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/*
* Copyright 2000-2016 Vaadin Ltd.
*
* 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.vaadin.util;
import java.nio.charset.Charset;
/**
* Utilities related to various encoding schemes.
*
* @author Vaadin Ltd
* @since 7.7.7
*/
public final class EncodeUtil {
private static final Charset UTF8 = Charset.forName("UTF-8");
private EncodeUtil() {
// Static utils only
}
/**
* Encodes the given string to UTF-8 <code>value-chars</code> as defined in
* RFC5987 for use in e.g. the <code>Content-Disposition</code> HTTP header.
*
* @param value
* the string to encode, not <code>null</code>
* @return the encoded string
*/
public static String rfc5987Encode(String value) {
StringBuilder builder = new StringBuilder();
for (int i = 0; i < value.length();) {
int cp = value.codePointAt(i);
if (cp < 127 && (Character.isLetterOrDigit(cp) || cp == '.')) {
builder.append((char) cp);
} else {
// Create string from a single code point
String cpAsString = new String(new int[] { cp }, 0, 1);
appendHexBytes(builder, cpAsString.getBytes(UTF8));
}
// Advance to the next code point
i += Character.charCount(cp);
}
return builder.toString();
}
private static void appendHexBytes(StringBuilder builder, byte[] bytes) {
for (byte byteValue : bytes) {
// mask with 0xFF to compensate for "negative" values
int intValue = byteValue & 0xFF;
String hexCode = Integer.toString(intValue, 16);
builder.append('%').append(hexCode);
}
}
}
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