fix lseek underflow problem

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@1767 bbd45198-f89e-11dd-88c7-29a3b14d5316

components/dfs/src/dfs_posix.c

-/*
- * File      : dfs_posix.c
- * This file is part of Device File System in RT-Thread RTOS
- * COPYRIGHT (C) 2004-2010, RT-Thread Development Team
- *
- * The license and distribution terms for this file may be
- * found in the file LICENSE in this distribution or at
- * http://www.rt-thread.org/license/LICENSE.
- *
- * Change Logs:
- * Date           Author       Notes
- * 2009-05-27     Yi.qiu       The first version
- */
-
-#include <dfs.h>
-#include <dfs_posix.h>
-
-/**
- * @addtogroup FsPosixApi
- */
-/*@{*/
-
-/**
- * this function is a POSIX compliant version, which will open a file and return
- * a file descriptor.
- *
- * @param file the path name of file.
- * @param flags the file open flags.
- * @param mode
- *
- * @return the non-negative integer on successful open, others for failed.
- */
-int open(const char *file, int flags, int mode)
-{
-	int fd, result;
-	struct dfs_fd* d;
-
-	/* allocate a fd */
-	fd = fd_new();
-	if (fd < 0) return -1;
-	d  = fd_get(fd);
-
-	result = dfs_file_open(d, file, flags);
-	if (result < 0)
-	{
-		rt_set_errno(result);
-
-		/* release the ref-count of fd */
-		fd_put(d);
-		fd_put(d);
-
-		return -1;
-	}
-
-	/* release the ref-count of fd */
-	fd_put(d);
-	return fd;
-}
-
-/**
- * this function is a POSIX compliant version, which will close the open
- * file descriptor.
- *
- * @param fd the file descriptor.
- *
- * @return 0 on successful, -1 on failed.
- */
-int close(int fd)
-{
-	int result;
-	struct dfs_fd* d;
-
-	d = fd_get(fd);
-	if (d == RT_NULL)
-	{
-		rt_set_errno(-RT_ERROR);
-		return -1;
-	}
-
-	result = dfs_file_close(d);
-	fd_put(d);
-
-	if (result < 0)
-	{
-		rt_set_errno(result);
-		return -1;
-	}
-
-	fd_put(d);
-	return 0;
-}
-
-/**
- * this function is a POSIX compliant version, which will read specified data buffer 
- * length for an open file descriptor.
- * 
- * @param fd the file descriptor.
- * @param buf the buffer to save the read data.
- * @param len the maximal length of data buffer
- *
- * @return the actual read data buffer length
- */
-int read(int fd, void *buf, size_t len)
-{
-	int result;
-	struct dfs_fd* d;
-
-	/* get the fd */
-	d  = fd_get(fd);
-	if (d == RT_NULL)
-	{
-		rt_set_errno(-RT_ERROR);
-		return -1;
-	}
-
-	result = dfs_file_read(d, buf, len);
-	if (result < 0)
-	{
-		rt_set_errno(result);
-		fd_put(d);
-
-		return -1;
-	}
-
-	/* release the ref-count of fd */
-	fd_put(d);
-	return result;
-}
-
-/**
- * this function is a POSIX compliant version, which will write pecified data buffer
- * length for an open file descriptor.
- *
- * @param fd the file descriptor
- * @param buf the data buffer to be written.
- * @param len the data buffer length.
- *
- * @return the actual written data buffer length.
- */
-int write(int fd, const void *buf, size_t len)
-{
-	int result;
-	struct dfs_fd* d;
-
-	/* get the fd */
-	d  = fd_get(fd);
-	if (d == RT_NULL)
-	{
-		rt_set_errno(-RT_ERROR);
-		return -1;
-	}
-
-	result = dfs_file_write(d, buf, len);
-	if (result < 0)
-	{
-		rt_set_errno(result);
-		fd_put(d);
-
-		return -1;
-	}
-
-	/* release the ref-count of fd */
-	fd_put(d);
-	return result;
-}
-
-/**
- * this function is a POSIX compliant version, which will seek the offset for an
- * open file descriptor.
- *
- * @param fd the file descriptor.
- * @param offset the offset to be seeked.
