text: // Licensed to the Apache Software Foundation (ASF) under one
  // or more contributor license agreements.  See the NOTICE file
  // distributed with this work for additional information
  // regarding copyright ownership.  The ASF licenses this file
  // to you 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 <stdint.h>
  
  #include <memory>
  
  #include "common/status.h"
  
  namespace doris {
  
  class FileReader {
  public:
      virtual ~FileReader() {}
      virtual Status open() = 0;
      // Read content to 'buf', 'buf_len' is the max size of this buffer.
      // Return ok when read success, and 'bytes_read' is set to size of read content
      // If reach to end of file, the eof is set to true. meanwhile 'bytes_read'
      // is set to zero.
      virtual Status read(uint8_t* buf, int64_t buf_len, int64_t* bytes_read, bool* eof) = 0;
      virtual Status readat(int64_t position, int64_t nbytes, int64_t* bytes_read, void* out) = 0;
  
      /**
       * This interface is used read a whole message, For example: read a message from kafka.
       *
       * if read eof then return Status::OK and length is set 0 and buf is set NULL,
       *  other return readed bytes.
       */
      virtual Status read_one_message(std::unique_ptr<uint8_t[]>* buf, int64_t* length) = 0;
      virtual int64_t size() = 0;
      virtual Status seek(int64_t position) = 0;
      virtual Status tell(int64_t* position) = 0;
      virtual void close() = 0;
      virtual bool closed() = 0;
  };
  
  } // namespace doris
  