507 lines
12 KiB
C
507 lines
12 KiB
C
/*-
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* Copyright (c) 2003-2004 Tim Kientzle
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer
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* in this position and unchanged.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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/*-
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* This is a new directory-walking system that addresses a number
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* of problems I've had with fts(3). In particular, it has no
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* pathname-length limits (other than the size of 'int'), handles
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* deep logical traversals, uses considerably less memory, and has
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* an opaque interface (easier to modify in the future).
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*
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* Internally, it keeps a single list of "tree_entry" items that
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* represent filesystem objects that require further attention.
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* Non-directories are not kept in memory: they are pulled from
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* readdir(), returned to the client, then freed as soon as possible.
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* Any directory entry to be traversed gets pushed onto the stack.
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*
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* There is surprisingly little information that needs to be kept for
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* each item on the stack. Just the name, depth (represented here as the
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* string length of the parent directory's pathname), and some markers
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* indicating how to get back to the parent (via chdir("..") for a
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* regular dir or via fchdir(2) for a symlink).
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*/
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#include "bsdtar_platform.h"
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__FBSDID("$FreeBSD$");
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#include <sys/stat.h>
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#include <dirent.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include "tree.h"
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/*
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* TODO:
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* 1) Loop checking.
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* 3) Arbitrary logical traversals by closing/reopening intermediate fds.
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*/
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struct tree_entry {
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struct tree_entry *next;
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struct tree_entry *parent;
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char *name;
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size_t dirname_length;
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dev_t dev;
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ino_t ino;
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int fd;
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int flags;
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};
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/* Definitions for tree_entry.flags bitmap. */
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#define isDir 1 /* This entry is a regular directory. */
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#define isDirLink 2 /* This entry is a symbolic link to a directory. */
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#define needsPreVisit 4 /* This entry needs to be previsited. */
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#define needsPostVisit 8 /* This entry needs to be postvisited. */
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/*
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* Local data for this package.
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*/
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struct tree {
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struct tree_entry *stack;
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struct tree_entry *current;
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DIR *d;
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int initialDirFd;
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int flags;
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int visit_type;
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int tree_errno; /* Error code from last failed operation. */
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char *buff;
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const char *basename;
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size_t buff_length;
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size_t path_length;
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size_t dirname_length;
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int depth;
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int openCount;
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int maxOpenCount;
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struct stat lst;
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struct stat st;
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};
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/* Definitions for tree.flags bitmap. */
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#define needsReturn 8 /* Marks first entry as not having been returned yet. */
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#define hasStat 16 /* The st entry is set. */
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#define hasLstat 32 /* The lst entry is set. */
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#ifdef HAVE_DIRENT_D_NAMLEN
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/* BSD extension; avoids need for a strlen() call. */
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#define D_NAMELEN(dp) (dp)->d_namlen
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#else
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#define D_NAMELEN(dp) (strlen((dp)->d_name))
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#endif
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#if 0
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#include <stdio.h>
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void
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tree_dump(struct tree *t, FILE *out)
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{
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struct tree_entry *te;
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fprintf(out, "\tdepth: %d\n", t->depth);
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fprintf(out, "\tbuff: %s\n", t->buff);
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fprintf(out, "\tpwd: "); fflush(stdout); system("pwd");
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fprintf(out, "\taccess: %s\n", t->basename);
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fprintf(out, "\tstack:\n");
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for(te = t->stack; te != NULL; te = te->next) {
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fprintf(out, "\t\tte->name: %s%s%s\n", te->name,
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te->flags & needsPreVisit ? "" : " *",
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t->current == te ? " (current)" : "");
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}
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}
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#endif
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/*
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* Add a directory path to the current stack.
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*/
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static void
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tree_push(struct tree *t, const char *path)
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{
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struct tree_entry *te;
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te = malloc(sizeof(*te));
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memset(te, 0, sizeof(*te));
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te->next = t->stack;
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t->stack = te;
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te->fd = -1;
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te->name = strdup(path);
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te->flags = needsPreVisit | needsPostVisit;
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te->dirname_length = t->dirname_length;
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}
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/*
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* Append a name to the current path.
