fuse_lowlevel.h

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/**
 * 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
 */
int fuse_reply_buf(fuse_req_t req, const char *buf, size_t size);

/**
 * Reply with data vector
 *
 * Possible requests:
 *   read, readdir, getxattr, listxattr
 *
 * @param req request handle
 * @param iov the vector containing the data
 * @param count the size of vector
 * @return zero for success, -errno for failure to send reply
 */
int fuse_reply_iov(fuse_req_t req, const struct iovec *iov, int count);

/**
 * Reply with filesystem statistics
 *
 * Possible requests:
 *   statfs
 *
 * @param req request handle
 * @param stbuf filesystem statistics
 * @return zero for success, -errno for failure to send reply
 */
int fuse_reply_statfs(fuse_req_t req, const struct statvfs *stbuf);

/**
 * Reply with needed buffer size
 *
 * Possible requests:
 *   getxattr, listxattr
 *
 * @param req request handle
 * @param count the buffer size needed in bytes
 * @return zero for success, -errno for failure to send reply
 */
int fuse_reply_xattr(fuse_req_t req, size_t count);

/**
 * Reply with file lock information
 *
 * Possible requests:
 *   getlk
 *
 * @param req request handle
 * @param lock the lock information
 * @return zero for success, -errno for failure to send reply
 */
int fuse_reply_lock(fuse_req_t req, struct flock *lock);

/**
 * Reply with block index
 *
 * Possible requests:
 *   bmap
 *
 * @param req request handle
 * @param idx block index within device 
 * @return zero for success, -errno for failure to send reply
 */
int fuse_reply_bmap(fuse_req_t req, uint64_t idx);

/* ----------------------------------------------------------- *
 * Filling a buffer in readdir                                 *
 * ----------------------------------------------------------- */

/**
 * Add a directory entry to the buffer
 *
 * Buffer needs to be large enough to hold the entry.  Of it's not,
 * then the entry is not filled in but the size of the entry is still
 * returned.  The caller can check this by comparing the bufsize
 * parameter with the returned entry size.  If the entry size is
 * larger than the buffer size, the operation failed.
 *
 * From the 'stbuf' argument the st_ino field and bits 12-15 of the
 * st_mode field are used.  The other fields are ignored.
 *
 * Note: offsets do not necessarily represent physical offsets, and
 * could be any marker, that enables the implementation to find a
 * specific point in the directory stream.
 *
 * @param req request handle
 * @param buf the point where the new entry will be added to the buffer
 * @param bufsize remaining size of the buffer
 * @param the name of the entry
 * @param stbuf the file attributes
 * @param off the offset of the next entry
 * @return the space needed for the entry
 */
size_t fuse_add_direntry(fuse_req_t req, char *buf, size_t bufsize,
                         const char *name, const struct stat *stbuf,
                         off_t off);

/* ----------------------------------------------------------- *
 * Utility functions                                           *
 * ----------------------------------------------------------- */

/**
 * Get the userdata from the request
 *
 * @param req request handle
 * @return the user data passed to fuse_lowlevel_new()
 */
void *fuse_req_userdata(fuse_req_t req);

/**
 * Get the context from the request
 *
 * The pointer returned by this function will only be valid for the
 * request's lifetime
 *
 * @param req request handle
 * @return the context structure
 */
const struct fuse_ctx *fuse_req_ctx(fuse_req_t req);

/**
 * Callback function for an interrupt
 *
 * @param req interrupted request
 * @param data user data
 */
typedef void (*fuse_interrupt_func_t)(fuse_req_t req, void *data);

/**
 * Register/unregister callback for an interrupt
 *
 * If an interrupt has already happened, then the callback function is
 * called from within this function, hence it's not possible for
 * interrupts to be lost.
 *
 * @param req request handle
 * @param func the callback function or NULL for unregister
 * @parm data user data passed to the callback function
 */
void fuse_req_interrupt_func(fuse_req_t req, fuse_interrupt_func_t func,
                             void *data);

/**
 * Check if a request has already been interrupted
 *
 * @param req request handle
 * @return 1 if the request has been interrupted, 0 otherwise
 */
int fuse_req_interrupted(fuse_req_t req);

/* ----------------------------------------------------------- *
 * Filesystem setup                                            *
 * ----------------------------------------------------------- */

/**
 * Create a low level session
 *
 * @param args argument vector
 * @param op the low level filesystem operations
 * @param op_size sizeof(struct fuse_lowlevel_ops)
 * @param userdata user data
 * @return the created session object, or NULL on failure
 */
struct fuse_session *fuse_lowlevel_new(struct fuse_args *args,
                                       const struct fuse_lowlevel_ops *op,
                                       size_t op_size, void *userdata);

/* ----------------------------------------------------------- *
 * Session interface                                           *
 * ----------------------------------------------------------- */

/**
 * Session operations
 *
 * This is used in session creation
 */
struct fuse_session_ops {
    /**
     * Hook to process a request (mandatory)
     *
     * @param data user data passed to fuse_session_new()
     * @param buf buffer containing the raw request
     * @param len request length
     * @param ch channel on which the request was received
     */
    void (*process) (void *data, const char *buf, size_t len,
                     struct fuse_chan *ch);

    /**
     * Hook for session exit and reset (optional)
     *
     * @param data user data passed to fuse_session_new()
     * @param val exited status (1 - exited, 0 - not exited)
     */
    void (*exit) (void *data, int val);

    /**
     * Hook for querying the current exited status (optional)
     *
     * @param data user data passed to fuse_session_new()
     * @return 1 if exited, 0 if not exited
     */
    int (*exited) (void *data);

