edu.mit.csail.aeolus.api
Class AeolusFileInputStream

java.lang.Object
  edu.mit.csail.aeolus.api.AeolusFileInputStream

public class AeolusFileInputStream
extends java.lang.Object

An Aeolus file input stream can be used for reading data from a given file.

The stream will only be created and opened if the requester labels allow reading from the file.

If the file contents are changed after the stream has been opened, the subsequent read operation from this stream will fail.

If the caller labels change and no longer allow the read, the stream will be closed.

Constructor Summary

AeolusFileInputStream(java.lang.String hostname, java.lang.String filePath)
Creates a filestream for reading from the file specified by filePath on hostname

Method Summary

void	close() Closes the stream.
int	read(byte[] buffer) Reads bytes from the file into the specified buffer.
int	read(byte[] buffer, int offset, int count) Reads bytes from the file into the specified buffer.

Methods inherited from class java.lang.Object

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

Constructor Detail

AeolusFileInputStream

public AeolusFileInputStream(java.lang.String hostname,
                             java.lang.String filePath)
                      throws java.io.FileNotFoundException,
                             java.io.IOException,
                             AeolusException

Creates a filestream for reading from the file specified by filePath on hostname

Parameters:

hostname - - node where the file is stored

filePath - - path to the file on hostname

Throws:

InfoFlowControlException - - if caller labels don't allow reading from the file or reading from a higher parent directory if the file is missing

java.io.FileNotFoundException - - if the file does not exist on the hostname

AeolusException - - if a FileSystemClient can not be created

java.io.IOException - - if an I/O error occurs while opening the file stream (e.g. when retrieving file labels)

Method Detail

close

public void close()
           throws java.io.IOException,
                  AeolusException

Closes the stream. Any subsequent attempts to access this stream will fail with an IOException.

Throws:

java.io.IOException - - if this stream has already been closed

AeolusException

read

public int read(byte[] buffer)
         throws java.io.IOException,
                AeolusException,
                InfoFlowControlException

Reads bytes from the file into the specified buffer. Up to buffer.length bytes will be read from the file.

Parameters:

buffer - - array to store the data into

Returns:

the actual number of bytes read

Throws:

java.io.IOException - - if an I/O error occurred while reading from the file (e.g. the stream has been closed)

InfoFlowControlException - - if labels don't allow the read

AeolusException

read

public int read(byte[] buffer,
                int offset,
                int count)
         throws java.io.IOException,
                AeolusException,
                InfoFlowControlException

Reads bytes from the file into the specified buffer. Up to count bytes will be stored in the buffer starting at the given offset in the buffer.

Returns:

the actual number of bytes read or -1 if end of file has been reached

Throws:

java.io.IOException - - if an I/O error occurred while reading from the file (e.g. the stream has been closed)

InfoFlowControlException - - if labels don't allow the read

IoException - - if the stream is closed

AeolusException