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// Copyright (c) 2013 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 <memory>
#include "base/memory/ref_counted.h"
#include "base/sequenced_task_runner_helpers.h"
#include "content/browser/webui/url_data_manager.h"
#include "content/common/content_export.h"
namespace base {
class RefCountedMemory;
namespace content {
class URLDataManagerBackend;
class URLDataSource;
class URLDataSourceImpl;
// Trait used to handle deleting a URLDataSource. Deletion happens on the UI
// thread.
// Implementation note: the normal shutdown sequence is for the UI loop to
// stop pumping events then the IO loop and thread are stopped. When the
// URLDataSources are no longer referenced (which happens when IO thread stops)
// they get added to the UI message loop for deletion. But because the UI loop
// has stopped by the time this happens the URLDataSources would be leaked.
// To make sure URLDataSources are properly deleted URLDataManager manages
// deletion of the URLDataSources. When a URLDataSource is no longer referenced
// it is added to |data_sources_| and a task is posted to the UI thread to
// handle the actual deletion. During shutdown |DeleteDataSources| is invoked so
// that all pending URLDataSources are properly deleted.
struct DeleteURLDataSource {
static void Destruct(const URLDataSourceImpl* data_source) {
// A URLDataSource is an object that can answer requests for data
// asynchronously. URLDataSources are collectively owned with refcounting smart
// pointers and should never be deleted on the IO thread, since their calls
// are handled almost always on the UI thread and there's a possibility of a
// data race. The |DeleteDataSource| trait above is used to enforce this.
class URLDataSourceImpl : public base::RefCountedThreadSafe<
URLDataSourceImpl, DeleteURLDataSource> {
// See source_name_ below for docs on that parameter. Takes ownership of
// |source|.
URLDataSourceImpl(const std::string& source_name,
URLDataSource* source);
// Report that a request has resulted in the data |bytes|.
// If the request can't be satisfied, pass NULL for |bytes| to indicate
// the request is over.
virtual void SendResponse(int request_id,
scoped_refptr<base::RefCountedMemory> bytes);
const std::string& source_name() const { return source_name_; }
URLDataSource* source() const { return source_.get(); }
virtual ~URLDataSourceImpl();
friend class URLDataManager;
friend class URLDataManagerBackend;
friend class base::DeleteHelper<URLDataSourceImpl>;
// SendResponse invokes this on the IO thread. Notifies the backend to
// handle the actual work of sending the data.
virtual void SendResponseOnIOThread(
int request_id,
scoped_refptr<base::RefCountedMemory> bytes);
// The name of this source.
// E.g., for favicons, this could be "favicon", which results in paths for
// specific resources like "favicon/34" getting sent to this source.
const std::string source_name_;
// This field is set and maintained by URLDataManagerBackend. It is set when
// the DataSource is added, and unset if the DataSource is removed. A
// DataSource can be removed in two ways: the URLDataManagerBackend is
// deleted, or another DataSource is registered with the same name. backend_
// should only be accessed on the IO thread. This reference can't be via a
// scoped_refptr else there would be a cycle between the backend and data
// source.
URLDataManagerBackend* backend_;
std::unique_ptr<URLDataSource> source_;
} // namespace content