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();

[michaeln, 2012/01/31 22:45:32]

Since sql::Connection dtor will close automatically for you, maybe we don't have
a use case for an explicit close method just yet.

(although i expect we will have a use case when we get to supporting
context->PurgeMemory) 

[benm (inactive), 2012/02/01 15:42:09]

Close is private and useful in the unit tests. I could move it into the test
fixture I guess for now, but given as you say we'll likely need it in the
future, shall I just leave it here? I guess that we don't need to call it from
the dtor here though.

+}
+
+bool DomStorageDatabase::LazyOpen() {

[michaeln, 2012/01/31 22:45:32]

can you reorder the methods in the .cc file to match the order in which they're
declared in the .h file

[benm (inactive), 2012/02/01 15:42:09]

Done.

+  if (IsOpen())
+    return true;
+
+  db_.reset(new sql::Connection());
+  bool is_open = db_->Open(file_path_);
+  db_->set_error_delegate(GetErrorHandlerForDomStorageDatabase());

[michaeln, 2012/01/31 22:45:32]

If the db->Open() method can invoke the error delegate (i'm not sure if it can),
we probably want to attach it prior to calling Open(). And if not, no reason to
attach it if Open() failes.  Is the is_open local needed?

[benm (inactive), 2012/02/01 15:42:09]

The docs in sql::Connection actually say that it should be called before Open,
so I imagine Open can invoke the ErrorDelegate. Will move. is_open is left over
from a previous version when I was using it for other things... can remove now.

+
+  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\""));
+
+  // Ensure we're at the correct version.
+  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();

[michaeln, 2012/01/31 22:45:32]

style nit: since the if { block } has brackets, the else { block } should too,
also there's some nesting here that maybe could get flattened out given early
returns

[benm (inactive), 2012/02/01 15:42:09]

gah, webkit style on the brain :)

+}
+
+void DomStorageDatabase::Close() {
+  if (!LazyOpen())

[michaeln, 2012/01/31 22:45:32]

at this point, there's no reason to open if not already open

[benm (inactive), 2012/02/01 15:42:09]

Good spot, think I was a little too generous with search/replace :)

+    return;
+
+  db_->Close();
+  db_.reset(NULL);
+}
+
+bool DomStorageDatabase::CreateTable() {
+  // Current version is 2.
+  return CreateTableV2();
+}
+
+bool DomStorageDatabase::CreateTableV2() {
+  if (!LazyOpen())
+    return false;
+
+  return db_->Execute(
+      "CREATE TABLE IF NOT EXISTS ItemTable ("
+      "key TEXT UNIQUE ON CONFLICT REPLACE, "
+      "value BLOB NOT NULL ON CONFLICT FAIL)");
+}
+
+void DomStorageDatabase::ReadAllValues(
+    DomStorageDatabase::ValuesMap* result) {
+  if (!LazyOpen())
+    return;
+
+  sql::Statement stmt(db_->GetCachedStatement(SQL_FROM_HERE,
+                                              "SELECT * from ItemTable"));
+  DCHECK(stmt.is_valid());
+  if (!stmt)
+    return;
+
+  while (stmt.Step()) {
+    string16 key = stmt.ColumnString16(0);
+    string16 value;
+    stmt.ColumnBlobAsString16(1, &value);
+    (*result)[key] = value;
+  }
+}
+
+bool DomStorageDatabase::WriteValues(const ValuesMap& values) {
+  if (!LazyOpen())
+    return false;
+
+  ValuesMap::const_iterator it = values.begin();
+  sql::Transaction transaction(db_.get());
+  if (!transaction.Begin())
+    return false;
+
+  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.data(), value.length() * sizeof(char16));
+    DCHECK(stmt.is_valid());
+    stmt.Run();
+  }
+  transaction.Commit();
+  return true;

[michaeln, 2012/01/31 22:45:32]

return transaction.Commit();

[benm (inactive), 2012/02/01 15:42:09]

Done.

+}
+
+bool DomStorageDatabase::RemoveValues(const ValuesSet& keys) {
+  if (!LazyOpen())
+    return false;
+
+  ValuesSet::const_iterator it = keys.begin();
+
+  sql::Transaction transaction(db_.get());
+  if (!transaction.Begin())
+    return false;
+
+  for ( ; it != keys.end(); ++it) {
+    sql::Statement stmt(db_->GetCachedStatement(SQL_FROM_HERE,
+        "DELETE FROM ItemTable WHERE key=?"));
+    stmt.BindString16(0, *it);
+    DCHECK(stmt.is_valid());
+    stmt.Run();
+  }
+  transaction.Commit();
+  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;
+  }
+
+  {

[michaeln, 2012/01/31 22:45:32]

why the extra scope

[benm (inactive), 2012/02/01 15:42:09]

hmm, I think I used to have some extra stuff after the transaction was done but
before the function returned, so the extra scope was to make sure it got cleaned
up asap. No need for it now though

+    sql::Transaction migration(db_.get());
+    if (migration.Begin()) {
+      if (db_->Execute("DROP TABLE ItemTable")) {
+        CreateTableV2();
+        if (WriteValues(values)) {
+          migration.Commit();

[michaeln, 2012/01/31 22:45:32]

return migration.Commit()?

[benm (inactive), 2012/02/01 15:42:09]

Done.

+          return true;
+        }
+      }
+    }
+  }
+  return false;
+}
+
+}  // namespace dom_storage