org.apache.derby.io
Interface StorageRandomAccessFile

All Superinterfaces:
java.io.DataInput, java.io.DataOutput
All Known Implementing Classes:
DirRandomAccessFile, DirRandomAccessFile4, VirtualRandomAccessFile

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.
 int read(byte[] b, int off, int len)
          Reads up to len bytes of data from this file into an array of bytes.
 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

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

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

getFilePointer

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

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

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

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

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.

read

int read(byte[] b,
         int off,
         int len)
         throws java.io.IOException
Reads up to len bytes of data from this file into an array of bytes. This method blocks until at least one byte of input is available.

Parameters:
b - the buffer into which the data is read.
off - the start offset in array b at which the data is written.
len - the maximum number of bytes read.
Returns:
the total number of bytes read into the buffer, or -1 if there is no more data because the end of the file has been reached.
Throws:
java.io.IOException - If the first byte cannot be read for any reason other than end of file, or if the random access file has been closed, or if some other I/O error occurs.
java.lang.NullPointerException - If b is null.
java.lang.IndexOutOfBoundsException - If off is negative, len is negative, or len is greater than b.length - off

Built on Thu 2011-03-10 11:54:14+0000, from revision ???

Apache Derby V10.6 Internals - Copyright © 2004,2007 The Apache Software Foundation. All Rights Reserved.