1   /* Copyright 2002-2024 CS GROUP
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.utils;
18  
19  import java.util.Locale;
20  
21  import org.hipparchus.util.RyuDouble;
22  
23  /** Formatter used to produce strings from data with high accuracy.
24   * <p>
25   * When producing test output from computed data, we want the shortest
26   * decimal representation of a floating point number that maintains
27   * round-trip safety. That is, a correct parser can recover the exact
28   * original number.
29   * </p>
30   * <p>
31   * For efficiency, this class uses the {@link RyuDouble Ryū} algorithm
32   * for producing shortest string representation with round-trip safety.
33   * </p>
34   * @author Luc Maisonobe
35   * @since 11.0
36   */
37  public class AccurateFormatter {
38  
39      /**
40       * Standardized locale to use, to ensure files can be exchanged without
41       * internationalization issues.
42       */
43      public static final Locale STANDARDIZED_LOCALE = Locale.US;
44  
45      /** String format used for dates. **/
46      private static final String DATE_FORMAT = "%04d-%02d-%02dT%02d:%02d:%s";
47  
48      /** Low switch level for exponential format in dates (will never be reached due to {@link #LOW_TRUNCATION}). */
49      private static final int LOW_EXP = -18;
50  
51      /** Truncation level for seconds, to avoid scientific format). */
52      private static final double LOW_TRUNCATION = 1.0e-15;
53  
54      /** Private constructor for a utility class.
55       */
56      private AccurateFormatter() {
57          // nothing to do
58      }
59  
60      /** Format a double number.
61       * @param value number to format
62       * @return number formatted to full accuracy
63       */
64      public static String format(final double value) {
65          return RyuDouble.doubleToString(value);
66      }
67  
68      /** Format a date.
69       * @param year year
70       * @param month month
71       * @param day day
72       * @param hour hour
73       * @param minute minute
74       * @param seconds seconds
75       * @return date formatted to full accuracy
76       */
77      public static String format(final int year, final int month, final int day,
78                                  final int hour, final int minute, final double seconds) {
79          final double truncated = seconds < LOW_TRUNCATION ? 0.0 : seconds;
80          final String s = RyuDouble.doubleToString(truncated, LOW_EXP, RyuDouble.DEFAULT_HIGH_EXP);
81          return String.format(STANDARDIZED_LOCALE, DATE_FORMAT,
82                               year, month, day,
83                               hour, minute, s.charAt(1) == '.' ? "0" + s : s);
84      }
85  
86  }