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// 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.
#ifndef CONTENT_BROWSER_LOADER_RESOURCE_SCHEDULER_H_
#define CONTENT_BROWSER_LOADER_RESOURCE_SCHEDULER_H_
#include <map>
#include <set>
#include "base/basictypes.h"
#include "base/compiler_specific.h"
#include "base/memory/scoped_ptr.h"
#include "base/threading/non_thread_safe.h"
#include "content/common/content_export.h"
#include "net/base/priority_queue.h"
#include "net/base/request_priority.h"
namespace net {
class URLRequest;
}
namespace content {
class ResourceThrottle;
// There is one ResourceScheduler. All renderer-initiated HTTP requests are
// expected to pass through it.
//
// There are two types of input to the scheduler:
// 1. Requests to start, cancel, or finish fetching a resource.
// 2. Notifications for renderer events, such as new tabs, navigation and
// painting.
//
// These input come from different threads, so they may not be in sync. The UI
// thread is considered the authority on renderer lifetime, which means some
// IPCs may be meaningless if they arrive after the UI thread signals a renderer
// has been deleted.
//
// The ResourceScheduler tracks many Clients, which should correlate with tabs.
// A client is uniquely identified by its child_id and route_id.
//
// Each Client may have many Requests in flight. Requests are uniquely
// identified within a Client by its ScheduledResourceRequest.
//
// Users should call ScheduleRequest() to notify this ResourceScheduler of a
// new request. The returned ResourceThrottle should be destroyed when the load
// finishes or is canceled.
//
// The scheduler may defer issuing the request via the ResourceThrottle
// interface or it may alter the request's priority by calling set_priority() on
// the URLRequest.
class CONTENT_EXPORT ResourceScheduler : public base::NonThreadSafe {
public:
ResourceScheduler();
~ResourceScheduler();
// Requests that this ResourceScheduler schedule, and eventually loads, the
// specified |url_request|. Caller should delete the returned ResourceThrottle
// when the load completes or is canceled.
scoped_ptr<ResourceThrottle> ScheduleRequest(
int child_id, int route_id, net::URLRequest* url_request);
// Signals from the UI thread, posted as tasks on the IO thread:
// Called when a renderer is created.
void OnClientCreated(int child_id, int route_id);
// Called when a renderer is destroyed.
void OnClientDeleted(int child_id, int route_id);
// Signals from IPC messages directly from the renderers:
// Called when a client navigates to a new main document.
void OnNavigate(int child_id, int route_id);
// Called when the client has parsed the <body> element. This is a signal that
// resource loads won't interfere with first paint.
void OnWillInsertBody(int child_id, int route_id);
private:
class RequestQueue;
class ScheduledResourceRequest;
struct Client;
typedef int64 ClientId;
typedef std::map<ClientId, Client*> ClientMap;
typedef std::set<ScheduledResourceRequest*> RequestSet;
// Called when a ScheduledResourceRequest is destroyed.
void RemoveRequest(ScheduledResourceRequest* request);
// Unthrottles the |request| and adds it to |client|.
void StartRequest(ScheduledResourceRequest* request, Client* client);
// Update the queue position for |request|, possibly causing it to start
// loading.
//
// Queues are maintained for each priority level. When |request| is
// reprioritized, it will move to the end of the queue for that priority
// level.
void ReprioritizeRequest(ScheduledResourceRequest* request,
net::RequestPriority new_priority);
// Attempts to load any pending requests in |client|, based on the
// results of ShouldStartRequest().
void LoadAnyStartablePendingRequests(Client* client);
// Returns the number of requests with priority < LOW that are currently in
// flight.
size_t GetNumDelayableRequestsInFlight(Client* client) const;
// Returns true if the request should start. This is the core scheduling
// algorithm.
bool ShouldStartRequest(ScheduledResourceRequest* request,
Client* client) const;
// Returns the client ID for the given |child_id| and |route_id| combo.
ClientId MakeClientId(int child_id, int route_id);
ClientMap client_map_;
RequestSet unowned_requests_;
};
} // namespace content
#endif // CONTENT_BROWSER_LOADER_RESOURCE_SCHEDULER_H_
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