View Javadoc
1    /*
2    * Licensed to the Apache Software Foundation (ASF) under one
3    * or more contributor license agreements.  See the NOTICE file
4    * distributed with this work for additional information
5    * regarding copyright ownership.  The ASF licenses this file
6    * to you under the Apache License, Version 2.0 (the
7    * "License"); you may not use this file except in compliance
8    * with the License.  You may obtain a copy of the License at
9    *
10   *     http://www.apache.org/licenses/LICENSE-2.0
11   *
12   * Unless required by applicable law or agreed to in writing, software
13   * distributed under the License is distributed on an "AS IS" BASIS,
14   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15   * See the License for the specific language governing permissions and
16   * limitations under the License.
17   */
18  package org.apache.commons.crypto.stream.input;
19  
20  import java.io.Closeable;
21  import java.io.IOException;
22  import java.io.InputStream;
23  import java.nio.ByteBuffer;
24  import java.nio.channels.ReadableByteChannel;
25  
26  import org.apache.commons.crypto.stream.CryptoInputStream;
27  
28  /**
29   * The Input interface abstract the input source of
30   * {@link CryptoInputStream} so that different implementation of input can
31   * be used. The implementation Input interface will usually wraps an input
32   * mechanism such as {@link InputStream} or
33   * {@link ReadableByteChannel}.
34   */
35  public interface Input extends Closeable {
36      /**
37       * Returns an estimate of the number of bytes that can be read (or skipped
38       * over) from this input without blocking by the next invocation of a method
39       * for this input stream. The next invocation might be the same thread or
40       * another thread. A single read or skip of this many bytes will not block,
41       * but may read or skip fewer bytes.
42       *
43       * <p>
44       * It is never correct to use the return value of this method to allocate a
45       * buffer intended to hold all data in this stream.
46       *
47       * @return an estimate of the number of bytes that can be read (or skipped
48       *         over) from this input stream without blocking or {@code 0} when
49       *         it reaches the end of the input stream.
50       * @throws IOException if an I/O error occurs.
51       */
52      int available() throws IOException;
53  
54      /**
55       * Closes this input and releases any system resources associated with the
56       * under layer input.
57       *
58       * @throws IOException if an I/O error occurs.
59       */
60      @Override
61      void close() throws IOException;
62  
63      /**
64       * Reads a sequence of bytes from input into the given buffer.
65       *
66       * <p>
67       * An attempt is made to read up to <i>r</i> bytes from the input, where
68       * <i>r</i> is the number of bytes remaining in the buffer, that is,
69       * {@code dst.remaining()}, at the moment this method is invoked.
70       *
71       * <p>
72       * Suppose that a byte sequence of length <i>n</i> is read, where {@code 0}
73       * &nbsp;{@code <=}&nbsp;<i>n</i>&nbsp;{@code <=}&nbsp;<i>r</i>.
74       * This byte sequence will be transferred into the buffer so that the first
75       * byte in the sequence is at index <i>p</i> and the last byte is at index
76       * <i>p</i>&nbsp;{@code +}&nbsp;<i>n</i>&nbsp;{@code -}&nbsp;{@code 1},
77       * where <i>p</i> is the buffer's position at the moment this method is
78       * invoked. Upon return the buffer's position will be equal to
79       * <i>p</i>&nbsp;{@code +}&nbsp;<i>n</i>; its limit will not have changed.
80       *
81       * @param dst The buffer into which bytes are to be transferred.
82       * @return the total number of bytes read into the buffer, or
83       *         {@code -1} if there is no more data because the end of the
84       *         stream has been reached.
85       * @throws IOException If some other I/O error occurs.
86       */
87      int read(ByteBuffer dst) throws IOException;
88  
89      /**
90       * Reads up to the specified number of bytes from a given position within a
91       * stream and return the number of bytes read. This does not change the
92       * current offset of the stream and is thread-safe.
93       *
94       * An implementation may not support positioned read. If the implementation
95       * doesn't support positioned read, it throws UnsupportedOperationException.
96       *
97       * @param position the given position within a stream.
98       * @param buffer the buffer into which the data is read.
99       * @param offset the start offset in array buffer.
100      * @param length the maximum number of bytes to read.
101      * @return the total number of bytes read into the buffer, or
102      *         {@code -1} if there is no more data because the end of the
103      *         stream has been reached.
104      * @throws IOException if an I/O error occurs.
105      */
106     int read(long position, byte[] buffer, int offset, int length)
107             throws IOException;
108 
109     /**
110      * Seeks to the given offset from the start of the stream. The next read()
111      * will be from that location.
112      *
113      * An implementation may not support seek. If the implementation doesn't
114      * support seek, it throws UnsupportedOperationException.
115      *
116      * @param position the offset from the start of the stream.
117      * @throws IOException if an I/O error occurs.
118      */
119     void seek(long position) throws IOException;
120 
121     /**
122      * Skips over and discards {@code n} bytes of data from this input The
123      * {@code skip} method may, for a variety of reasons, end up skipping
124      * over some smaller number of bytes, possibly {@code 0}. This may
125      * result from any of a number of conditions; reaching end of file before
126      * {@code n} bytes have been skipped is only one possibility. The
127      * actual number of bytes skipped is returned. If {@code n} is
128      * negative, no bytes are skipped.
129      *
130      * <p>
131      * The {@code skip} method of this class creates a byte array and then
132      * repeatedly reads into it until {@code n} bytes have been read or the
133      * end of the stream has been reached. Subclasses are encouraged to provide
134      * a more efficient implementation of this method. For instance, the
135      * implementation may depend on the ability to seek.
136      *
137      * @param n the number of bytes to be skipped.
138      * @return the actual number of bytes skipped.
139      * @throws IOException if the stream does not support seek, or if some
140      *            other I/O error occurs.
141      */
142     long skip(long n) throws IOException;
143 }