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*/
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static void
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tree_append(struct tree *t, const char *name, size_t name_length)
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{
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char *p;
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if (t->buff != NULL)
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t->buff[t->dirname_length] = '\0';
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/* Strip trailing '/' from name, unless entire name is "/". */
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while (name_length > 1 && name[name_length - 1] == '/')
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name_length--;
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/* Resize pathname buffer as needed. */
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while (name_length + 1 + t->dirname_length >= t->buff_length) {
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t->buff_length *= 2;
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if (t->buff_length < 1024)
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t->buff_length = 1024;
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t->buff = realloc(t->buff, t->buff_length);
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}
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p = t->buff + t->dirname_length;
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t->path_length = t->dirname_length + name_length;
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/* Add a separating '/' if it's needed. */
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if (t->dirname_length > 0 && p[-1] != '/') {
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*p++ = '/';
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t->path_length ++;
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}
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strncpy(p, name, name_length);
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p[name_length] = '\0';
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t->basename = p;
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}
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/*
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* Open a directory tree for traversal.
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*/
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struct tree *
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tree_open(const char *path)
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{
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struct tree *t;
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t = malloc(sizeof(*t));
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memset(t, 0, sizeof(*t));
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tree_append(t, path, strlen(path));
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t->initialDirFd = open(".", O_RDONLY);
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/*
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* During most of the traversal, items are set up and then
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* returned immediately from tree_next(). That doesn't work
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* for the very first entry, so we set a flag for this special
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* case.
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*/
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t->flags = needsReturn;
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return (t);
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}
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/*
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* We've finished a directory; ascend back to the parent.
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*/
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static void
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tree_ascend(struct tree *t)
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{
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struct tree_entry *te;
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te = t->stack;
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t->depth--;
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if (te->flags & isDirLink) {
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fchdir(te->fd);
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close(te->fd);
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t->openCount--;
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} else {
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chdir("..");
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}
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}
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/*
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* Pop the working stack.
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*/
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static void
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tree_pop(struct tree *t)
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{
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struct tree_entry *te;
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t->buff[t->dirname_length] = '\0';
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if (t->stack == t->current && t->current != NULL)
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t->current = t->current->parent;
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te = t->stack;
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t->stack = te->next;
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t->dirname_length = te->dirname_length;
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t->basename = t->buff + t->dirname_length;
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/* Special case: starting dir doesn't skip leading '/'. */
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if (t->dirname_length > 0)
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t->basename++;
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free(te->name);
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free(te);
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}
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/*
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* Get the next item in the tree traversal.
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*/
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int
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tree_next(struct tree *t)
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{
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struct dirent *de = NULL;
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/* Handle the startup case by returning the initial entry. */
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if (t->flags & needsReturn) {
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t->flags &= ~needsReturn;
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return (t->visit_type = TREE_REGULAR);
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}
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while (t->stack != NULL) {
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/* If there's an open dir, get the next entry from there. */
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while (t->d != NULL) {
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de = readdir(t->d);
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if (de == NULL) {
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closedir(t->d);
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t->d = NULL;
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} else if (de->d_name[0] == '.'
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&& de->d_name[1] == '\0') {
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/* Skip '.' */
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} else if (de->d_name[0] == '.'
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&& de->d_name[1] == '.'
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&& de->d_name[2] == '\0') {
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/* Skip '..' */
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} else {
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/*
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* Append the path to the current path
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* and return it.
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*/
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tree_append(t, de->d_name, D_NAMELEN(de));
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t->flags &= ~hasLstat;
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t->flags &= ~hasStat;
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return (t->visit_type = TREE_REGULAR);
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}
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}
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/* If the current dir needs to be visited, set it up. */
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if (t->stack->flags & needsPreVisit) {
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t->current = t->stack;
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tree_append(t, t->stack->name, strlen(t->stack->name));
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t->stack->flags &= ~needsPreVisit;
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/* If it is a link, set up fd for the ascent. */
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if (t->stack->flags & isDirLink) {
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t->stack->fd = open(".", O_RDONLY);
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t->openCount++;
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if (t->openCount > t->maxOpenCount)
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t->maxOpenCount = t->openCount;
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}
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t->dirname_length = t->path_length;
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if (chdir(t->stack->name) != 0) {
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/* chdir() failed; return error */
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tree_pop(t);
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t->tree_errno = errno;
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return (t->visit_type = TREE_ERROR_DIR);
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}
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t->d = opendir(".");
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if (t->d == NULL) {
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tree_pop(t);
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t->tree_errno = errno;
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return (t->visit_type = TREE_ERROR_DIR);
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}
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t->depth++;
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t->flags &= ~hasLstat;
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t->flags &= ~hasStat;
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t->basename = ".";
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return (t->visit_type = TREE_POSTDESCENT);
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}
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/* We've done everything necessary for the top stack entry. */
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if (t->stack->flags & needsPostVisit) {
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tree_ascend(t);
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tree_pop(t);
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t->flags &= ~hasLstat;
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t->flags &= ~hasStat;
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return (t->visit_type = TREE_POSTASCENT);
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}
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}
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return (t->visit_type = 0);
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}
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/*
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* Return error code.
