Package db.buffers

Interface BufferFile

All Known Subinterfaces:

ManagedBufferFile

All Known Implementing Classes:

BufferFileAdapter, LocalBufferFile, LocalManagedBufferFile, ManagedBufferFileAdapter

public interface BufferFile

BufferFile facilitates read/write access to buffer oriented file. Access to related resources, such as parameters and change data, is also facilitated.

Method Summary

Modifier and Type	Method	Description
void	clearParameters()	Deletes all parameters
void	close()	Close the buffer file.
boolean	delete()	Delete this buffer file if writable.
void	dispose()	Dispose of this buffer file object.
DataBuffer	get(DataBuffer buf, int index)	Get the specified buffer.
int	getBufferSize()	Return the actual size of a user data buffer.
int[]	getFreeIndexes()	Returns the list of free indexes sorted by value.
int	getIndexCount()	Returns the number of allocated buffer indexes.
int	getParameter(java.lang.String name)	Get a the stored value for a named parameter.
java.lang.String[]	getParameterNames()	Returns a list of all parameter names.
boolean	isReadOnly()	Returns true if this file may not be modified via the buffer put method.
void	put(DataBuffer buf, int index)	Store a data buffer at the specified block index.
void	setFreeIndexes(int[] indexes)	Sets the list of free buffer indexes.
void	setParameter(java.lang.String name, int value)	Set the integer value for a named parameter.
boolean	setReadOnly()	If file is open read-write, the modified contents are flushed and the file re-opened as read-only.

Method Detail

isReadOnly

boolean isReadOnly()
            throws java.io.IOException

Returns true if this file may not be modified via the buffer put method. A read-only file may be considered "updateable" if the canSave method returns true. The term "updateable" means that a Save file can be obtained via the getSaveFile method.

Throws:

java.io.IOException - if an I/O error occurs

setReadOnly

boolean setReadOnly()
             throws java.io.IOException

If file is open read-write, the modified contents are flushed and the file re-opened as read-only. This is also used to commit a new version if the file had been modified for update.

Returns:

true if successfully transitioned from read-write to read-only

Throws:

java.io.IOException - if an I/O error occurs

getParameter

int getParameter(java.lang.String name)
          throws java.util.NoSuchElementException,
                 java.io.IOException

Get a the stored value for a named parameter.

Parameters:

name - parameter name

Returns:

integer value

Throws:

java.util.NoSuchElementException - thrown if parameter not found

java.io.IOException

setParameter

void setParameter(java.lang.String name,
                  int value)
           throws java.io.IOException

Set the integer value for a named parameter.

Parameters:

name - parameter name

value - parameter value

Throws:

java.io.IOException

clearParameters

void clearParameters()
              throws java.io.IOException

Deletes all parameters

Throws:

java.io.IOException

getParameterNames

java.lang.String[] getParameterNames()
                              throws java.io.IOException

Returns a list of all parameter names.

Throws:

java.io.IOException

getBufferSize

int getBufferSize()
           throws java.io.IOException

Return the actual size of a user data buffer. This value should be used when constructing DataBuffer objects.

Returns:

DataBuffer data size as a number of bytes

Throws:

java.io.IOException - if an I/O error occurs

getIndexCount

int getIndexCount()
           throws java.io.IOException

Returns the number of allocated buffer indexes. When a new buffer is allocated, and the file size grows, the buffer will remain allocated although it may be added to the list of free-indexes. A file will never shrink in size due to this permanent allocation.

Throws:

java.io.IOException

getFreeIndexes

int[] getFreeIndexes()
              throws java.io.IOException

Returns the list of free indexes sorted by value. The management of the free-index-list is implementation specific.

Throws:

java.io.IOException

setFreeIndexes

void setFreeIndexes(int[] indexes)
             throws java.io.IOException

Sets the list of free buffer indexes. The management of the free-index-list is implementation specific.

Parameters:

indexes -

Throws:

java.io.IOException

close

void close()
    throws java.io.IOException

Close the buffer file. If the file was open for write access, all buffers are flushed and the file header updated. Once closed, this object is immediately disposed and may no longer be used.

Throws:

java.io.IOException - if an I/O error occurs

delete

boolean delete()
        throws java.io.IOException

Delete this buffer file if writable. Once deleted, this object is immediately disposed and may no longer be used.

Returns:

true if deleted, false if the file is read-only

Throws:

java.io.IOException - if an I/O error occurs.

dispose

void dispose()

Dispose of this buffer file object. If file is not readOnly and has not been closed, an attempt will be made to delete the associated file(s). Once disposed, it may no longer be used.

get

DataBuffer get(DataBuffer buf,
               int index)
        throws java.io.IOException

Get the specified buffer. DataBuffer data and flags are read from the file at index and stored within the supplied DataBuffer object. If the read buffer is empty, the DataBuffer's data field will remain unchanged (which could be null).

Parameters:

buf - a buffer whose data array will be filled-in or replaced.

index - index of buffer to be read. First user buffer is at index 0.

Throws:

java.io.EOFException - if the requested buffer index is greater than the number of available buffers of the end-of-file was encountered while reading the buffer.

java.io.IOException - if an I/O error occurs

put

void put(DataBuffer buf,
         int index)
  throws java.io.IOException

Store a data buffer at the specified block index.

Parameters:

buf - data buffer

index - block index

Throws:

java.io.IOException - thrown if an IO error occurs