1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF 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.apache.commons.text.translate;
18
19 import java.io.IOException;
20 import java.io.StringWriter;
21 import java.io.Writer;
22 import java.util.Locale;
23
24 /**
25 * An API for translating text.
26 * Its core use is to escape and unescape text. Because escaping and unescaping
27 * is completely contextual, the API does not present two separate signatures.
28 *
29 * @since 1.0
30 */
31 public abstract class CharSequenceTranslator {
32
33 static final char[] HEX_DIGITS = new char[] {'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'};
34
35 /**
36 * Translate a set of codepoints, represented by an int index into a CharSequence,
37 * into another set of codepoints. The number of codepoints consumed must be returned,
38 * and the only IOExceptions thrown must be from interacting with the Writer so that
39 * the top level API may reliably ignore StringWriter IOExceptions.
40 *
41 * @param input CharSequence that is being translated
42 * @param index int representing the current point of translation
43 * @param out Writer to translate the text to
44 * @return int count of codepoints consumed
45 * @throws IOException if and only if the Writer produces an IOException
46 */
47 public abstract int translate(CharSequence input, int index, Writer out) throws IOException;
48
49 /**
50 * Helper for non-Writer usage.
51 * @param input CharSequence to be translated
52 * @return String output of translation
53 */
54 public final String translate(final CharSequence input) {
55 if (input == null) {
56 return null;
57 }
58 try {
59 final StringWriter writer = new StringWriter(input.length() * 2);
60 translate(input, writer);
61 return writer.toString();
62 } catch (final IOException ioe) {
63 // this should never ever happen while writing to a StringWriter
64 throw new RuntimeException(ioe);
65 }
66 }
67
68 /**
69 * Translate an input onto a Writer. This is intentionally final as its algorithm is
70 * tightly coupled with the abstract method of this class.
71 *
72 * @param input CharSequence that is being translated
73 * @param out Writer to translate the text to
74 * @throws IOException if and only if the Writer produces an IOException
75 */
76 public final void translate(final CharSequence input, final Writer out) throws IOException {
77 if (out == null) {
78 throw new IllegalArgumentException("The Writer must not be null");
79 }
80 if (input == null) {
81 return;
82 }
83 int pos = 0;
84 final int len = input.length();
85 while (pos < len) {
86 final int consumed = translate(input, pos, out);
87 if (consumed == 0) {
88 // inlined implementation of Character.toChars(Character.codePointAt(input, pos))
89 // avoids allocating temp char arrays and duplicate checks
90 final char c1 = input.charAt(pos);
91 out.write(c1);
92 pos++;
93 if (Character.isHighSurrogate(c1) && pos < len) {
94 final char c2 = input.charAt(pos);
95 if (Character.isLowSurrogate(c2)) {
96 out.write(c2);
97 pos++;
98 }
99 }
100 continue;
101 }
102 // contract with translators is that they have to understand codepoints
103 // and they just took care of a surrogate pair
104 for (int pt = 0; pt < consumed; pt++) {
105 pos += Character.charCount(Character.codePointAt(input, pos));
106 }
107 }
108 }
109
110 /**
111 * Helper method to create a merger of this translator with another set of
112 * translators. Useful in customizing the standard functionality.
113 *
114 * @param translators CharSequenceTranslator array of translators to merge with this one
115 * @return CharSequenceTranslator merging this translator with the others
116 */
117 public final CharSequenceTranslator with(final CharSequenceTranslator... translators) {
118 final CharSequenceTranslator[] newArray = new CharSequenceTranslator[translators.length + 1];
119 newArray[0] = this;
120 System.arraycopy(translators, 0, newArray, 1, translators.length);
121 return new AggregateTranslator(newArray);
122 }
123
124 /**
125 * <p>Returns an upper case hexadecimal <code>String</code> for the given
126 * character.</p>
127 *
128 * @param codepoint The codepoint to convert.
129 * @return An upper case hexadecimal <code>String</code>
130 */
131 public static String hex(final int codepoint) {
132 return Integer.toHexString(codepoint).toUpperCase(Locale.ENGLISH);
133 }
134
135 }