1/* 2 * Copyright (c) 2008, 2016, 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 26package sun.nio.fs; 27 28import java.net.FileNameMap; 29import java.net.URLConnection; 30import java.nio.file.Path; 31import java.nio.file.spi.FileTypeDetector; 32import java.util.Locale; 33import java.io.IOException; 34 35/** 36 * Base implementation of FileTypeDetector 37 */ 38 39public abstract class AbstractFileTypeDetector 40 extends FileTypeDetector 41{ 42 protected AbstractFileTypeDetector() { 43 super(); 44 } 45 46 /** 47 * Returns the extension of a file name, specifically the portion of the 48 * parameter string after the first dot. If the parameter is {@code null}, 49 * empty, does not contain a dot, or the dot is the last character, then an 50 * empty string is returned, otherwise the characters after the dot are 51 * returned. 52 * 53 * @param name A file name 54 * @return The characters after the first dot or an empty string. 55 */ 56 protected final String getExtension(String name) { 57 String ext = ""; 58 if (name != null && !name.isEmpty()) { 59 int dot = name.indexOf('.'); 60 if ((dot >= 0) && (dot < name.length() - 1)) { 61 ext = name.substring(dot + 1); 62 } 63 } 64 return ext; 65 } 66 67 /** 68 * Invokes the appropriate probe method to guess a file's content type, 69 * and checks that the content type's syntax is valid. 70 */ 71 @Override 72 public final String probeContentType(Path file) throws IOException { 73 if (file == null) 74 throw new NullPointerException("'file' is null"); 75 String result = implProbeContentType(file); 76 77 // Fall back to content types property. 78 if (result == null) { 79 Path fileName = file.getFileName(); 80 if (fileName != null) { 81 FileNameMap fileNameMap = URLConnection.getFileNameMap(); 82 result = fileNameMap.getContentTypeFor(fileName.toString()); 83 } 84 } 85 86 return (result == null) ? null : parse(result); 87 } 88 89 /** 90 * Probes the given file to guess its content type. 91 */ 92 protected abstract String implProbeContentType(Path file) 93 throws IOException; 94 95 /** 96 * Parses a candidate content type into its type and subtype, returning 97 * null if either token is invalid. 98 */ 99 private static String parse(String s) { 100 int slash = s.indexOf('/'); 101 int semicolon = s.indexOf(';'); 102 if (slash < 0) 103 return null; // no subtype 104 String type = s.substring(0, slash).trim().toLowerCase(Locale.ENGLISH); 105 if (!isValidToken(type)) 106 return null; // invalid type 107 String subtype = (semicolon < 0) ? s.substring(slash + 1) : 108 s.substring(slash + 1, semicolon); 109 subtype = subtype.trim().toLowerCase(Locale.ENGLISH); 110 if (!isValidToken(subtype)) 111 return null; // invalid subtype 112 StringBuilder sb = new StringBuilder(type.length() + subtype.length() + 1); 113 sb.append(type); 114 sb.append('/'); 115 sb.append(subtype); 116 return sb.toString(); 117 } 118 119 /** 120 * Special characters 121 */ 122 private static final String TSPECIALS = "()<>@,;:/[]?=\\\""; 123 124 /** 125 * Returns true if the character is a valid token character. 126 */ 127 private static boolean isTokenChar(char c) { 128 return (c > 040) && (c < 0177) && (TSPECIALS.indexOf(c) < 0); 129 } 130 131 /** 132 * Returns true if the given string is a legal type or subtype. 133 */ 134 private static boolean isValidToken(String s) { 135 int len = s.length(); 136 if (len == 0) 137 return false; 138 for (int i = 0; i < len; i++) { 139 if (!isTokenChar(s.charAt(i))) 140 return false; 141 } 142 return true; 143 } 144} 145