org.tranche.flatfile
Class DataBlock

java.lang.Object
  org.tranche.commons.Debuggable
      org.tranche.flatfile.DataBlock

All Implemented Interfaces:

java.lang.Comparable

public class DataBlock
extends org.tranche.commons.Debuggable
implements java.lang.Comparable

Represents a block of data. Might have more than one file in it.

Note that the following critical activities are synchronized on the DataBlock object:

• Adding bytes to data block
• Checking whether data block has bytes
• Getting bytes from data block
• Deleting block
• Getting hashes in data block

Author:

Jayson Falkner - jfalkner@umich.edu, Bryan E. Smith - bryanesmith@gmail.com

Field Summary

static BigHash	HASH_LENGTH_ZERO
static int	HEADERS_PER_FILE The amount of headers per file.
static int	MAX_BLOCK_SIZE The maximum DataBlock size, in bytes.

Constructor Summary

DataBlock(java.lang.String filename, DataDirectoryConfiguration ddc, DataBlockUtil dbu)

Method Summary

void	addBytes(BigHash hash, boolean isMetaData, byte[] bytes) Add a chunk to this DataBlock.
void	addBytes(BigHash hash, boolean isMetaData, byte[] bytes, int recursionCount) Add a chunk to this DataBlock.
int	compareTo(java.lang.Object o) Compare underlying files for DataBlock instances.
void	deleteBytes(BigHash hash, boolean isMetaData) Delete the bytes (chunk) from this DataBlock based on hash.
java.lang.String	getAbsolutePath() Get absolute path to underlying file for DataBlock.
byte[]	getBytes(BigHash hash, boolean isMetaData) Returns the bytes (chunk) representing by the hash, or throws a FileNotFoundException if not found.
byte[]	getBytes(int o, int s) Uses cached information to get chunk.
java.util.List<BigHash>	getHashes(boolean isMetaData) Returns the list of either data or meta-data hashes stored in this block.
protected DataBlock[]	getSubBlocks() Return the subblocks for this DataBlock.
boolean	hasBytes(BigHash hash, boolean isMetaData) Check whether the bytes (chunk) represented by the hash exist in this DataBlock instance.
boolean	isDirectory() Returns true if this DataBlock is a directory.
boolean	isMerging() Returns true if this file is half-way through a merge.
long	length() Return the size in bytes of the underlying file for the DataBlock instance.
protected boolean	moveToDataDirectoryConfiguration(DataDirectoryConfiguration newDDC) The data block moves itself.

Methods inherited from class org.tranche.commons.Debuggable

debugErr, debugErr, debugOut, isDebug, setDebug

Methods inherited from class java.lang.Object

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

Field Detail

HASH_LENGTH_ZERO

public static BigHash HASH_LENGTH_ZERO

MAX_BLOCK_SIZE

public static final int MAX_BLOCK_SIZE

The maximum DataBlock size, in bytes.

See Also:

Constant Field Values

HEADERS_PER_FILE

public static final int HEADERS_PER_FILE

The amount of headers per file.

Each header's size in bytes is equal to BigHash.HASH_LENGTH + 1 + 1 + 4 + 4. Every new block will start with this many headers. To get the blocks size, you must also include all the data in the block.

See Also:

Constant Field Values

Constructor Detail

DataBlock

public DataBlock(java.lang.String filename,
                 DataDirectoryConfiguration ddc,
                 DataBlockUtil dbu)

Parameters:

filename -

ddc -

dbu -

Method Detail

isDirectory

public final boolean isDirectory()

Returns true if this DataBlock is a directory. (I.e., it has children DataBlock instances.)

Returns:

getAbsolutePath

public final java.lang.String getAbsolutePath()

Get absolute path to underlying file for DataBlock. No guarentee if regular file or directory.

Returns:

The absolute path to the file

isMerging

public final boolean isMerging()

Returns true if this file is half-way through a merge.

Returns:

length

public final long length()

Return the size in bytes of the underlying file for the DataBlock instance.

Returns:

getHashes

public final java.util.List<BigHash> getHashes(boolean isMetaData)
                                        throws java.lang.Exception

Returns the list of either data or meta-data hashes stored in this block. If true is passed as a parameter, only meta-data is returned. Otherwise only data hashes are returned.

Parameters:

isMetaData -

Returns:

Throws:

java.lang.Exception

getBytes

public final byte[] getBytes(int o,
                             int s)
                      throws java.lang.Exception

Uses cached information to get chunk.

Parameters:

o - Offset of chunk

s - Size of chunk

Returns:

Bytes for chunk

Throws:

java.lang.Exception

getBytes

public final byte[] getBytes(BigHash hash,
                             boolean isMetaData)
                      throws java.lang.Exception

Returns the bytes (chunk) representing by the hash, or throws a FileNotFoundException if not found.

Parameters:

hash -

isMetaData -

Returns:

Throws:

java.lang.Exception

hasBytes

public final boolean hasBytes(BigHash hash,
                              boolean isMetaData)
                       throws java.lang.Exception

Check whether the bytes (chunk) represented by the hash exist in this DataBlock instance.

Parameters:

hash -

isMetaData -

Returns:

Throws:

java.lang.Exception

addBytes

public final void addBytes(BigHash hash,
                           boolean isMetaData,
                           byte[] bytes)
                    throws java.lang.Exception

Add a chunk to this DataBlock.

Parameters:

hash -

isMetaData -

bytes -

Throws:

java.lang.Exception

addBytes

public final void addBytes(BigHash hash,
                           boolean isMetaData,
                           byte[] bytes,
                           int recursionCount)
                    throws java.lang.Exception

Add a chunk to this DataBlock.

Parameters:

hash -

isMetaData -

bytes -

recursionCount - The number of times this has been recursively called while waiting for DataBlock to merge. (After a certain number of times, this will fail and throw an exception.)

Throws:

java.lang.Exception

deleteBytes

public final void deleteBytes(BigHash hash,
                              boolean isMetaData)
                       throws java.lang.Exception

Delete the bytes (chunk) from this DataBlock based on hash.

Parameters:

hash -

isMetaData -

Throws:

java.lang.Exception

compareTo

public final int compareTo(java.lang.Object o)

Compare underlying files for DataBlock instances.

Specified by:

compareTo in interface java.lang.Comparable

Parameters:

o -

Returns:

getSubBlocks

protected final DataBlock[] getSubBlocks()

Return the subblocks for this DataBlock.

Returns:

moveToDataDirectoryConfiguration

protected final boolean moveToDataDirectoryConfiguration(DataDirectoryConfiguration newDDC)
                                                  throws java.lang.Exception

The data block moves itself. This synchronized method places the data block in a new DataDirectoryConfiguration.

The intended use for this method is to balance a server's data across data directories.

Parameters:

newDDC -

Returns:

Throws:

java.lang.Exception