ewe.database
Interface DatabaseStream

All Known Implementing Classes:

RandomAccessDatabaseStream

public interface DatabaseStream

This is not part of the Ewe Simple Database specification. This is used for an actual implementation of Simple Database, specifically by RecordFile.

Method Summary

boolean	atEOF(long location)
boolean	canWrite() Tests if the DatabaseStream was opened in read-write mode as opposed to read-ony mode.
void	close()
void	delete()
void	flush()
int	getFirstDataLocation() Return the location of where you can store your data.
Time	getModifiedTime()
long	length()
void	readAll(long location, byte[] data, int offset, int length) This throws an exception if all the specified bytes are not found at the specified location.
int	readIntAt(long location)
void	rename(String newName)
void	reopen() Reopen the stream after a temporaryClose().
void	safeWrite(long location, int data) A safeWrite() is one where the integer data is either stored completely at the specified location or not at all.
void	safeWrite(long location1, int data1, long location2, int data2)
void	safeWrite(long location1, int data1, long location2, int data2, long location3, int data3, long location4, int data4)
boolean	setDecryptor(DataProcessor decryptor)
boolean	setDecryptorAndEncryptor(DataProcessor decryptor, DataProcessor encryptor)
boolean	setModifiedTime(Time t)
boolean	temporaryClose() Close the stream temporarily.
boolean	truncateTo(long length) Try to truncate to a particular length.
void	writeAll(long location, byte[] data, int offset, int length)
void	writeIntAt(long location, int value)
void	zero(long location, int numBytes) This should extend the Stream if necessary.

Method Detail

getFirstDataLocation

public int getFirstDataLocation()

Return the location of where you can store your data. This should be at a 16-byte border.

safeWrite

public void safeWrite(long location,
                      int data)
               throws IOException

A safeWrite() is one where the integer data is either stored completely at the specified location or not at all. If for some reason, the application should fail during the safe write (assuming that there is no problem with the file) then either the write had no effect, OR, the write would be completed the next time the file is opened.

Throws:

IOException

safeWrite

public void safeWrite(long location1,
                      int data1,
                      long location2,
                      int data2)
               throws IOException

Throws:

IOException

safeWrite

public void safeWrite(long location1,
                      int data1,
                      long location2,
                      int data2,
                      long location3,
                      int data3,
                      long location4,
                      int data4)
               throws IOException

Throws:

IOException

readIntAt

public int readIntAt(long location)
              throws IOException

Throws:

IOException

writeIntAt

public void writeIntAt(long location,
                       int value)
                throws IOException

Throws:

IOException

writeAll

public void writeAll(long location,
                     byte[] data,
                     int offset,
                     int length)
              throws IOException

Throws:

IOException

readAll

public void readAll(long location,
                    byte[] data,
                    int offset,
                    int length)
             throws IOException

This throws an exception if all the specified bytes are not found at the specified location.

Throws:

IOException

zero

public void zero(long location,
                 int numBytes)
          throws IOException

This should extend the Stream if necessary.

Throws:

IOException

truncateTo

public boolean truncateTo(long length)
                   throws IOException

Try to truncate to a particular length. If the truncate is not possible because of restrictions on the underlying Stream, this returns false. An IOException is only thrown if there is a serious IO error which indicates IO should be abandonded.

Throws:

IOException

setDecryptor

public boolean setDecryptor(DataProcessor decryptor)
                     throws IOException

Throws:

IOException

setDecryptorAndEncryptor

public boolean setDecryptorAndEncryptor(DataProcessor decryptor,
                                        DataProcessor encryptor)
                                 throws IOException

Throws:

IOException

atEOF

public boolean atEOF(long location)
              throws IOException

Throws:

IOException

length

public long length()
            throws IOException

Throws:

IOException

flush

public void flush()
           throws IOException

Throws:

IOException

close

public void close()
           throws IOException

Throws:

IOException

delete

public void delete()
            throws IOException

Throws:

IOException

rename

public void rename(String newName)
            throws IOException

Throws:

IOException

getModifiedTime

public Time getModifiedTime()
                     throws IOException

Throws:

IOException

setModifiedTime

public boolean setModifiedTime(Time t)
                        throws IOException

Throws:

IOException

temporaryClose

public boolean temporaryClose()
                       throws IOException

Close the stream temporarily. Can be opened with re-open.

Returns:

true if it was actually closed.

Throws:

IOException - if an error occurs.

reopen

public void reopen()
            throws IOException

Reopen the stream after a temporaryClose(). The file position will be unspecified after this call.

Throws:

IOException - if an error occurs.

canWrite

public boolean canWrite()

Tests if the DatabaseStream was opened in read-write mode as opposed to read-ony mode.