org.cdlib.xtf.util
Class SubFileReader

Object
  SubStoreReader
      SubFileReader

 class SubFileReader
extends SubStoreReader

Reads a single sub-file within a StructuredFile. A sub-file provides standard DataInput/DataOutput facilities, and takes care of reading from the correct subset of the main StructuredFile.

Author:

Martin Haye

Field Summary

private long	curPos Current read position within the subfile
private RandomAccessFile	file Actual disk file to write to
private StructuredFile	parent The structured file that owns this Subfile
private long	segLength Length of this subfile
private long	segOffset Absolute file position for the subfile's start

Constructor Summary

SubFileReader(RandomAccessFile file, StructuredFile parent, long segOffset, long segLength)
Construct a subfile reader.

Method Summary

private void	checkLength(int nBytes) Ensure that the sub-file has room to read the specified number of bytes.
void	close()
long	getFilePointer()
long	length()
void	read(byte[] b, int off, int len)
byte	readByte()
int	readInt()
void	seek(long pos)

Methods inherited from class SubStoreReader

read

Methods inherited from class Object

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

Field Detail

file

private RandomAccessFile file

Actual disk file to write to

parent

private StructuredFile parent

The structured file that owns this Subfile

segOffset

private long segOffset

Absolute file position for the subfile's start

segLength

private long segLength

Length of this subfile

curPos

private long curPos

Current read position within the subfile

Constructor Detail

SubFileReader

SubFileReader(RandomAccessFile file,
              StructuredFile parent,
              long segOffset,
              long segLength)
        throws IOException

Construct a subfile reader. Reads will be constrained to the specified limit.

Parameters:

file - Disk file to attach to

parent - Structured file to attach to

segOffset - Beginning offset of the segment

segLength - Length of the segment

Throws:

IOException

Method Detail

close

public void close()
           throws IOException

Specified by:

close in class SubStoreReader

Throws:

IOException

getFilePointer

public long getFilePointer()
                    throws IOException

Specified by:

getFilePointer in class SubStoreReader

Throws:

IOException

length

public long length()
            throws IOException

Specified by:

length in class SubStoreReader

Throws:

IOException

checkLength

private void checkLength(int nBytes)
                  throws IOException

Ensure that the sub-file has room to read the specified number of bytes. As a side-effect, we also check that the main file position is current for this sub-file, and if not, we save the position for the other sub-file and restore ours.

Parameters:

nBytes - Amount of space desired

Throws:

IOException

read

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

Specified by:

read in class SubStoreReader

Throws:

IOException

seek

public void seek(long pos)
          throws IOException

Specified by:

seek in class SubStoreReader

Throws:

IOException

readByte

public byte readByte()
              throws IOException

Specified by:

readByte in class SubStoreReader

Throws:

IOException

readInt

public int readInt()
            throws IOException

Specified by:

readInt in class SubStoreReader

Throws:

IOException