/*-

 * Copyright (c) 2003-2007 Tim Kientzle

 * All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 * 1. Redistributions of source code must retain the above copyright

 *    notice, this list of conditions and the following disclaimer.

 * 2. Redistributions in binary form must reproduce the above copyright

 *    notice, this list of conditions and the following disclaimer in the

 *    documentation and/or other materials provided with the distribution.

 *

 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``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 AUTHOR(S) 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.

 */

/*-

 * This is a new directory-walking system that addresses a number

 * of problems I've had with fts(3).  In particular, it has no

 * pathname-length limits (other than the size of 'int'), handles

 * deep logical traversals, uses considerably less memory, and has

 * an opaque interface (easier to modify in the future).

 *

 * Internally, it keeps a single list of "tree_entry" items that

 * represent filesystem objects that require further attention.

 * Non-directories are not kept in memory: they are pulled from

 * readdir(), returned to the client, then freed as soon as possible.

 * Any directory entry to be traversed gets pushed onto the stack.

 *

 * There is surprisingly little information that needs to be kept for

 * each item on the stack.  Just the name, depth (represented here as the

 * string length of the parent directory's pathname), and some markers

 * indicating how to get back to the parent (via chdir("..") for a

 * regular dir or via fchdir(2) for a symlink).

 */

#include "tree_config.h"

__FBSDID("$FreeBSD$");

#ifdef HAVE_SYS_STAT_H

#include <sys/stat.h>

#endif

#ifdef HAVE_DIRENT_H

#include <dirent.h>

#endif

#ifdef HAVE_ERRNO_H

#include <errno.h>

#endif

#ifdef HAVE_FCNTL_H

#include <fcntl.h>

#endif

#ifdef HAVE_STDLIB_H

#include <stdlib.h>

#endif

#ifdef HAVE_STRING_H

#include <string.h>

#endif

#ifdef HAVE_UNISTD_H

#include <unistd.h>

#endif

#include "tree.h"

/*

 * TODO:

 *    1) Loop checking.

 *    3) Arbitrary logical traversals by closing/reopening intermediate fds.

 */

struct tree_entry {

	struct tree_entry *next;

	struct tree_entry *parent;

	char *name;

	size_t dirname_length;

	dev_t dev;

	ino_t ino;

	int fd;

	int flags;

};

/* Definitions for tree_entry.flags bitmap. */

#define	isDir 1 /* This entry is a regular directory. */

#define	isDirLink 2 /* This entry is a symbolic link to a directory. */

#define	needsPreVisit 4 /* This entry needs to be previsited. */

#define	needsPostVisit 8 /* This entry needs to be postvisited. */

/*

 * Local data for this package.

 */

struct tree {

	struct tree_entry	*stack;

	struct tree_entry	*current;

	DIR	*d;

	int	 initialDirFd;

	int	 flags;

	int	 visit_type;

	int	 tree_errno; /* Error code from last failed operation. */

	char	*buff;

	const char	*basename;

	size_t	 buff_length;

	size_t	 path_length;

	size_t	 dirname_length;

	int	 depth;

	int	 openCount;

	int	 maxOpenCount;

	struct stat	lst;

	struct stat	st;

};

/* Definitions for tree.flags bitmap. */

#define needsReturn 8  /* Marks first entry as not having been returned yet. */

#define hasStat 16  /* The st entry is set. */

#define hasLstat 32 /* The lst entry is set. */

#ifdef HAVE_DIRENT_D_NAMLEN

/* BSD extension; avoids need for a strlen() call. */

#define D_NAMELEN(dp)	(dp)->d_namlen

#else

#define D_NAMELEN(dp)	(strlen((dp)->d_name))

#endif

#if 0

#include <stdio.h>

void

tree_dump(struct tree *t, FILE *out)

{

	struct tree_entry *te;

	fprintf(out, "\tdepth: %d\n", t->depth);

	fprintf(out, "\tbuff: %s\n", t->buff);

	fprintf(out, "\tpwd: "); fflush(stdout); system("pwd");

	fprintf(out, "\taccess: %s\n", t->basename);

	fprintf(out, "\tstack:\n");

	for (te = t->stack; te != NULL; te = te->next) {

		fprintf(out, "\t\tte->name: %s%s%s\n", te->name,

		    te->flags & needsPreVisit ? "" : " *",

		    t->current == te ? " (current)" : "");

	}

}

#endif

/*

 * Add a directory path to the current stack.

 */

static void

tree_push(struct tree *t, const char *path)

{

	struct tree_entry *te;

	te = malloc(sizeof(*te));

	memset(te, 0, sizeof(*te));

	te->next = t->stack;

	t->stack = te;

	te->fd = -1;

	te->name = strdup(path);

	te->flags = needsPreVisit | needsPostVisit;

	te->dirname_length = t->dirname_length;

}

/*

 * Append a name to the current path.

