/*
* Copyright (c) 2007 Henri Sivonen
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
* DEALINGS IN THE SOFTWARE.
*/
package nu.validator.htmlparser.io;
import java.io.IOException;
import nu.validator.htmlparser.common.ByteReadable;
/**
* The BOM sniffing part of the HTML5 encoding sniffing algorithm.
*
* @version $Id$
* @author hsivonen
*/
public final class BomSniffer {
private final ByteReadable source;
/**
* @param source
*/
public BomSniffer(final ByteReadable source) {
this.source = source;
}
Encoding sniff() throws IOException {
int b = source.readByte();
if (b == 0xEF) { // UTF-8
b = source.readByte();
if (b == 0xBB) {
b = source.readByte();
if (b == 0xBF) {
return Encoding.UTF8;
} else {
return null;
}
} else {
return null;
}
} else if (b == 0xFF) { // little-endian
b = source.readByte();
if (b == 0xFE) {
return Encoding.UTF16LE;
} else {
return null;
}
} else if (b == 0xFE) { // big-endian UTF-16
b = source.readByte();
if (b == 0xFF) {
return Encoding.UTF16BE;
} else {
return null;
}
} else {
return null;
}
}
}