org.apache.derby.io
Interface StorageRandomAccessFile

All Superinterfaces:
java.io.DataInput, java.io.DataOutput
All Known Implementing Classes:
DirRandomAccessFile

public interface StorageRandomAccessFile
extends java.io.DataInput, java.io.DataOutput

This interface abstracts an object that implements reading and writing on a random access file. It extends DataInput and DataOutput, so it implicitly contains all the methods of those interfaces. Any method in this interface that also appears in the java.io.RandomAccessFile class should behave as the java.io.RandomAccessFile method does.

Each StorageRandomAccessFile has an associated file pointer, a byte offset in the file. All reading and writing takes place at the file pointer offset and advances it.

An implementation of StorageRandomAccessFile need not be thread safe. The database engine single-threads access to each StorageRandomAccessFile instance. Two threads will not access the same StorageRandomAccessFile instance at the same time.

See Also:
java.io.RandomAccessFile

Method Summary
 void close()
          Closes this file.
 long getFilePointer()
          Get the current offset in this file.
 long length()
          Gets the length of this file.
 void seek(long newFilePointer)
          Set the file pointer.
 void setLength(long newLength)
          Sets the length of this file, either extending or truncating it.
 void sync(boolean metaData)
          Force any changes out to the persistent store.
 
Methods inherited from interface java.io.DataInput
readBoolean, readByte, readChar, readDouble, readFloat, readFully, readFully, readInt, readLine, readLong, readShort, readUnsignedByte, readUnsignedShort, readUTF, skipBytes
 
Methods inherited from interface java.io.DataOutput
write, write, write, writeBoolean, writeByte, writeBytes, writeChar, writeChars, writeDouble, writeFloat, writeInt, writeLong, writeShort, writeUTF
 

Method Detail

close

public void close()
           throws java.io.IOException
Closes this file.

Throws:
java.io.IOException - - if an I/O error occurs.

getFilePointer

public long getFilePointer()
                    throws java.io.IOException
Get the current offset in this file.

Returns:
the current file pointer.
Throws:
java.io.IOException - - if an I/O error occurs.

length

public long length()
            throws java.io.IOException
Gets the length of this file.

Returns:
the number of bytes this file.
Throws:
java.io.IOException - - if an I/O error occurs.

seek

public void seek(long newFilePointer)
          throws java.io.IOException
Set the file pointer. It may be moved beyond the end of the file, but this does not change the length of the file. The length of the file is not changed until data is actually written..

Parameters:
newFilePointer - the new file pointer, measured in bytes from the beginning of the file.
Throws:
java.io.IOException - - if newFilePointer is less than 0 or an I/O error occurs.

setLength

public void setLength(long newLength)
               throws java.io.IOException
Sets the length of this file, either extending or truncating it.

If the file is extended then the contents of the extension are not defined.

If the file is truncated and the file pointer is greater than the new length then the file pointer is set to the new length.

Parameters:
newLength - The new file length.
Throws:
java.io.IOException - If an I/O error occurs.

sync

public void sync(boolean metaData)
          throws java.io.IOException
Force any changes out to the persistent store. If the database is to be transient, that is, if the database does not survive a restart, then the sync method implementation need not do anything.

Parameters:
metaData - If true then this method must force both changes to the file's contents and metadata to be written to storage; if false, it need only force file content changes to be written. The implementation is allowed to ignore this parameter and always force out metadata changes.
Throws:
SyncFailedException - if a possibly recoverable error occurs.
java.io.IOException - If an IO error occurs.


Apache Derby V10.0 Engine Documentation - Copyright © 1997,2004 The Apache Software Foundation or its licensors, as applicable.