1 /*
   2  * Copyright (c) 2008, 2015, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package sun.nio.fs;
  27 
  28 import java.nio.file.Path;
  29 import java.nio.file.spi.FileTypeDetector;
  30 import java.util.Locale;
  31 import java.io.IOException;
  32 
  33 /**
  34  * Base implementation of FileTypeDetector
  35  */
  36 
  37 public abstract class AbstractFileTypeDetector
  38     extends FileTypeDetector
  39 {
  40     protected AbstractFileTypeDetector() {
  41         super();
  42     }
  43 
  44     // Get the extension of a file name.
  45     protected static String getExtension(String name) {
  46         String ext = "";
  47         if (name != null && !name.isEmpty()) {
  48             int dot = name.indexOf('.');
  49             if ((dot >= 0) && (dot < name.length() - 1)) {
  50                 ext = name.substring(dot + 1);
  51             }
  52         }
  53         return ext;
  54     }
  55 
  56     /**
  57      * Invokes the appropriate probe method to guess a file's content type,
  58      * and checks that the content type's syntax is valid.
  59      */
  60     @Override
  61     public final String probeContentType(Path file) throws IOException {
  62         if (file == null)
  63             throw new NullPointerException("'file' is null");
  64         String result = implProbeContentType(file);
  65         return (result == null) ? null : parse(result);
  66     }
  67 
  68     /**
  69      * Probes the given file to guess its content type.
  70      */
  71     protected abstract String implProbeContentType(Path file)
  72         throws IOException;
  73 
  74     /**
  75      * Parses a candidate content type into its type and subtype, returning
  76      * null if either token is invalid.
  77      */
  78     private static String parse(String s) {
  79         int slash = s.indexOf('/');
  80         int semicolon = s.indexOf(';');
  81         if (slash < 0)
  82             return null;  // no subtype
  83         String type = s.substring(0, slash).trim().toLowerCase(Locale.ENGLISH);
  84         if (!isValidToken(type))
  85             return null;  // invalid type
  86         String subtype = (semicolon < 0) ? s.substring(slash + 1) :
  87             s.substring(slash + 1, semicolon);
  88         subtype = subtype.trim().toLowerCase(Locale.ENGLISH);
  89         if (!isValidToken(subtype))
  90             return null;  // invalid subtype
  91         StringBuilder sb = new StringBuilder(type.length() + subtype.length() + 1);
  92         sb.append(type);
  93         sb.append('/');
  94         sb.append(subtype);
  95         return sb.toString();
  96     }
  97 
  98     /**
  99      * Special characters
 100      */
 101     private static final String TSPECIALS = "()<>@,;:/[]?=\\\"";
 102 
 103     /**
 104      * Returns true if the character is a valid token character.
 105      */
 106     private static boolean isTokenChar(char c) {
 107         return (c > 040) && (c < 0177) && (TSPECIALS.indexOf(c) < 0);
 108     }
 109 
 110     /**
 111      * Returns true if the given string is a legal type or subtype.
 112      */
 113     private static boolean isValidToken(String s) {
 114         int len = s.length();
 115         if (len == 0)
 116             return false;
 117         for (int i = 0; i < len; i++) {
 118             if (!isTokenChar(s.charAt(i)))
 119                 return false;
 120         }
 121         return true;
 122     }
 123 }