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/*
* Copyright (c) 2008, 2016, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package sun.nio.fs;
import java.net.FileNameMap;
import java.net.URLConnection;
import java.nio.file.Path;
import java.nio.file.spi.FileTypeDetector;
import java.util.Locale;
import java.io.IOException;
/**
* Base implementation of FileTypeDetector
*/
public abstract class AbstractFileTypeDetector
extends FileTypeDetector
{
protected AbstractFileTypeDetector() {
super();
}
/**
* Returns the extension of a file name, specifically the portion of the
* parameter string after the first dot. If the parameter is {@code null},
* empty, does not contain a dot, or the dot is the last character, then an
* empty string is returned, otherwise the characters after the dot are
* returned.
*
* @param name A file name
* @return The characters after the first dot or an empty string.
*/
protected final String getExtension(String name) {
String ext = "";
if (name != null && !name.isEmpty()) {
int dot = name.indexOf('.');
if ((dot >= 0) && (dot < name.length() - 1)) {
ext = name.substring(dot + 1);
}
}
return ext;
}
/**
* Invokes the appropriate probe method to guess a file's content type,
* and checks that the content type's syntax is valid.
*/
@Override
public final String probeContentType(Path file) throws IOException {
if (file == null)
throw new NullPointerException("'file' is null");
String result = implProbeContentType(file);
// Fall back to content types property.
if (result == null) {
Path fileName = file.getFileName();
if (fileName != null) {
FileNameMap fileNameMap = URLConnection.getFileNameMap();
result = fileNameMap.getContentTypeFor(fileName.toString());
}
}
return (result == null) ? null : parse(result);
}
/**
* Probes the given file to guess its content type.
*/
protected abstract String implProbeContentType(Path file)
throws IOException;
/**
* Parses a candidate content type into its type and subtype, returning
* null if either token is invalid.
*/
private static String parse(String s) {
int slash = s.indexOf('/');
int semicolon = s.indexOf(';');
if (slash < 0)
return null; // no subtype
String type = s.substring(0, slash).trim().toLowerCase(Locale.ENGLISH);
if (!isValidToken(type))
return null; // invalid type
String subtype = (semicolon < 0) ? s.substring(slash + 1) :
s.substring(slash + 1, semicolon);
subtype = subtype.trim().toLowerCase(Locale.ENGLISH);
if (!isValidToken(subtype))
return null; // invalid subtype
StringBuilder sb = new StringBuilder(type.length() + subtype.length() + 1);
sb.append(type);
sb.append('/');
sb.append(subtype);
return sb.toString();
}
/**
* Special characters
*/
private static final String TSPECIALS = "()<>@,;:/[]?=\\\"";
/**
* Returns true if the character is a valid token character.
*/
private static boolean isTokenChar(char c) {
return (c > 040) && (c < 0177) && (TSPECIALS.indexOf(c) < 0);
}
/**
* Returns true if the given string is a legal type or subtype.
*/
private static boolean isValidToken(String s) {
int len = s.length();
if (len == 0)
return false;
for (int i = 0; i < len; i++) {
if (!isTokenChar(s.charAt(i)))
return false;
}
return true;
}
}