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