async/cancellation_token.cc

// Copyright 2026 Google LLC
//
// 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
//
//    https://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.
//

#include "async/cancellation_token.h"

#include <cstdint>
#include <utility>
#include <vector>

#include "absl/functional/any_invocable.h"
#include "absl/synchronization/mutex.h"

namespace credentio {

void CancellationState::Cancel() {
  std::vector<absl::AnyInvocable<void()>> to_run;

  {
    absl::MutexLock lock(mutex_);
    if (cancelled_) return;
    cancelled_ = true;

    to_run.reserve(callbacks_.size());
    for (auto& pair : callbacks_) {
      to_run.push_back(std::move(pair.second));
    }
    callbacks_.clear();
  }

  // Execute callbacks without holding the lock to avoid deadlocks.
  for (auto& cb : to_run) {
    if (cb) {
      cb();
    }
  }
}

uint64_t CancellationState::RegisterCallback(absl::AnyInvocable<void()> cb) {
  {
    absl::MutexLock lock(mutex_);
    if (!cancelled_) {
      uint64_t id = next_id_++;
      callbacks_[id] = std::move(cb);
      return id;
    }
  }

  // If already cancelled, execute immediately and return 0 (no unregister
  // needed).
  if (cb) {
    cb();
  }
  return 0;
}

void CancellationState::DeregisterCallback(uint64_t id) {
  absl::MutexLock lock(mutex_);
  callbacks_.erase(id);
}

}  // namespace credentio