de.schlichtherle.io.rof
Class FilterReadOnlyFile

java.lang.Object
  de.schlichtherle.io.rof.AbstractReadOnlyFile
      de.schlichtherle.io.rof.FilterReadOnlyFile

All Implemented Interfaces:

ReadOnlyFile

Direct Known Subclasses:

BufferedReadOnlyFile, CipherReadOnlyFile, CountingReadOnlyFile

public class FilterReadOnlyFile
extends AbstractReadOnlyFile

A base class for any class which wants to decorate a ReadOnlyFile.

Note that subclasses of this class often implement their own virtual file pointer. Thus, if you would like to access the underlying ReadOnlyFile again after you have finished working with the FilteredReadOnlyFile, you should synchronize their file pointers a'la:

     ReadOnlyFile rof = new SimpleReadOnlyFile(new File("HelloWorld.java"));
     try {
         ReadOnlyFile frof = new FilteredReadOnlyFile(rof);
         try {
             // Do any file input on brof here...
             frof.seek(1);
         } finally {
             // Synchronize the file pointers.
             rof.seek(frof.getFilePointer());
         }
         // This assertion would fail if we hadn't done the file pointer
         // synchronization!
         assert rof.getFilePointer() == 1;
     } finally {
         rof.close();
     }
 

This does not apply to this base class, however.

Subclasses implemententing their own virtual file pointer should add a note referring to this classes Javadoc like this:

Note: This class implements its own virtual file pointer. Thus, if you would like to access the underlying ReadOnlyFile again after you have finished working with an instance of this class, you should synchronize their file pointers using the pattern as described in FilterReadOnlyFile.

Version:

$Id: FilterReadOnlyFile.java 06f3ba684701 2010/11/04 01:15:55 christian $

Author:

Christian Schlichtherle

Field Summary

protected ReadOnlyFile

rof The read only file to be filtered.

Constructor Summary

FilterReadOnlyFile(ReadOnlyFile rof)
Creates a new instance of FilterReadOnlyFile, which filters the given read only file.

Method Summary

void	close()
long	getFilePointer()
long	length()
int	read()
int	read(byte[] b, int off, int len) Reads up to len bytes of data from this read only file into the given array.
void	seek(long pos) Sets the file pointer offset, measured from the beginning of this file, at which the next read occurs.

Methods inherited from class de.schlichtherle.io.rof.AbstractReadOnlyFile

read, readFully, readFully, skipBytes

Methods inherited from class java.lang.Object

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

Field Detail

rof

protected ReadOnlyFile rof

The read only file to be filtered.

Constructor Detail

FilterReadOnlyFile

public FilterReadOnlyFile(ReadOnlyFile rof)

Creates a new instance of FilterReadOnlyFile, which filters the given read only file.

Method Detail

length

public long length()
            throws IOException

Throws:

IOException

getFilePointer

public long getFilePointer()
                    throws IOException

Throws:

IOException

seek

public void seek(long pos)
          throws IOException

Description copied from interface: ReadOnlyFile

Sets the file pointer offset, measured from the beginning of this file, at which the next read occurs. Whether the offset may be set beyond the end of the file is up to the implementor. For example, the SimpleReadOnlyFile subclasses RandomAccessFile and passes "r" as a parameter to the superclass constructor. On the Windows platform, this implementation allows to seek past the end of file, but on the Linux platform it doesn't.

Parameters:

pos - The offset position, measured in bytes from the beginning of the file, at which to set the file pointer.

Throws:

IOException - If pos is less than 0 or if an I/O error occurs.

read

public int read()
         throws IOException

Throws:

IOException

read

public int read(byte[] b,
                int off,
                int len)
         throws IOException

Description copied from interface: ReadOnlyFile

Reads up to len bytes of data from this read only file into the given array. This method blocks until at least one byte of input is available.

Parameters:

b - The buffer to fill with data.

off - The start offset of the data.

len - The maximum number of bytes to read.

Returns:

The total number of bytes read, or -1 if there is no more data because the end of the file has been reached.

Throws:

IOException - On any I/O related issue.

close

public void close()
           throws IOException

Throws:

IOException