Package db.buffers

Class LocalManagedBufferFile

java.lang.Object
db.buffers.LocalBufferFile
db.buffers.LocalManagedBufferFile
All Implemented Interfaces:
BufferFile, ManagedBufferFile
public class LocalManagedBufferFile extends LocalBufferFile implements ManagedBufferFile
LocalManagedBufferFile implements a BufferFile as block-oriented random-access file which utilizes a BufferFileManager to identify and facilitate versioning of buffer files. This type of buffer file supports both save-as and save operations. The file format used is identical to a LocalBufferFile, although additional support is provided for associated files which facilitate versioning (e.g., ChangeMapFile, VersionFile, and changed data files).

  • Constructor Details

    • LocalManagedBufferFile

      public LocalManagedBufferFile(int bufferSize, BufferFileManager bfManager, long checkinId) throws IOException
      Open the initial version of a block file for writing.
      Parameters:
      bufferSize - user buffer size
      bfManager - buffer file version manager
      checkinId - the checkinId for creating a versioned buffer file.
      Throws:
      IOException - if an IO error occurs or the incorrect magicNumber was read from the file.

    • LocalManagedBufferFile

      public LocalManagedBufferFile(BufferFileManager bfManager, boolean versionUpdateEnabled, int minChangeDataVer, long checkinId) throws IOException
      Open the current version of an existing block file as read-only.
      Parameters:
      bfManager - buffer file version manager
      versionUpdateEnabled - if true Save support is enabled (pre-save starts automatically).
      minChangeDataVer - indicates the oldest change data buffer file to be included. A -1 indicates only the last change data buffer file is applicable.
      checkinId - the checkinId for versioned buffer files which are opened for update.
      Throws:
      IOException - if an IO error occurs or the incorrect magicNumber was read from the file.

    • LocalManagedBufferFile

      public LocalManagedBufferFile(BufferFileManager bfManager, int version, int minChangeDataVer) throws IOException
      Open an older version of an existing buffer file as read-only and NOT UPDATEABLE (bfMgr remains null). Version files must exist for all versions starting with the requested version. These version files will be used in conjunction with the current buffer file to emulate an older version buffer file.
      Parameters:
      bfManager - buffer file version manager
      version - version of file to be opened
      minChangeDataVer - indicates the oldest change data buffer file to be included. A -1 indicates only the last change data buffer file is applicable.
      Throws:
      IOException - if an IO error occurs or a problem with the version reconstruction.

  • Method Details

    • getNextChangeDataFile

      public BufferFile getNextChangeDataFile(boolean getFirst) throws IOException
      Description copied from interface: ManagedBufferFile
      Get the next change data file which corresponds to this buffer file. This method acts like an iterator which each successive invocation returning the next available file. Null is returned when no more files are available. The invoker is responsible for closing each file returned. It is highly recommended that each file be closed prior to requesting the next file.
      Specified by:
      getNextChangeDataFile in interface ManagedBufferFile
      Parameters:
      getFirst - causes the iterator to reset and return the first available file.
      Throws:
      IOException - if an I/O error occurs

    • getCheckinID

      public long getCheckinID()
      Description copied from interface: ManagedBufferFile
      Returns the checkin ID corresponding to this buffer file. The returned value is only valid if this buffer file has an associated buffer file manager and is either being created (see isReadOnly) or is intended for update (see canSave).
      Specified by:
      getCheckinID in interface ManagedBufferFile

    • setVersionComment

      public void setVersionComment(String comment) throws IOException
      Description copied from interface: ManagedBufferFile
      Set the comment which will be associated with this buffer file if saved. The comment must be set prior to invoking close or setReadOnly.
      Specified by:
      setVersionComment in interface ManagedBufferFile
      Parameters:
      comment - comment text
      Throws:
      IOException - if an I/O error occurs

    • 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
      Overrides:
      get in class LocalBufferFile
      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
      Overrides:
      put in class LocalBufferFile
      Parameters:
      buf - data buffer
      index - block index
      Throws:
      IOException - thrown if an IO error occurs

    • 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
      Overrides:
      setReadOnly in class LocalBufferFile
      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
      Overrides:
      close in class LocalBufferFile
      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
      Overrides:
      delete in class LocalBufferFile
      Returns:
      true if deleted, false if the file is read-only

