jhplot.io
Class BaseRecordsFile

java.lang.Object
  jhplot.io.BaseRecordsFile

Direct Known Subclasses:

RecordsFile

public abstract class BaseRecordsFile
extends Object

Field Summary

protected static long	DATA_START_HEADER_LOCATION
protected long	dataStartPtr
protected static int	FILE_HEADERS_REGION_LENGTH
protected static int	INDEX_ENTRY_LENGTH
protected static int	MAX_KEY_LENGTH
protected static long	NUM_RECORDS_HEADER_LOCATION
protected static int	RECORD_HEADER_LENGTH

Constructor Summary

protected	BaseRecordsFile(String dbPath, int initialSize) Creates a new database file, initializing the appropriate headers.
protected	BaseRecordsFile(String dbPath, String accessFlags) Opens an existing database file and initializes the dataStartPtr.

Method Summary

protected void	addEntryToIndex(String key, RecordHeader newRecord, int currentNumRecords) Appends an entry to end of index.
protected abstract RecordHeader	allocateRecord(String key, int dataLength) Locates space for a new record of dataLength size and initializes a RecordHeader.
void	close() Closes the file.
protected void	deleteEntryFromIndex(String key, RecordHeader header, int currentNumRecords) Removes the record from the index.
void	deleteRecord(String key) Deletes a record.
abstract Enumeration	enumerateKeys() Returns an Enumeration of the keys of all records in the database.
protected long	getFileLength()
abstract int	getNumRecords() Returns the number or records in the database.
protected abstract RecordHeader	getRecordAt(long targetFp) Returns the record to which the target file pointer belongs - meaning the specified location in the file is part of the record data of the RecordHeader which is returned.
protected long	indexPositionToKeyFp(int pos) Returns a file pointer in the index pointing to the first byte in the key located at the given index position.
void	insertRecord(RecordWriter rw) Adds the given record to the database.
protected void	insureIndexSpace(int requiredNumRecords)
protected abstract RecordHeader	keyToRecordHeader(String key) Maps a key to a record header.
protected long	readDataStartHeader() Reads the data start pointer header from the file.
protected int	readNumRecordsHeader() Reads the number of records header from the file.
RecordReader	readRecord(String key) Reads a record.
protected byte[]	readRecordData(RecordHeader header) Reads the record data for the given record header.
protected byte[]	readRecordData(String key) Reads the data for the record with the given key.
abstract boolean	recordExists(String key) Checks there is a record with the given key.
protected void	setFileLength(long l)
void	updateRecord(RecordWriter rw) Updates an existing record.
protected void	writeDataStartPtrHeader(long dataStartPtr) Writes the data start pointer header to the file.
protected void	writeNumRecordsHeader(int numRecords) Writes the number of records header to the file.
protected void	writeRecordData(RecordHeader header, byte[] data) Updates the contents of the given record.
protected void	writeRecordData(RecordHeader header, RecordWriter rw) Updates the contents of the given record.
protected void	writeRecordHeaderToIndex(RecordHeader header) Writes the ith record header to the index.

Methods inherited from class java.lang.Object

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

Field Detail

dataStartPtr

protected long dataStartPtr

FILE_HEADERS_REGION_LENGTH

protected static final int FILE_HEADERS_REGION_LENGTH

See Also:

Constant Field Values

RECORD_HEADER_LENGTH

protected static final int RECORD_HEADER_LENGTH

See Also:

Constant Field Values

MAX_KEY_LENGTH

protected static final int MAX_KEY_LENGTH

See Also:

Constant Field Values

INDEX_ENTRY_LENGTH

protected static final int INDEX_ENTRY_LENGTH

See Also:

Constant Field Values

NUM_RECORDS_HEADER_LOCATION

protected static final long NUM_RECORDS_HEADER_LOCATION

See Also:

Constant Field Values

DATA_START_HEADER_LOCATION

protected static final long DATA_START_HEADER_LOCATION

See Also:

Constant Field Values

Constructor Detail

BaseRecordsFile

protected BaseRecordsFile(String dbPath,
                          int initialSize)
                   throws IOException,
                          RecordsFileException

Creates a new database file, initializing the appropriate headers. Enough space is allocated in the index for the specified initial size.

Throws:

IOException

RecordsFileException

BaseRecordsFile

protected BaseRecordsFile(String dbPath,
                          String accessFlags)
                   throws IOException,
                          RecordsFileException

Opens an existing database file and initializes the dataStartPtr. The accessFlags parameter can be "r" or "rw" -- as defined in RandomAccessFile.