- * @param whence the directory of seek.
- *
- * @return the current file position, or -1 on failed.
- */
-off_t lseek(int fd, off_t offset, int whence)
-{
-	int result;
-	struct dfs_fd* d;
-
-	d  = fd_get(fd);
-	if (d == RT_NULL)
-	{
-		rt_set_errno(-RT_ERROR);
-		return -1;
-	}
-
-	switch (whence)
-	{
-	case DFS_SEEK_SET:
-		break;
-
-	case DFS_SEEK_CUR:
-		offset += d->pos;
-		break;
-
-	case DFS_SEEK_END:
-		offset += d->size;
-		break;
-	}
-
-	result = dfs_file_lseek(d, offset);
-	if (result < 0)
-	{
-		rt_set_errno(result);
-		fd_put(d);
-		return -1;
-	}
-
-	/* release the ref-count of fd */
-	fd_put(d);
-	return offset;
-}
-
-/**
- * this function is a POSIX compliant version, which will rename old file name to
- * new file name.
- *
- * @param old the old file name.
- * @param new the new file name.
- *
- * @return 0 on successful, -1 on failed.
- *
- * note: the old and new file name must be belong to a same file system.
- */
-int rename(const char* old, const char* new)
-{
-	int result;
-
-	result = dfs_file_rename(old, new);
-	if (result < 0)
-	{
-		rt_set_errno(result);
-		return -1;
-	}
-	return 0;
-}
-
-/**
- * this function is a POSIX compliant version, which will unlink (remove) a 
- * specified path file from file system.
- * 
- * @param pathname the specified path name to be unlinked.
- *
- * @return 0 on successful, -1 on failed.
- */
-int unlink(const char *pathname)
-{
-	int result;
-
-	result = dfs_file_unlink(pathname);
-	if (result < 0)
-	{
-		rt_set_errno(result);
-		return -1;
-	}
-	return 0;
-}
-
-/**
- * this function is a POSIX compliant version, which will get file information.
- * 
- * @param file the file name
- * @param buf the data buffer to save stat description.
- *
- * @return 0 on successful, -1 on failed.
- */
-int stat(const char *file, struct stat *buf)
-{
-	int result;
-
-	result = dfs_file_stat(file, buf);
-	if (result < 0)
-	{
-		rt_set_errno(result);
-		return -1;
-	}
-	return result;
-}
-
-/**
- * this function is a POSIX compliant version, which will get file status.
- *
- * @param fildes the file description
- * @param buf the data buffer to save stat description.
- */
-int fstat(int fildes, struct stat *buf)
-{
-	struct dfs_fd* d;
-
-	/* get the fd */
-	d  = fd_get(fildes);
-	if (d == RT_NULL)
-	{
-		rt_set_errno(-RT_ERROR);
-		return -1;
-	}
-
-	/* it's the root directory */
-	buf->st_dev   = 0;
-
-	buf->st_mode = DFS_S_IFREG | DFS_S_IRUSR | DFS_S_IRGRP | DFS_S_IROTH |
-			DFS_S_IWUSR | DFS_S_IWGRP | DFS_S_IWOTH;
-	if (d->type == FT_DIRECTORY)
-	{
-		buf->st_mode &= ~DFS_S_IFREG;
-		buf->st_mode |= DFS_S_IFDIR | DFS_S_IXUSR | DFS_S_IXGRP | DFS_S_IXOTH;
-	}
-
-	buf->st_size  = d->size;
-	buf->st_mtime = 0;
-	buf->st_blksize = 512;
-
-	fd_put(d);
-
-	return DFS_STATUS_OK;
-}
-
-/**
- * this function is a POSIX compliant version, which will return the 
- * information about a mounted file system.
- * 
- * @param path the path which mounted file system.
- * @param buf the buffer to save the returned information.
- *
- * @return 0 on successful, others on failed.
- */
-int statfs(const char *path, struct statfs *buf)
-{
-	int result;
-
-	result = dfs_statfs(path, buf);
-	if (result < 0)
-	{
-		rt_set_errno(result);
-		return -1;
-	}
-
-	return result;
-}
-
-/**
- * this function is a POSIX compliant version, which will make a directory
- *
- * @param path the directory path to be made.
