Create a class to represent a DOM Storage Database.

webkit/dom_storage/dom_storage_database.cc

+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "webkit/dom_storage/dom_storage_database.h"
+
+#include <string>
+
+#include "base/logging.h"
+#include "base/utf_string_conversions.h"
+#include "sql/diagnostic_error_delegate.h"
+#include "sql/statement.h"
+#include "sql/transaction.h"
+
+namespace {
+
+class HistogramUniquifier {
+ public:
+  static const char* name() { return "Sqlite.DomStorageDatabase.Error"; }
+};
+
+sql::ErrorDelegate* GetErrorHandlerForDomStorageDatabase() {
+  return new sql::DiagnosticErrorDelegate<HistogramUniquifier>();
+}
+
+}  // anon namespace
+
+namespace dom_storage {
+
+DomStorageDatabase::DomStorageDatabase(const FilePath& file_path)
+    : file_path_(file_path),
+      db_(NULL) {
+  DCHECK(!file_path_.empty());
+}
+
+DomStorageDatabase::~DomStorageDatabase() {
+  if (IsOpen())
+    Close();
+}
+
+bool DomStorageDatabase::Open() {
+  if (IsOpen())
+    return true;
+
+  db_.reset(new sql::Connection());
+  bool is_open = db_->Open(file_path_);
+  db_->set_error_delegate(GetErrorHandlerForDomStorageDatabase());
+
+  if (!is_open) {
+    LOG(WARNING) << "Unable to open Database at " << file_path_.value();
+    return false;
+  }
+
+  // sql::Connection uses UTF-8 encoding, but WebCore style databases use
+  // UTF-16, so ensure we match.
+  ignore_result(db_->Execute("PRAGMA encoding=\"UTF-16\""));
+
+  return is_open;
+}
+
+bool DomStorageDatabase::Init() {
+  if (!IsOpen())
+    return false;
+
+  if (db_->DoesTableExist("ItemTable")) {
+    if (UpgradeVersion1To2IfNeeded())
+      return true;
+    else {
+      // Upgrade failed, drop table and start fresh.
+      if (db_->Execute("DROP TABLE ItemTable"))
+        return CreateTable();
+      else
+        return false;
+    }
+  } else
+    return CreateTable();
+}
+
+void DomStorageDatabase::Close() {
+  if (!IsOpen())
+    return;
+
+  db_->Close();
+  db_.reset(NULL);
+}
+
+bool DomStorageDatabase::CreateTable() {
+  // Current version is 2.
+  return CreateTableV2();
+}
+
+bool DomStorageDatabase::CreateTableV2() {
+  if (!IsOpen())
+    return false;
+
+  return db_->Execute(
+      "CREATE TABLE IF NOT EXISTS ItemTable ("
+      "key TEXT UNIQUE ON CONFLICT REPLACE, "
+      "value BLOB NOT NULL ON CONFLICT FAIL)");
+}
+
+DomStorageDatabase::ValuesMap DomStorageDatabase::ReadAllValues() const {
+    ValuesMap values;
+  if (!IsOpen())
+    return values;
+
+  sql::Statement stmt(db_->GetCachedStatement(SQL_FROM_HERE,
+                                              "SELECT * from ItemTable"));
+  DCHECK(stmt.is_valid());
+  if (stmt) {
+    while (stmt.Step()) {
+      string16 key = stmt.ColumnString16(0);
+      string16 value(reinterpret_cast<const char16*>(stmt.ColumnBlob(1)));

[michaeln, 2012/01/31 03:11:16]

Can these values have embedded NULLs in them and is there any guarantee that the
value is NULL terminated? Seems like we need a ColumnBlobAsString16 helper
somewhere.

[benm (inactive), 2012/01/31 15:10:53]

I'm writing out using c_str(), so I think it should be ok to assume null
terminated. But embedded nulls would be a problem if they were present in the
original input as it would have only written up to the first null (the -1 in the
BindBlob call).

+      values[key] = value;
+
+    }
+  }
+
+  return values;
+}
+
+bool DomStorageDatabase::WriteValues(const ValuesMap& values) {
+  if (!IsOpen())
+    return false;
+
+  ValuesMap::const_iterator it = values.begin();
+  for(; it != values.end(); ++it) {
+    sql::Statement stmt(db_->GetCachedStatement(SQL_FROM_HERE,
+        "INSERT INTO ItemTable VALUES (?,?)"));
+    string16 key = it->first;
+    string16 value = it->second;
+    stmt.BindString16(0, key);
+    stmt.BindBlob(1, value.c_str(), -1);

[michaeln, 2012/01/31 03:11:16]

do we have to be explicit about the length here?

  bool BindBlob(int col, const void* value, int value_len);

[benm (inactive), 2012/01/31 15:10:53]

-1 says to write up to the first null, so not as long as the blob is null
terminated and there are no embedded nulls. Null terminated is OK as I'm using
c_str(), but embedded nulls... not so sure.

+    DCHECK(stmt.is_valid());
+    stmt.Run();
+  }
+  return true;
+}
+
+bool DomStorageDatabase::RemoveValues(const ValuesSet& keys) {
+  if (!IsOpen())
+    return false;
+
+  ValuesSet::const_iterator it = keys.begin();
+  for ( ; it != keys.end(); ++it) {

[michaeln, 2012/01/31 03:11:16]

We'll want to put multiple write statements in a transactions.

[benm (inactive), 2012/01/31 15:10:53]

Done (and for Write above).

+    sql::Statement stmt(db_->GetCachedStatement(SQL_FROM_HERE,
+        "DELETE FROM ItemTable WHERE key=?"));
+    stmt.BindString16(0, *it);
+    DCHECK(stmt.is_valid());
+    stmt.Run();
+  }
+
+  return true;
+}
+
+bool DomStorageDatabase::UpgradeVersion1To2IfNeeded() {
+  sql::Statement stmt(db_->GetCachedStatement(SQL_FROM_HERE,
+      "SELECT * FROM ItemTable"));
+  DCHECK(stmt.is_valid());
+  if (!stmt)
+    return false;
+
+  // Quick check to see if we need to upgrade or not. The single
+  // effect of V1 -> V2 is to change the value column from type
+  // TEXT to type BLOB.
+  sql::ColType valueColumnType = stmt.DeclaredColumnType(1);
+  if (valueColumnType == sql::COLUMN_TYPE_BLOB)
+    return true;
+
+  if (valueColumnType != sql::COLUMN_TYPE_TEXT) {
+    // Something is messed up. This is not a V1 database.
+    return false;
+  }
+
+  // Need to migrate from TEXT value column to BLOB.
+  ValuesMap values;
+  while (stmt.Step()) {
+    string16 key = stmt.ColumnString16(0);
+    string16 value = stmt.ColumnString16(1);
+    values[key] = value;
+  }
+
+  {
+    sql::Transaction migration(db_.get());
+    if (migration.Begin()) {
+      if (db_->Execute("DROP TABLE ItemTable")) {
+        CreateTableV2();
+        if (WriteValues(values)) {
+          migration.Commit();
+          return true;
+        }
+      }
+    }
+  }
+  return false;
+}
+
+}  // namespace dom_storage