    /**
     * Hook for cleaning up the channel on destroy (optional)
     *
     * @param data user data passed to fuse_session_new()
     */
    void (*destroy) (void *data);
};

/**
 * Create a new session
 *
 * @param op session operations
 * @param data user data
 * @return new session object, or NULL on failure
 */
struct fuse_session *fuse_session_new(struct fuse_session_ops *op, void *data);

/**
 * Assign a channel to a session
 *
 * Note: currently only a single channel may be assigned.  This may
 * change in the future
 *
 * If a session is destroyed, the assigned channel is also destroyed
 *
 * @param se the session
 * @param ch the channel
 */
void fuse_session_add_chan(struct fuse_session *se, struct fuse_chan *ch);

/**
 * Remove a channel from a session
 *
 * If the channel is not assigned to a session, then this is a no-op
 *
 * @param ch the channel to remove
 */
void fuse_session_remove_chan(struct fuse_chan *ch);

/**
 * Iterate over the channels assigned to a session
 *
 * The iterating function needs to start with a NULL channel, and
 * after that needs to pass the previously returned channel to the
 * function.
 *
 * @param se the session
 * @param ch the previous channel, or NULL
 * @return the next channel, or NULL if no more channels exist
 */
struct fuse_chan *fuse_session_next_chan(struct fuse_session *se,
                                         struct fuse_chan *ch);

/**
 * Process a raw request
 *
 * @param se the session
 * @param buf buffer containing the raw request
 * @param len request length
 * @param ch channel on which the request was received
 */
void fuse_session_process(struct fuse_session *se, const char *buf, size_t len,
                          struct fuse_chan *ch);

/**
 * Destroy a session
 *
 * @param se the session
 */
void fuse_session_destroy(struct fuse_session *se);

/**
 * Exit a session
 *
 * @param se the session
 */
void fuse_session_exit(struct fuse_session *se);

/**
 * Reset the exited status of a session
 *
 * @param se the session
 */
void fuse_session_reset(struct fuse_session *se);

/**
 * Query the exited status of a session
 *
 * @param se the session
 * @return 1 if exited, 0 if not exited
 */
int fuse_session_exited(struct fuse_session *se);

/**
 * Enter a single threaded event loop
 *
 * @param se the session
 * @return 0 on success, -1 on error
 */
int fuse_session_loop(struct fuse_session *se);

/**
 * Enter a multi-threaded event loop
 *
 * @param se the session
 * @return 0 on success, -1 on error
 */
int fuse_session_loop_mt(struct fuse_session *se);

/* ----------------------------------------------------------- *
 * Channel interface                                           *
 * ----------------------------------------------------------- */

/**
 * Channel operations
 *
 * This is used in channel creation
 */
struct fuse_chan_ops {
    /**
     * Hook for receiving a raw request
     *
     * @param ch pointer to the channel
     * @param buf the buffer to store the request in
     * @param size the size of the buffer
     * @return the actual size of the raw request, or -1 on error
     */
    int (*receive)(struct fuse_chan **chp, char *buf, size_t size);

    /**
     * Hook for sending a raw reply
     *
     * A return value of -ENOENT means, that the request was
     * interrupted, and the reply was discarded
     *
     * @param ch the channel
     * @param iov vector of blocks
     * @param count the number of blocks in vector
     * @return zero on success, -errno on failure
     */
    int (*send)(struct fuse_chan *ch, const struct iovec iov[], size_t count);

    /**
     * Destroy the channel
     *
     * @param ch the channel
     */
    void (*destroy)(struct fuse_chan *ch);
};

/**
 * Create a new channel
 *
 * @param op channel operations
 * @param fd file descriptor of the channel
 * @param bufsize the minimal receive buffer size
 * @param data user data
 * @return the new channel object, or NULL on failure
 */
struct fuse_chan *fuse_chan_new(struct fuse_chan_ops *op, int fd,
                                size_t bufsize, void *data);

/**
 * Query the file descriptor of the channel
 *
 * @param ch the channel
 * @return the file descriptor passed to fuse_chan_new()
 */
int fuse_chan_fd(struct fuse_chan *ch);

/**
 * Query the minimal receive buffer size
 *
 * @param ch the channel
 * @return the buffer size passed to fuse_chan_new()
 */
size_t fuse_chan_bufsize(struct fuse_chan *ch);

/**
 * Query the user data
 *
 * @param ch the channel
 * @return the user data passed to fuse_chan_new()
 */
void *fuse_chan_data(struct fuse_chan *ch);

/**
 * Query the session to which this channel is assigned
 *
 * @param ch the channel
 * @return the session, or NULL if the channel is not assigned
 */
struct fuse_session *fuse_chan_session(struct fuse_chan *ch);

/**
 * Receive a raw request
 *
 * A return value of -ENODEV means, that the filesystem was unmounted
 *
 * @param ch pointer to the channel
 * @param buf the buffer to store the request in
 * @param size the size of the buffer
 * @return the actual size of the raw request, or -errno on error
 */
int fuse_chan_recv(struct fuse_chan **ch, char *buf, size_t size);

/**
 * Send a raw reply
 *
 * A return value of -ENOENT means, that the request was
 * interrupted, and the reply was discarded
 *
 * @param ch the channel
 * @param iov vector of blocks
 * @param count the number of blocks in vector
 * @return zero on success, -errno on failure
 */
int fuse_chan_send(struct fuse_chan *ch, const struct iovec iov[],
                   size_t count);

/**
 * Destroy a channel
 *
 * @param ch the channel
 */
void fuse_chan_destroy(struct fuse_chan *ch);

#ifdef __cplusplus
}
#endif

#endif /* _FUSE_LOWLEVEL_H_ */