Class Kernel

close(int): Closes the specified file descriptor.
creat(String, short): Creates a file or directory with the specified mode.
exit(int): Terminate the current "process".
finalize(int): End the simulation and exit.
fstat(int, Stat): Obtain information for an open file.
getErrno(): Get the value of errno for the current process.
initialize(): Initialize the file simulator kernel.
lseek(int, int, int): Set the current file pointer for a file.
open(String, int): Opens a file or directory for reading, writing, or both reading and writing.
perror(String): Prints a system error message.
read(int, byte[], int): Read bytes from a file.
readdir(int, DirectoryEntry): Reads a directory entry from a file descriptor for an open directory.
setErrno(int): Set the value of errno for the current process.
stat(String, Stat): Obtain information about a named file.
sync(): First commits inodes to buffers, and then buffers to disk.
write(int, byte[], int): Write bytes to a file.
writedir(int, DirectoryEntry): Writes a directory entry from a file descriptor for an open directory.

PROGRAM_NAME

 public static final String PROGRAM_NAME

The name this program uses when displaying any error messages it generates internally.

EPERM

 public static final int EPERM

Not owner.

ENOENT

 public static final int ENOENT

No such file or directory.

EBADF

 public static final int EBADF

Bad file number.

EACCES

 public static final int EACCES

Permission denied.

EEXIST

 public static final int EEXIST

File exists.

EXDEV

 public static final int EXDEV

Cross-device link.

ENOTDIR

 public static final int ENOTDIR

Not a directory.

EISDIR

 public static final int EISDIR

Is a directory.

EINVAL

 public static final int EINVAL

Invalid argument.

ENFILE

 public static final int ENFILE

File table overflow.

EMFILE

 public static final int EMFILE

Too many open files.

EFBIG

 public static final int EFBIG

File too large.

ENOSPC

 public static final int ENOSPC

No space left on device.

EROFS

 public static final int EROFS

Read-only file system.

EMLINK

 public static final int EMLINK

Too many links.

sys_nerr

 public static final int sys_nerr

Number of errors messages defined in sys_errlist

Simulates unix system variable:

   int sys_nerr;

sys_errlist

 public static final String sys_errlist[]

The array of kernel error messages.

Simulates unix system variable:

   const char *sys_errlist[];

S_IFMT

 public static final short S_IFMT

File type mask

S_IFREG

 public static final short S_IFREG

Regular file

S_IFMPB

 public static final short S_IFMPB

Multiplexed block special

S_IFBLK

 public static final short S_IFBLK

Block Special

S_IFDIR

 public static final short S_IFDIR

Directory

S_IFMPC

 public static final short S_IFMPC

Multiplexed character special

S_IFCHR

 public static final short S_IFCHR

Character special

S_ISUID

 public static final short S_ISUID

Set user id on execution

S_ISGID

 public static final short S_ISGID

Set group id on execution

S_ISVTX

 public static final short S_ISVTX

Save swapped text even after use

S_IRWXU

 public static final short S_IRWXU

User (file owner) has read, write and execute permission

S_IRUSR

 public static final short S_IRUSR

User has read permission

S_IREAD

 public static final short S_IREAD

User has read permission

S_IWUSR

 public static final short S_IWUSR

User has write permission

S_IWRITE

 public static final short S_IWRITE

User has write permission

S_IXUSR

 public static final short S_IXUSR

User has execute permission

S_IEXEC

 public static final short S_IEXEC

User has execute permission

S_IRWXG

 public static final short S_IRWXG

Group has read, write and execute permission

S_IRGRP

 public static final short S_IRGRP

Group has read permission

S_IWGRP

 public static final short S_IWGRP

Group has write permission

S_IXGRP

 public static final short S_IXGRP

Group has execute permission

S_IRWXO

 public static final short S_IRWXO

Others have read, write and execute permission

S_IROTH

 public static final short S_IROTH

Others have read permission

S_IWOTH

 public static final short S_IWOTH

Others have write permisson

S_IXOTH

 public static final short S_IXOTH

Others have execute permission

O_RDONLY

 public static final int O_RDONLY

Open with read-only access.

O_WRONLY

 public static final int O_WRONLY

Open with write-only access.

O_RDWR

 public static final int O_RDWR

Open for read or write access.

MAX_OPEN_FILE_SYSTEMS

 public static int MAX_OPEN_FILE_SYSTEMS

openFileSystems

 public static FileSystem openFileSystems[]

ROOT_FILE_SYSTEM

 public static short ROOT_FILE_SYSTEM

Kernel

 public Kernel()

perror

 public static void perror(String s)

Prints a system error message. The actual text written to stderr is the given string, followed by a colon, a space, the message text, and a newline. It is customary to give the name of the program as the argument to perror.

Parameters:: s - the program name

setErrno

 public static void setErrno(int newErrno)

Set the value of errno for the current process.

Simulates the unix variable:

   extern int errno ;

See Also:: getErrno

getErrno

 public static int getErrno()

Get the value of errno for the current process.

Simulates the unix variable:

   extern int errno ;

See Also:: setErrno

close

 public static int close(int fd)

Closes the specified file descriptor.

Simulates the unix system call:

   int close(int fd);

Parameters:: fd - the file descriptor of the file to close
Returns:: Zero if the file is closed; -1 if the file descriptor is invalid.

creat

 public static int creat(String pathname,
                         short mode) throws Exception

Creates a file or directory with the specified mode.

