Index: net/base/prioritized_dispatcher.h |
diff --git a/net/base/prioritized_dispatcher.h b/net/base/prioritized_dispatcher.h |
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index e4f1019d76ca5fe17c92f2c9f0527d297a29bdc4..0000000000000000000000000000000000000000 |
--- a/net/base/prioritized_dispatcher.h |
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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 NET_BASE_PRIORITIZED_DISPATCHER_H_ |
-#define NET_BASE_PRIORITIZED_DISPATCHER_H_ |
- |
-#include <vector> |
- |
-#include "net/base/net_export.h" |
-#include "net/base/priority_queue.h" |
- |
-namespace net { |
- |
-// A priority-based dispatcher of jobs. Dispatch order is by priority (highest |
-// first) and then FIFO. The dispatcher enforces limits on the number of running |
-// jobs. It never revokes a job once started. The job must call OnJobFinished |
-// once it finishes in order to dispatch further jobs. |
-// |
-// This class is NOT thread-safe which is enforced by the underlying |
-// non-thread-safe PriorityQueue. All operations are O(p) time for p priority |
-// levels. It is safe to execute any method, including destructor, from within |
-// Job::Start. |
-// |
-class NET_EXPORT_PRIVATE PrioritizedDispatcher { |
- public: |
- class Job; |
- typedef PriorityQueue<Job*>::Priority Priority; |
- |
- // Describes the limits for the number of jobs started by the dispatcher. |
- // For example, |total_jobs| = 30 and |reserved_slots| = { 0, 5, 10, 5 } allow |
- // for at most 30 running jobs in total. Jobs at priority 0 can't use slots |
- // reserved for higher priorities, so they are limited to 10. |
- // If there are already 24 jobs running, then only 6 more jobs can start. No |
- // jobs at priority 1 or below can start. After one more job starts, no jobs |
- // at priority 2 or below can start, since the remaining 5 slots are reserved |
- // for priority 3 or above. |
- struct NET_EXPORT_PRIVATE Limits { |
- Limits(Priority num_priorities, size_t total_jobs); |
- ~Limits(); |
- |
- // Total allowed running jobs. |
- size_t total_jobs; |
- // Number of slots reserved for each priority and higher. |
- // Sum of |reserved_slots| must be no greater than |total_jobs|. |
- std::vector<size_t> reserved_slots; |
- }; |
- |
- // An interface to the job dispatched by PrioritizedDispatcher. The dispatcher |
- // does not own the Job but expects it to live as long as the Job is queued. |
- // Use Cancel to remove Job from queue before it is dispatched. The Job can be |
- // deleted after it is dispatched or canceled, or the dispatcher is destroyed. |
- class Job { |
- public: |
- // Note: PrioritizedDispatcher will never delete a Job. |
- virtual ~Job() {} |
- // Called when the dispatcher starts the job. Once the job finishes, it must |
- // call OnJobFinished. |
- virtual void Start() = 0; |
- }; |
- |
- // A handle to the enqueued job. The handle becomes invalid when the job is |
- // canceled, updated, or started. |
- typedef PriorityQueue<Job*>::Pointer Handle; |
- |
- // Creates a dispatcher enforcing |limits| on number of running jobs. |
- explicit PrioritizedDispatcher(const Limits& limits); |
- |
- ~PrioritizedDispatcher(); |
- |
- size_t num_running_jobs() const { return num_running_jobs_; } |
- size_t num_queued_jobs() const { return queue_.size(); } |
- size_t num_priorities() const { return max_running_jobs_.size(); } |
- |
- // Adds |job| with |priority| to the dispatcher. If limits permit, |job| is |
- // started immediately. Returns handle to the job or null-handle if the job is |
- // started. The dispatcher does not own |job|, but |job| must live as long as |
- // it is queued in the dispatcher. |
- Handle Add(Job* job, Priority priority); |
- |
- // Just like Add, except that it adds Job at the font of queue of jobs with |
- // priorities of |priority|. |
- Handle AddAtHead(Job* job, Priority priority); |
- |
- // Removes the job with |handle| from the queue. Invalidates |handle|. |
- // Note: a Handle is valid iff the job is in the queue, i.e. has not Started. |
- void Cancel(const Handle& handle); |
- |
- // Cancels and returns the oldest-lowest-priority Job invalidating any |
- // handles to it. Returns NULL if the queue is empty. |
- Job* EvictOldestLowest(); |
- |
- // Moves the queued job with |handle| to the end of all values with priority |
- // |priority| and returns the updated handle, or null-handle if it starts the |
- // job. Invalidates |handle|. No-op if priority did not change. |
- Handle ChangePriority(const Handle& handle, Priority priority); |
- |
- // Notifies the dispatcher that a running job has finished. Could start a job. |
- void OnJobFinished(); |
- |
- // Retrieves the Limits that |this| is currently using. This may not exactly |
- // match the Limits this was created with. In particular, the number of slots |
- // reserved for the lowest priority will always be 0, even if it was non-zero |
- // in the Limits passed to the constructor or to SetLimits. |
- Limits GetLimits() const; |
- |
- // Updates |max_running_jobs_| to match |limits|. Starts jobs if new limit |
- // allows. Does not stop jobs if the new limits are lower than the old ones. |
- void SetLimits(const Limits& limits); |
- |
- // Set the limits to zero for all priorities, allowing no new jobs to start. |
- void SetLimitsToZero(); |
- |
- private: |
- // Attempts to dispatch the job with |handle| at priority |priority| (might be |
- // different than |handle.priority()|. Returns true if successful. If so |
- // the |handle| becomes invalid. |
- bool MaybeDispatchJob(const Handle& handle, Priority priority); |
- |
- // Attempts to dispatch the next highest priority job in the queue. Returns |
- // true if successful, and all handles to that job become invalid. |
- bool MaybeDispatchNextJob(); |
- |
- // Queue for jobs that need to wait for a spare slot. |
- PriorityQueue<Job*> queue_; |
- // Maximum total number of running jobs allowed after a job at a particular |
- // priority is started. If a greater or equal number of jobs are running, then |
- // another job cannot be started. |
- std::vector<size_t> max_running_jobs_; |
- // Total number of running jobs. |
- size_t num_running_jobs_; |
- |
- DISALLOW_COPY_AND_ASSIGN(PrioritizedDispatcher); |
-}; |
- |
-} // namespace net |
- |
-#endif // NET_BASE_PRIORITIZED_DISPATCHER_H_ |