/*
* #!
* Ontopia Engine
* #-
* Copyright (C) 2001 - 2013 The Ontopia Project
* #-
* 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 net.ontopia.topicmaps.utils.ltm;
import java.io.IOException;
import java.io.PushbackInputStream;
import net.ontopia.utils.OntopiaRuntimeException;
import net.ontopia.topicmaps.impl.utils.EncodingSnifferIF;
/**
* INTERNAL: An encoding sniffer for LTM.
*/
public class LTMEncodingSniffer implements EncodingSnifferIF {
public String guessEncoding(PushbackInputStream stream) throws IOException {
String encoding;
// Look to seee if there's a UTF-8 BOM (Byte Order Mark) at the
// start of the stream.
byte[] bomBuffer = new byte[3];
boolean foundBom = false;
int bytesread = stream.read(bomBuffer, 0, 3);
if (bytesread == 3) {
// Check if bomBuffer contains the UTF-8 BOM. Casts necessary to deal
// with signedness issues. (Java needs unsigned byte!)
foundBom = (bomBuffer[0] == (byte) 0xEF &&
bomBuffer[1] == (byte) 0xBB &&
bomBuffer[2] == (byte) 0xBF);
if (!foundBom)
stream.unread(bomBuffer, 0, 3);
}
if (foundBom)
encoding = "utf-8";
else
encoding = "iso-8859-1";
// Now look for an encoding declaration
byte[] buf = new byte[50];
int read = stream.read(buf, 0, 50);
if (read != -1) {
String start = new String(buf);
stream.unread(buf, 0, read);
// Get the encoding (if any) declared in the document.
if (start.startsWith("@\"")) {
int end = start.indexOf("\"", 2);
if (end != -1)
encoding = start.substring(2, end);
}
// If a BOM is found then the encoding must be utf-8.
if (foundBom && encoding != null && !encoding.equals("utf-8"))
throw new OntopiaRuntimeException("Contradicting encoding information."
+ " The BOM indicates that the encoding should be utf-8,"
+ " but the encoding is declared to be: " + encoding + ".");
return encoding;
}
return encoding;
}
}