110 lines
3.5 KiB
C++
110 lines
3.5 KiB
C++
/* Copyright (C) 2009 J.F.Dockes
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the
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* Free Software Foundation, Inc.,
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* 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*/
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#ifndef _circache_h_included_
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#define _circache_h_included_
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/**
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* A data cache implemented as a circularly managed file
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*
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* A single file is used to stored objects. The file grows to a
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* specified maximum size, then is rewritten from the start,
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* overwriting older entries.
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*
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* Data objects inside the cache each have two parts: a data segment and an
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* attribute (metadata) dictionary.
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* They are named using the same identifiers that are used inside the Recoll
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* index (the UDI).
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*
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* Inside the file. the UDIs are stored inside the entry dictionary
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* under the key "udi".
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*
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* It is assumed that the dictionary are small (they are routinely read/parsed)
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*
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* A problem with this approach is that repetitively storing the same
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* object will evict all others. This could be somewhat optimized by reusing
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* the last entry if it has the same udi as the one written, but not done
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* currently.
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*/
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#include <sys/types.h>
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#include <string>
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#ifndef NO_NAMESPACES
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using std::string;
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#endif
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class ConfSimple;
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class CirCacheInternal;
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class CirCache {
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public:
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CirCache(const string& dir);
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virtual ~CirCache();
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virtual string getReason();
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enum CreateFlags {CC_CRNONE=0,
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// Unique entries: erase older instances when same udi
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// is stored.
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CC_CRUNIQUE=1,
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// Truncate file (restart from scratch).
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CC_CRTRUNCATE = 2};
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virtual bool create(off_t maxsize, int flags);
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enum OpMode {CC_OPREAD, CC_OPWRITE};
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virtual bool open(OpMode mode);
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virtual bool get(const string& udi, string& dic, string& data,
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int instance = -1);
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// Note: the dicp MUST have an udi entry
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enum PutFlags {NoCompHint = 1};
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virtual bool put(const string& udi, const ConfSimple *dicp,
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const string& data, unsigned int flags = 0);
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virtual bool erase(const string& udi);
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/** Walk the archive.
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*
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* Maybe we'll have separate iterators one day, but this is good
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* enough for now. No put() operations should be performed while
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* using these.
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*/
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/** Back to oldest */
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virtual bool rewind(bool& eof);
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/** Get entry under cursor */
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virtual bool getCurrent(string& udi, string& dic, string& data);
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/** Get current entry udi only. Udi can be empty (erased empty), caller
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* should call again */
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virtual bool getCurrentUdi(string& udi);
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/** Skip to next. (false && !eof) -> error, (false&&eof)->EOF. */
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virtual bool next(bool& eof);
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/* Debug. This writes the entry headers to stdout */
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virtual bool dump();
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protected:
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CirCacheInternal *m_d;
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string m_dir;
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private:
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CirCache(const CirCache&) {}
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CirCache& operator=(const CirCache&) {return *this;}
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};
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#endif /* _circache_h_included_ */
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