155 lines
6.6 KiB
Java
155 lines
6.6 KiB
Java
/*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership.
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* The ASF licenses this file to You under the Apache License, Version 2.0
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* (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.apache.commons.text.translate;
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import java.io.IOException;
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import java.io.StringWriter;
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import java.io.UncheckedIOException;
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import java.io.Writer;
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import java.util.Locale;
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import org.apache.commons.lang3.Validate;
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import org.checkerframework.checker.index.qual.LTLengthOf;
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import org.checkerframework.checker.index.qual.NonNegative;
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import org.checkerframework.checker.index.qual.Positive;
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import org.checkerframework.common.value.qual.MinLen;
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/**
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* An API for translating text.
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* Its core use is to escape and unescape text. Because escaping and unescaping
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* is completely contextual, the API does not present two separate signatures.
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*
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* @since 1.0
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*/
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public abstract class CharSequenceTranslator {
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/**
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* Array containing the hexadecimal alphabet.
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*/
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static final char[] HEX_DIGITS = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' };
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/**
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* Returns an upper case hexadecimal {@code String} for the given
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* character.
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*
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* @param codePoint The code point to convert.
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* @return An upper case hexadecimal {@code String}
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*/
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public static String hex(final int codePoint) {
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return Integer.toHexString(codePoint).toUpperCase(Locale.ENGLISH);
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}
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/**
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* Helper for non-Writer usage.
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* @param input CharSequence to be translated
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* @return String output of translation
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*/
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public final String translate(final CharSequence input) {
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if (input == null) {
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return null;
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}
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try {
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final StringWriter writer = new StringWriter(input.length() * 2);
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translate(input, writer);
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return writer.toString();
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} catch (final IOException ioe) {
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// this should never ever happen while writing to a StringWriter
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throw new UncheckedIOException(ioe);
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}
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}
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/**
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* Translate a set of code points, represented by an int index into a CharSequence,
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* into another set of code points. The number of code points consumed must be returned,
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* and the only IOExceptions thrown must be from interacting with the Writer so that
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* the top level API may reliably ignore StringWriter IOExceptions.
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*
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* @param input CharSequence that is being translated
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* @param index int representing the current point of translation
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* @param writer Writer to translate the text to
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* @return int count of code points consumed
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* @throws IOException if and only if the Writer produces an IOException
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*/
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public abstract int translate(@MinLen(1) CharSequence input,
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@NonNegative @LTLengthOf("#1") int index,
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Writer writer) throws IOException;
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/**
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* Translate an input onto a Writer. This is intentionally final as its algorithm is
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* tightly coupled with the abstract method of this class.
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*
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* @param input CharSequence that is being translated
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* @param writer Writer to translate the text to
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* @throws IOException if and only if the Writer produces an IOException
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*/
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public final void translate(final CharSequence input, final Writer writer) throws IOException {
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Validate.isTrue(writer != null, "The Writer must not be null");
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if (input == null) {
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return;
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}
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int pos = 0;
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final int len = input.length();
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while (pos < len) {
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assert input.length() >= 1 : "@AssumeAssertion(index): Trivially true since we enter the loop";
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final int consumed = translate(input, pos, writer);
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if (consumed == 0) {
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// inlined implementation of Character.toChars(Character.codePointAt(input, pos))
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// avoids allocating temp char arrays and duplicate checks
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final char c1 = input.charAt(pos);
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writer.write(c1);
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pos++;
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if (Character.isHighSurrogate(c1) && pos < len) {
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final char c2 = input.charAt(pos);
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if (Character.isLowSurrogate(c2)) {
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writer.write(c2);
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pos++;
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}
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}
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continue;
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}
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// contract with translators is that they have to understand code points
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// and they just took care of a surrogate pair
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// Added pos < len as defensive condition for possibly buggy implementations of translate returning wrong
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// number of codepoints consumed
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for (int pt = 0; pt < consumed && pos < len; pt++) {
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int increment = Character.charCount(Character.codePointAt(input, pos));
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assert pos + increment <= len : "@AssumeAssertion(index): increment corresponds to the number of bytes" +
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"of char codepoint at position index[pos]. Adding this quantity results in a valid index or in" +
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"the length of the string.";
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pos += increment;
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}
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}
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}
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/**
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* Helper method to create a merger of this translator with another set of
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* translators. Useful in customizing the standard functionality.
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*
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* @param translators CharSequenceTranslator array of translators to merge with this one
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* @return CharSequenceTranslator merging this translator with the others
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*/
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public final CharSequenceTranslator with(final CharSequenceTranslator... translators) {
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final @Positive int newArrayLen = translators.length + 1;
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final CharSequenceTranslator[] newArray = new CharSequenceTranslator[newArrayLen];
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newArray[0] = this;
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assert translators.length == newArray.length - 1 : "@AssumeAssertion(index): by construction of newArray and newArrayLen";
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System.arraycopy(translators, 0, newArray, 1, translators.length);
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return new AggregateTranslator(newArray);
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}
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}
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