moss.ipc
Class MPipe

java.lang.Object
  moss.ipc.MPipe

All Implemented Interfaces:

MFileOps

public class MPipe
extends java.lang.Object
implements MFileOps

This implements the "pipe" IPC mechanism

Field Summary

Fields inherited from interface moss.fs.MFileOps

F_GETFL, F_OK, F_SETFL, LSEEK_BEG, LSEEK_CUR, LSEEK_END, O_CLOEXEC, O_NONBLOCK, OPEN_CREAT, OPEN_READ, OPEN_TRUNC, OPEN_WRITE, R_OK, W_OK, X_OK

Constructor Summary

MPipe()
initialises the pipe to its blank state

Method Summary

int	close(MFile handle) called when closing (destroying) a pipe
int	fcntl(MFile handle, int op, int arg) not supported by pipes
int	lseek(MFile handle, int offset, int whence) not supported by pipes
int	open(MFile handle, int flags) called when creating a pipe; stores reference to self in the file-handle.
int	read(MFile handle, byte[] buffer, int count) called to read data from a pipe
int	write(MFile handle, byte[] buffer, int count) called to write data into the pipe

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

MPipe

public MPipe()

initialises the pipe to its blank state

Method Detail

open

public int open(MFile handle,
                int flags)

called when creating a pipe; stores reference to self in the file-handle. to determine whether it is the reading or writer, `flags' is either OPEN_READ or OPEN_WRITE.

Specified by:

open in interface MFileOps

Parameters:

handle - file-handle

flags - open flags

Returns:

0 on success or < 0 on error

close

public int close(MFile handle)

called when closing (destroying) a pipe

Specified by:

close in interface MFileOps

Parameters:

handle - file-handle

Returns:

0 on success or < 0 on error

lseek

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

not supported by pipes

Specified by:

lseek in interface MFileOps

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

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

called to read data from a pipe

Specified by:

read in interface MFileOps

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 on error

write

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

called to write data into the pipe

Specified by:

write in interface MFileOps

Parameters:

handle - file handle

buffer - data to write

count - number of bytes to write

Returns:

number of bytes written or < 0 on error

fcntl

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

not supported by pipes

Specified by:

fcntl in interface MFileOps

Parameters:

handle - file-handle

op - operation to perform

arg - argument to operation (if applicable)

Returns:

>= 0 on success, or < 0 indicating failure