Mega Code Archive
Unescape any MySQL escape sequences
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import java.util.StringTokenizer;
/* Copyright (c) 2008 Google Inc.
*
* 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.gdata.util.common.base;
/**
* Some common string manipulation utilities.
*/
public class Util{
/**
* Unescape any MySQL escape sequences.
* See MySQL language reference Chapter 6 at
* <a href="http://www.mysql.com/doc/">http://www.mysql.com/doc/</a>.
* This function will <strong>not</strong> work for other SQL-like
* dialects.
* @param s string to unescape, with the surrounding quotes.
* @return unescaped string, without the surrounding quotes.
* @exception IllegalArgumentException if s is not a valid MySQL string.
*/
public static String unescapeMySQLString(String s)
throws IllegalArgumentException {
// note: the same buffer is used for both reading and writing
// it works because the writer can never outrun the reader
char chars[] = s.toCharArray();
// the string must be quoted 'like this' or "like this"
if (chars.length < 2 || chars[0] != chars[chars.length-1] ||
(chars[0] != '\'' && chars[0] != '"')) {
throw new IllegalArgumentException("not a valid MySQL string: " + s);
}
// parse the string and decode the backslash sequences; in addition,
// quotes can be escaped 'like this: ''', "like this: """, or 'like this: "'
int j = 1; // write position in the string (never exceeds read position)
int f = 0; // state: 0 (normal), 1 (backslash), 2 (quote)
for (int i = 1; i < chars.length - 1; i++) {
if (f == 0) { // previous character was normal
if (chars[i] == '\\') {
f = 1; // backslash
} else if (chars[i] == chars[0]) {
f = 2; // quoting character
} else {
chars[j++] = chars[i];
}
} else if (f == 1) { // previous character was a backslash
switch (chars[i]) {
case '0': chars[j++] = '\0'; break;
case '\'': chars[j++] = '\''; break;
case '"': chars[j++] = '"'; break;
case 'b': chars[j++] = '\b'; break;
case 'n': chars[j++] = '\n'; break;
case 'r': chars[j++] = '\r'; break;
case 't': chars[j++] = '\t'; break;
case 'z': chars[j++] = '\032'; break;
case '\\': chars[j++] = '\\'; break;
default:
// if the character is not special, backslash disappears
chars[j++] = chars[i];
break;
}
f = 0;
} else { // previous character was a quote
// quoting characters must be doubled inside a string
if (chars[i] != chars[0]) {
throw new IllegalArgumentException("not a valid MySQL string: " + s);
}
chars[j++] = chars[0];
f = 0;
}
}
// string contents cannot end with a special character
if (f != 0) {
throw new IllegalArgumentException("not a valid MySQL string: " + s);
}
// done
return new String(chars, 1, j - 1);
}
}
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