text: // Copyright 2021 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_RESOURCE_QUOTA_THREAD_QUOTA_H
  #define GRPC_CORE_LIB_RESOURCE_QUOTA_THREAD_QUOTA_H
  
  #include <grpc/support/port_platform.h>
  
  #include <cstddef>
  
  #include "src/core/lib/gprpp/ref_counted.h"
  #include "src/core/lib/gprpp/sync.h"
  
  namespace grpc_core {
  
  // Tracks the amount of threads in a resource quota.
  class ThreadQuota : public RefCounted<ThreadQuota> {
   public:
    ThreadQuota();
    ~ThreadQuota() override;
  
    ThreadQuota(const ThreadQuota&) = delete;
    ThreadQuota& operator=(const ThreadQuota&) = delete;
  
    // Set the maximum number of threads that can be used by this quota.
    // If there are more, new reservations will fail until the quota is available.
    void SetMax(size_t new_max);
  
    // Try to allocate some number of threads.
    // Returns true if the allocation succeeded, false otherwise.
    bool Reserve(size_t num_threads);
  
    // Release some number of threads.
    void Release(size_t num_threads);
  
   private:
    Mutex mu_;
    size_t allocated_ ABSL_GUARDED_BY(mu_) = 0;
    size_t max_ ABSL_GUARDED_BY(mu_) = std::numeric_limits<size_t>::max();
  };
  
  }  // namespace grpc_core
  
  #endif  // GRPC_CORE_LIB_RESOURCE_QUOTA_THREAD_QUOTA_H
  