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/*
 * Copyright (c) 2008 Jakub Jermar
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/** @addtogroup fs
 * @{
 */ 

#ifndef VFS_VFS_H_
#define VFS_VFS_H_

#include <ipc/ipc.h>
#include <libadt/list.h>
#include <atomic.h>
#include <rwlock.h>
#include <sys/types.h>
#include <bool.h>

#define dprintf(...)    printf(__VA_ARGS__)

#define VFS_FIRST   IPC_FIRST_USER_METHOD

#define IPC_METHOD_TO_VFS_OP(m) ((m) - VFS_FIRST)   

typedef enum {
    VFS_REGISTER = VFS_FIRST,
    VFS_MOUNT,
    VFS_UNMOUNT,
    VFS_LOOKUP,
    VFS_OPEN,
    VFS_CREATE,
    VFS_CLOSE,
    VFS_READ,
    VFS_WRITE,
    VFS_SEEK,
    VFS_RENAME,
    VFS_UNLINK,
    VFS_LAST,       /* keep this the last member of the enum */
} vfs_request_t;


/**
 * An instance of this structure is associated with a particular FS operation.
 * It tells VFS if the FS supports the operation or maybe if a default one
 * should be used.
 */
typedef enum {
    VFS_OP_NULL = 0,
    VFS_OP_DEFAULT,
    VFS_OP_DEFINED
} vfs_op_t;

#define FS_NAME_MAXLEN  20

/**
 * A structure like this is passed to VFS by each individual FS upon its
 * registration. It assosiates a human-readable identifier with each
 * registered FS. More importantly, through this structure, the FS announces
 * what operations it supports.
 */
typedef struct {
    /** Unique identifier of the fs. */
    char name[FS_NAME_MAXLEN + 1];
    
    /** Operations. */
    vfs_op_t ops[VFS_LAST - VFS_FIRST];
} vfs_info_t;

/**
 * A structure like this will be allocated for each registered file system.
 */
typedef struct {
    link_t fs_link;
    vfs_info_t vfs_info;
    int fs_handle;
    atomic_t phone_futex;   /**< Phone serializing futex. */
    ipcarg_t phone;
} fs_info_t;

/**
 * VFS_PAIR uniquely represents a file system instance.
 */
#define VFS_PAIR    \
    int fs_handle;  \
    int dev_handle; 

/**
 * VFS_TRIPLET uniquely identifies a file system node (e.g. directory, file) but
 * doesn't contain any state. For a stateful structure, see vfs_node_t.
 *
 * @note    fs_handle, dev_handle and index are meant to be returned in one
 *      IPC reply.
 */
#define VFS_TRIPLET \
    VFS_PAIR;   \
    uint64_t index;

typedef struct {
    VFS_PAIR;
} vfs_pair_t;

typedef struct {
    VFS_TRIPLET;
} vfs_triplet_t;

/**
 * Instances of this type represent an active, in-memory VFS node and any state
 * which may be associated with it.
 */
typedef struct {
    VFS_TRIPLET;        /**< Identity of the node. */
    unsigned refcnt;    /**< Usage counter. */
    link_t nh_link;     /**< Node hash-table link. */
    size_t size;        /**< Cached size of the file. */

    /**
     * Holding this rwlock prevents modifications of the node's contents.
     */
    rwlock_t contents_rwlock;
} vfs_node_t;

/**
 * Instances of this type represent an open file. If the file is opened by more
 * than one task, there will be a separate structure allocated for each task.
 */
typedef struct {
    /** Serializes access to this open file. */
    futex_t lock;

    vfs_node_t *node;
    
    /** Number of file handles referencing this file. */
    unsigned refcnt;

    /** Current position in the file. */
    off_t pos;
} vfs_file_t;

extern link_t fs_head;      /**< List of registered file systems. */

extern vfs_triplet_t rootfs;    /**< Root node of the root file system. */

#define MAX_PATH_LEN        (64 * 1024)

#define PLB_SIZE        (2 * MAX_PATH_LEN)

/** Each instance of this type describes one path lookup in progress. */
typedef struct {
    link_t  plb_link;   /**< Active PLB entries list link. */
    unsigned index;     /**< Index of the first character in PLB. */
    size_t len;     /**< Number of characters in this PLB entry. */
} plb_entry_t;

extern atomic_t plb_futex;  /**< Futex protecting plb and plb_head. */
extern uint8_t *plb;        /**< Path Lookup Buffer */
extern link_t plb_head;     /**< List of active PLB entries. */

/** Holding this rwlock prevents changes in file system namespace. */ 
extern rwlock_t namespace_rwlock;

extern int vfs_grab_phone(int);
extern void vfs_release_phone(int);

extern int fs_name_to_handle(char *, bool);

extern int vfs_lookup_internal(char *, size_t, vfs_triplet_t *, vfs_pair_t *);

extern bool vfs_nodes_init(void);
extern vfs_node_t *vfs_node_get(vfs_triplet_t *);
extern void vfs_node_put(vfs_node_t *);

#define MAX_OPEN_FILES  128

extern bool vfs_files_init(void);
extern vfs_file_t *vfs_file_get(int);
extern int vfs_fd_alloc(void);
extern void vfs_fd_free(int);

extern void vfs_file_addref(vfs_file_t *);
extern void vfs_file_delref(vfs_file_t *);

extern void vfs_node_addref(vfs_node_t *);
extern void vfs_node_delref(vfs_node_t *);

extern void vfs_register(ipc_callid_t, ipc_call_t *);
extern void vfs_mount(ipc_callid_t, ipc_call_t *);
extern void vfs_open(ipc_callid_t, ipc_call_t *);
extern void vfs_read(ipc_callid_t, ipc_call_t *);
extern void vfs_write(ipc_callid_t, ipc_call_t *);
extern void vfs_seek(ipc_callid_t, ipc_call_t *);

#endif

/**
 * @}
 */