- * @param mode 
- *
- * @return 0 on successful, others on failed.
- */
-int mkdir (const char *path, mode_t mode)
-{
-	int fd;
-	struct dfs_fd* d;
-	int result;
-
-	fd = fd_new();
-	if (fd == -1) { rt_kprintf("no fd\n"); return -1; }
-
-	d = fd_get(fd);
-
-	result = dfs_file_open(d, path, DFS_O_DIRECTORY | DFS_O_CREAT);
-
-	if (result < 0)
-	{
-		rt_set_errno(result);
-		fd_put(d);
-		return -1;
-	}
-
-	dfs_file_close(d);
-	fd_put(d);
-	return 0;
-}
-#ifdef RT_USING_FINSH
-#include <finsh.h>
-FINSH_FUNCTION_EXPORT(mkdir, create a directory);
-#endif
-
-/**
- * this function is a POSIX compliant version, which will remove a directory.
- *
- * @param pathname the path name to be removed.
- * 
- * @return 0 on sucessfull, others on failed.
- */
-int rmdir(const char *pathname)
-{
-	int result;
-
-	result = dfs_file_unlink(pathname);
-	if (result < 0)
-	{
-		rt_set_errno(result);
-		return -1;
-	}
-
-	return 0;
-}
-
-/**
- * this function is a POSIX compliant version, which will open a directory.
- *
- * @param name the path name to be open.
- *
- * @return the DIR pointer of directory, NULL on open failed.
- */
-DIR* opendir(const char* name)
-{
-	struct dfs_fd* d;
-	int fd, result;
-	DIR* t;
-
-	t = RT_NULL;
-
-	/* allocate a fd */
-	fd = fd_new();
-	if (fd == -1) { rt_kprintf("no fd\n"); return RT_NULL; }
-	d  = fd_get(fd);
-
-	result = dfs_file_open(d, name, DFS_O_RDONLY | DFS_O_DIRECTORY);
-	if (result >= 0)
-	{
-		/* open successfully */
-		t = (DIR *) rt_malloc (sizeof(DIR));
-		if (t == RT_NULL)
-		{
-			dfs_file_close(d);
-			fd_put(d);
-		}
-		else
-		{
-		    rt_memset(t, 0, sizeof(DIR));
-		    t->fd = fd;
-		}
-		fd_put(d);
-		return t;
-	}
-
-	/* open failed */
-	fd_put(d);
-	fd_put(d);
-	rt_set_errno(result);
-
-	return RT_NULL;
-}
-
-/**
- * this function is a POSIX compliant version, which will return a pointer 
- * to a dirent structure representing the next directory entry in the 
- * directory stream.
- *
- * @param d the directory stream pointer.
- *
- * @return the next directory entry, NULL on the end of directory or failed.
- */
-struct dirent* readdir(DIR *d)
-{
-	int result;
-	struct dfs_fd* fd;
-
-	fd = fd_get(d->fd);
-	if (fd == RT_NULL)
-	{
-		rt_set_errno(-RT_ERROR);
-		return RT_NULL;
-	}
-
-	if (!d->num || (d->cur += ((struct dirent*)(d->buf + d->cur))->d_reclen) >= d->num)
-	{
-		/* get a new entry */
-		result = dfs_file_getdents(fd, (struct dirent*)d->buf, sizeof(d->buf) - 1);
-		if (result <= 0)
-		{
-			rt_set_errno(result);
-			fd_put(fd);
-
-			return RT_NULL;
-		}
-
-		d->num = result;
-		d->cur = 0; /* current entry index */
-	}
-
-	fd_put(fd);
-	return (struct dirent*)(d->buf+d->cur);
-}
-
-/**
- * this function is a POSIX compliant version, which will return current 
- * location in directory stream.
- * 
- * @param d the directory stream pointer.
- *
- * @return the current location in directory stream.
- */
-long telldir(DIR *d)
-{
-	struct dfs_fd* fd;
-	long result;
-
-	fd = fd_get(d->fd);
-	if (fd == RT_NULL)
-	{
-		rt_set_errno(-RT_ERROR);
-		return 0;
-	}
-
-	result = fd->pos - d->num + d->cur;
-	fd_put(fd);
-
-	return result;
-}
-
-/**
- * this function is a POSIX compliant version, which will set position of 
- * next directory structure in the directory stream.
