callback_scheduler.h

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// Copyright 2026 The A11 Authors.
 
#ifndef A11_CONCURRENCY_CALLBACK_SCHEDULER_H_
#define A11_CONCURRENCY_CALLBACK_SCHEDULER_H_
 
#include <cstddef>
#include <deque>
 
#include <absl/functional/any_invocable.h>
 
#include "thread/boost_primitives.h"
 
namespace a11::internal {
 
// A fair, stackless callback pump. Instances must have process lifetime because
// posted callbacks retain a raw pointer to the scheduler, while queued work
// owns the state it operates on.
class CallbackScheduler {
 public:
  explicit CallbackScheduler(size_t max_callbacks_per_turn = 64)
      : max_callbacks_per_turn_(max_callbacks_per_turn) {}
 
  CallbackScheduler(const CallbackScheduler&) = delete;
  CallbackScheduler& operator=(const CallbackScheduler&) = delete;
 
  void Schedule(absl::AnyInvocable<void() &&> callback);
 
 private:
  void Run();
 
  const size_t max_callbacks_per_turn_;
  thread::Mutex mu_;
  std::deque<absl::AnyInvocable<void() &&>> callbacks_ ABSL_GUARDED_BY(mu_);
  bool scheduled_ ABSL_GUARDED_BY(mu_) = false;
};
 
}  // namespace a11::internal
 
#endif  // A11_CONCURRENCY_CALLBACK_SCHEDULER_H_