libminifi/include/io/FileStream.h

/**
 *
 * 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 <memory>
#include <vector>
#include <fstream>
#include <string>
#include "BaseStream.h"
#include "core/logging/LoggerFactory.h"

namespace org::apache::nifi::minifi::io {

/**
 * Purpose: File Stream Base stream extension. This is intended to be a thread safe access to
 * read/write to the local file system.
 *
 * Design: Simply extends BaseStream and overrides readData/writeData to allow a sink to the
 * fstream object.
 */
class FileStream : public io::BaseStream {
 public:
  /**
   * File Stream constructor that accepts an fstream shared pointer.
   * It must already be initialized for read and write.
   */
  explicit FileStream(std::filesystem::path path, uint32_t offset, bool write_enable = false);

  /**
   * File Stream constructor that accepts an fstream shared pointer.
   * It must already be initialized for read and write.
   * @param path path to file
   * @param append identifies if this is an append or overwriting the file
   */
  explicit FileStream(std::filesystem::path path, bool append = false);

  ~FileStream() override {
    close();
  }

  void close() final;
  /**
   * Skip to the specified offset.
   * @param offset offset to which we will skip
   */
  void seek(size_t offset) override;

  [[nodiscard]] size_t tell() const override;

  [[nodiscard]] size_t size() const override {
    return length_;
  }

  using BaseStream::read;
  using BaseStream::write;

  /**
   * Reads data and places it into buf
   * @param buf buffer in which we extract data
   * @param buflen
   */
  size_t read(gsl::span<std::byte> buf) override;

  /**
   * writes value to stream
   * @param value value to write
   * @param size size of value
   */
  size_t write(const uint8_t *value, size_t size) override;

 private:
  void seekToEndOfFile(const char* caller_error_msg);

  std::mutex file_lock_;
  std::unique_ptr<std::fstream> file_stream_;
  size_t offset_;
  std::filesystem::path path_;
  size_t length_;

  std::shared_ptr<core::logging::Logger> logger_ = core::logging::LoggerFactory<FileStream>::getLogger();
};

}  // namespace org::apache::nifi::minifi::io