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*/
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int
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tree_errno(struct tree *t)
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{
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return (t->tree_errno);
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}
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/*
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* Called by the client to mark the directory just returned from
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* tree_next() as needing to be visited.
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*/
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void
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tree_descend(struct tree *t)
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{
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if (t->visit_type != TREE_REGULAR)
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return;
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if (tree_current_is_physical_dir(t)) {
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tree_push(t, t->basename);
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t->stack->flags |= isDir;
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} else if (tree_current_is_dir(t)) {
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tree_push(t, t->basename);
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t->stack->flags |= isDirLink;
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}
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}
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/*
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* Get the stat() data for the entry just returned from tree_next().
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*/
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const struct stat *
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tree_current_stat(struct tree *t)
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{
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if (!(t->flags & hasStat)) {
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if (stat(t->basename, &t->st) != 0)
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return NULL;
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t->flags |= hasStat;
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}
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return (&t->st);
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}
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/*
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* Get the lstat() data for the entry just returned from tree_next().
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*/
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const struct stat *
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tree_current_lstat(struct tree *t)
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{
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if (!(t->flags & hasLstat)) {
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if (lstat(t->basename, &t->lst) != 0)
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return NULL;
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t->flags |= hasLstat;
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}
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return (&t->lst);
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}
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/*
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* Test whether current entry is a dir or dir link.
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*/
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int
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tree_current_is_dir(struct tree *t)
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{
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/* If we've already pulled stat(), just use that. */
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if (t->flags & hasStat)
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return (S_ISDIR(tree_current_stat(t)->st_mode));
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/* If we've already pulled lstat(), we may be able to use that. */
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if (t->flags & hasLstat) {
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/* If lstat() says it's a dir, it must be a dir. */
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if (S_ISDIR(tree_current_lstat(t)->st_mode))
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return 1;
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/* If it's not a dir and not a link, we're done. */
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if (!S_ISLNK(tree_current_lstat(t)->st_mode))
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return 0;
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/*
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* If the above two tests fail, then it's a link, but
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* we don't know whether it's a link to a dir or a
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* non-dir.
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*/
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}
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/* TODO: Use a more efficient mechanism when available. */
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return (S_ISDIR(tree_current_stat(t)->st_mode));
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}
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/*
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* Test whether current entry is a physical directory.
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*/
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int
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tree_current_is_physical_dir(struct tree *t)
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{
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/* If we've already pulled lstat(), just use that. */
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if (t->flags & hasLstat)
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return (S_ISDIR(tree_current_lstat(t)->st_mode));
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/* TODO: Use a more efficient mechanism when available. */
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return (S_ISDIR(tree_current_lstat(t)->st_mode));
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}
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/*
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* Test whether current entry is a symbolic link.
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*/
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int
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tree_current_is_physical_link(struct tree *t)
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{
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/* If we've already pulled lstat(), just use that. */
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if (t->flags & hasLstat)
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return (S_ISLNK(tree_current_lstat(t)->st_mode));
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/* TODO: Use a more efficient mechanism when available. */
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return (S_ISLNK(tree_current_lstat(t)->st_mode));
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}
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/*
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* Return the access path for the entry just returned from tree_next().
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*/
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const char *
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tree_current_access_path(struct tree *t)
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{
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return (t->basename);
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}
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/*
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* Return the full path for the entry just returned from tree_next().
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*/
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const char *
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tree_current_path(struct tree *t)
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{
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return (t->buff);
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}
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/*
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* Return the length of the path for the entry just returned from tree_next().
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*/
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size_t
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tree_current_pathlen(struct tree *t)
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{
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return (t->path_length);
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}
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/*
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* Return the nesting depth of the entry just returned from tree_next().
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*/
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int
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tree_current_depth(struct tree *t)
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{
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return (t->depth);
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}
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/*
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* Terminate the traversal and release any resources.
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*/
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void
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tree_close(struct tree *t)
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{
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/* Release anything remaining in the stack. */
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while (t->stack != NULL)
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tree_pop(t);
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if (t->buff)
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free(t->buff);
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/* chdir() back to where we started. */
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if (t->initialDirFd >= 0) {
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fchdir(t->initialDirFd);
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close(t->initialDirFd);
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t->initialDirFd = -1;
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}
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free(t);
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}
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