/*
* This file is part of the Wayback archival access software
* (http://archive-access.sourceforge.net/projects/wayback/).
*
* Licensed to the Internet Archive (IA) by one or more individual
* contributors.
*
* The IA licenses this file to You 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 org.archive.wayback.replay.charset;
import java.io.IOException;
import java.io.InputStream;
import java.nio.charset.Charset;
import java.nio.charset.IllegalCharsetNameException;
import java.util.Iterator;
import java.util.Map;
import org.archive.wayback.core.Resource;
import org.archive.wayback.core.WaybackRequest;
import org.archive.wayback.replay.TagMagix;
import org.mozilla.universalchardet.UniversalDetector;
/**
* Abstract class containing common methods for determining the character
* encoding of a text Resource, most of which should be refactored into a
* Util package.
* @author brad
*
*/
public abstract class CharsetDetector {
// hand off this many bytes to the chardet library
protected final static int MAX_CHARSET_READAHEAD = 65536;
// ...if it also includes "charset="
protected final static String CHARSET_TOKEN = "charset=";
// ...and if the chardet library fails, use the Content-Type header
protected final static String HTTP_CONTENT_TYPE_HEADER = "Content-Type";
/** the default charset name to use when giving up */
public final static String DEFAULT_CHARSET = "UTF-8";
protected boolean isCharsetSupported(String charsetName) {
// can you believe that this throws a runtime? Just asking if it's
// supported!!?! They coulda just said "no"...
if(charsetName == null) {
return false;
}
try {
return Charset.isSupported(charsetName);
} catch(IllegalCharsetNameException e) {
return false;
}
}
protected String mapCharset(String orig) {
String lc = orig.toLowerCase();
if(lc.contains("iso8859-1") || lc.contains("iso-8859-1")) {
return "cp1252";
}
return orig;
}
protected String contentTypeToCharset(final String contentType) {
int offset =
contentType.toUpperCase().indexOf(CHARSET_TOKEN.toUpperCase());
if (offset != -1) {
String cs = contentType.substring(offset + CHARSET_TOKEN.length());
if(isCharsetSupported(cs)) {
return mapCharset(cs);
}
// test for extra spaces... there's at least one page out there that
// indicates it's charset with:
// <meta http-equiv="Content-type" content="text/html; charset=i so-8859-1">
// bad web page!
if(isCharsetSupported(cs.replace(" ", ""))) {
return mapCharset(cs.replace(" ", ""));
}
}
return null;
}
/**
* Attempt to divine the character encoding of the document from the
* Content-Type HTTP header (with a "charset=")
*
* @param resource
* @return String character set found or null if the header was not present
* @throws IOException
*/
protected String getCharsetFromHeaders(Resource resource)
throws IOException {
String charsetName = null;
Map<String,String> httpHeaders = resource.getHttpHeaders();
Iterator<String> keys = httpHeaders.keySet().iterator();
String ctype = null;
while(keys.hasNext()) {
String headerKey = keys.next();
String keyCmp = headerKey.toUpperCase().trim();
if(keyCmp.equals(HTTP_CONTENT_TYPE_HEADER.toUpperCase())) {
ctype = httpHeaders.get(headerKey);
break;
}
}
if (ctype != null) {
charsetName = contentTypeToCharset(ctype);
}
return charsetName;
}
/**
* Attempt to find a META tag in the HTML that hints at the character set
* used to write the document.
*
* @param resource
* @return String character set found from META tags in the HTML
* @throws IOException
*/
protected String getCharsetFromMeta(InputStream resource) throws IOException {
String charsetName = null;
byte[] bbuffer = new byte[MAX_CHARSET_READAHEAD];
resource.mark(MAX_CHARSET_READAHEAD);
resource.read(bbuffer, 0, MAX_CHARSET_READAHEAD);
resource.reset();
// convert to UTF-8 String -- which hopefully will not mess up the
// characters we're interested in...
StringBuilder sb = new StringBuilder(new String(bbuffer,DEFAULT_CHARSET));
String metaContentType = TagMagix.getTagAttrWhere(sb, "META",
"content", "http-equiv", "Content-Type");
if(metaContentType != null) {
charsetName = contentTypeToCharset(metaContentType);
}
return charsetName;
}
/**
* Attempts to figure out the character set of the document using
* the excellent juniversalchardet library.
*
* @param resource
* @return String character encoding found, or null if nothing looked good.
* @throws IOException
*/
protected String getCharsetFromBytes(InputStream resource) throws IOException {
String charsetName = null;
byte[] bbuffer = new byte[MAX_CHARSET_READAHEAD];
// (1)
UniversalDetector detector = new UniversalDetector(null);
// (2)
resource.mark(MAX_CHARSET_READAHEAD);
int len = resource.read(bbuffer, 0, MAX_CHARSET_READAHEAD);
resource.reset();
detector.handleData(bbuffer, 0, len);
// (3)
detector.dataEnd();
// (4)
charsetName = detector.getDetectedCharset();
// (5)
detector.reset();
if(isCharsetSupported(charsetName)) {
return charsetName;
}
return null;
}
/**
* @param resource (presumably text) Resource to determine the charset
* @param request WaybackRequest which may contain additional hints to
* processing
* @return String charset name for the Resource
* @throws IOException if there are problems reading the Resource
*/
public abstract String getCharset(Resource resource, WaybackRequest request)
throws IOException;
}