 */

static void

tree_append(struct tree *t, const char *name, size_t name_length)

{

	char *p;

	if (t->buff != NULL)

		t->buff[t->dirname_length] = '\0';

	/* Strip trailing '/' from name, unless entire name is "/". */

	while (name_length > 1 && name[name_length - 1] == '/')

		name_length--;

	/* Resize pathname buffer as needed. */

	while (name_length + 1 + t->dirname_length >= t->buff_length) {

		t->buff_length *= 2;

		if (t->buff_length < 1024)

			t->buff_length = 1024;

		t->buff = realloc(t->buff, t->buff_length);

	}

	p = t->buff + t->dirname_length;

	t->path_length = t->dirname_length + name_length;

	/* Add a separating '/' if it's needed. */

	if (t->dirname_length > 0 && p[-1] != '/') {

		*p++ = '/';

		t->path_length ++;

	}

	strncpy(p, name, name_length);

	p[name_length] = '\0';

	t->basename = p;

}

/*

 * Open a directory tree for traversal.

 */

struct tree *

tree_open(const char *path)

{

	struct tree *t;

	t = malloc(sizeof(*t));

	memset(t, 0, sizeof(*t));

	tree_append(t, path, strlen(path));

	t->initialDirFd = open(".", O_RDONLY);

	/*

	 * During most of the traversal, items are set up and then

	 * returned immediately from tree_next().  That doesn't work

	 * for the very first entry, so we set a flag for this special

	 * case.

	 */

	t->flags = needsReturn;

	return (t);

}

/*

 * We've finished a directory; ascend back to the parent.

 */

static void

tree_ascend(struct tree *t)

{

	struct tree_entry *te;

	te = t->stack;

	t->depth--;

	if (te->flags & isDirLink) {

		fchdir(te->fd);

		close(te->fd);

		t->openCount--;

	} else {

		chdir("..");

	}

}

/*

 * Pop the working stack.

 */

static void

tree_pop(struct tree *t)

{

	struct tree_entry *te;

	t->buff[t->dirname_length] = '\0';

	if (t->stack == t->current && t->current != NULL)

		t->current = t->current->parent;

	te = t->stack;

	t->stack = te->next;

	t->dirname_length = te->dirname_length;

	t->basename = t->buff + t->dirname_length;

	/* Special case: starting dir doesn't skip leading '/'. */

	if (t->dirname_length > 0)

		t->basename++;

	free(te->name);

	free(te);

}

/*

 * Get the next item in the tree traversal.

 */

int

tree_next(struct tree *t)

{

	struct dirent *de = NULL;

	/* Handle the startup case by returning the initial entry. */

	if (t->flags & needsReturn) {

		t->flags &= ~needsReturn;

		return (t->visit_type = TREE_REGULAR);

	}

	while (t->stack != NULL) {

		/* If there's an open dir, get the next entry from there. */

		while (t->d != NULL) {

			de = readdir(t->d);

			if (de == NULL) {

				closedir(t->d);

				t->d = NULL;

			} else if (de->d_name[0] == '.'

			    && de->d_name[1] == '\0') {

				/* Skip '.' */

			} else if (de->d_name[0] == '.'

			    && de->d_name[1] == '.'

			    && de->d_name[2] == '\0') {

				/* Skip '..' */

			} else {

				/*

				 * Append the path to the current path

				 * and return it.

				 */

				tree_append(t, de->d_name, D_NAMELEN(de));

				t->flags &= ~hasLstat;

				t->flags &= ~hasStat;

				return (t->visit_type = TREE_REGULAR);

			}

		}

		/* If the current dir needs to be visited, set it up. */

		if (t->stack->flags & needsPreVisit) {

			t->current = t->stack;

			tree_append(t, t->stack->name, strlen(t->stack->name));

			t->stack->flags &= ~needsPreVisit;

			/* If it is a link, set up fd for the ascent. */

			if (t->stack->flags & isDirLink) {

				t->stack->fd = open(".", O_RDONLY);

				t->openCount++;

				if (t->openCount > t->maxOpenCount)

					t->maxOpenCount = t->openCount;

			}

			t->dirname_length = t->path_length;

			if (chdir(t->stack->name) != 0) {

				/* chdir() failed; return error */

				tree_pop(t);

				t->tree_errno = errno;

				return (t->visit_type = TREE_ERROR_DIR);

			}

			t->depth++;

			t->d = opendir(".");

			if (t->d == NULL) {

				tree_ascend(t); /* Undo "chdir" */

				tree_pop(t);

				t->tree_errno = errno;

				return (t->visit_type = TREE_ERROR_DIR);

			}

			t->flags &= ~hasLstat;

			t->flags &= ~hasStat;

			t->basename = ".";

			return (t->visit_type = TREE_POSTDESCENT);

		}

		/* We've done everything necessary for the top stack entry. */

		if (t->stack->flags & needsPostVisit) {

			tree_ascend(t);

			tree_pop(t);

			t->flags &= ~hasLstat;

			t->flags &= ~hasStat;

			return (t->visit_type = TREE_POSTASCENT);

		}

	}

	return (t->visit_type = 0);

}

/*

 * Return error code.

