Package db.buffers

Class LocalBufferFile

java.lang.Object
db.buffers.LocalBufferFile
All Implemented Interfaces:
BufferFile
Direct Known Subclasses:
LocalManagedBufferFile
public class LocalBufferFile extends Object implements BufferFile
LocalBufferFile implements a BufferFile as block-oriented random-access file. This type of buffer file supports save-as but does not support the save operation.

  • Field Details

  • Constructor Details

    • LocalBufferFile

      public LocalBufferFile(File file, int bufferSize) throws IOException
      Create a new buffer file for writing. If the file does not exist and create is true, a new buffer file will be created. The file will be saved when closed.
      Parameters:
      file - buffer file
      bufferSize - user buffer size
      Throws:
      DuplicateFileException - if file already exists
      IOException - if an I/O error occurs during file creation

    • LocalBufferFile

      public LocalBufferFile(File file, boolean readOnly) throws IOException
      Open an existing block file.
      Parameters:
      file - block file
      readOnly - if true the file will be opened read-only
      Throws:
      IOException - if an error occurs or the incorrect magicNumber was read from the file.

  • Method Details

    • poke

      public static void poke(File file, int bufferIndex, DataBuffer buf) throws IOException
      Modify an existing buffer file.

      WARNING! Use with extreme caution since this modifies the original file and could destroy data if used improperly.

      Parameters:
      file - block file
      bufferIndex - the index at which to place the buffer
      buf - the buffer add to the file
      Throws:
      IOException - if an I/O error occurs

    • peek

      public static DataBuffer peek(File file, int bufferIndex) throws IOException
      Read a buffer from an existing buffer file.
      Parameters:
      file - block file
      bufferIndex - the index from which to read the buffer
      Returns:
      the buffer
      Throws:
      IOException - if an I/O error occurs

    • getFile

      public File getFile()
      Returns the physical file associated with this BufferFile.
      Returns:
      the file

    • isReadOnly

      public boolean isReadOnly()
      Description copied from interface: BufferFile
      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.
      Specified by:
      isReadOnly in interface BufferFile

    • getParameter

      public int getParameter(String name) throws NoSuchElementException
      Description copied from interface: BufferFile
      Get a the stored value for a named parameter.
      Specified by:
      getParameter in interface BufferFile
      Parameters:
      name - parameter name
      Returns:
      integer value
      Throws:
      NoSuchElementException - thrown if parameter not found

    • setParameter

      public void setParameter(String name, int value)
      Description copied from interface: BufferFile
      Set the integer value for a named parameter.
      Specified by:
      setParameter in interface BufferFile
      Parameters:
      name - parameter name
      value - parameter value

    • clearParameters

      public void clearParameters()
      Description copied from interface: BufferFile
      Deletes all parameters
      Specified by:
      clearParameters in interface BufferFile

    • getParameterNames

      public String[] getParameterNames()
      Description copied from interface: BufferFile
      Returns a list of all parameter names.
      Specified by:
      getParameterNames in interface BufferFile

    • getFreeIndexes

      public int[] getFreeIndexes()
      Description copied from interface: BufferFile
      Returns the list of free indexes sorted by value. The management of the free-index-list is implementation specific.
      Specified by:
      getFreeIndexes in interface BufferFile

    • setFreeIndexes

      public void setFreeIndexes(int[] indexes)
      Description copied from interface: BufferFile
      Sets the list of free buffer indexes. The management of the free-index-list is implementation specific.
      Specified by:
      setFreeIndexes in interface BufferFile

    • getDataBuffer

      public static DataBuffer getDataBuffer(BufferFileBlock block)
      Generate a DataBuffer instance which corresponds to the specified block based upon LocalBufferFile block usage.
      Parameters:
      block - the buffer file block to be converted
      Returns:
      DataBuffer instance or null if head block. If empty block DataBuffer will have null data

    • getBufferFileBlock

      public static BufferFileBlock getBufferFileBlock(DataBuffer buf, int bufferSize)
      Generate a BufferFileBlock instance which corresponds to the specified DataBuffer based upon LocalBufferFile block usage. This should generally not be used for writing empty blocks since they will not be properly linked which is normally handled during header flush which is performed by BufferFile close on files being written.
      Parameters:
      buf - the data buffer to be converted
      bufferSize - data buffer size used for integrity check and generating empty buffer
      Returns:
      BufferFileBlock instance.

