1 /* 2 * Copyright (c) 2008, 2012, 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 /** 41 * Invokes the appropriate probe method to guess a file's content type, 42 * and checks that the content type's syntax is valid. 43 */ 44 @Override 45 public final String probeContentType(Path file) throws IOException { 46 if (file == null) 47 throw new NullPointerException("'file' is null"); 48 String result = implProbeContentType(file); 49 return (result == null) ? null : parse(result); 50 } 51 52 /** 53 * Probes the given file to guess its content type. 54 */ 55 protected abstract String implProbeContentType(Path file) 56 throws IOException; 57 58 /** 59 * Parses a candidate content type into its type and subtype, returning 60 * null if either token is invalid. 61 */ 62 private static String parse(String s) { 63 int slash = s.indexOf('/'); 64 int semicolon = s.indexOf(';'); 65 if (slash < 0) 66 return null; // no subtype 67 String type = s.substring(0, slash).trim().toLowerCase(Locale.ENGLISH); 68 if (!isValidToken(type)) 69 return null; // invalid type 70 String subtype = (semicolon < 0) ? s.substring(slash + 1) : 71 s.substring(slash + 1, semicolon); 72 subtype = subtype.trim().toLowerCase(Locale.ENGLISH); 73 if (!isValidToken(subtype)) 74 return null; // invalid subtype 75 StringBuilder sb = new StringBuilder(type.length() + subtype.length() + 1); 76 sb.append(type); 77 sb.append('/'); 78 sb.append(subtype); 79 return sb.toString(); 80 } 81 82 /** 83 * Special characters 84 */ 85 private static final String TSPECIALS = "()<>@,;:/[]?=\\\""; 86 87 /** 88 * Returns true if the character is a valid token character. 89 */ 90 private static boolean isTokenChar(char c) { 91 return (c > 040) && (c < 0177) && (TSPECIALS.indexOf(c) < 0); 92 } 93 94 /** 95 * Returns true if the given string is a legal type or subtype. 96 */ 97 private static boolean isValidToken(String s) { 98 int len = s.length(); 99 if (len == 0) 100 return false; 101 for (int i = 0; i < len; i++) { 102 if (!isTokenChar(s.charAt(i))) 103 return false; 104 } 105 return true; 106 } 107 }