 */

int

tree_errno(struct tree *t)

{

	return (t->tree_errno);

}

/*

 * Called by the client to mark the directory just returned from

 * tree_next() as needing to be visited.

 */

void

tree_descend(struct tree *t)

{

	if (t->visit_type != TREE_REGULAR)

		return;

	if (tree_current_is_physical_dir(t)) {

		tree_push(t, t->basename);

		t->stack->flags |= isDir;

	} else if (tree_current_is_dir(t)) {

		tree_push(t, t->basename);

		t->stack->flags |= isDirLink;

	}

}

/*

 * Get the stat() data for the entry just returned from tree_next().

 */

const struct stat *

tree_current_stat(struct tree *t)

{

	if (!(t->flags & hasStat)) {

		if (stat(t->basename, &t->st) != 0)

			return NULL;

		t->flags |= hasStat;

	}

	return (&t->st);

}

/*

 * Get the lstat() data for the entry just returned from tree_next().

 */

const struct stat *

tree_current_lstat(struct tree *t)

{

	if (!(t->flags & hasLstat)) {

		if (lstat(t->basename, &t->lst) != 0)

			return NULL;

		t->flags |= hasLstat;

	}

	return (&t->lst);

}

/*

 * Test whether current entry is a dir or link to a dir.

 */

int

tree_current_is_dir(struct tree *t)

{

	const struct stat *st;

	/*

	 * If we already have lstat() info, then try some

	 * cheap tests to determine if this is a dir.

	 */

	if (t->flags & hasLstat) {

		/* If lstat() says it's a dir, it must be a dir. */

		if (S_ISDIR(tree_current_lstat(t)->st_mode))

			return 1;

		/* Not a dir; might be a link to a dir. */

		/* If it's not a link, then it's not a link to a dir. */

		if (!S_ISLNK(tree_current_lstat(t)->st_mode))

			return 0;

		/*

		 * It's a link, but we don't know what it's a link to,

		 * so we'll have to use stat().

		 */

	}

	st = tree_current_stat(t);

	/* If we can't stat it, it's not a dir. */

	if (st == NULL)

		return 0;

	/* Use the definitive test.  Hopefully this is cached. */

	return (S_ISDIR(st->st_mode));

}

/*

 * Test whether current entry is a physical directory.  Usually, we

 * already have at least one of stat() or lstat() in memory, so we

 * use tricks to try to avoid an extra trip to the disk.

 */

int

tree_current_is_physical_dir(struct tree *t)

{

	const struct stat *st;

	/*

	 * If stat() says it isn't a dir, then it's not a dir.

	 * If stat() data is cached, this check is free, so do it first.

	 */

	if ((t->flags & hasStat)

	    && (!S_ISDIR(tree_current_stat(t)->st_mode)))

		return 0;

	/*

	 * Either stat() said it was a dir (in which case, we have

	 * to determine whether it's really a link to a dir) or

	 * stat() info wasn't available.  So we use lstat(), which

	 * hopefully is already cached.

	 */

	st = tree_current_lstat(t);

	/* If we can't stat it, it's not a dir. */

	if (st == NULL)

		return 0;

	/* Use the definitive test.  Hopefully this is cached. */

	return (S_ISDIR(st->st_mode));

}

/*

 * Test whether current entry is a symbolic link.

 */

int

tree_current_is_physical_link(struct tree *t)

{

	const struct stat *st = tree_current_lstat(t);

	if (st == NULL)

		return 0;

	return (S_ISLNK(st->st_mode));

}

/*

 * Return the access path for the entry just returned from tree_next().

 */

const char *

tree_current_access_path(struct tree *t)

{

	return (t->basename);

}

/*

 * Return the full path for the entry just returned from tree_next().

 */

const char *

tree_current_path(struct tree *t)

{

	return (t->buff);

}

/*

 * Return the length of the path for the entry just returned from tree_next().

 */

size_t

tree_current_pathlen(struct tree *t)

{

	return (t->path_length);

}

/*

 * Return the nesting depth of the entry just returned from tree_next().

 */

int

tree_current_depth(struct tree *t)

{

	return (t->depth);

}

/*

 * Terminate the traversal and release any resources.

 */

void

tree_close(struct tree *t)

{

	/* Release anything remaining in the stack. */

	while (t->stack != NULL)

		tree_pop(t);

	if (t->buff)

		free(t->buff);

	/* chdir() back to where we started. */

	if (t->initialDirFd >= 0) {

		fchdir(t->initialDirFd);

		close(t->initialDirFd);

		t->initialDirFd = -1;

	}

	free(t);

}