127 lines
5.7 KiB
C++
127 lines
5.7 KiB
C++
#ifndef TEST_VENDOR_LIB_ASYNC_MANAGER_H_
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#define TEST_VENDOR_LIB_ASYNC_MANAGER_H_
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#include <time.h>
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#include <chrono>
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#include <cstdint>
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#include <functional>
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#include <map>
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#include <memory>
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#include <mutex>
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#include <set>
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#include <utility>
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#include "errno.h"
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#include "stdio.h"
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namespace rootcanal {
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using TaskCallback = std::function<void(void)>;
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using ReadCallback = std::function<void(int)>;
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using CriticalCallback = std::function<void(void)>;
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using AsyncTaskId = uint16_t;
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using AsyncUserId = uint16_t;
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constexpr uint16_t kInvalidTaskId = 0;
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// Manages tasks that should be done in the future. It can watch file
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// descriptors to call a given callback when it is certain that a non-blocking
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// read is possible or can call a callback at a specific time (approximately)
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// and (optionally) repeat the call periodically.
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// The class is thread safe in the sense that all its member functions can be
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// called simultaneously from different concurrent threads. The exception to
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// this rule is the class destructor, which is unsafe to call concurrently with
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// calls to other class member functions. This exception also has its own
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// exception: it is safe to destroy the object even if some of its callbacks may
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// call its member functions, because the destructor will make sure all callback
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// calling threads are stopped before actually destroying anything. Callbacks
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// that wait for file descriptor always run on the same thread, so there is no
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// need of additional synchronization between them. The same applies to task
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// callbacks since they also run on a thread of their own, however it is
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// possible for a read callback and a task callback to execute at the same time
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// (they are guaranteed to run in different threads) so synchronization is
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// needed to access common state (other than the internal state of the
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// AsyncManager class). While not required, it is strongly recommended to use
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// the Synchronize(const CriticalCallback&) member function to execute code
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// inside critical sections. Callbacks passed to this method on the same
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// AsyncManager object from different threads are granted to *NOT* run
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// concurrently.
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class AsyncManager {
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public:
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// Starts watching a file descriptor in a separate thread. The
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// on_read_fd_ready_callback() will be asynchronously called when it is
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// guaranteed that a call to read() on the FD will not block. No promise is
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// made about when in the future the callback will be called, in particular,
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// it is perfectly possible to have it called before this function returns. A
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// return of 0 means success, an error code is returned otherwise.
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int WatchFdForNonBlockingReads(int file_descriptor,
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const ReadCallback& on_read_fd_ready_callback);
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// If the fd was not being watched before the call will be ignored.
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void StopWatchingFileDescriptor(int file_descriptor);
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// Get an identifier for the scheduler so that tasks can be cancelled per user
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AsyncUserId GetNextUserId();
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// Schedules an action to occur in the future. Even if the delay given is not
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// positive the callback will be called asynchronously.
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AsyncTaskId ExecAsync(AsyncUserId user_id, std::chrono::milliseconds delay,
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const TaskCallback& callback);
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// Schedules an action to occur periodically in the future. If the delay given
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// is not positive the callback will be asynchronously called once for each
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// time in the past that it should have been called and then scheduled for
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// future times.
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AsyncTaskId ExecAsyncPeriodically(AsyncUserId user_id,
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std::chrono::milliseconds delay,
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std::chrono::milliseconds period,
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const TaskCallback& callback);
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// Cancels the/every future occurrence of the action specified by this id.
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// The following invariants will hold:
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// - The task will not be invoked after this method returns
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// - If the task is currently running it will block until the task is
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// completed, unless cancel is called from the running task.
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bool CancelAsyncTask(AsyncTaskId async_task_id);
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// Cancels the/every future occurrence of the action specified by this id.
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// The following invariants will hold:
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// - The task will not be invoked after this method returns
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// - If the task is currently running it will block until the task is
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// completed, unless cancel is called from the running task.
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bool CancelAsyncTasksFromUser(AsyncUserId user_id);
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// Execs the given code in a synchronized manner. It is guaranteed that code
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// given on (possibly)concurrent calls to this member function on the same
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// AsyncManager object will never be executed simultaneously. It is the
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// class's user's responsibility to ensure that no calls to Synchronize are
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// made from inside a CriticalCallback, since that would cause a lock to be
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// acquired twice with unpredictable results. It is strongly recommended to
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// have very simple CriticalCallbacks, preferably using lambda expressions.
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void Synchronize(const CriticalCallback&);
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AsyncManager();
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AsyncManager(const AsyncManager&) = delete;
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AsyncManager& operator=(const AsyncManager&) = delete;
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~AsyncManager();
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private:
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// Implementation of the FD watching part of AsyncManager, extracted to its
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// own class for clarity purposes.
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class AsyncFdWatcher;
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// Implementation of the asynchronous tasks part of AsyncManager, extracted to
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// its own class for clarity purposes.
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class AsyncTaskManager;
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// Kept as pointers because we may want to support resetting either without
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// destroying the other one
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std::unique_ptr<AsyncFdWatcher> fdWatcher_p_;
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std::unique_ptr<AsyncTaskManager> taskManager_p_;
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std::mutex synchronization_mutex_;
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};
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} // namespace rootcanal
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#endif // TEST_VENDOR_LIB_ASYNC_MANAGER_H_
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