text: // Copyright 2022 PingCAP, Ltd.
  //
  // 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.
  
  #pragma once
  
  #include <IO/BufferWithOwnMemory.h>
  #include <IO/ReadBuffer.h>
  #include <fcntl.h>
  
  #include <ctime>
  #include <functional>
  #include <string>
  
  #ifdef __APPLE__
  #include <common/apple_rt.h>
  #endif
  
  namespace DB
  {
  class ReadBufferFromFileBase : public BufferWithOwnMemory<ReadBuffer>
  {
  public:
      ReadBufferFromFileBase(size_t buf_size, char * existing_memory, size_t alignment);
      ReadBufferFromFileBase(ReadBufferFromFileBase &&) = default;
      virtual ~ReadBufferFromFileBase();
      off_t seek(off_t off, int whence = SEEK_SET);
      virtual off_t getPositionInFile() = 0;
      virtual std::string getFileName() const = 0;
      virtual int getFD() const = 0;
  
      /// It is possible to get information about the time of each reading.
      struct ProfileInfo
      {
          size_t bytes_requested;
          size_t bytes_read;
          size_t nanoseconds;
      };
  
      using ProfileCallback = std::function<void(ProfileInfo)>;
  
      /// CLOCK_MONOTONIC_COARSE is more than enough to track long reads - for example, hanging for a second.
      void setProfileCallback(const ProfileCallback & profile_callback_, clockid_t clock_type_ = CLOCK_MONOTONIC_COARSE)
      {
          profile_callback = profile_callback_;
          clock_type = clock_type_;
      }
  
  protected:
      ProfileCallback profile_callback;
      clockid_t clock_type;
  
      virtual off_t doSeek(off_t off, int whence) = 0;
  };
  
  } // namespace DB
  