moss.fs
Interface MFileOps

All Known Implementing Classes:

MJavaConsole, MPipe, MRamdisk

public interface MFileOps

This interface defines kernel "file-operations". Besides its obvious use for "real" file-handling, it is used to interface any stream in general, including pipes, character devices and block devices. Character devices treat read/write in the way that would be expected, lseek() is probably meaningless though. Block devices treat read/write/lseek a bit differently: read() must be called with the correct sized block of data (ie, the device block-size) write() must be used in similar manner lseek() offsets are block offsets, not byte-offsets. BEG/CUR/END are still valid, however How a block-device handles its own internal management of the "offset" is up to it.. i'd suggest all operations sharing a common offset, that is the block offset, which read() and write() increment.

Field Summary

static int	F_GETFL get file-descriptor flags
static int	F_OK file exists
static int	F_SETFL set file-descriptor flags
static int	LSEEK_BEG seek from beginning of file
static int	LSEEK_CUR seek from current offset
static int	LSEEK_END seek from end of file
static int	O_CLOEXEC close on exec flag
static int	O_NONBLOCK non-blocking flag
static int	OPEN_CREAT create file if it doesn't exist
static int	OPEN_READ open file for reading
static int	OPEN_TRUNC truncate the file (empty it) if it exists
static int	OPEN_WRITE open file for writing
static int	R_OK file is readable
static int	W_OK file is writable
static int	X_OK file is executable

Method Summary

int	close(MFile handle) used to close the file.
int	fcntl(MFile handle, int op, int arg) file-handle control
int	lseek(MFile handle, int offset, int whence) seek to a specific offset
int	open(MFile handle, int flags) used to open the file.
int	read(MFile handle, byte[] buffer, int count) read bytes from file
int	write(MFile handle, byte[] buffer, int count) write bytes to file

Field Detail

F_GETFL

static final int F_GETFL

get file-descriptor flags

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Constant Field Values

F_SETFL

static final int F_SETFL

set file-descriptor flags

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O_NONBLOCK

static final int O_NONBLOCK

non-blocking flag

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O_CLOEXEC

static final int O_CLOEXEC

close on exec flag

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OPEN_READ

static final int OPEN_READ

open file for reading

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OPEN_WRITE

static final int OPEN_WRITE

open file for writing

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OPEN_CREAT

static final int OPEN_CREAT

create file if it doesn't exist

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OPEN_TRUNC

static final int OPEN_TRUNC

truncate the file (empty it) if it exists

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LSEEK_BEG

static final int LSEEK_BEG

seek from beginning of file

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LSEEK_CUR

static final int LSEEK_CUR

seek from current offset

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LSEEK_END

static final int LSEEK_END

seek from end of file

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F_OK

static final int F_OK

file exists

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R_OK

static final int R_OK

file is readable

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W_OK

static final int W_OK

file is writable

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X_OK

static final int X_OK

file is executable

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Method Detail

open

int open(MFile handle,
         int flags)

used to open the file. This is only ever called once for each file-handle when the file is opened for the first time.

Parameters:

handle - file-handle of file being opened

flags - open flags (for devices, minor number is (flags >> 16))

Returns:

0 on success or < 0 indicating error

close

int close(MFile handle)

used to close the file. This is only ever called once for each file-handle.

Parameters:

handle - file-handle of file being closed

Returns:

0 on success or < 0 indicating error

lseek

int lseek(MFile handle,
          int offset,
          int whence)

seek to a specific offset

Parameters:

handle - file-handle

offset - byte-offset relative to "whence" (block offset for block devices)

whence - constant indicating position seek should occur from

Returns:

new absolute offset or < 0 indicating error

read

int read(MFile handle,
         byte[] buffer,
         int count)

read bytes from file

Parameters:

handle - file-handle

buffer - buffer where data will be stored

count - maximum number of bytes to read

Returns:

number of bytes read, 0 on end-of-file or < 0 indicating error

write

int write(MFile handle,
          byte[] buffer,
          int count)

write bytes to file

Parameters:

handle - file-handle

buffer - data to write

count - maximum number of bytes to write

Returns:

number of bytes written or < 0 indicating error

fcntl

int fcntl(MFile handle,
          int op,
          int arg)

file-handle control

Parameters:

handle - file-handle

op - operation to perform

arg - argument to operation (if applicable)

Returns:

>= 0 on success, or < 0 indicating failure