/*    FUSE: Filesystem in Userspace    Copyright (C) 2001-2006  Miklos Szeredi <miklos@szeredi.hu>    This program can be distributed under the terms of the GNU LGPL.    See the file COPYING.LIB.*/#ifndef _FUSE_LOWLEVEL_H_#define _FUSE_LOWLEVEL_H_/* =========================================================== * * Low level API                                               * * =========================================================== *//* IMPORTANT: you should define FUSE_USE_VERSION before including this   header.  To use the newest API define it to 25 (recommended for any   new application), to use the old API define it to 24 (default) */#ifndef FUSE_USE_VERSION#define FUSE_USE_VERSION 24#endif#include "fuse_common.h"#include <utime.h>#include <sys/types.h>#include <sys/stat.h>#include <sys/statvfs.h>#include <sys/uio.h>#ifdef __cplusplusextern "C" {#endif/* ----------------------------------------------------------- * * Miscellaneous definitions                                   * * ----------------------------------------------------------- *//** The node ID of the root inode */#define FUSE_ROOT_ID 1/** Inode number type */typedef unsigned long fuse_ino_t;/** Request pointer type */typedef struct fuse_req *fuse_req_t;/** * Session * * This provides hooks for processing requests, and exiting */struct fuse_session;/** * Channel * * A communication channel, providing hooks for sending and receiving * messages */struct fuse_chan;/** Directory entry parameters supplied to fuse_reply_entry() */struct fuse_entry_param {    /** Unique inode number     *     * In lookup, zero means negative entry (from version 2.5)     * Returning ENOENT also means negative entry, but by setting zero     * ino the kernel may cache negative entries for entry_timeout     * seconds.     */    fuse_ino_t ino;    /** The ino/generation pair should be unique for the filesystem's        lifetime */    unsigned long generation;    /** Inode attributes */    struct stat attr;    /** Validity timeout (in seconds) for the attributes */    double attr_timeout;    /** Validity timeout (in seconds) for the name */    double entry_timeout;};/** Additional context associated with requests */struct fuse_ctx {    /** User ID of the calling process */    uid_t uid;    /** Group ID of the calling process */    gid_t gid;    /** Thread ID of the calling process */    pid_t pid;};/* 'to_set' flags in setattr */#define FUSE_SET_ATTR_MODE	(1 << 0)#define FUSE_SET_ATTR_UID	(1 << 1)#define FUSE_SET_ATTR_GID	(1 << 2)#define FUSE_SET_ATTR_SIZE	(1 << 3)#define FUSE_SET_ATTR_ATIME	(1 << 4)#define FUSE_SET_ATTR_MTIME	(1 << 5)/* ----------------------------------------------------------- * * Request methods and replies                                 * * ----------------------------------------------------------- *//** * Low level filesystem operations * * Most of the methods (with the exception of init and destroy) * receive a request handle (fuse_req_t) as their first argument. * This handle must be passed to one of the specified reply functions. * * This may be done inside the method invocation, or after the call * has returned.  The request handle is valid until one of the reply * functions is called. * * Other pointer arguments (name, fuse_file_info, etc) are not valid * after the call has returned, so if they are needed later, their * contents have to be copied. * * The filesystem sometimes needs to handle a return value of -ENOENT * from the reply function, which means, that the request was * interrupted, and the reply discarded.  For example if * fuse_reply_open() return -ENOENT means, that the release method for * this file will not be called. */struct fuse_lowlevel_ops {    /**     * Initialize filesystem     *     * Called before any other filesystem method     *     * There's no reply to this function     *     * @param userdata the user data passed to fuse_lowlevel_new()     */    void (*init) (void *userdata);    /**     * Clean up filesystem     *     * Called on filesystem exit     *     * There's no reply to this function     *     * @param userdata the user data passed to fuse_lowlevel_new()     */    void (*destroy) (void *userdata);    /**     * Look up a directory entry by name     *     * Valid replies:     *   fuse_reply_entry()     *   fuse_reply_err()     *     * @param req request handle     * @param parent inode number of the parent directory     * @param name the name to look up     */    void (*lookup) (fuse_req_t req, fuse_ino_t parent, const char *name);    /**     * Forget about an inode     *     * The nlookup parameter indicates the number of lookups     * previously performed on this inode.     *     * If the filesystem implements inode lifetimes, it is recommended     * that inodes acquire a single reference on each lookup, and lose     * nlookup references on each forget.     *     * The filesystem may ignore forget calls, if the inodes don't     * need to have a limited lifetime.     *     * On unmount it is not guaranteed, that all referenced inodes     * will receive a forget message.     *     * Valid replies:     *   fuse_reply_none()     *     * @param req request handle     * @param ino the inode number     * @param nlookup the number of lookups to forget     */    void (*forget) (fuse_req_t req, fuse_ino_t ino, unsigned long nlookup);    /**     * Get file attributes     *     * Valid replies:     *   fuse_reply_attr()     *   fuse_reply_err()     *     * @param req request handle     * @param ino the inode number     * @param fi for future use, currently always NULL     */    void (*getattr) (fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi);    /**     * Set file attributes     *     * In the 'attr' argument only members indicated by the 'to_set'     * bitmask contain valid values.  