    • get

      public DataBuffer get(DataBuffer buf, int index) throws IOException
      Description copied from interface: BufferFile
      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).
      Specified by:
      get in interface BufferFile
      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:
      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.
      IOException - if an I/O error occurs

    • put

      public void put(DataBuffer buf, int index) throws IOException
      Description copied from interface: BufferFile
      Store a data buffer at the specified block index.
      Specified by:
      put in interface BufferFile
      Parameters:
      buf - data buffer
      index - block index
      Throws:
      IOException - thrown if an IO error occurs

    • getBufferSize

      public int getBufferSize()
      Description copied from interface: BufferFile
      Return the actual size of a user data buffer. This value should be used when constructing DataBuffer objects.
      Specified by:
      getBufferSize in interface BufferFile
      Returns:
      DataBuffer data size as a number of bytes

    • getIndexCount

      public int getIndexCount()
      Description copied from interface: BufferFile
      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.
      Specified by:
      getIndexCount in interface BufferFile

    • dispose

      public void dispose()
      Description copied from interface: BufferFile
      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.
      Specified by:
      dispose in interface BufferFile

    • setReadOnly

      public boolean setReadOnly() throws IOException
      Description copied from interface: BufferFile
      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.
      Specified by:
      setReadOnly in interface BufferFile
      Returns:
      true if successfully transitioned from read-write to read-only
      Throws:
      IOException - if an I/O error occurs

    • close

      public void close() throws IOException
      Description copied from interface: BufferFile
      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.
      Specified by:
      close in interface BufferFile
      Throws:
      IOException - if an I/O error occurs

    • delete

      public boolean delete()
      Description copied from interface: BufferFile
      Delete this buffer file if writable. Once deleted, this object is immediately disposed and may no longer be used.
      Specified by:
      delete in interface BufferFile
      Returns:
      true if deleted, false if the file is read-only

    • clone

      public void clone(File destinationFile, TaskMonitor monitor) throws IOException, CancelledException
      Clone this buffer file to the specified file. The file must not already exist. If the operation is cancelled or an error occurs the file is not created.
      Parameters:
      destinationFile - destination file
      monitor - progress monitor
      Throws:
      IOException - if IO error occurs.
      CancelledException - if the monitor cancels the operation.

    • toString

      public String toString()
      Overrides:
      toString in class Object

    • getInputBlockStream

      public InputBlockStream getInputBlockStream() throws IOException
      Obtain a direct stream to read all blocks of this buffer file
      Returns:
      input block stream
      Throws:
      IOException - if there is an exception creating the stream

    • getOutputBlockStream

      public OutputBlockStream getOutputBlockStream(int blockCount) throws IOException
      Obtain a direct stream to write blocks to this buffer file
      Parameters:
      blockCount - number of blocks to be transferred
      Returns:
      output block stream
      Throws:
      IOException - if an I/O error occurs

    • copyFile

      public static void copyFile(BufferFile srcFile, BufferFile destFile, ChangeMap changeMap, TaskMonitor monitor) throws IOException, CancelledException
      Copy the complete content of a specified srcFile into a destFile excluding file ID. Both files remain open.
      Parameters:
      srcFile - open buffer file
      destFile - empty buffer file which is open for writing.
      changeMap - optional change map which indicates those buffers which must be copied. Any buffer index outside the range of the change map will also be copied.
      monitor - progress monitor
      Throws:
      IOException - if IO error occurs.
      CancelledException - if the monitor cancels the operation.

    • cleanupOldPreSaveFiles

      public static void cleanupOldPreSaveFiles(File dir, long beforeNow)
      Attempt to remove all pre-save files. Those still open by an existing process should not be removed by the operating system.
      Parameters:
      dir - data directory containing pre-save files
      beforeNow - if not 0, file mod time must be less than the specified time