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/*
* Copyright (C) 2009 The Guava Authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.common.escape;
import java.util.HashMap;
import java.util.Map;
/**
* A factory for Escaper instances used to escape strings for safe use in Java.
*
* <p>This is a subset of source code escapers that are in the process of being open-sources as part
* of guava, see: https://github.com/google/guava/issues/1620
*/
// TODO(cushon): migrate to the guava version once it is open-sourced, and delete this
public final class SourceCodeEscapers {
private SourceCodeEscapers() {}
// For each xxxEscaper() method, please add links to external reference pages
// that are considered authoritative for the behavior of that escaper.
// From: http://en.wikipedia.org/wiki/ASCII#ASCII_printable_characters
private static final char PRINTABLE_ASCII_MIN = 0x20; // ' '
private static final char PRINTABLE_ASCII_MAX = 0x7E; // '~'
private static final char[] HEX_DIGITS = "0123456789abcdef".toCharArray();
/**
* Returns an {@link Escaper} instance that escapes special characters in a string so it can
* safely be included in either a Java character literal or string literal. This is the preferred
* way to escape Java characters for use in String or character literals.
*
* <p>See: <a href= "http://java.sun.com/docs/books/jls/third_edition/html/lexical.html#101089"
* >The Java Language Specification</a> for more details.
*/
public static CharEscaper javaCharEscaper() {
return JAVA_CHAR_ESCAPER;
}
private static final CharEscaper JAVA_CHAR_ESCAPER;
static {
Map<Character, String> javaMap = new HashMap<>();
javaMap.put('\b', "\\b");
javaMap.put('\f', "\\f");
javaMap.put('\n', "\\n");
javaMap.put('\r', "\\r");
javaMap.put('\t', "\\t");
javaMap.put('\"', "\\\"");
javaMap.put('\\', "\\\\");
javaMap.put('\'', "\\'");
JAVA_CHAR_ESCAPER = new JavaCharEscaper(javaMap);
}
// This escaper does not produce octal escape sequences. See:
// http://java.sun.com/docs/books/jls/third_edition/html/lexical.html#101089
// "Octal escapes are provided for compatibility with C, but can express
// only Unicode values \u0000 through \u00FF, so Unicode escapes are
// usually preferred."
private static class JavaCharEscaper extends ArrayBasedCharEscaper {
JavaCharEscaper(Map<Character, String> replacements) {
super(replacements, PRINTABLE_ASCII_MIN, PRINTABLE_ASCII_MAX);
}
@Override
protected char[] escapeUnsafe(char c) {
return asUnicodeHexEscape(c);
}
}
// Helper for common case of escaping a single char.
private static char[] asUnicodeHexEscape(char c) {
// Equivalent to String.format("\\u%04x", (int)c);
char[] r = new char[6];
r[0] = '\\';
r[1] = 'u';
r[5] = HEX_DIGITS[c & 0xF];
c >>>= 4;
r[4] = HEX_DIGITS[c & 0xF];
c >>>= 4;
r[3] = HEX_DIGITS[c & 0xF];
c >>>= 4;
r[2] = HEX_DIGITS[c & 0xF];
return r;
}
}
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