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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.lang3.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 3.0
30   * @version $Id: CharSequenceTranslator.java 1568612 2014-02-15 10:35:35Z britter $
31   */
32  public abstract class CharSequenceTranslator {
33  
34      /**
35       * Translate a set of codepoints, represented by an int index into a CharSequence, 
36       * into another set of codepoints. The number of codepoints consumed must be returned, 
37       * and the only IOExceptions thrown must be from interacting with the Writer so that 
38       * the top level API may reliably ignore StringWriter IOExceptions. 
39       *
40       * @param input CharSequence that is being translated
41       * @param index int representing the current point of translation
42       * @param out Writer to translate the text to
43       * @return int count of codepoints consumed
44       * @throws IOException if and only if the Writer produces an IOException
45       */
46      public abstract int translate(CharSequence input, int index, Writer out) throws IOException;
47  
48      /**
49       * Helper for non-Writer usage. 
50       * @param input CharSequence to be translated
51       * @return String output of translation
52       */
53      public final String translate(final CharSequence input) {
54          if (input == null) {
55              return null;
56          }
57          try {
58              final StringWriter writer = new StringWriter(input.length() * 2);
59              translate(input, writer);
60              return writer.toString();
61          } catch (final IOException ioe) {
62              // this should never ever happen while writing to a StringWriter
63              throw new RuntimeException(ioe);
64          }
65      }
66  
67      /**
68       * Translate an input onto a Writer. This is intentionally final as its algorithm is 
69       * tightly coupled with the abstract method of this class. 
70       *
71       * @param input CharSequence that is being translated
72       * @param out Writer to translate the text to
73       * @throws IOException if and only if the Writer produces an IOException
74       */
75      public final void translate(final CharSequence input, final Writer out) throws IOException {
76          if (out == null) {
77              throw new IllegalArgumentException("The Writer must not be null");
78          }
79          if (input == null) {
80              return;
81          }
82          int pos = 0;
83          final int len = input.length();
84          while (pos < len) {
85              final int consumed = translate(input, pos, out);
86              if (consumed == 0) {
87                  final char[] c = Character.toChars(Character.codePointAt(input, pos));
88                  out.write(c);
89                  pos+= c.length;
90                  continue;
91              }
92              // contract with translators is that they have to understand codepoints
93              // and they just took care of a surrogate pair
94              for (int pt = 0; pt < consumed; pt++) {
95                  pos += Character.charCount(Character.codePointAt(input, pos));
96              }
97          }
98      }
99  
100     /**
101      * Helper method to create a merger of this translator with another set of 
102      * translators. Useful in customizing the standard functionality.
103      *
104      * @param translators CharSequenceTranslator array of translators to merge with this one
105      * @return CharSequenceTranslator merging this translator with the others
106      */
107     public final CharSequenceTranslator with(final CharSequenceTranslator... translators) {
108         final CharSequenceTranslator[] newArray = new CharSequenceTranslator[translators.length + 1];
109         newArray[0] = this;
110         System.arraycopy(translators, 0, newArray, 1, translators.length);
111         return new AggregateTranslator(newArray);
112     }
113 
114     /**
115      * <p>Returns an upper case hexadecimal <code>String</code> for the given
116      * character.</p>
117      *
118      * @param codepoint The codepoint to convert.
119      * @return An upper case hexadecimal <code>String</code>
120      */
121     public static String hex(final int codepoint) {
122         return Integer.toHexString(codepoint).toUpperCase(Locale.ENGLISH);
123     }
124 
125 }