Add pause/resume functionality to precache

components/precache/core/precache_session_table.cc

+// Copyright 2016 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 "components/precache/core/precache_session_table.h"
+
+#include <string>
+
+#include "base/logging.h"
+#include "base/time/time.h"
+#include "components/precache/core/proto/unfinished_work.pb.h"
+#include "sql/connection.h"
+#include "sql/statement.h"
+
+using sql::Statement;
+
+namespace precache {
+
+PrecacheSessionTable::PrecacheSessionTable() : db_(nullptr) {}
+
+PrecacheSessionTable::~PrecacheSessionTable() {}
+
+bool PrecacheSessionTable::Init(sql::Connection* db) {
+  DCHECK(!db_);  // Init must only be called once.
+  DCHECK(db);    // The database connection must be non-NULL.
+  db_ = db;
+  return CreateTableIfNonExistent();
+}
+
+// Store unfinished work.
+void PrecacheSessionTable::SaveUnfinishedWork(
+    std::unique_ptr<PrecacheUnfinishedWork> unfinished_work) {
+  Statement statement(db_->GetCachedStatement(
+      SQL_FROM_HERE,
+      "INSERT OR REPLACE INTO precache_session (type, value) VALUES(?,?)"));
+  statement.BindInt(0, static_cast<int>(UNFINISHED_WORK));
+  statement.BindString(1, unfinished_work->SerializeAsString());
+  statement.Run();
+}
+
+// Retrieve unfinished work.
+std::unique_ptr<PrecacheUnfinishedWork>
+PrecacheSessionTable::GetUnfinishedWork() {
+  Statement statement(db_->GetCachedStatement(
+      SQL_FROM_HERE, "SELECT value from precache_session where type=?"));
+  statement.BindInt(0, static_cast<int>(UNFINISHED_WORK));
+  std::unique_ptr<PrecacheUnfinishedWork> unfinished_work(
+      new PrecacheUnfinishedWork());
+  if (statement.Step())
+    unfinished_work->ParseFromString(statement.ColumnString(0));
+  return unfinished_work;
+}
+
+
+
+void PrecacheSessionTable::DeleteUnfinishedWork() {
+  Statement statement(
+      db_->GetCachedStatement(
+          SQL_FROM_HERE, "DELETE FROM precache_session where type=?"));
+  statement.BindInt(0, static_cast<int>(UNFINISHED_WORK));
+  statement.Run();
+}
+
+bool PrecacheSessionTable::CreateTableIfNonExistent() {
+  return db_->Execute(
+      "CREATE TABLE IF NOT EXISTS precache_session (type INTEGER PRIMARY KEY, "
+      "value STRING)");
+}
+
+}  // namespace precache