    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     */
    017    package org.apache.commons.lang3.text.translate;
    018
    019    import java.io.IOException;
    020    import java.io.StringWriter;
    021    import java.io.Writer;
    022    import java.util.Locale;
    023
    024    /**
    025     * An API for translating text.
    026     * Its core use is to escape and unescape text. Because escaping and unescaping
    027     * is completely contextual, the API does not present two separate signatures.
    028     *
    029     * @since 3.0
    030     * @version $Id: CharSequenceTranslator.java 1146844 2011-07-14 18:49:51Z mbenson $
    031     */
    032    public abstract class CharSequenceTranslator {
    033
    034        /**
    035         * Translate a set of codepoints, represented by an int index into a CharSequence,
    036         * into another set of codepoints. The number of codepoints consumed must be returned,
    037         * and the only IOExceptions thrown must be from interacting with the Writer so that
    038         * the top level API may reliable ignore StringWriter IOExceptions.
    039         *
    040         * @param input CharSequence that is being translated
    041         * @param index int representing the current point of translation
    042         * @param out Writer to translate the text to
    043         * @return int count of codepoints consumed
    044         * @throws IOException if and only if the Writer produces an IOException
    045         */
    046        public abstract int translate(CharSequence input, int index, Writer out) throws IOException;
    047
    048        /**
    049         * Helper for non-Writer usage.
    050         * @param input CharSequence to be translated
    051         * @return String output of translation
    052         */
    053        public final String translate(CharSequence input) {
    054            if (input == null) {
    055                return null;
    056            }
    057            try {
    058                StringWriter writer = new StringWriter(input.length() * 2);
    059                translate(input, writer);
    060                return writer.toString();
    061            } catch (IOException ioe) {
    062                // this should never ever happen while writing to a StringWriter
    063                throw new RuntimeException(ioe);
    064            }
    065        }
    066
    067        /**
    068         * Translate an input onto a Writer. This is intentionally final as its algorithm is
    069         * tightly coupled with the abstract method of this class.
    070         *
    071         * @param input CharSequence that is being translated
    072         * @param out Writer to translate the text to
    073         * @throws IOException if and only if the Writer produces an IOException
    074         */
    075        public final void translate(CharSequence input, Writer out) throws IOException {
    076            if (out == null) {
    077                throw new IllegalArgumentException("The Writer must not be null");
    078            }
    079            if (input == null) {
    080                return;
    081            }
    082            int pos = 0;
    083            int len = input.length();
    084            while (pos < len) {
    085                int consumed = translate(input, pos, out);
    086                if (consumed == 0) {
    087                    char[] c = Character.toChars(Character.codePointAt(input, pos));
    088                    out.write(c);
    089                    pos+= c.length;
    090                    continue;
    091                }
    092    //          // contract with translators is that they have to understand codepoints
    093    //          // and they just took care of a surrogate pair
    094                for (int pt = 0; pt < consumed; pt++) {
    095                    pos += Character.charCount(Character.codePointAt(input, pos));
    096                }
    097            }
    098        }
    099
    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(CharSequenceTranslator... translators) {
    108            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(int codepoint) {
    122            return Integer.toHexString(codepoint).toUpperCase(Locale.ENGLISH);
    123        }
    124
    125    }