Other members contain undefined     * values.     *     * If the setattr was invoked from the ftruncate() system call     * under Linux kernel versions 2.6.15 or later, the fi->fh will     * contain the value set by the open method or will be undefined     * if the open method didn't set any value.  Otherwise (not     * ftruncate call, or kernel version earlier than 2.6.15) the fi     * parameter will be NULL.     *     * Valid replies:     *   fuse_reply_attr()     *   fuse_reply_err()     *     * @param req request handle     * @param ino the inode number     * @param attr the attributes     * @param to_set bit mask of attributes which should be set     * @param fi file information, or NULL     *     * Changed in version 2.5:     *     file information filled in for ftruncate     */    void (*setattr) (fuse_req_t req, fuse_ino_t ino, struct stat *attr,                    int to_set, struct fuse_file_info *fi);    /**     * Read symbolic link     *     * Valid replies:     *   fuse_reply_readlink     *   fuse_reply_err     *     * @param req request handle     * @param ino the inode number     */    void (*readlink) (fuse_req_t req, fuse_ino_t ino);    /**     * Create file node     *     * Create a regular file, character device, block device, fifo or     * socket node.     *     * Valid replies:     *   fuse_reply_entry     *   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 rdev the device number (only valid if created file is a device)     */    void (*mknod) (fuse_req_t req, fuse_ino_t parent, const char *name,                   mode_t mode, dev_t rdev);    /**     * Create a directory     *     * Valid replies:     *   fuse_reply_entry     *   fuse_reply_err     *     * @param req request handle     * @param parent inode number of the parent directory     * @param name to create     * @param mode with which to create the new file     */    void (*mkdir) (fuse_req_t req, fuse_ino_t parent, const char *name,                   mode_t mode);    /**     * Remove a file     *     * Valid replies:     *   fuse_reply_err     *     * @param req request handle     * @param parent inode number of the parent directory     * @param name to remove     */    void (*unlink) (fuse_req_t req, fuse_ino_t parent, const char *name);    /**     * Remove a directory     *     * Valid replies:     *   fuse_reply_err     *     * @param req request handle     * @param parent inode number of the parent directory     * @param name to remove     */    void (*rmdir) (fuse_req_t req, fuse_ino_t parent, const char *name);    /**     * Create a symbolic link     *     * Valid replies:     *   fuse_reply_entry     *   fuse_reply_err     *     * @param req request handle     * @param link the contents of the symbolic link     * @param parent inode number of the parent directory     * @param name to create     */    void (*symlink) (fuse_req_t req, const char *link, fuse_ino_t parent,                     const char *name);    /** Rename a file     *     * Valid replies:     *   fuse_reply_err     *     * @param req request handle     * @param parent inode number of the old parent directory     * @param name old name     * @param newparent inode number of the new parent directory     * @param newname new name     */    void (*rename) (fuse_req_t req, fuse_ino_t parent, const char *name,                    fuse_ino_t newparent, const char *newname);    /**     * Create a hard link     *     * Valid replies:     *   fuse_reply_entry     *   fuse_reply_err     *     * @param req request handle     * @param ino the old inode number     * @param newparent inode number of the new parent directory     * @param newname new name to create     */    void (*link) (fuse_req_t req, fuse_ino_t ino, fuse_ino_t newparent,                  const char *newname);    /**     * Open a file     *     * Open flags (with the exception of O_CREAT, O_EXCL, O_NOCTTY and     * O_TRUNC) 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).     *     * Filesystem may also implement stateless file I/O and not store     * anything in fi->fh.     *     * 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.     *     * Valid replies:     *   fuse_reply_open     *   fuse_reply_err     *     * @param req request handle     * @param ino the inode number     * @param fi file information     */    void (*open) (fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi);    /**     * Read data     *     * Read should send exactly the number of bytes requested except     * on EOF or error, otherwise the rest of the data will be     * substituted with zeroes.  An exception to this is when the file     * has been opened in 'direct_io' mode, in which case the return     * value of the read system call will reflect the return value of     * this operation.     *     * fi->fh will contain the value set by the open method, or will     * be undefined if the open 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 number of bytes to read     * @param off offset to read from     * @param fi file information     */    void (*read) (fuse_req_t req, fuse_ino_t ino, size_t size, off_t off,                  struct fuse_file_info *fi);    /**     * Write data     *     * Write should return exactly the number of bytes requested     * except on error.  An exception to this is when the file has     * been opened in 'direct_io' mode, in which case the return value     * of the write system call will reflect the return value of this     * operation.     *     * fi->fh will contain the value set by the open method, or will     * be undefined if the open method didn't set any value.     *     * Valid replies:     *   fuse_reply_write     *   fuse_reply_err     *     * @param req request handle     * @param ino the inode number