const char *path, __nftw_func_t func, int descriptors, int flags)
{
    return ftw_startup (path, 1, func, descriptors, flags);
}