/*
 * Virtual filesystem structures and routines
 * Copyright (c) 2003, Jeffrey K. Hollingsworth <hollings@cs.umd.edu>
 * Copyright (c) 2003, David H. Hovemeyer <daveho@cs.umd.edu>
 * $Revision: 1.43 $
 * 
 * This is free software.  You are permitted to use,
 * redistribute, and modify it as specified in the file "COPYING".
 */

#ifndef GEEKOS_VFS_H
#define GEEKOS_VFS_H

#ifdef GEEKOS

#include <geekos/ktypes.h>
#include <geekos/list.h>
#include <geekos/fileio.h>
#include <geekos/blockdev.h>

/*
 * Returned by Read_Entry() function to indicate that there
 * are no more directory entries.
 */
#define VFS_NO_MORE_DIR_ENTRIES 1

struct Mount_Point;
struct File;
struct Mount_Point_Ops;
struct File_Ops;

/*
 * Operations providing support for formatting and mounting
 * filesystem instances.
 */
struct Filesystem_Ops {
    int (*Format)(struct Block_Device *blockDev);
    int (*Mount)(struct Mount_Point *mountPoint);
};

/* A mounted filesystem instance. */
struct Mount_Point {
    struct Mount_Point_Ops *ops; /* Operations that can be performed on the mount. */
    char *pathPrefix;		 /* Path prefix where fs is mounted. */
    struct Block_Device *dev;	 /* Block device filesystem is mounted on. */
    void *fsData;		 /* For use by the filesystem implementation. */
    DEFINE_LINK(Mount_Point_List, Mount_Point);
};

/* Operations that can be performed on a mounted filesystem. */
struct Mount_Point_Ops {
    int (*Open)(struct Mount_Point *mountPoint, const char *path, int mode, struct File **pFile);
    int (*Create_Directory)(struct Mount_Point *mountPoint, const char *path);
    int (*Open_Directory)(struct Mount_Point *mountPoint, const char *path, struct File **pDir);
    int (*Stat)(struct Mount_Point *mountPoint, const char *path, struct VFS_File_Stat *stat);
    int (*Sync)(struct Mount_Point *mountPoint);
    int (*Delete)(struct Mount_Point *mountPoint, const char *path);
    /* TODO: ACLs */
};

/* An opened file or directory. */
struct File {
    /*
     * Filesystem mount function is responsible for initializing
     * the following fields:
     */
    struct File_Ops *ops;	 /* Operations that can be performed on the file. */
    ulong_t filePos;		 /* Current position in the file. */
    ulong_t endPos;		 /* End position (i.e., the length of the file). */
    void *fsData;		 /* For use by the filesystem implementation. */

    /*
     * VFS Open(), Create_Directory(), and Open_Directory() functions
     * are responsible for initializing the following fields:
     */
    int mode;			 /* Mode (read vs. write). */
    struct Mount_Point *mountPoint; /* Mounted filesystem file is part of. */
};

/* Operations that can be performed on a File. */
struct File_Ops {
    int (*FStat)(struct File *file, struct VFS_File_Stat *stat);
    int (*Read)(struct File *file, void *buf, ulong_t numBytes);
    int (*Write)(struct File *file, void *buf, ulong_t numBytes);
    int (*Seek)(struct File *file, ulong_t pos);
    int (*Close)(struct File *file);
    int (*Read_Entry)(struct File *dir, struct VFS_Dir_Entry *entry);  /* Read next directory entry. */
};

/*
 * A mounted filesystem may register a contiguous range of sectors
 * as a paging device.  The disk space in the paging file will be
 * used to store the data of pages that have been temporarily evicted
 * due to a memory shortage.
 */
struct Paging_Device {
    char *fileName;		 /* Name of paging file. */
    struct Block_Device *dev;	 /* Block device for paging file. */
    ulong_t startSector;	 /* Start sector of paging file. */
    ulong_t numSectors;		 /* Number of sectors in paging file. */
};

/*
 * VFS functions.
 */

/* Filesystem operations. */
bool Register_Filesystem(const char *fsName, struct Filesystem_Ops *fsOps);
int Format(const char *devname, const char *fstype);
int Mount(const char *devname, const char *pathPrefix, const char *fstype);

/* Mount point operations. */
int Open(const char *path, int mode, struct File **pFile);
int Close(struct File *file);
int Stat(const char *path, struct VFS_File_Stat *stat);
int Sync(void);

/* File operations. */
struct File *Allocate_File(struct File_Ops *ops, int filePos, int endPos, void *fsData,
    int mode, struct Mount_Point *mountPoint);
int FStat(struct File *file, struct VFS_File_Stat *stat);
int Read(struct File *file, void *buf, ulong_t len);
int Write(struct File *file, void *buf, ulong_t len);
int Read_Fully(const char *path, void **pBuffer, ulong_t *pLen);

/* Directory operations. */
int Create_Directory(const char *path);
int Open_Directory(const char *path, struct File **pDir);
int Read_Entry(struct File *file, struct VFS_Dir_Entry *entry);

/*
 * Paging device functions.
 */
void Register_Paging_Device(struct Paging_Device *pagingDevice);
struct Paging_Device *Get_Paging_Device(void);

#endif /* GEEKOS */

#endif /* GEEKOS_VFS_H */