001/* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017package org.apache.commons.text.translate; 018 019import java.io.IOException; 020import java.io.StringWriter; 021import java.io.Writer; 022import java.util.Locale; 023 024import org.apache.commons.lang3.Validate; 025 026/** 027 * An API for translating text. 028 * Its core use is to escape and unescape text. Because escaping and unescaping 029 * is completely contextual, the API does not present two separate signatures. 030 * 031 * @since 1.0 032 */ 033public abstract class CharSequenceTranslator { 034 035 /** 036 * Array containing the hexadecimal alphabet. 037 */ 038 static final char[] HEX_DIGITS = new char[] {'0', '1', '2', '3', 039 '4', '5', '6', '7', 040 '8', '9', 'A', 'B', 041 'C', 'D', 'E', 'F'}; 042 043 /** 044 * Translate a set of codepoints, represented by an int index into a CharSequence, 045 * into another set of codepoints. The number of codepoints consumed must be returned, 046 * and the only IOExceptions thrown must be from interacting with the Writer so that 047 * the top level API may reliably ignore StringWriter IOExceptions. 048 * 049 * @param input CharSequence that is being translated 050 * @param index int representing the current point of translation 051 * @param out Writer to translate the text to 052 * @return int count of codepoints consumed 053 * @throws IOException if and only if the Writer produces an IOException 054 */ 055 public abstract int translate(CharSequence input, int index, Writer out) throws IOException; 056 057 /** 058 * Helper for non-Writer usage. 059 * @param input CharSequence to be translated 060 * @return String output of translation 061 */ 062 public final String translate(final CharSequence input) { 063 if (input == null) { 064 return null; 065 } 066 try { 067 final StringWriter writer = new StringWriter(input.length() * 2); 068 translate(input, writer); 069 return writer.toString(); 070 } catch (final IOException ioe) { 071 // this should never ever happen while writing to a StringWriter 072 throw new RuntimeException(ioe); 073 } 074 } 075 076 /** 077 * Translate an input onto a Writer. This is intentionally final as its algorithm is 078 * tightly coupled with the abstract method of this class. 079 * 080 * @param input CharSequence that is being translated 081 * @param out Writer to translate the text to 082 * @throws IOException if and only if the Writer produces an IOException 083 */ 084 public final void translate(final CharSequence input, final Writer out) throws IOException { 085 Validate.isTrue(out != null, "The Writer must not be null"); 086 if (input == null) { 087 return; 088 } 089 int pos = 0; 090 final int len = input.length(); 091 while (pos < len) { 092 final int consumed = translate(input, pos, out); 093 if (consumed == 0) { 094 // inlined implementation of Character.toChars(Character.codePointAt(input, pos)) 095 // avoids allocating temp char arrays and duplicate checks 096 final char c1 = input.charAt(pos); 097 out.write(c1); 098 pos++; 099 if (Character.isHighSurrogate(c1) && pos < len) { 100 final char c2 = input.charAt(pos); 101 if (Character.isLowSurrogate(c2)) { 102 out.write(c2); 103 pos++; 104 } 105 } 106 continue; 107 } 108 // contract with translators is that they have to understand codepoints 109 // and they just took care of a surrogate pair 110 for (int pt = 0; pt < consumed; pt++) { 111 pos += Character.charCount(Character.codePointAt(input, pos)); 112 } 113 } 114 } 115 116 /** 117 * Helper method to create a merger of this translator with another set of 118 * translators. Useful in customizing the standard functionality. 119 * 120 * @param translators CharSequenceTranslator array of translators to merge with this one 121 * @return CharSequenceTranslator merging this translator with the others 122 */ 123 public final CharSequenceTranslator with(final CharSequenceTranslator... translators) { 124 final CharSequenceTranslator[] newArray = new CharSequenceTranslator[translators.length + 1]; 125 newArray[0] = this; 126 System.arraycopy(translators, 0, newArray, 1, translators.length); 127 return new AggregateTranslator(newArray); 128 } 129 130 /** 131 * <p>Returns an upper case hexadecimal {@code String} for the given 132 * character.</p> 133 * 134 * @param codepoint The codepoint to convert. 135 * @return An upper case hexadecimal {@code String} 136 */ 137 public static String hex(final int codepoint) { 138 return Integer.toHexString(codepoint).toUpperCase(Locale.ENGLISH); 139 } 140 141}