Logback: the reliable, generic, fast and flexible logging framework.
Copyright (C) 1999-2015, QOS.ch. All rights reserved.
This program and the accompanying materials are dual-licensed under
either the terms of the Eclipse Public License v1.0 as published by
the Eclipse Foundation
  or (per the licensee's choosing)
under the terms of the GNU Lesser General Public License version 2.1
as published by the Free Software Foundation.
/**
 * Logback: the reliable, generic, fast and flexible logging framework.
 * Copyright (C) 1999-2015, QOS.ch. All rights reserved.
 *
 * This program and the accompanying materials are dual-licensed under
 * either the terms of the Eclipse Public License v1.0 as published by
 * the Eclipse Foundation
 *
 *   or (per the licensee's choosing)
 *
 * under the terms of the GNU Lesser General Public License version 2.1
 * as published by the Free Software Foundation.
 */
package ch.qos.logback.core.helpers;

import java.util.regex.Pattern;

Utility class for transforming strings.
Author:
Ceki Gülcü, Michael A. McAngus/**
 * Utility class for transforming strings.
 * 
 * @author Ceki Gülcü
 * @author Michael A. McAngus
 */
public class Transform {
    private static final String CDATA_START = "<![CDATA[";
    private static final String CDATA_END = "]]>";
    private static final String CDATA_PSEUDO_END = "]]&gt;";
    private static final String CDATA_EMBEDED_END = CDATA_END + CDATA_PSEUDO_END + CDATA_START;
    private static final int CDATA_END_LEN = CDATA_END.length();
    private static final Pattern UNSAFE_XML_CHARS = Pattern.compile("[\u0000-\u0008\u000b\u000c\u000e-\u001f<>&'\"]");

    
This method takes a string which may contain HTML tags (ie, <b>,
<table>, etc) and replaces any '<','>' ... characters with
respective predefined entity references.
Params:
input – 
         The text to be converted./**
     * This method takes a string which may contain HTML tags (ie, &lt;b&gt;,
     * &lt;table&gt;, etc) and replaces any '<','>' ... characters with
     * respective predefined entity references.
     * 
     * @param input
     *          The text to be converted.
     */
    public static String escapeTags(final String input) {
        if (input == null || input.length() == 0 || !UNSAFE_XML_CHARS.matcher(input).find()) {
            return input;
        }
        StringBuffer buf = new StringBuffer(input);
        return escapeTags(buf);
    }

    
This method takes a StringBuilder which may contain HTML tags (ie, <b>,
<table>, etc) and replaces any '<' and '>' characters with
respective predefined entity references.
Params:
buf – StringBuffer to transform
Returns:
/**
     * This method takes a StringBuilder which may contain HTML tags (ie, &lt;b&gt;,
     * &lt;table&gt;, etc) and replaces any '<' and '>' characters with
     * respective predefined entity references.
     * @param buf StringBuffer to transform
     * @return

     */
    public static String escapeTags(final StringBuffer buf) {
        for (int i = 0; i < buf.length(); i++) {
            char ch = buf.charAt(i);
            switch (ch) {
            case '\t':
            case '\n':
            case '\r':
                // These characters are below '\u0020' but are allowed:
                break;
            case '&':
                buf.replace(i, i + 1, "&amp;");
                break;
            case '<':
                buf.replace(i, i + 1, "&lt;");
                break;
            case '>':
                buf.replace(i, i + 1, "&gt;");
                break;
            case '"':
                buf.replace(i, i + 1, "&quot;");
                break;
            case '\'':
                buf.replace(i, i + 1, "&#39;");
                break;
            default:
                if (ch < '\u0020') {
                    // These characters are not allowed,
                    // replace them with "Object replacement character":
                    buf.replace(i, i + 1, "\uFFFD");
                }
                break;
            }
        }
        return buf.toString();
    }

    
Ensures that embedded CDEnd strings (]]>) are handled properly within
message, NDC and throwable tag text.
Params:
output – 
         Writer. The initial CDSutart () and final CDEnd () of
         the CDATA section are the responsibility of the calling method.
str – 
         The String that is inserted into an existing CDATA Section./**
     * Ensures that embedded CDEnd strings (]]>) are handled properly within
     * message, NDC and throwable tag text.
     * 
     * @param output
     *          Writer. The initial CDSutart (<![CDATA[) and final CDEnd (]]>) of
     *          the CDATA section are the responsibility of the calling method.
     * 
     * @param str
     *          The String that is inserted into an existing CDATA Section.
     */
    public static void appendEscapingCDATA(StringBuilder output, String str) {
        if (str == null) {
            return;
        }

        int end = str.indexOf(CDATA_END);

        if (end < 0) {
            output.append(str);

            return;
        }

        int start = 0;

        while (end > -1) {
            output.append(str.substring(start, end));
            output.append(CDATA_EMBEDED_END);
            start = end + CDATA_END_LEN;

            if (start < str.length()) {
                end = str.indexOf(CDATA_END, start);
            } else {
                return;
            }
        }

        output.append(str.substring(start));
    }
}