Interface StorageRandomAccessFile

All Superinterfaces:

DataInput, DataOutput

All Known Implementing Classes:

DirRandomAccessFile, VirtualRandomAccessFile

public interface StorageRandomAccessFile
extends DataInput, 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

Modifier and Type	Method	Description
StorageRandomAccessFile	clone()	Clone this file abstraction
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()	Force any changes out to the persistent store.

Methods inherited from interface DataInput

readBoolean, readByte, readChar, readDouble, readFloat, readFully, readFully, readInt, readLine, readLong, readShort, readUnsignedByte, readUnsignedShort, readUTF, skipBytes

Methods inherited from interface DataOutput

write, write, write, writeBoolean, writeByte, writeBytes, writeChar, writeChars, writeDouble, writeFloat, writeInt, writeLong, writeShort, writeUTF

Method Details

close

void close()
    throws IOException

Closes this file.

Throws:

IOException - - if an I/O error occurs.

getFilePointer

long getFilePointer()
             throws IOException

Get the current offset in this file.

Returns:

the current file pointer.

Throws:

IOException - - if an I/O error occurs.

length

long length()
     throws IOException

Gets the length of this file.

Returns:

the number of bytes this file.

Throws:

IOException - - if an I/O error occurs.

seek

void seek(long newFilePointer)
   throws 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:

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

setLength

void setLength(long newLength)
        throws 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:

IOException - If an I/O error occurs.

sync

void sync()
   throws 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.

Throws:

SyncFailedException - if a possibly recoverable error occurs.

IOException - If an IO error occurs.

read

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

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.

NullPointerException - If b is null.

IndexOutOfBoundsException - If off is negative, len is negative, or len is greater than b.length - off

clone

StorageRandomAccessFile clone()

Clone this file abstraction