fuse_lowlevel.h

UNIX/LINUX下面的用户文件系统

     * @param buf data to write
     * @param size number of bytes to write
     * @param off offset to write to
     * @param fi file information
     */
    void (*write) (fuse_req_t req, fuse_ino_t ino, const char *buf,
                   size_t size, off_t off, struct fuse_file_info *fi);

    /**
     * Flush method
     *
     * This is called on each close() of the opened file.
     *
     * Since file descriptors can be duplicated (dup, dup2, fork), for
     * one open call there may be many flush calls.
     *
     * Filesystems shouldn't assume that flush will always be called
     * after some writes, or that if will be called at all.
     *
     * fi->fh will contain the value set by the open method, or will
     * be undefined if the open method didn't set any value.
     *
     * NOTE: the name of the method is misleading, since (unlike
     * fsync) the filesystem is not forced to flush pending writes.
     * One reason to flush data, is if the filesystem wants to return
     * write errors.
     *
     * Valid replies:
     *   fuse_reply_err
     *
     * @param req request handle
     * @param ino the inode number
     * @param fi file information
     */
    void (*flush) (fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi);

    /**
     * Release an open file
     *
     * Release is called when there are no more references to an open
     * file: all file descriptors are closed and all memory mappings
     * are unmapped.
     *
     * For every open call there will be exactly one release call.
     *
     * The filesystem may reply with an error, but error values are
     * not returned to close() or munmap() which triggered the
     * release.
     *
     * fi->fh will contain the value set by the open method, or will
     * be undefined if the open method didn't set any value.
     * fi->flags will contain the same flags as for open.
     *
     * Valid replies:
     *   fuse_reply_err
     *
     * @param req request handle
     * @param ino the inode number
     * @param fi file information
     */
    void (*release) (fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi);

    /**
     * Synchronize file contents
     *
     * If the datasync parameter is non-zero, then only the user data
     * should be flushed, not the meta data.
     *
     * Valid replies:
     *   fuse_reply_err
     *
     * @param req request handle
     * @param ino the inode number
     * @param datasync flag indicating if only data should be flushed
     * @param fi file information
     */
    void (*fsync) (fuse_req_t req, fuse_ino_t ino, int datasync,
                   struct fuse_file_info *fi);

    /**
     * Open a directory
     *
     * Filesystem may store an arbitrary file handle (pointer, index,
     * etc) in fi->fh, and use this in other all other directory
     * stream operations (readdir, releasedir, fsyncdir).
     *
     * Filesystem may also implement stateless directory I/O and not
     * store anything in fi->fh, though that makes it impossible to
     * implement standard conforming directory stream operations in
     * case the contents of the directory can change between opendir
     * and releasedir.
     *
     * Valid replies:
     *   fuse_reply_open
     *   fuse_reply_err
     *
     * @param req request handle
     * @param ino the inode number
     * @param fi file information
     */
    void (*opendir) (fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi);

    /**
     * Read directory
     *
     * Send a buffer filled using fuse_add_dirent(), with size not
     * exceeding the requested size.  Send an empty buffer on end of
     * stream.
     *
     * fi->fh will contain the value set by the opendir method, or
     * will be undefined if the opendir method didn't set any value.
     *
     * Valid replies:
     *   fuse_reply_buf
     *   fuse_reply_err
     *
     * @param req request handle
     * @param ino the inode number
     * @param size maximum number of bytes to send
     * @param off offset to continue reading the directory stream
     * @param fi file information
     */
    void (*readdir) (fuse_req_t req, fuse_ino_t ino, size_t size, off_t off,
                     struct fuse_file_info *fi);

    /**
     * Release an open directory
     *
     * For every opendir call there will be exactly one releasedir
     * call.
     *
     * Any errors sent by releasedir will be ignored.
     *
     * fi->fh will contain the value set by the opendir method, or
     * will be undefined if the opendir method didn't set any value.
     *
     * Valid replies:
     *   fuse_reply_err
     *
     * @param req request handle
     * @param ino the inode number
     * @param fi file information
     */
    void (*releasedir) (fuse_req_t req, fuse_ino_t ino,
                        struct fuse_file_info *fi);

    /**
     * Synchronize directory contents
     *
     * If the datasync parameter is non-zero, then only the directory
     * contents should be flushed, not the meta data.
     *
     * fi->fh will contain the value set by the opendir method, or
     * will be undefined if the opendir method didn't set any value.
     *
     * Valid replies:
     *   fuse_reply_err
     *
     * @param req request handle
     * @param ino the inode number
     * @param datasync flag indicating if only data should be flushed
     * @param fi file information
     */
    void (*fsyncdir) (fuse_req_t req, fuse_ino_t ino, int datasync,
                      struct fuse_file_info *fi);

    /**
     * Get file system statistics
     *
     * Valid replies:
     *   fuse_reply_statfs
     *   fuse_reply_err
     *
     * @param req request handle
     */
    void (*statfs) (fuse_req_t req);

    /**
     * Set an extended attribute
     *
     * Valid replies:
     *   fuse_reply_err
     */
    void (*setxattr) (fuse_req_t req, fuse_ino_t ino, const char *name,
                      const char *value, size_t size, int flags);

    /**
     * Get an extended attribute
     *
     * If size is zero, the size of the value should be sent with
     * fuse_reply_xattr.
     *
     * If the size is non-zero, and the value fits in the buffer, the
     * value should be sent with fuse_reply_buf.
     *
     * If the size is too small for the value, the ERANGE error should
     * be sent.
     *
     * Valid replies:
     *   fuse_reply_buf
     *   fuse_reply_xattr
     *   fuse_reply_err
     *
     * @param req request handle
     * @param ino the inode number
     * @param name of the extended attribute
     * @param size maximum size of the value to send
     */
    void (*getxattr) (fuse_req_t req, fuse_ino_t ino, const char *name,
                      size_t size);