- *
- * @param d the directory stream.
- * @param offset the offset in directory stream.
- */
-void seekdir(DIR *d, off_t offset)
-{
-	struct dfs_fd* fd;
-
-	fd = fd_get(d->fd);
-	if (fd == RT_NULL)
-	{
-		rt_set_errno(-RT_ERROR);
-		return ;
-	}
-
-	/* seek to the offset position of directory */
-	if (dfs_file_lseek(fd, offset) >= 0) d->num = d->cur = 0;
-	fd_put(fd);
-}
-
-/**
- * this function is a POSIX compliant version, which will reset directory stream.
- *
- * @param d the directory stream.
- */
-void rewinddir(DIR *d)
-{
-	struct dfs_fd* fd;
-
-	fd = fd_get(d->fd);
-	if (fd == RT_NULL)
-	{
-		rt_set_errno(-RT_ERROR);
-		return ;
-	}
-
-	/* seek to the beginning of directory */
-	if (dfs_file_lseek(fd, 0) >= 0) d->num = d->cur = 0;
-	fd_put(fd);
-}
-
-/**
- * this function is a POSIX compliant version, which will close a directory 
- * stream.
- * 
- * @param d the directory stream.
- *
- * @return 0 on successful, -1 on failed.
- */
-int closedir(DIR* d)
-{
-	int result;
-	struct dfs_fd* fd;
-
-	fd = fd_get(d->fd);
-	if (fd == RT_NULL)
-	{
-		rt_set_errno(-RT_ERROR);
-		return -1;
-	}
-
-	result = dfs_file_close(fd);
-	fd_put(fd);
-
-	fd_put(fd);
-	rt_free(d);
-
-	if (result < 0)
-	{
-		rt_set_errno(result);
-		return -1;
-	}
-	else return 0;
-}
-
-#ifdef DFS_USING_WORKDIR
-/**
- * this function is a POSIX compliant version, which will change working directory.
- * 
- * @param path the path name to be changed to.
- *
- * @return 0 on successful, -1 on failed.
- */
-int chdir(const char *path)
-{
-	char* fullpath;
-	DIR* d;
-
-	if(path == RT_NULL)
-	{
-		dfs_lock();
-		rt_kprintf("%s\n", working_directory);
-		dfs_unlock();
-		return 0;
-	}
-
-	if (rt_strlen(path) > DFS_PATH_MAX)
-		return -1;
-
-	fullpath = dfs_normalize_path(NULL, path);
-	if (fullpath == RT_NULL)
-		return -1; /* build path failed */
-
-	dfs_lock();
-	d = opendir(fullpath);
-	if (d == RT_NULL)
-	{
-		rt_free(fullpath);
-		/* this is a not exist directory */
-		dfs_unlock();
-		return -1;
-	}
-
-	/* close directory stream */
-	closedir(d);
-
-	/* copy full path to working directory */
-	strncpy(working_directory, fullpath, DFS_PATH_MAX);
-	rt_free(fullpath); /* release normalize directory path name */
-
-	dfs_unlock();
-
-	return 0;
-}
-#ifdef RT_USING_FINSH
-FINSH_FUNCTION_EXPORT_ALIAS(chdir, cd, change current working directory);
-#endif
-#endif
-
-/**
- * this function is a POSIX compliant version, which will return current 
- * working directory.
- *
- * @param buf the returned current directory.
- * @param size the buffer size.
- *
- * @return the returned current directory.
- */
-char *getcwd(char *buf, size_t size)
-{
-#ifdef DFS_USING_WORKDIR
-	rt_enter_critical();
-	rt_strncpy(buf, working_directory, size);
-	rt_exit_critical();
-#else
-	rt_kprintf("WARNING: not support working directory\n");
-#endif
-	return buf;
-}
-
-/* @} */
+/*
+ * File      : dfs_posix.c
+ * This file is part of Device File System in RT-Thread RTOS
+ * COPYRIGHT (C) 2004-2010, RT-Thread Development Team
+ *
+ * The license and distribution terms for this file may be
+ * found in the file LICENSE in this distribution or at
+ * http://www.rt-thread.org/license/LICENSE.
