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/*
* Copyright (C) 2017 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef INCLUDE_PERFETTO_BASE_TASK_RUNNER_H_
#define INCLUDE_PERFETTO_BASE_TASK_RUNNER_H_
#include <functional>
#include "perfetto/base/export.h"
namespace perfetto {
namespace base {
// A generic interface to allow the library clients to interleave the execution
// of the tracing internals in their runtime environment.
// The expectation is that all tasks, which are queued either via PostTask() or
// AddFileDescriptorWatch(), are executed on the same sequence (either on the
// same thread, or on a thread pool that gives sequencing guarantees).
//
// Tasks are never executed synchronously inside PostTask and there is a full
// memory barrier between tasks.
//
// All methods of this interface can be called from any thread.
class PERFETTO_EXPORT TaskRunner {
public:
virtual ~TaskRunner();
// Schedule a task for immediate execution. Immediate tasks are always
// executed in the order they are posted. Can be called from any thread.
virtual void PostTask(std::function<void()>) = 0;
// Schedule a task for execution after |delay_ms|. Note that there is no
// strict ordering guarantee between immediate and delayed tasks. Can be
// called from any thread.
virtual void PostDelayedTask(std::function<void()>, uint32_t delay_ms) = 0;
// Schedule a task to run when |fd| becomes readable. The same |fd| can only
// be monitored by one function. Note that this function only needs to be
// implemented on platforms where the built-in ipc framework is used. Can be
// called from any thread.
// TODO(skyostil): Refactor this out of the shared interface.
virtual void AddFileDescriptorWatch(int fd, std::function<void()>) = 0;
// Remove a previously scheduled watch for |fd|. If this is run on the target
// thread of this TaskRunner, guarantees that the task registered to this fd
// will not be executed after this function call. Can be called from any
// thread.
virtual void RemoveFileDescriptorWatch(int fd) = 0;
// Checks if the current thread is the same thread where the TaskRunner's task
// run. This allows single threaded task runners (like the ones used in
// perfetto) to inform the caller that anything posted will run on the same
// thread/sequence. This can allow some callers to skip PostTask and instead
// directly execute the code. Can be called from any thread.
virtual bool RunsTasksOnCurrentThread() const = 0;
};
} // namespace base
} // namespace perfetto
#endif // INCLUDE_PERFETTO_BASE_TASK_RUNNER_H_
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