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1 : : /** @file chert_termlist.h
2 : : * @brief A TermList in a chert database.
3 : : */
4 : : /* Copyright (C) 2007,2008,2010 Olly Betts
5 : : *
6 : : * This program is free software; you can redistribute it and/or modify
7 : : * it under the terms of the GNU General Public License as published by
8 : : * the Free Software Foundation; either version 2 of the License, or
9 : : * (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 : : #ifndef XAPIAN_INCLUDED_CHERT_TERMLIST_H
22 : : #define XAPIAN_INCLUDED_CHERT_TERMLIST_H
23 : :
24 : : #include <string>
25 : :
26 : : #include <xapian/base.h>
27 : : #include <xapian/positioniterator.h>
28 : : #include <xapian/types.h>
29 : :
30 : : namespace Xapian {
31 : : namespace Internal {
32 : : class ExpandStats;
33 : : }
34 : : }
35 : :
36 : : #include "chert_database.h"
37 : : #include "termlist.h"
38 : : #include "chert_table.h"
39 : :
40 : : /// A TermList in a chert database.
41 [ + + ][ # # ]: 50703 : class ChertTermList : public TermList {
42 : : /// Don't allow assignment.
43 : : void operator=(const ChertTermList &);
44 : :
45 : : /// Don't allow copying.
46 : : ChertTermList(const ChertTermList &);
47 : :
48 : : /// The database we're reading data from.
49 : : Xapian::Internal::RefCntPtr<const ChertDatabase> db;
50 : :
51 : : /// The document id that this TermList is for.
52 : : Xapian::docid did;
53 : :
54 : : /// The length of document @a did.
55 : : chert_doclen_t doclen;
56 : :
57 : : /// The number of entries in this termlist.
58 : : Xapian::termcount termlist_size;
59 : :
60 : : /// The tag value from the termlist table which holds the encoded termlist.
61 : : std::string data;
62 : :
63 : : /** Current position with the encoded tag value held in @a data.
64 : : *
65 : : * If we've iterated to the end of the list, this gets set to NULL.
66 : : */
67 : : const char *pos;
68 : :
69 : : /// Pointer to the end of the encoded tag value.
70 : : const char *end;
71 : :
72 : : /// The termname at the current position.
73 : : std::string current_term;
74 : :
75 : : /// The wdf for the term at the current position.
76 : : Xapian::termcount current_wdf;
77 : :
78 : : /** The term frequency for the term at the current position.
79 : : *
80 : : * This will have the value 0 if the term frequency has not yet been
81 : : * looked up in the database (so it needs to be mutable).
82 : : */
83 : : mutable Xapian::doccount current_termfreq;
84 : :
85 : : public:
86 : : /// Create a new ChertTermList object for document @a did_ in DB @a db_
87 : : ChertTermList(Xapian::Internal::RefCntPtr<const ChertDatabase> db_,
88 : : Xapian::docid did_);
89 : :
90 : : /** Return the length of this document.
91 : : *
92 : : * This is a non-virtual method, used by ChertDatabase.
93 : : */
94 : : chert_doclen_t get_doclength() const;
95 : :
96 : : /** Return approximate size of this termlist.
97 : : *
98 : : * For a ChertTermList, this value will always be exact.
99 : : */
100 : : Xapian::termcount get_approx_size() const;
101 : :
102 : : /// Collate weighting information for the current term.
103 : : void accumulate_stats(Xapian::Internal::ExpandStats & stats) const;
104 : :
105 : : /// Return the termname at the current position.
106 : : std::string get_termname() const;
107 : :
108 : : /// Return the wdf for the term at the current position.
109 : : Xapian::termcount get_wdf() const;
110 : :
111 : : /** Return the term frequency for the term at the current position.
112 : : *
113 : : * In order to be able to support updating databases efficiently, we can't
114 : : * store this value in the termlist table, so it has to be read from the
115 : : * postlist table, which is relatively expensive (compared to reading the
116 : : * wdf for example).
117 : : */
118 : : Xapian::doccount get_termfreq() const;
119 : :
120 : : /** Advance the current position to the next term in the termlist.
121 : : *
122 : : * The list starts before the first term in the list, so next()
123 : : * must be called before any methods which need the context of
124 : : * the current position.
125 : : *
126 : : * @return Always returns 0 for a ChertTermList.
127 : : */
128 : : TermList * next();
129 : :
130 : : TermList * skip_to(const std::string & term);
131 : :
132 : : /// Return true if the current position is past the last term in this list.
133 : : bool at_end() const;
134 : :
135 : : /// Return the length of the position list for the current position.
136 : : Xapian::termcount positionlist_count() const;
137 : :
138 : : /// Return a PositionIterator for the current position.
139 : : Xapian::PositionIterator positionlist_begin() const;
140 : : };
141 : :
142 : : #endif // XAPIAN_INCLUDED_CHERT_TERMLIST_H
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