+ *
+ * Change Logs:
+ * Date           Author       Notes
+ * 2009-05-27     Yi.qiu       The first version
+ */
+
+#include <dfs.h>
+#include <dfs_posix.h>
+
+/**
+ * @addtogroup FsPosixApi
+ */
+/*@{*/
+
+/**
+ * this function is a POSIX compliant version, which will open a file and return
+ * a file descriptor.
+ *
+ * @param file the path name of file.
+ * @param flags the file open flags.
+ * @param mode
+ *
+ * @return the non-negative integer on successful open, others for failed.
+ */
+int open(const char *file, int flags, int mode)
+{
+	int fd, result;
+	struct dfs_fd* d;
+
+	/* allocate a fd */
+	fd = fd_new();
+	if (fd < 0) return -1;
+	d  = fd_get(fd);
+
+	result = dfs_file_open(d, file, flags);
+	if (result < 0)
+	{
+		rt_set_errno(result);
+
+		/* release the ref-count of fd */
+		fd_put(d);
+		fd_put(d);
+
+		return -1;
+	}
+
+	/* release the ref-count of fd */
+	fd_put(d);
+	return fd;
+}
+
+/**
+ * this function is a POSIX compliant version, which will close the open
+ * file descriptor.
+ *
+ * @param fd the file descriptor.
+ *
+ * @return 0 on successful, -1 on failed.
+ */
+int close(int fd)
+{
+	int result;
+	struct dfs_fd* d;
+
+	d = fd_get(fd);
+	if (d == RT_NULL)
+	{
+		rt_set_errno(-RT_ERROR);
+		return -1;
+	}
+
+	result = dfs_file_close(d);
+	fd_put(d);
+
+	if (result < 0)
+	{
+		rt_set_errno(result);
+		return -1;
+	}
+
+	fd_put(d);
+	return 0;
+}
+
+/**
+ * this function is a POSIX compliant version, which will read specified data buffer 
+ * length for an open file descriptor.
+ * 
+ * @param fd the file descriptor.
+ * @param buf the buffer to save the read data.
+ * @param len the maximal length of data buffer
+ *
+ * @return the actual read data buffer length
+ */
+int read(int fd, void *buf, size_t len)
+{
+	int result;
+	struct dfs_fd* d;
+
+	/* get the fd */
+	d  = fd_get(fd);
+	if (d == RT_NULL)
+	{
+		rt_set_errno(-RT_ERROR);
+		return -1;
+	}
+
+	result = dfs_file_read(d, buf, len);
+	if (result < 0)
+	{
+		rt_set_errno(result);
+		fd_put(d);
+
+		return -1;
+	}
+
+	/* release the ref-count of fd */
+	fd_put(d);
+	return result;
+}
+
+/**
+ * this function is a POSIX compliant version, which will write pecified data buffer
+ * length for an open file descriptor.
+ *
+ * @param fd the file descriptor
+ * @param buf the data buffer to be written.
+ * @param len the data buffer length.
+ *
+ * @return the actual written data buffer length.
+ */
+int write(int fd, const void *buf, size_t len)
+{
+	int result;
+	struct dfs_fd* d;
+
+	/* get the fd */
+	d  = fd_get(fd);
+	if (d == RT_NULL)
+	{
+		rt_set_errno(-RT_ERROR);
+		return -1;
+	}
+
+	result = dfs_file_write(d, buf, len);
+	if (result < 0)
+	{
+		rt_set_errno(result);
+		fd_put(d);
+
+		return -1;
+	}
+
+	/* release the ref-count of fd */
+	fd_put(d);
+	return result;
+}
+
+/**
+ * this function is a POSIX compliant version, which will seek the offset for an
+ * open file descriptor.
+ *
+ * @param fd the file descriptor.
+ * @param offset the offset to be seeked.
+ * @param whence the directory of seek.
+ *
+ * @return the current file position, or -1 on failed.
