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/*
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* Ottoman.h
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* Ottoman
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*
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* Created by Jens Alfke on 8/31/09.
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* Copyright 2009 Jens Alfke. All rights reserved.
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* BSD-Licensed: See the file "LICENSE.txt" for details.
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*/
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#ifndef _MOOSEYARD_OTTOMAN_
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#define _MOOSEYARD_OTTOMAN_
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namespace Mooseyard {
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class ChunkIterator;
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class Dictionary;
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class File;
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class VersionDictionary;
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class OverlayDictionary;
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/** A version-controlled persistent dictionary.
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Each version is stored as a VersionDictionary, unsaved changes as an OverlayDictionary. */
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class Ottoman {
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public:
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/** Creates an "untitled" Ottoman with no file and no lastVersion.
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After adding values to the currentVersion, use saveAs to save it. */
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Ottoman ();
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/** Opens an existing Ottoman file. */
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explicit Ottoman (const char *filename, bool writeable =true);
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/** Closes an Ottoman. */
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virtual ~Ottoman();
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/** The current filename, or NULL if the receiver is still in the "untitled" state. */
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virtual const char* filename() const {return _filename;}
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/** The latest saved version of the dictionary.
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Earlier versions can be accessed through its previousVersion() accessor.
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This will be NULL if the receiver is still in the "untitled" state. */
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virtual VersionDictionary* lastVersion() const {return _lastVersion;}
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/** A mutable overlay representing the current state of the dictionary.
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Changes are made in memory until save() is called.
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This will be NULL if the receiver was opened read-only (writeable=false). */
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virtual OverlayDictionary* currentVersion() const {return _current;}
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/** Has the on-disk file been updated with newer revisions than what I know about? */
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virtual bool needsSync() const;
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/** Reads any newer versions from disk.
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Returns true if new versions were read, false if there were none.
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Afterwards, lastVersion() will return the latest version in the file.
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(The old lastVersion dictionary is still around, so you can save a pointer to it
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before the call and use it later to see what changed.)
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Changes made to the currentVersion dictionary are not lost, but are now relative
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to the new lastVersion. You may want to scan them and resolve conflicts. */
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virtual bool sync();
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/** Saves the current version to the file, by appending.
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Returns false if there is a version conflict; in that case you need to call sync(),
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possibly resolve conflicts, and then call save() again. */
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virtual bool save();
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/** Saves the current version to the file, by writing to a new temporary file and
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then atomically replacing the original.
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Older versions, and older copies of the data, are not preserved, so this
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will typically shrink the file quite a bit.
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Returns false if there is a version conflict. */
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virtual bool saveAndCompact();
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/** Saves the current version to a new file, leaving the new file open,
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so subsequent saves will be written to it. */
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virtual void saveAs (const char *newFilename, bool overwriteAllowed =true);
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/** Scans the file for damage. Returns true if the file is OK, false if problems are found.
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If the 'repair' flag is set, will truncate the file to the last valid version. */
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bool scavenge (bool repair =false);
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ChunkIterator* chunkIterator() const; // for testing purposes
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private:
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Ottoman(const Ottoman&); // forbid copying/assignment
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Ottoman& operator=(const Ottoman&);
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void _open();
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void _append (File *dstFile);
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File* _writeTo (const char *dstFileName, bool overwriteAllowed);
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bool _writeable;
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File *_file;
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char *_filename;
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VersionDictionary *_lastVersion;
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OverlayDictionary *_current;
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};
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}
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#endif // _MOOSEYARD_OTTOMAN_
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