grpc/src/core/lib/gprpp/sync.h

/*
 *
 * Copyright 2019 gRPC authors.
 *
 * 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 GRPC_CORE_LIB_GPRPP_SYNC_H
#define GRPC_CORE_LIB_GPRPP_SYNC_H

#include <grpc/impl/codegen/port_platform.h>

#include <grpc/impl/codegen/log.h>
#include <grpc/impl/codegen/sync.h>
#include <grpc/support/sync.h>
#include <grpc/support/time.h>

// The core library is not accessible in C++ codegen headers, and vice versa.
// Thus, we need to have duplicate headers with similar functionality.
// Make sure any change to this file is also reflected in
// include/grpcpp/impl/codegen/sync.h.
//
// Whenever possible, prefer using this file over <grpcpp/impl/codegen/sync.h>
// since this file doesn't rely on g_core_codegen_interface and hence does not
// pay the costs of virtual function calls.

namespace grpc_core {

class Mutex {
 public:
  Mutex() { gpr_mu_init(&mu_); }
  ~Mutex() { gpr_mu_destroy(&mu_); }

  Mutex(const Mutex&) = delete;
  Mutex& operator=(const Mutex&) = delete;

  gpr_mu* get() { return &mu_; }
  const gpr_mu* get() const { return &mu_; }

 private:
  gpr_mu mu_;
};

// MutexLock is a std::
class MutexLock {
 public:
  explicit MutexLock(Mutex* mu) : mu_(mu->get()) { gpr_mu_lock(mu_); }
  explicit MutexLock(gpr_mu* mu) : mu_(mu) { gpr_mu_lock(mu_); }
  ~MutexLock() { gpr_mu_unlock(mu_); }

  MutexLock(const MutexLock&) = delete;
  MutexLock& operator=(const MutexLock&) = delete;

 private:
  gpr_mu* const mu_;
};

class ReleasableMutexLock {
 public:
  explicit ReleasableMutexLock(Mutex* mu) : mu_(mu->get()) { gpr_mu_lock(mu_); }
  explicit ReleasableMutexLock(gpr_mu* mu) : mu_(mu) { gpr_mu_lock(mu_); }
  ~ReleasableMutexLock() {
    if (!released_) gpr_mu_unlock(mu_);
  }

  ReleasableMutexLock(const ReleasableMutexLock&) = delete;
  ReleasableMutexLock& operator=(const ReleasableMutexLock&) = delete;

  void Lock() {
    GPR_DEBUG_ASSERT(released_);
    gpr_mu_lock(mu_);
    released_ = false;
  }

  void Unlock() {
    GPR_DEBUG_ASSERT(!released_);
    released_ = true;
    gpr_mu_unlock(mu_);
  }

 private:
  gpr_mu* const mu_;
  bool released_ = false;
};

class CondVar {
 public:
  CondVar() { gpr_cv_init(&cv_); }
  ~CondVar() { gpr_cv_destroy(&cv_); }

  CondVar(const CondVar&) = delete;
  CondVar& operator=(const CondVar&) = delete;

  void Signal() { gpr_cv_signal(&cv_); }
  void Broadcast() { gpr_cv_broadcast(&cv_); }

  int Wait(Mutex* mu) { return Wait(mu, gpr_inf_future(GPR_CLOCK_REALTIME)); }
  int Wait(Mutex* mu, const gpr_timespec& deadline) {
    return gpr_cv_wait(&cv_, mu->get(), deadline);
  }

  template <typename Predicate>
  void WaitUntil(Mutex* mu, Predicate pred) {
    while (!pred()) {
      Wait(mu, gpr_inf_future(GPR_CLOCK_REALTIME));
    }
  }

  // Returns true iff we timed-out
  template <typename Predicate>
  bool WaitUntil(Mutex* mu, Predicate pred, const gpr_timespec& deadline) {
    while (!pred()) {
      if (Wait(mu, deadline)) return true;
    }
    return false;
  }

 private:
  gpr_cv cv_;
};

}  // namespace grpc_core

#endif /* GRPC_CORE_LIB_GPRPP_SYNC_H */