+ */
+off_t lseek(int fd, off_t offset, int whence)
+{
+	int result;
+	struct dfs_fd* d;
+
+	d  = fd_get(fd);
+	if (d == RT_NULL)
+	{
+		rt_set_errno(-RT_ERROR);
+		return -1;
+	}
+
+	switch (whence)
+	{
+	case DFS_SEEK_SET:
+		break;
+
+	case DFS_SEEK_CUR:
+		offset += d->pos;
+		break;
+
+	case DFS_SEEK_END:
+		offset += d->size;
+		break;
+	}
+
+	if( offset < 0 )
+	{
+		rt_set_errno(EINVAL);
+		return -1;
+	}
+	result = dfs_file_lseek(d, offset);
+	if (result < 0)
+	{
+		rt_set_errno(result);
+		fd_put(d);
+		return -1;
+	}
+
+	/* release the ref-count of fd */
+	fd_put(d);
+	return offset;
+}
+
+/**
+ * this function is a POSIX compliant version, which will rename old file name to
+ * new file name.
+ *
+ * @param old the old file name.
+ * @param new the new file name.
+ *
+ * @return 0 on successful, -1 on failed.
+ *
+ * note: the old and new file name must be belong to a same file system.
+ */
+int rename(const char* old, const char* new)
+{
+	int result;
+
+	result = dfs_file_rename(old, new);
+	if (result < 0)
+	{
+		rt_set_errno(result);
+		return -1;
+	}
+	return 0;
+}
+
+/**
+ * this function is a POSIX compliant version, which will unlink (remove) a 
+ * specified path file from file system.
+ * 
+ * @param pathname the specified path name to be unlinked.
+ *
+ * @return 0 on successful, -1 on failed.
+ */
+int unlink(const char *pathname)
+{
+	int result;
+
+	result = dfs_file_unlink(pathname);
+	if (result < 0)
+	{
+		rt_set_errno(result);
+		return -1;
+	}
+	return 0;
+}
+
+/**
+ * this function is a POSIX compliant version, which will get file information.
+ * 
+ * @param file the file name
+ * @param buf the data buffer to save stat description.
+ *
+ * @return 0 on successful, -1 on failed.
+ */
+int stat(const char *file, struct stat *buf)
+{
+	int result;
+
+	result = dfs_file_stat(file, buf);
+	if (result < 0)
+	{
+		rt_set_errno(result);
+		return -1;
+	}
+	return result;
+}
+
+/**
+ * this function is a POSIX compliant version, which will get file status.
+ *
+ * @param fildes the file description
+ * @param buf the data buffer to save stat description.
+ */
+int fstat(int fildes, struct stat *buf)
+{
+	struct dfs_fd* d;
+
+	/* get the fd */
+	d  = fd_get(fildes);
+	if (d == RT_NULL)
+	{
+		rt_set_errno(-RT_ERROR);
+		return -1;
+	}
+
+	/* it's the root directory */
+	buf->st_dev   = 0;
+
+	buf->st_mode = DFS_S_IFREG | DFS_S_IRUSR | DFS_S_IRGRP | DFS_S_IROTH |
+			DFS_S_IWUSR | DFS_S_IWGRP | DFS_S_IWOTH;
+	if (d->type == FT_DIRECTORY)
+	{
+		buf->st_mode &= ~DFS_S_IFREG;
+		buf->st_mode |= DFS_S_IFDIR | DFS_S_IXUSR | DFS_S_IXGRP | DFS_S_IXOTH;
+	}
+
+	buf->st_size  = d->size;
+	buf->st_mtime = 0;
+	buf->st_blksize = 512;
+
+	fd_put(d);
+
+	return DFS_STATUS_OK;
+}
+
+/**
+ * this function is a POSIX compliant version, which will return the 
+ * information about a mounted file system.
+ * 
+ * @param path the path which mounted file system.
+ * @param buf the buffer to save the returned information.
+ *
+ * @return 0 on successful, others on failed.
+ */
+int statfs(const char *path, struct statfs *buf)
+{
+	int result;
+
+	result = dfs_statfs(path, buf);
+	if (result < 0)
+	{
+		rt_set_errno(result);
+		return -1;
+	}
+
+	return result;
+}
+
+/**
+ * this function is a POSIX compliant version, which will make a directory
+ *
+ * @param path the directory path to be made.
