/*-
* 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);
}