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/*******************************************************************************
* Copyright (c) 2005, 2007 Oracle. All rights reserved.
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v1.0, which accompanies this distribution
* and is available at http://www.eclipse.org/legal/epl-v10.html.
*
* Contributors:
* Oracle - initial API and implementation
******************************************************************************/
package org.eclipse.jpt.utility.internal;
import java.io.IOException;
import java.io.Reader;
import java.io.StringReader;
/**
* This encoder will replace any of a specified set of characters with an XML
* "character reference": '/' => "/"
*/
public final class XMLStringEncoder {
/** The set of characters to be converted into XML character references. */
private final char[] chars;
/** Cache the value of the highest character in the set above. */
private final char maxChar;
// ********** constructors/initialization **********
/**
* Construct an encoder that converts the specified set of characters
* into XML character references.
*/
public XMLStringEncoder(char[] chars) {
super();
if (chars == null) {
throw new NullPointerException();
}
// the ampersand must be included since it is the escape character
if (CollectionTools.contains(chars, '&')) {
this.chars = chars;
} else {
this.chars = CollectionTools.add(chars, '&');
}
this.maxChar = this.calculateMaxInvalidFileNameChar();
}
/**
* Calculate the maximum value of the set of characters to be converted
* into XML character references. This will be used to short-circuit the
* search for a character in the set.
* @see #charIsToBeEncoded(char)
*/
private char calculateMaxInvalidFileNameChar() {
char[] localChars = this.chars;
char max = 0;
for (int i = localChars.length; i-- > 0; ) {
char c = localChars[i];
if (max < c) {
max = c;
}
}
return max;
}
// ********** API **********
/**
* Return the specified string with any characters in the set
* replaced with XML character references.
*/
public String encode(String s) {
int len = s.length();
// allow for a few encoded characters
StringBuilder sb = new StringBuilder(len + 20);
for (int i = 0; i < len; i++) {
this.appendCharacterTo(s.charAt(i), sb);
}
return sb.toString();
}
/**
* Return the specified string with any XML character references
* replaced by the characters themselves.
*/
public String decode(String s) {
StringBuilder sb = new StringBuilder(s.length());
StringBuilder temp = new StringBuilder(); // performance tweak
this.decodeTo(new StringReader(s), sb, temp);
return sb.toString();
}
// ********** internal methods **********
/**
* Append the specified character to the string buffer,
* converting it to an XML character reference if necessary.
*/
private void appendCharacterTo(char c, StringBuilder sb) {
if (this.charIsToBeEncoded(c)) {
this.appendCharacterReferenceTo(c, sb);
} else {
sb.append(c);
}
}
/**
* Return whether the specified character is one of the characters
* to be converted to XML character references.
*/
private boolean charIsToBeEncoded(char c) {
return (c <= this.maxChar) && CollectionTools.contains(this.chars, c);
}
/**
* Append the specified character's XML character reference to the
* specified string buffer (e.g. '/' => "/").
*/
private void appendCharacterReferenceTo(char c, StringBuilder sb) {
sb.append("&#x");
sb.append(Integer.toString(c, 16));
sb.append(';');
}
private void decodeTo(Reader reader, StringBuilder sb, StringBuilder temp) {
try {
this.decodeTo_(reader, sb, temp);
} catch (IOException ex) {
throw new RuntimeException(ex);
}
}
private void decodeTo_(Reader reader, StringBuilder sb, StringBuilder temp) throws IOException {
int c = reader.read();
while (c != -1) {
if (c == '&') {
this.decodeCharacterReferenceTo(reader, sb, temp);
} else {
sb.append((char) c);
}
c = reader.read();
}
reader.close();
}
private void decodeCharacterReferenceTo(Reader reader, StringBuilder sb, StringBuilder temp) throws IOException {
int c = reader.read();
this.checkChar(c, '#');
c = reader.read();
this.checkChar(c, 'x');
temp.setLength(0); // re-use temp
c = reader.read();
while (c != ';') {
this.checkEndOfStream(c);
temp.append((char) c);
c = reader.read();
}
String charValue = temp.toString();
if (charValue.length() == 0) {
throw new IllegalStateException("missing numeric string");
}
sb.append((char) Integer.parseInt(charValue, 16));
}
private void checkChar(int c, int expected) {
this.checkEndOfStream(c);
if (c != expected) {
throw new IllegalStateException("expected '" + (char) expected + "', but encountered '" + (char) c + "'");
}
}
private void checkEndOfStream(int c) {
if (c == -1) {
throw new IllegalStateException("unexpected end of string");
}
}
}
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