Class DirCacheEditor

  • public class DirCacheEditor
    extends Object
    Updates a DirCache by supplying discrete edit commands.

    An editor updates a DirCache by taking a list of DirCacheEditor.PathEdit commands and executing them against the entries of the destination cache to produce a new cache. This edit style allows applications to insert a few commands and then have the editor compute the proper entry indexes necessary to perform an efficient in-order update of the index records. This can be easier to use than DirCacheBuilder.

    See Also:
    • Field Detail

      • cache

        protected DirCache cache
        The cache instance this editor updates during finish().
      • entries

        protected DirCacheEntry[] entries
        Entry table this builder will eventually replace into cache.

        Use fastAdd(DirCacheEntry) or fastKeep(int, int) to make additions to this table. The table is automatically expanded if it is too small for a new addition.

        Typically the entries in here are sorted by their path names, just like they are in the DirCache instance.

      • entryCnt

        protected int entryCnt
        Total number of valid entries in entries.
    • Constructor Detail

      • DirCacheEditor

        protected DirCacheEditor​(DirCache dc,
                                 int ecnt)
        Construct a new editor.
        dc - the cache this editor will eventually update.
        ecnt - estimated number of entries the editor will have upon completion. This sizes the initial entry table.
    • Method Detail

      • add

        public void add​(DirCacheEditor.PathEdit edit)
        Append one edit command to the list of commands to be applied.

        Edit commands may be added in any order chosen by the application. They are automatically rearranged by the builder to provide the most efficient update possible.

        edit - another edit command.
      • commit

        public boolean commit()
                       throws IOException
        Finish, write, commit this change, and release the index lock.

        If this method fails (returns false) the lock is still released.

        This is a utility method for applications as the finish-write-commit pattern is very common after using a builder to update entries.

        true if the commit was successful and the file contains the new data; false if the commit failed and the file remains with the old data.
        IOException - the output file could not be created. The caller no longer holds the lock.
      • finish

        public void finish()
        Finish this builder and update the destination DirCache.

        When this method completes this builder instance is no longer usable by the calling application. A new builder must be created to make additional changes to the index entries.

        After completion the DirCache returned by getDirCache() will contain all modifications.

        Note to implementors: Make sure entries is fully sorted then invoke replace() to update the DirCache with the new table.

      • getDirCache

        public DirCache getDirCache()
        Get the DirCache
        the cache we will update on finish().
      • fastAdd

        protected void fastAdd​(DirCacheEntry newEntry)
        Append one entry into the resulting entry list.

        The entry is placed at the end of the entry list. The caller is responsible for making sure the final table is correctly sorted.

        The entries table is automatically expanded if there is insufficient space for the new addition.

        newEntry - the new entry to add.
      • fastKeep

        protected void fastKeep​(int pos,
                                int cnt)
        Add a range of existing entries from the destination cache.

        The entries are placed at the end of the entry list, preserving their current order. The caller is responsible for making sure the final table is correctly sorted.

        This method copies from the destination cache, which has not yet been updated with this editor's new table. So all offsets into the destination cache are not affected by any updates that may be currently taking place in this editor.

        The entries table is automatically expanded if there is insufficient space for the new additions.

        pos - first entry to copy from the destination cache.
        cnt - number of entries to copy.
      • replace

        protected void replace()
        Update the DirCache with the contents of entries.

        This method should be invoked only during an implementation of finish(), and only after entries is sorted.