xapian-core/backends/glass/glass_valuelist.cc

   1 /** @file glass_valuelist.cc
   2  * @brief Glass class for value streams.
   3  */
   4 /* Copyright (C) 2007,2008,2009 Olly Betts
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License as
   8  * published by the Free Software Foundation; either version 2 of the
   9  * License, or (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
  19  */
  20
  21 #include <config.h>
  22
  23 #include "glass_valuelist.h"
  24
  25 #include "glass_cursor.h"
  26 #include "glass_database.h"
  27 #include "omassert.h"
  28 #include "str.h"
  29
  30 using namespace Glass;
  31 using namespace std;
  32
  33 bool
  34 GlassValueList::update_reader()
  35 {
  36     Xapian::docid first_did = docid_from_key(slot, cursor->current_key);
  37     if (!first_did) return false;
  38
  39     cursor->read_tag();
  40     const string & tag = cursor->current_tag;
  41     reader.assign(tag.data(), tag.size(), first_did);
  42     return true;
  43 }
  44
  45 GlassValueList::~GlassValueList()
  46 {
  47     delete cursor;
  48 }
  49
  50 Xapian::docid
  51 GlassValueList::get_docid() const
  52 {
  53     Assert(!at_end());
  54     return reader.get_docid();
  55 }
  56
  57 Xapian::valueno
  58 GlassValueList::get_valueno() const
  59 {
  60     return slot;
  61 }
  62
  63 std::string
  64 GlassValueList::get_value() const
  65 {
  66     Assert(!at_end());
  67     return reader.get_value();
  68 }
  69
  70 bool
  71 GlassValueList::at_end() const
  72 {
  73     return cursor == NULL;
  74 }
  75
  76 void
  77 GlassValueList::next()
  78 {
  79     if (!cursor) {
  80         cursor = db->get_postlist_cursor();
  81         if (!cursor) return;
  82         cursor->find_entry_ge(make_valuechunk_key(slot, 1));
  83     } else if (!reader.at_end()) {
  84         reader.next();
  85         if (!reader.at_end()) return;
  86         cursor->next();
  87     }
  88
  89     if (!cursor->after_end()) {
  90         if (update_reader()) {
  91             if (!reader.at_end()) return;
  92         }
  93     }
  94
  95     // We've reached the end.
  96     delete cursor;
  97     cursor = NULL;
  98 }
  99
 100 void
 101 GlassValueList::skip_to(Xapian::docid did)
 102 {
 103     if (!cursor) {
 104         cursor = db->get_postlist_cursor();
 105         if (!cursor) return;
 106     } else if (!reader.at_end()) {
 107         reader.skip_to(did);
 108         if (!reader.at_end()) return;
 109     }
 110
 111     if (!cursor->find_entry(make_valuechunk_key(slot, did))) {
 112         if (update_reader()) {
 113             reader.skip_to(did);
 114             if (!reader.at_end()) return;
 115         }
 116         // The requested docid is between two chunks.
 117         cursor->next();
 118     }
 119
 120     // Either an exact match, or in a gap before the start of a chunk.
 121     if (!cursor->after_end()) {
 122         if (update_reader()) {
 123             if (!reader.at_end()) return;
 124         }
 125     }
 126
 127     // We've reached the end.
 128     delete cursor;
 129     cursor = NULL;
 130 }
 131
 132 bool
 133 GlassValueList::check(Xapian::docid did)
 134 {
 135     if (!cursor) {
 136         cursor = db->get_postlist_cursor();
 137         if (!cursor) return true;
 138     } else if (!reader.at_end()) {
 139         // Check for the requested docid in the current block.
 140         reader.skip_to(did);
 141         if (!reader.at_end()) return true;
 142     }
 143
 144     // Try moving to the appropriate chunk.
 145     if (!cursor->find_entry(make_valuechunk_key(slot, did))) {
 146         // We're in a chunk which might contain the docid.
 147         if (update_reader()) {
 148             reader.skip_to(did);
 149             if (!reader.at_end()) return true;
 150         }
 151         return false;
 152     }
 153
 154     // We had an exact match for a chunk starting with specified docid.
 155     Assert(!cursor->after_end());
 156     if (!update_reader()) {
 157         // We found the exact key we built, so it must match the slot.
 158         // Therefore update_reader() "can't possibly fail".
 159         Assert(false);
 160     }
 161
 162     return true;
 163 }
 164
 165 string
 166 GlassValueList::get_description() const
 167 {
 168     string desc("GlassValueList(slot=");
 169     desc += str(slot);
 170     desc += ')';
 171     return desc;
 172 }