Throws:

IOException

RecordsFileException

Method Detail

enumerateKeys

public abstract Enumeration enumerateKeys()

Returns an Enumeration of the keys of all records in the database.

getNumRecords

public abstract int getNumRecords()

Returns the number or records in the database.

recordExists

public abstract boolean recordExists(String key)

Checks there is a record with the given key.

keyToRecordHeader

protected abstract RecordHeader keyToRecordHeader(String key)
                                           throws RecordsFileException

Maps a key to a record header.

Throws:

RecordsFileException

allocateRecord

protected abstract RecordHeader allocateRecord(String key,
                                               int dataLength)
                                        throws RecordsFileException,
                                               IOException

Locates space for a new record of dataLength size and initializes a RecordHeader.

Throws:

RecordsFileException

IOException

getRecordAt

protected abstract RecordHeader getRecordAt(long targetFp)
                                     throws RecordsFileException

Returns the record to which the target file pointer belongs - meaning the specified location in the file is part of the record data of the RecordHeader which is returned. Returns null if the location is not part of a record. (O(n) mem accesses)

Throws:

RecordsFileException

getFileLength

protected long getFileLength()
                      throws IOException

Throws:

IOException

setFileLength

protected void setFileLength(long l)
                      throws IOException

Throws:

IOException

readNumRecordsHeader

protected int readNumRecordsHeader()
                            throws IOException

Reads the number of records header from the file.

Throws:

IOException

writeNumRecordsHeader

protected void writeNumRecordsHeader(int numRecords)
                              throws IOException

Writes the number of records header to the file.

Throws:

IOException

readDataStartHeader

protected long readDataStartHeader()
                            throws IOException

Reads the data start pointer header from the file.

Throws:

IOException

writeDataStartPtrHeader

protected void writeDataStartPtrHeader(long dataStartPtr)
                                throws IOException

Writes the data start pointer header to the file.

Throws:

IOException

indexPositionToKeyFp

protected long indexPositionToKeyFp(int pos)

Returns a file pointer in the index pointing to the first byte in the key located at the given index position.

writeRecordHeaderToIndex

protected void writeRecordHeaderToIndex(RecordHeader header)
                                 throws IOException

Writes the ith record header to the index.

Throws:

IOException

addEntryToIndex

protected void addEntryToIndex(String key,
                               RecordHeader newRecord,
                               int currentNumRecords)
                        throws IOException,
                               RecordsFileException

Appends an entry to end of index. Assumes that insureIndexSpace() has already been called.

Throws:

IOException

RecordsFileException

deleteEntryFromIndex

protected void deleteEntryFromIndex(String key,
                                    RecordHeader header,
                                    int currentNumRecords)
                             throws IOException,
                                    RecordsFileException

Removes the record from the index. Replaces the target with the entry at the end of the index.

Throws:

IOException

RecordsFileException

insertRecord

public void insertRecord(RecordWriter rw)
                  throws RecordsFileException,
                         IOException

Adds the given record to the database.

Throws:

RecordsFileException

IOException

updateRecord

public void updateRecord(RecordWriter rw)
                  throws RecordsFileException,
                         IOException

Updates an existing record. If the new contents do not fit in the original record, then the update is handled by deleting the old record and adding the new.

Throws:

RecordsFileException

IOException

readRecord

public RecordReader readRecord(String key)
                        throws RecordsFileException,
                               IOException

Reads a record.

Throws:

RecordsFileException

IOException

readRecordData

protected byte[] readRecordData(String key)
                         throws IOException,
                                RecordsFileException

Reads the data for the record with the given key.

Throws:

IOException

RecordsFileException

readRecordData

protected byte[] readRecordData(RecordHeader header)
                         throws IOException

Reads the record data for the given record header.

Throws:

IOException

writeRecordData

protected void writeRecordData(RecordHeader header,
                               RecordWriter rw)
                        throws IOException,
                               RecordsFileException

Updates the contents of the given record. A RecordsFileException is thrown if the new data does not fit in the space allocated to the record. The header's data count is updated, but not written to the file.

Throws:

IOException

RecordsFileException

writeRecordData

protected void writeRecordData(RecordHeader header,
                               byte[] data)
                        throws IOException,
                               RecordsFileException

Updates the contents of the given record. A RecordsFileException is thrown if the new data does not fit in the space allocated to the record. The header's data count is updated, but not written to the file.

Throws:

IOException

RecordsFileException

deleteRecord

public void deleteRecord(String key)
                  throws RecordsFileException,
                         IOException

Deletes a record.

Throws:

RecordsFileException

IOException

insureIndexSpace

protected void insureIndexSpace(int requiredNumRecords)
                         throws RecordsFileException,
                                IOException

Throws:

RecordsFileException

IOException

close

public void close()
           throws IOException,
                  RecordsFileException

Closes the file.

Throws:

IOException

RecordsFileException