Creates a new file or prepares to rewrite an existing file. If the file does not exist, it is given the mode specified. If the file does exist, it is truncated to length zero. The file is opened for writing and its file descriptor is returned.

Simulates the unix system call:

   int creat(const char *pathname, mode_t mode);

Parameters:: pathname - the name of the file or directory to create; mode - the file or directory protection mode for the new file
Returns:: the file descriptor (a non-negative integer); -1 if a needed directory is not searchable, if the file does not exist and the directory in which it is to be created is not writable, if the file does exist and is unwritable, if the file is a directory, or if there are already too many open files.
Throws: Exception: if any underlying action causes an exception to be thrown

exit

 public static void exit(int status) throws Exception

Terminate the current "process". Any open files will be closed.

Simulates the unix system call:

   exit(int status);

Note: If this is the last process to terminate, this method calls finalize().

Parameters:: status - the exit status
Throws: Exception: if any underlying Exception is thrown

lseek

 public static int lseek(int fd,
                         int offset,
                         int whence)

Set the current file pointer for a file. The current file position is updated based on the values of offset and whence. If whence is 0, the new position is offset bytes from the beginning of the file. If whence is 1, the new position is the current position plus the value of offset. If whence is 2, the new position is the size of the file plus the offset value. Note that offset may be negative if whence is 1 or 2, as long as the resulting position is not less than zero. It is valid to position past the end of the file, but it is not valid to read past the end of the file.

Simulates the unix system call:

   lseek( int filedes , int offset , int whence );

Parameters:: fd - the file descriptor; offset - the offset; whence - 0 = from beginning of file; 1 = from current position ; 2 = from end of file

open

 public static int open(String pathname,
                        int flags) throws Exception

Opens a file or directory for reading, writing, or both reading and writing.

The file is positioned at the beginning (byte 0). The returned file descriptor must be used for subsequent calls for other input and output functions on the file.

Simulates the unix system call:

   int open(const char *pathname, int flags );

Parameters:: pathname - the name of the file or directory to create; flags - the flags to use when opening the file: O_RDONLY, O_WRONLY, or O_RDWR.
Returns:: the file descriptor (a non-negative integer); -1 if the file does not exist, if one of the necessary directories does not exist or is unreadable, if the file is not readable (resp. writable), or if too many files are open.
Throws: Exception: if any underlying action causes an exception to be thrown

read

 public static int read(int fd,
                        byte buf[],
                        int count) throws Exception

Read bytes from a file.

Simulates the unix system call:

   int read(int fd, void *buf, size_t count);

Parameters:: fd - the file descriptor of a file open for reading; buf - an array of bytes into which bytes are read; count - the number of bytes to read from the file
Returns:: the number of bytes actually read; or -1 if an error occurs.
Throws: Exception: if any underlying action causes Exception to be thrown

readdir

 public static int readdir(int fd,
                           DirectoryEntry dirp) throws Exception

Reads a directory entry from a file descriptor for an open directory.

Simulates the unix system call:

   int readdir(unsigned int fd, struct dirent *dirp ) ;

Note that count is ignored in the unix call.

Parameters:: fd - the file descriptor for the directory being read; dirp - the directory entry into which data should be copied
Returns:: number of bytes read; 0 if end of directory; -1 if the file descriptor is invalid, or if the file is not opened for read access.
Throws: Exception: if any underlying action causes Exception to be thrown

fstat

 public static int fstat(int fd,
                         Stat buf) throws Exception

Obtain information for an open file.

Simulates the unix system call:

   int fstat(int filedes, struct stat *buf);

Throws: Exception: if any underlying action causes Exception to be thrown

stat

 public static int stat(String name,
                        Stat buf) throws Exception

Obtain information about a named file.

Simulates the unix system call:

   int stat(const char *name, struct stat *buf);

Throws: Exception: if any underlying action causes Exception to be thrown

sync

 public static void sync()

First commits inodes to buffers, and then buffers to disk.

Simulates unix system call:

   int sync(void);

write

 public static int write(int fd,
                         byte buf[],
                         int count) throws Exception

Write bytes to a file.

Simulates the unix system call:

   int write(int fd, const void *buf, size_t count);

Throws: Exception: if any underlying action causes Exception to be thrown

writedir

 public static int writedir(int fd,
                            DirectoryEntry dirp) throws Exception

Writes a directory entry from a file descriptor for an open directory.

Simulates the unix system call:

   int readdir(unsigned int fd, struct dirent *dirp ) ;

Note that count is ignored in the unix call.

Parameters:: fd - the file descriptor for the directory being read; dirp - the directory entry into which data should be copied
Returns:: number of bytes read; 0 if end of directory; -1 if the file descriptor is invalid, or if the file is not opened for read access.
Throws: Exception: if any underlying action causes Exception to be thrown

initialize

 public static void initialize()

Initialize the file simulator kernel. This should be the first call in any simulation program. You can think of this as the method which "boots" the kernel. This method opens the "filesys.conf" file (or the file named by the system property "filesys.conf") and reads any properties given in that file, including the filesystem.root.filename and filesystem.root.mode ("r", "rw").

finalize

 public static void finalize(int status) throws Exception

End the simulation and exit. Terminates any remaining "processes", flushes all file system blocks to "disk", and exit the simulation program. This method is generally called by exit() when the last process terminates. However, it may also be called directly to gracefully end the simlation.

Parameters:: status - the status to use with System.exit()
Throws: Exception: if any underlying operation causes and exception to be thrown.