+ * @param mode 
+ *
+ * @return 0 on successful, others on failed.
+ */
+int mkdir (const char *path, mode_t mode)
+{
+	int fd;
+	struct dfs_fd* d;
+	int result;
+
+	fd = fd_new();
+	if (fd == -1) { rt_kprintf("no fd\n"); return -1; }
+
+	d = fd_get(fd);
+
+	result = dfs_file_open(d, path, DFS_O_DIRECTORY | DFS_O_CREAT);
+
+	if (result < 0)
+	{
+		rt_set_errno(result);
+		fd_put(d);
+		return -1;
+	}
+
+	dfs_file_close(d);
+	fd_put(d);
+	return 0;
+}
+#ifdef RT_USING_FINSH
+#include <finsh.h>
+FINSH_FUNCTION_EXPORT(mkdir, create a directory);
+#endif
+
+/**
+ * this function is a POSIX compliant version, which will remove a directory.
+ *
+ * @param pathname the path name to be removed.
+ * 
+ * @return 0 on sucessfull, others on failed.
+ */
+int rmdir(const char *pathname)
+{
+	int result;
+
+	result = dfs_file_unlink(pathname);
+	if (result < 0)
+	{
+		rt_set_errno(result);
+		return -1;
+	}
+
+	return 0;
+}
+
+/**
+ * this function is a POSIX compliant version, which will open a directory.
+ *
+ * @param name the path name to be open.
+ *
+ * @return the DIR pointer of directory, NULL on open failed.
+ */
+DIR* opendir(const char* name)
+{
+	struct dfs_fd* d;
+	int fd, result;
+	DIR* t;
+
+	t = RT_NULL;
+
+	/* allocate a fd */
+	fd = fd_new();
+	if (fd == -1) { rt_kprintf("no fd\n"); return RT_NULL; }
+	d  = fd_get(fd);
+
+	result = dfs_file_open(d, name, DFS_O_RDONLY | DFS_O_DIRECTORY);
+	if (result >= 0)
+	{
+		/* open successfully */
+		t = (DIR *) rt_malloc (sizeof(DIR));
+		if (t == RT_NULL)
+		{
+			dfs_file_close(d);
+			fd_put(d);
+		}
+		else
+		{
+		    rt_memset(t, 0, sizeof(DIR));
+		    t->fd = fd;
+		}
+		fd_put(d);
+		return t;
+	}
+
+	/* open failed */
+	fd_put(d);
+	fd_put(d);
+	rt_set_errno(result);
+
+	return RT_NULL;
+}
+
+/**
+ * this function is a POSIX compliant version, which will return a pointer 
+ * to a dirent structure representing the next directory entry in the 
+ * directory stream.
+ *
+ * @param d the directory stream pointer.
+ *
+ * @return the next directory entry, NULL on the end of directory or failed.
+ */
+struct dirent* readdir(DIR *d)
+{
+	int result;
+	struct dfs_fd* fd;
+
+	fd = fd_get(d->fd);
+	if (fd == RT_NULL)
+	{
+		rt_set_errno(-RT_ERROR);
+		return RT_NULL;
+	}
+
+	if (!d->num || (d->cur += ((struct dirent*)(d->buf + d->cur))->d_reclen) >= d->num)
+	{
+		/* get a new entry */
+		result = dfs_file_getdents(fd, (struct dirent*)d->buf, sizeof(d->buf) - 1);
+		if (result <= 0)
+		{
+			rt_set_errno(result);
+			fd_put(fd);
+
+			return RT_NULL;
+		}
+
+		d->num = result;
+		d->cur = 0; /* current entry index */
+	}
+
+	fd_put(fd);
+	return (struct dirent*)(d->buf+d->cur);
+}
+
+/**
+ * this function is a POSIX compliant version, which will return current 
+ * location in directory stream.
+ * 
+ * @param d the directory stream pointer.
+ *
+ * @return the current location in directory stream.
