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   /*
    * Copyright 2020 The Netty Project
    *
    * The Netty Project 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:
    *
    * https://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.
   */
  package io.netty.handler.pcap;
  
  import io.netty.buffer.ByteBuf;
  
  import java.io.IOException;
  import java.io.OutputStream;
  
  final class PcapHeaders {
  
      /**
       * Pcap Global Header built from:
       * <ol>
       *      <li> magic_number </li>
       *      <li> version_major </li>
       *      <li> version_minor </li>
       *      <li> thiszone </li>
       *      <li> sigfigs </li>
       *      <li> snaplen </li>
       *      <li> network </li>
       * </ol>
       */
      private static final byte[] GLOBAL_HEADER = {-95, -78, -61, -44, 0, 2, 0, 4, 0, 0,
              0, 0, 0, 0, 0, 0, 0, 0, -1, -1, 0, 0, 0, 1};
  
      private PcapHeaders() {
          // Prevent outside initialization
      }
  
      /**
       * Writes the Pcap Global Header to the provided {@code OutputStream}
       *
       * @param outputStream OutputStream where Pcap data will be written.
       * @throws IOException if there is an error writing to the {@code OutputStream}
       */
      static void writeGlobalHeader(OutputStream outputStream) throws IOException {
          outputStream.write(GLOBAL_HEADER);
      }
  
      /**
       * Write Pcap Packet Header
       *
       * @param byteBuf  ByteBuf where we'll write header data
       * @param ts_sec   timestamp seconds
       * @param ts_usec  timestamp microseconds
       * @param incl_len number of octets of packet saved in file
       * @param orig_len actual length of packet
       */
      static void writePacketHeader(ByteBuf byteBuf, int ts_sec, int ts_usec, int incl_len, int orig_len) {
          byteBuf.writeInt(ts_sec);
          byteBuf.writeInt(ts_usec);
          byteBuf.writeInt(incl_len);
          byteBuf.writeInt(orig_len);
      }
  }