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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    *
9    *     http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  package org.apache.tika.detect;
18  
19  import java.io.IOException;
20  import java.io.InputStream;
21  
22  import org.apache.tika.metadata.Metadata;
23  import org.apache.tika.mime.MediaType;
24  
25  /**
26   * Content type detector. Implementations of this interface use various
27   * heuristics to detect the content type of a document based on given
28   * input metadata or the first few bytes of the document stream.
29   *
30   * @since Apache Tika 0.3
31   */
32  public interface Detector {
33  
34      /**
35       * Detects the content type of the given input document. Returns
36       * <code>application/octet-stream</code> if the type of the document
37       * can not be detected.
38       * <p>
39       * If the document input stream is not available, then the first
40       * argument may be <code>null</code>. Otherwise the detector may
41       * read bytes from the start of the stream to help in type detection.
42       * The given stream is guaranteed to support the
43       * {@link InputStream#markSupported() mark feature} and the detector
44       * is expected to {@link InputStream#mark(int) mark} the stream before
45       * reading any bytes from it, and to {@link InputStream#reset() reset}
46       * the stream before returning. The stream must not be closed by the
47       * detector.
48       * <p>
49       * The given input metadata is only read, not modified, by the detector.
50       *
51       * @param input document input stream, or <code>null</code>
52       * @param metadata input metadata for the document
53       * @return detected media type, or <code>application/octet-stream</code>
54       * @throws IOException if the document input stream could not be read
55       */
56      MediaType detect(InputStream input, Metadata metadata) throws IOException;
57  
58  }