    /**
     * List extended attribute names
     *
     * If size is zero, the total size of the attribute list should be
     * sent with fuse_reply_xattr.
     *
     * If the size is non-zero, and the null character separated
     * attribute list fits in the buffer, the list should be sent with
     * fuse_reply_buf.
     *
     * If the size is too small for the list, the ERANGE error should
     * be sent.
     *
     * Valid replies:
     *   fuse_reply_buf
     *   fuse_reply_xattr
     *   fuse_reply_err
     *
     * @param req request handle
     * @param ino the inode number
     * @param size maximum size of the list to send
     */
    void (*listxattr) (fuse_req_t req, fuse_ino_t ino, size_t size);

    /**
     * Remove an extended attribute
     *
     * Valid replies:
     *   fuse_reply_err
     *
     * @param req request handle
     * @param ino the inode number
     * @param name of the extended attribute
     */
    void (*removexattr) (fuse_req_t req, fuse_ino_t ino, const char *name);

    /**
     * Check file access permissions
     *
     * This will be called for the access() system call.  If the
     * 'default_permissions' mount option is given, this method is not
     * called.
     *
     * This method is not called under Linux kernel versions 2.4.x
     *
     * Introduced in version 2.5
     *
     * Valid replies:
     *   fuse_reply_err
     *
     * @param req request handle
     * @param ino the inode number
     * @param mask requested access mode
     */
    void (*access) (fuse_req_t req, fuse_ino_t ino, int mask);

    /**
     * Create and open a file
     *
     * If the file does not exist, first create it with the specified
     * mode, and then open it.
     *
     * Open flags (with the exception of O_NOCTTY) are available in
     * fi->flags.
     *
     * Filesystem may store an arbitrary file handle (pointer, index,
     * etc) in fi->fh, and use this in other all other file operations
     * (read, write, flush, release, fsync).
     *
     * There are also some flags (direct_io, keep_cache) which the
     * filesystem may set in fi, to change the way the file is opened.
     * See fuse_file_info structure in <fuse_common.h> for more details.
     *
     * If this method is not implemented or under Linux kernel
     * versions earlier than 2.6.15, the mknod() and open() methods
     * will be called instead.
     *
     * Introduced in version 2.5
     *
     * Valid replies:
     *   fuse_reply_create
     *   fuse_reply_err
     *
     * @param req request handle
     * @param parent inode number of the parent directory
     * @param name to create
     * @param mode file type and mode with which to create the new file
     * @param fi file information
     */
    void (*create) (fuse_req_t req, fuse_ino_t parent, const char *name,
                    mode_t mode, struct fuse_file_info *fi);
};

/**
 * Reply with an error code or success
 *
 * Possible requests:
 *   all except forget
 *
 * unlink, rmdir, rename, flush, release, fsync, fsyncdir, setxattr
 * and removexattr may send a zero code
 *
 * @param req request handle
 * @param err the positive error value, or zero for success
 * @return zero for success, -errno for failure to send reply
 */
int fuse_reply_err(fuse_req_t req, int err);

/**
 * Don't send reply
 *
 * Possible requests:
 *   forget
 *
 * @param req request handle
 */
void fuse_reply_none(fuse_req_t req);

/**
 * Reply with a directory entry
 *
 * Possible requests:
 *   lookup, mknod, mkdir, symlink, link
 *
 * @param req request handle
 * @param e the entry parameters
 * @return zero for success, -errno for failure to send reply
 */
int fuse_reply_entry(fuse_req_t req, const struct fuse_entry_param *e);

/**
 * Reply with a directory entry and open parameters
 *
 * currently the following members of 'fi' are used:
 *   fh, direct_io, keep_cache
 *
 * Possible requests:
 *   create
 *
 * @param req request handle
 * @param e the entry parameters
 * @param fi file information
 * @return zero for success, -errno for failure to send reply
 */
int fuse_reply_create(fuse_req_t req, const struct fuse_entry_param *e,
                      const struct fuse_file_info *fi);

/**
 * Reply with attributes
 *
 * Possible requests:
 *   getattr, setattr
 *
 * @param req request handle
 * @param the attributes
 * @param attr_timeout  validity timeout (in seconds) for the attributes
 * @return zero for success, -errno for failure to send reply
 */
int fuse_reply_attr(fuse_req_t req, const struct stat *attr,
                    double attr_timeout);

/**
 * Reply with the contents of a symbolic link
 *
 * Possible requests:
 *   readlink
 *
 * @param req request handle
 * @param link symbolic link contents
 * @return zero for success, -errno for failure to send reply
 */
int fuse_reply_readlink(fuse_req_t req, const char *link);

/**
 * Reply with open parameters
 *
 * currently the following members of 'fi' are used:
 *   fh, direct_io, keep_cache
 *
 * Possible requests:
 *   open, opendir
 *
 * @param req request handle
 * @param fi file information
 * @return zero for success, -errno for failure to send reply
 */
int fuse_reply_open(fuse_req_t req, const struct fuse_file_info *fi);

/**
 * Reply with number of bytes written
 *
 * Possible requests:
 *   write
 *
 * @param req request handle
 * @param count the number of bytes written
 * @return zero for success, -errno for failure to send reply
 */
int fuse_reply_write(fuse_req_t req, size_t count);

/**
 * Reply with data
 *
 * Possible requests:
 *   read, readdir, getxattr, listxattr
 *
 * @param req request handle
 * @param buf buffer containing data
 * @param size the size of data in bytes
 * @return zero for success, -errno for failure to send reply
 */