1   /* Copyright 2022-2025 Thales Alenia Space
2    * Licensed to CS GROUP (CS) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * CS licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    *
9    *   http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  package org.orekit.gnss.metric.parser;
18  
19  /** Encoded message as an hexadecimal characters sequence.
20   * @author Luc Maisonobe
21   * @since 11.0
22   */
23  public class HexadecimalSequenceEncodedMessage extends AbstractEncodedMessage {
24  
25      /** Hexadecimal radix. */
26      private static final int HEXA = 16;
27  
28      /** Characters sequence containing the message. */
29      private final CharSequence message;
30  
31      /** Index of current character in array. */
32      private int charIndex;
33  
34      /** Simple constructor.
35       * @param message characters sequence containing the message
36       */
37      public HexadecimalSequenceEncodedMessage(final CharSequence message) {
38          this.message = message;
39      }
40  
41      /** {@inheritDoc} */
42      @Override
43      public void start() {
44          super.start();
45          this.charIndex = -1;
46      }
47  
48      /** {@inheritDoc} */
49      @Override
50      protected int fetchByte() {
51          if (charIndex + 2 >= message.length()) {
52              return -1;
53          }
54          final int high = Character.digit(message.charAt(++charIndex), HEXA);
55          final int low  = Character.digit(message.charAt(++charIndex), HEXA);
56          return high << 4 | low;
57      }
58  
59  }