Top Description Methods
org.apache.derby.io

public Interface StorageRandomAccessFile

extends DataInput, DataOutput
Known Direct Implementers
org.apache.derby.impl.io.DirRandomAccessFile, org.apache.derby.impl.io.vfmem.VirtualRandomAccessFile
Imports
java.io.DataInput, .DataOutput, .FileNotFoundException, .EOFException, .IOException
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 TypeMethod and Description
public StorageRandomAccessFile
clone()

Clone this file abstraction

public void
close()

Closes this file.

public long

Returns:

the current file pointer.
getFilePointer()

Get the current offset in this file.

public long

Returns:

the number of bytes this file.
length()

Gets the length of this file.

public int

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.
read(byte[]
the buffer into which the data is read.
b, int
the start offset in array b at which the data is written.
off, int
the maximum number of bytes read.
len)

Reads up to len bytes of data from this file into an array of bytes.

public void
seek(long
the new file pointer, measured in bytes from the beginning of the file.
newFilePointer)

Set the file pointer.

public void
setLength(long
The new file length.
newLength)

Sets the length of this file, either extending or truncating it.

public void
sync()

Force any changes out to the persistent store.

Inherited from java.io.DataInput:
readBooleanreadBytereadCharreadDoublereadFloatreadFullyreadFullyreadIntreadLinereadLongreadShortreadUnsignedBytereadUnsignedShortreadUTFskipBytes
Inherited from java.io.DataOutput:
writewritewritewriteBooleanwriteBytewriteByteswriteCharwriteCharswriteDoublewriteFloatwriteIntwriteLongwriteShortwriteUTF

Method Detail

cloneback to summary
public StorageRandomAccessFile clone()

Clone this file abstraction

closeback to summary
public void close() throws IOException

Closes this file.

Exceptions
IOException:
- if an I/O error occurs.
getFilePointerback to summary
public long getFilePointer() throws IOException

Get the current offset in this file.

Returns:long

the current file pointer.

Exceptions
IOException:
- if an I/O error occurs.
lengthback to summary
public long length() throws IOException

Gets the length of this file.

Returns:long

the number of bytes this file.

Exceptions
IOException:
- if an I/O error occurs.
readback to summary
public 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:byte[]

the buffer into which the data is read.

off:int

the start offset in array b at which the data is written.

len:int

the maximum number of bytes read.

Returns:int

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.

Exceptions
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
seekback to summary
public 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:long

the new file pointer, measured in bytes from the beginning of the file.

Exceptions
IOException:
- if newFilePointer is less than 0 or an I/O error occurs.
setLengthback to summary
public 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:long

The new file length.

Exceptions
IOException:
If an I/O error occurs.
syncback to summary
public 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.

Exceptions
IOException:
If an IO error occurs.
SyncFailedException:
if a possibly recoverable error occurs.