1 // Copyright 2013 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 #include "chrome/browser/extensions/activity_log/database_string_table.h"
6
7 #include "base/strings/stringprintf.h"
8 #include "sql/connection.h"
9 #include "sql/statement.h"
10
11 using base::StringPrintf;
12
13 namespace extensions {
14
15 // A target maximum size (in number of entries) for the mapping tables. If the
16 // cache would grow larger than this, the size should be reduced.
17 static const size_t kMaximumCacheSize = 1000;
18
DatabaseStringTable(const std::string & table)19 DatabaseStringTable::DatabaseStringTable(const std::string& table)
20 : table_(table) {}
21
~DatabaseStringTable()22 DatabaseStringTable::~DatabaseStringTable() {}
23
Initialize(sql::Connection * connection)24 bool DatabaseStringTable::Initialize(sql::Connection* connection) {
25 if (!connection->DoesTableExist(table_.c_str())) {
26 return connection->Execute(StringPrintf(
27 "CREATE TABLE %s (id INTEGER PRIMARY KEY, value TEXT NOT NULL); "
28 "CREATE UNIQUE INDEX %s_index ON %s(value)",
29 table_.c_str(),
30 table_.c_str(),
31 table_.c_str()).c_str());
32 } else {
33 return true;
34 }
35 }
36
StringToInt(sql::Connection * connection,const std::string & value,int64 * id)37 bool DatabaseStringTable::StringToInt(sql::Connection* connection,
38 const std::string& value,
39 int64* id) {
40 std::map<std::string, int64>::const_iterator lookup =
41 value_to_id_.find(value);
42 if (lookup != value_to_id_.end()) {
43 *id = lookup->second;
44 return true;
45 }
46
47 // We will be adding data to the cache below--check the cache size now and
48 // reduce it if needed.
49 PruneCache();
50
51 // Operate on the assumption that the cache does a good job on
52 // frequently-used strings--if there is a cache miss, first act on the
53 // assumption that the string is not in the database either.
54 sql::Statement update(connection->GetUniqueStatement(
55 StringPrintf("INSERT OR IGNORE INTO %s(value) VALUES (?)", table_.c_str())
56 .c_str()));
57 update.BindString(0, value);
58 if (!update.Run())
59 return false;
60
61 if (connection->GetLastChangeCount() == 1) {
62 *id = connection->GetLastInsertRowId();
63 id_to_value_[*id] = value;
64 value_to_id_[value] = *id;
65 return true;
66 }
67
68 // The specified string may have already existed in the database, in which
69 // case the insert above will have been ignored. If this happens, do a
70 // lookup to find the old value.
71 sql::Statement query(connection->GetUniqueStatement(
72 StringPrintf("SELECT id FROM %s WHERE value = ?", table_.c_str())
73 .c_str()));
74 query.BindString(0, value);
75 if (!query.Step())
76 return false;
77 *id = query.ColumnInt64(0);
78 id_to_value_[*id] = value;
79 value_to_id_[value] = *id;
80 return true;
81 }
82
IntToString(sql::Connection * connection,int64 id,std::string * value)83 bool DatabaseStringTable::IntToString(sql::Connection* connection,
84 int64 id,
85 std::string* value) {
86 std::map<int64, std::string>::const_iterator lookup =
87 id_to_value_.find(id);
88 if (lookup != id_to_value_.end()) {
89 *value = lookup->second;
90 return true;
91 }
92
93 // We will be adding data to the cache below--check the cache size now and
94 // reduce it if needed.
95 PruneCache();
96
97 sql::Statement query(connection->GetUniqueStatement(
98 StringPrintf("SELECT value FROM %s WHERE id = ?", table_.c_str())
99 .c_str()));
100 query.BindInt64(0, id);
101 if (!query.Step())
102 return false;
103
104 *value = query.ColumnString(0);
105 id_to_value_[id] = *value;
106 value_to_id_[*value] = id;
107 return true;
108 }
109
ClearCache()110 void DatabaseStringTable::ClearCache() {
111 id_to_value_.clear();
112 value_to_id_.clear();
113 }
114
PruneCache()115 void DatabaseStringTable::PruneCache() {
116 if (id_to_value_.size() <= kMaximumCacheSize &&
117 value_to_id_.size() <= kMaximumCacheSize)
118 return;
119
120 // TODO(mvrable): Perhaps implement a more intelligent caching policy. For
121 // now, to limit memory usage we simply clear the entire cache when it would
122 // become too large. Data will be brought back in from the database as
123 // needed.
124 ClearCache();
125 }
126
127 } // namespace extensions
128