+ */
+long telldir(DIR *d)
+{
+	struct dfs_fd* fd;
+	long result;
+
+	fd = fd_get(d->fd);
+	if (fd == RT_NULL)
+	{
+		rt_set_errno(-RT_ERROR);
+		return 0;
+	}
+
+	result = fd->pos - d->num + d->cur;
+	fd_put(fd);
+
+	return result;
+}
+
+/**
+ * this function is a POSIX compliant version, which will set position of 
+ * next directory structure in the directory stream.
+ *
+ * @param d the directory stream.
+ * @param offset the offset in directory stream.
+ */
+void seekdir(DIR *d, off_t offset)
+{
+	struct dfs_fd* fd;
+
+	fd = fd_get(d->fd);
+	if (fd == RT_NULL)
+	{
+		rt_set_errno(-RT_ERROR);
+		return ;
+	}
+
+	/* seek to the offset position of directory */
+	if (dfs_file_lseek(fd, offset) >= 0) d->num = d->cur = 0;
+	fd_put(fd);
+}
+
+/**
+ * this function is a POSIX compliant version, which will reset directory stream.
+ *
+ * @param d the directory stream.
+ */
+void rewinddir(DIR *d)
+{
+	struct dfs_fd* fd;
+
+	fd = fd_get(d->fd);
+	if (fd == RT_NULL)
+	{
+		rt_set_errno(-RT_ERROR);
+		return ;
+	}
+
+	/* seek to the beginning of directory */
+	if (dfs_file_lseek(fd, 0) >= 0) d->num = d->cur = 0;
+	fd_put(fd);
+}
+
+/**
+ * this function is a POSIX compliant version, which will close a directory 
+ * stream.
+ * 
+ * @param d the directory stream.
+ *
+ * @return 0 on successful, -1 on failed.
+ */
+int closedir(DIR* d)
+{
+	int result;
+	struct dfs_fd* fd;
+
+	fd = fd_get(d->fd);
+	if (fd == RT_NULL)
+	{
+		rt_set_errno(-RT_ERROR);
+		return -1;
+	}
+
+	result = dfs_file_close(fd);
+	fd_put(fd);
+
+	fd_put(fd);
+	rt_free(d);
+
+	if (result < 0)
+	{
+		rt_set_errno(result);
+		return -1;
+	}
+	else return 0;
+}
+
+#ifdef DFS_USING_WORKDIR
+/**
+ * this function is a POSIX compliant version, which will change working directory.
+ * 
+ * @param path the path name to be changed to.
+ *
+ * @return 0 on successful, -1 on failed.
+ */
+int chdir(const char *path)
+{
+	char* fullpath;
+	DIR* d;
+
+	if(path == RT_NULL)
+	{
+		dfs_lock();
+		rt_kprintf("%s\n", working_directory);
+		dfs_unlock();
+		return 0;
+	}
+
+	if (rt_strlen(path) > DFS_PATH_MAX)
+		return -1;
+
+	fullpath = dfs_normalize_path(NULL, path);
+	if (fullpath == RT_NULL)
+		return -1; /* build path failed */
+
+	dfs_lock();
+	d = opendir(fullpath);
+	if (d == RT_NULL)
+	{
+		rt_free(fullpath);
+		/* this is a not exist directory */
+		dfs_unlock();
+		return -1;
+	}
+
+	/* close directory stream */
+	closedir(d);
+
+	/* copy full path to working directory */
+	strncpy(working_directory, fullpath, DFS_PATH_MAX);
+	rt_free(fullpath); /* release normalize directory path name */
+
+	dfs_unlock();
+
+	return 0;
+}
+#ifdef RT_USING_FINSH
+FINSH_FUNCTION_EXPORT_ALIAS(chdir, cd, change current working directory);
+#endif
+#endif
+
+/**
+ * this function is a POSIX compliant version, which will return current 
+ * working directory.
+ *
+ * @param buf the returned current directory.
+ * @param size the buffer size.
+ *
+ * @return the returned current directory.
+ */
+char *getcwd(char *buf, size_t size)
+{
+#ifdef DFS_USING_WORKDIR
+	rt_enter_critical();
+	rt_strncpy(buf, working_directory, size);
+	rt_exit_critical();
+#else
+	rt_kprintf("WARNING: not support working directory\n");
+#endif
+	return buf;
+}
+
+/* @} */