    • getForwardModMapData

      public byte[] getForwardModMapData(int oldVersion) throws IOException
      Description copied from interface: ManagedBufferFile
      Returns a bit map corresponding to all buffers modified since oldVersion. This identifies all buffers contained within the oldVersion which have been modified during any revision up until this file version. Buffers added since oldVersion are not identified NOTE: The bit mask may identify empty/free buffers within this file version.
      Specified by:
      getForwardModMapData in interface ManagedBufferFile
      Parameters:
      oldVersion - indicates the older version of this file for which a change map will be returned. This method may only be invoked if this file is at version 2 or higher, has an associated BufferFileManager and the oldVersion related files still exist.
      Returns:
      ModMap buffer change map data
      Throws:
      IOException - if an I/O error occurs

    • getSaveChangeDataFile

      public BufferFile getSaveChangeDataFile() throws IOException
      Description copied from interface: ManagedBufferFile
      Returns a temporary change data buffer file which should be used to store a application-level ChangeSet associated with this new buffer file version. The getSaveFile method must be successfully invoked prior to invoking this method.
      Specified by:
      getSaveChangeDataFile in interface ManagedBufferFile
      Returns:
      change data file or null if one is not available.
      Throws:
      IOException - if an I/O error occurs

    • createNewVersion

      public void createNewVersion(ManagedBufferFile destFile, String fileComment, TaskMonitor monitor) throws CancelledException, IOException
      Create a new buffer file version (used for check-in)
      Parameters:
      destFile - must be an versioned file representing an earlier version of srcFile.
      fileComment - a comment for the new version.
      monitor - the current monitor.
      Throws:
      CancelledException - if the operation is canceled.
      IOException - if the file is in an unexpected state.

    • getSaveFile

      public ManagedBufferFile getSaveFile() throws IOException
      Description copied from interface: ManagedBufferFile
      Returns a Save file if available. Returns null if a save can not be performed. This method may block for an extended period of time if the pre-save process has not already completed. This method does not accept a monitor since a remote TaskMonitor does not yet exist.
      Specified by:
      getSaveFile in interface ManagedBufferFile
      Throws:
      IOException - if an I/O error occurs

    • getSaveFile

      public LocalManagedBufferFile getSaveFile(TaskMonitor monitor) throws IOException, CancelledException
      Returns a Save file if available. Returns null if a save can not be performed. This method may block for an extended period of time if the pre-save process has not already completed. This method does not accept a monitor since a remote TaskMonitor does not yet exist.
      Parameters:
      monitor - optional monitor for canceling pre-save (may be null)
      Throws:
      IOException - if an I/O error occurs
      CancelledException - if monitor specified and pre-save cancelled

    • saveCompleted

      public void saveCompleted(boolean commit) throws IOException
      Description copied from interface: ManagedBufferFile
      After getting the save file, this method must be invoked to terminate the save.
      Specified by:
      saveCompleted in interface ManagedBufferFile
      Parameters:
      commit - if true the save file will be reopened as read-only for update. If false, the save file will be deleted and the object will become invalid.
      Throws:
      IOException

    • canSave

      public boolean canSave()
      Description copied from interface: ManagedBufferFile
      Returns true if a save file is provided for creating a new version of this buffer file.
      Specified by:
      canSave in interface ManagedBufferFile
      See Also:

    • getOutputBlockStream

      public OutputBlockStream getOutputBlockStream(int blockCount) throws IOException
      Obtain a direct stream to write blocks to this buffer file
      Overrides:
      getOutputBlockStream in class LocalBufferFile
      Parameters:
      blockCount - number of blocks to be transferred
      Returns:
      output block stream
      Throws:
      IOException

    • getInputBlockStream

      public InputBlockStream getInputBlockStream() throws IOException
      Obtain a direct stream to read all blocks of this buffer file
      Overrides:
      getInputBlockStream in class LocalBufferFile
      Returns:
      input block stream
      Throws:
      IOException

    • getInputBlockStream

      public InputBlockStream getInputBlockStream(byte[] changeMapData) throws IOException
      Obtain a direct stream to read modified blocks of this buffer file based upon the specified changeMap
      Returns:
      input block stream
      Throws:
      IOException

    • updateFrom

      public void updateFrom(ManagedBufferFile versionedBufferFile, int oldVersion, TaskMonitor monitor) throws IOException, CancelledException
      Create a new version of this file by updating it from a versionedBufferFile. This file must be open as read-only with versionUpdateEnabled and have been derived from an oldVersion of the versionedBufferFile (i.e., was based on a check-out of oldVersion). The save-file corresponding to this file is updated using those buffers which have been modified or added in the specified versionedBufferFile since olderVersion. When complete, this file should be closed as soon as possible.
      Parameters:
      versionedBufferFile - versioned buffer file
      oldVersion - older version of versionedBufferFile from which this buffer file originated.
      monitor - progress monitor
      Throws:
      IOException - if an I/O error occurs
      CancelledException - if monitor cancels operation