org.apache.derby.impl.io.vfmem

Class BlockedByteArray

java.lang.Object

org.apache.derby.impl.io.vfmem.BlockedByteArray

public class BlockedByteArray
extends java.lang.Object

Stores data in blocks, and supports reading/writing data from/into these blocks.

The blocked array is expanded and shrunk as required.

Constructor Summary

Constructors

Constructor and Description
BlockedByteArray() Creates a new blocked byte array with the default number of slots to hold byte arrays (blocks).

Method Summary

Modifier and Type	Method and Description
long	length() Returns the number of bytes allocated.
int	read(long pos) Returns the byte at the given position.
int	read(long pos, byte[] buf, int offset, int len) Reads up to len bytes.
void	setLength(long newLength) Changes the allocated length of the data.
int	writeByte(long pos, byte b) Writes the given byte into the blocked byte array.
int	writeBytes(long pos, byte[] buf, int offset, int len) Writes the given bytes into the blocked byte array.

Methods inherited from class java.lang.Object

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

Constructor Detail

BlockedByteArray

public BlockedByteArray()

Creates a new blocked byte array with the default number of slots to hold byte arrays (blocks).

No blocks are pre-allocated.

See Also:

INITIAL_BLOCK_HOLDER_SIZE

Method Detail

read

public int read(long pos)

Returns the byte at the given position.

Parameters:

pos - position to read from

Returns:

A single byte.

read

public int read(long pos,
                byte[] buf,
                int offset,
                int len)

Reads up to len bytes.

Parameters:

pos - the position to start reading at

buf - the destination buffer

offset - offset into the destination buffer

len - the number of bytes to read

Returns:

The number of bytes read.

length

public long length()

Returns the number of bytes allocated.

Returns:

Bytes allocated.

setLength

public void setLength(long newLength)

Changes the allocated length of the data.

If the new length is larger than the current length, the blocked byte array will be extended with new blocks. If the new length is smaller, existing (allocated) blocks will be removed if possible.

Parameters:

newLength - the new length of the allocated data in bytes

writeBytes

public int writeBytes(long pos,
                      byte[] buf,
                      int offset,
                      int len)

Writes the given bytes into the blocked byte array.

Parameters:

pos - the position to start writing at

buf - the source buffer

offset - the offset into the source buffer

len - the number of bytes to write

Returns:

The number of bytes written.

writeByte

public int writeByte(long pos,
                     byte b)

Writes the given byte into the blocked byte array.

Parameters:

pos - the position to write the byte at

b - the byte to write

Returns:

1, which is the number of bytes written.