1 package nom.tam.fits;
2
3 import java.io.Serializable;
4 import java.util.Hashtable;
5
6 import static nom.tam.fits.header.Standard.BITPIX;
7 import static nom.tam.fits.header.Standard.BLOCKED;
8 import static nom.tam.fits.header.Standard.END;
9 import static nom.tam.fits.header.Standard.EXTEND;
10 import static nom.tam.fits.header.Standard.GCOUNT;
11 import static nom.tam.fits.header.Standard.NAXIS;
12 import static nom.tam.fits.header.Standard.PCOUNT;
13 import static nom.tam.fits.header.Standard.SIMPLE;
14 import static nom.tam.fits.header.Standard.TFIELDS;
15 import static nom.tam.fits.header.Standard.THEAP;
16 import static nom.tam.fits.header.Standard.XTENSION;
17
18 /*
19 * #%L
20 * nom.tam FITS library
21 * %%
22 * Copyright (C) 2004 - 2024 nom-tam-fits
23 * %%
24 * This is free and unencumbered software released into the public domain.
25 *
26 * Anyone is free to copy, modify, publish, use, compile, sell, or
27 * distribute this software, either in source code form or as a compiled
28 * binary, for any purpose, commercial or non-commercial, and by any
29 * means.
30 *
31 * In jurisdictions that recognize copyright laws, the author or authors
32 * of this software dedicate any and all copyright interest in the
33 * software to the public domain. We make this dedication for the benefit
34 * of the public at large and to the detriment of our heirs and
35 * successors. We intend this dedication to be an overt act of
36 * relinquishment in perpetuity of all present and future rights to this
37 * software under copyright law.
38 *
39 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
40 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
41 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
42 * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
43 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
44 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
45 * OTHER DEALINGS IN THE SOFTWARE.
46 * #L%
47 */
48
49 /**
50 * This class implements a comparator which ensures that FITS keywords are written out in a proper order.
51 *
52 * @deprecated (<i>for internal use</i>) Visibility should be reduced to package level in the future
53 */
54 public class HeaderOrder implements java.util.Comparator<String>, Serializable {
55
56 /**
57 *
58 */
59 private static final long serialVersionUID = -5900038332559417655L;
60
61 /**
62 * This array defines the order of ordered keywords, except END (which we handle separately)
63 */
64 private static final String[] ORDER = {SIMPLE.key(), XTENSION.key(), BITPIX.key(), NAXIS.key(), PCOUNT.key(),
65 GCOUNT.key(), EXTEND.key(), TFIELDS.key(), BLOCKED.key(), THEAP.key()};
66
67 /**
68 * Every keyword is assigned an index. Because NAXIS can have 999 NAXISn variants, we'll space the indices of the
69 * ordered keys by 1000, to allow adding in 999 ordered variants between the major slots.
70 */
71 private static final int SPACING = 1000;
72
73 /**
74 * Keys that do not need ordering get an index that comes after the last ordered key, but before END.
75 */
76 private static final int UNORDERED = SPACING * ORDER.length;
77
78 /**
79 * The END keyword comes last, so assign it an index after unordered.
80 */
81 private static final int LAST = UNORDERED + SPACING;
82
83 /**
84 * Hash table for looking up the index of ordered keys.
85 */
86 private static final Hashtable<String, Integer> LOOKUP = new Hashtable<>();
87
88 // Initialize the hash lookup from the order array
89 static {
90 for (int i = 0; i < ORDER.length; i++) {
91 LOOKUP.put(ORDER[i], SPACING * i);
92 }
93 }
94
95 /**
96 * Returns a virtual ordering index of a given keyword. Keywords with lower indices should precede keywords that
97 * have higher indices. Order does not matter if the indices are the same.
98 *
99 * @param key FITS keyword
100 *
101 * @return The ordering index of that key
102 */
103 private static int indexOf(String key) {
104 if (key == null) {
105 return UNORDERED;
106 }
107 if (key.startsWith(NAXIS.key())) {
108 if (NAXIS.key().length() == key.length()) {
109 return LOOKUP.get(NAXIS.key());
110 }
111 try {
112 int i = Integer.parseInt(key.substring(NAXIS.key().length()));
113 if (i < 0 || i >= SPACING) {
114 return UNORDERED;
115 }
116 return LOOKUP.get(NAXIS.key()) + i;
117 } catch (NumberFormatException e) {
118 return UNORDERED;
119 }
120 }
121 if (key.equals(END.key())) {
122 return LAST;
123 }
124 Integer i = LOOKUP.get(key);
125 return i == null ? UNORDERED : i;
126 }
127
128 /**
129 * Determines the order in which the cards should be added to the header. This method assumes that the arguments are
130 * either the FITS Header keywords as strings, and some other type (or null) for comment style keywords.
131 *
132 * @return -1 if the first argument should be written first <br>
133 * 1 if the second argument should be written first <br>
134 * 0 if either is legal.
135 */
136 @Override
137 public int compare(String c1, String c2) {
138 int i1 = indexOf(c1);
139 int i2 = indexOf(c2);
140 if (i1 == i2) {
141 return 0;
142 }
143 return i1 < i2 ? -1 : 1;
144 }
145
146 }