xapian-core/backends/slowvaluelist.cc

   1 /** @file slowvaluelist.cc
   2  * @brief Slow implementation for backends which don't streamed values.
   3  */
   4 /* Copyright (C) 2008,2011,2013,2014,2018 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 "slowvaluelist.h"
  24
  25 #include "documentinternal.h"
  26 #include "str.h"
  27 #include "unicode/description_append.h"
  28
  29 #include "xapian/error.h"
  30
  31 #include <memory>
  32
  33 using namespace std;
  34
  35 Xapian::docid
  36 SlowValueList::get_docid() const
  37 {
  38     return current_did;
  39 }
  40
  41 string
  42 SlowValueList::get_value() const
  43 {
  44     return current_value;
  45 }
  46
  47 Xapian::valueno
  48 SlowValueList::get_valueno() const
  49 {
  50     return slot;
  51 }
  52
  53 bool
  54 SlowValueList::at_end() const
  55 {
  56     return last_docid == 0;
  57 }
  58
  59 void
  60 SlowValueList::next()
  61 {
  62     // Compare before incrementing, since last_docid could be the largest
  63     // representable value in which case current_did will wrap to zero before
  64     // exceeding it.
  65     while (current_did++ < last_docid) {
  66         try {
  67             // Open document lazily so that we don't waste time checking for
  68             // its existence.
  69             void * d = db->open_document(current_did, true);
  70             if (!d)
  71                 continue;
  72             unique_ptr<Xapian::Document::Internal>
  73                 doc(static_cast<Xapian::Document::Internal*>(d));
  74             string value = doc->get_value(slot);
  75             if (!value.empty()) {
  76                 swap(current_value, value);
  77                 return;
  78             }
  79         } catch (const Xapian::DocNotFoundError &) {
  80         }
  81     }
  82
  83     // Indicate that we're at_end().
  84     last_docid = 0;
  85 }
  86
  87 void
  88 SlowValueList::skip_to(Xapian::docid did)
  89 {
  90     if (did <= current_did) return;
  91     current_did = did - 1;
  92     next();
  93 }
  94
  95 bool
  96 SlowValueList::check(Xapian::docid did)
  97 {
  98     if (did <= current_did) {
  99         return !current_value.empty();
 100     }
 101
 102     if (did > last_docid) {
 103         // Indicate that we're at_end().
 104         last_docid = 0;
 105         return true;
 106     }
 107
 108     current_did = did;
 109     try {
 110         void * d = db->open_document(current_did, true);
 111         if (d) {
 112             unique_ptr<Xapian::Document::Internal>
 113                 doc(static_cast<Xapian::Document::Internal*>(d));
 114             current_value = doc->get_value(slot);
 115             if (!current_value.empty()) return true;
 116         }
 117     } catch (const Xapian::DocNotFoundError &) {
 118     }
 119     current_value = string();
 120     return false;
 121 }
 122
 123 string
 124 SlowValueList::get_description() const
 125 {
 126     string desc = "SlowValueList(slot=";
 127     desc += str(slot);
 128     if (last_docid != 0) {
 129         desc += ", docid=";
 130         desc += str(current_did);
 131         desc += ", value=\"";
 132         description_append(desc, current_value);
 133         desc += "\")";
 134     } else {
 135         desc += ", atend)";
 136     }
 137     return desc;
 138 }