matcher/branchpostlist.h

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/* branchpostlist.h: virtual base class for branched types of postlist
 *
 * Copyright 1999,2000,2001 BrightStation PLC
 * Copyright 2002 Ananova Ltd
 * Copyright 2003,2004,2007 Olly Betts
 * Copyright 2007 Lemur Consulting Ltd
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301
 * USA
 */

#ifndef OM_HGUARD_BRANCHPOSTLIST_H
#define OM_HGUARD_BRANCHPOSTLIST_H

#include "multimatch.h"
#include "postlist.h"

class BranchPostList : public PostList {
    private:
        // Prevent copying
        BranchPostList(const BranchPostList &);
        BranchPostList & operator=(const BranchPostList &);

    protected:
        PostList *l;

        PostList *r;

        MultiMatch *matcher;

        void handle_prune(PostList *&kid, PostList *ret) {
            if (ret) {
                delete kid;
                kid = ret;

                // now tell matcher that maximum weights need recalculation.
                matcher->recalc_maxweight();
            }
        }

    public:
        BranchPostList(PostList *l_, PostList *r_, MultiMatch *matcher_)
                : l(l_), r(r_), matcher(matcher_) {}

        virtual ~BranchPostList();

        virtual Xapian::termcount get_wdf() const;
};

// Helper functions - call next/skip_to on a postlist and handle any
// resulting prune
// 
// Returns true iff a prune was handled, so the caller can recalculate
// weights etc if necessary
inline bool
next_handling_prune(PostList * & pl, Xapian::weight w_min,
                    MultiMatch *matcher)
{
    PostList *p = pl->next(w_min);
    if (!p) return false;
    delete pl;
    pl = p;
    // now tell matcher that maximum weights need recalculation.
    if (matcher) matcher->recalc_maxweight();
    return true;
}

inline bool
skip_to_handling_prune(PostList * & pl, Xapian::docid did, Xapian::weight w_min,
                       MultiMatch *matcher)
{
    PostList *p = pl->skip_to(did, w_min);
    if (!p) return false;
    delete pl;
    pl = p;
    // now tell matcher that maximum weights need recalculation.
    if (matcher) matcher->recalc_maxweight();
    return true;
}

#endif /* OM_HGUARD_BRANCHPOSTLIST_H */

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