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| 1 | +/* | |
| 2 | + * Copyright (c) 2007, 2011, 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 java.nio.channels; | |
| 27 | + | |
| 28 | +import java.nio.ByteBuffer; | |
| 29 | +import java.io.IOException; | |
| 30 | + | |
| 31 | +/** | |
| 32 | + * A byte channel that maintains a current <i>position</i> and allows the | |
| 33 | + * position to be changed. | |
| 34 | + * | |
| 35 | + * <p> A seekable byte channel is connected to an entity, typically a file, | |
| 36 | + * that contains a variable-length sequence of bytes that can be read and | |
| 37 | + * written. The current position can be {@link #position() <i>queried</i>} and | |
| 38 | + * {@link #position(long) <i>modified</i>}. The channel also provides access to | |
| 39 | + * the current <i>size</i> of the entity to which the channel is connected. The | |
| 40 | + * size increases when bytes are written beyond its current size; the size | |
| 41 | + * decreases when it is {@link #truncate <i>truncated</i>}. | |
| 42 | + * | |
| 43 | + * <p> The {@link #position(long) position} and {@link #truncate truncate} methods | |
| 44 | + * which do not otherwise have a value to return are specified to return the | |
| 45 | + * channel upon which they are invoked. This allows method invocations to be | |
| 46 | + * chained. Implementations of this interface should specialize the return type | |
| 47 | + * so that method invocations on the implementation class can be chained. | |
| 48 | + * | |
| 49 | + * @since 1.7 | |
| 50 | + * @see java.nio.file.Files#newByteChannel | |
| 51 | + */ | |
| 52 | + | |
| 53 | +public interface SeekableByteChannel | |
| 54 | + extends ByteChannel | |
| 55 | +{ | |
| 56 | + /** | |
| 57 | + * Reads a sequence of bytes from this channel into the given buffer. | |
| 58 | + * | |
| 59 | + * <p> Bytes are read starting at this channel's current position, and | |
| 60 | + * then the position is updated with the number of bytes actually read. | |
| 61 | + * Otherwise this method behaves exactly as specified in the {@link | |
| 62 | + * ReadableByteChannel} interface. | |
| 63 | + */ | |
| 64 | + @Override | |
| 65 | + int read(ByteBuffer dst) throws IOException; | |
| 66 | + | |
| 67 | + /** | |
| 68 | + * Writes a sequence of bytes to this channel from the given buffer. | |
| 69 | + * | |
| 70 | + * <p> Bytes are written starting at this channel's current position, unless | |
| 71 | + * the channel is connected to an entity such as a file that is opened with | |
| 72 | + * the {@link java.nio.file.StandardOpenOption#APPEND APPEND} option, in | |
| 73 | + * which case the position is first advanced to the end. The entity to which | |
| 74 | + * the channel is connected is grown, if necessary, to accommodate the | |
| 75 | + * written bytes, and then the position is updated with the number of bytes | |
| 76 | + * actually written. Otherwise this method behaves exactly as specified by | |
| 77 | + * the {@link WritableByteChannel} interface. | |
| 78 | + */ | |
| 79 | + @Override | |
| 80 | + int write(ByteBuffer src) throws IOException; | |
| 81 | + | |
| 82 | + /** | |
| 83 | + * Returns this channel's position. | |
| 84 | + * | |
| 85 | + * @return This channel's position, | |
| 86 | + * a non-negative integer counting the number of bytes | |
| 87 | + * from the beginning of the entity to the current position | |
| 88 | + * | |
| 89 | + * @throws ClosedChannelException | |
| 90 | + * If this channel is closed | |
| 91 | + * @throws IOException | |
| 92 | + * If some other I/O error occurs | |
| 93 | + */ | |
| 94 | + long position() throws IOException; | |
| 95 | + | |
| 96 | + /** | |
| 97 | + * Sets this channel's position. | |
| 98 | + * | |
| 99 | + * <p> Setting the position to a value that is greater than the current size | |
| 100 | + * is legal but does not change the size of the entity. A later attempt to | |
| 101 | + * read bytes at such a position will immediately return an end-of-file | |
| 102 | + * indication. A later attempt to write bytes at such a position will cause | |
| 103 | + * the entity to grow to accommodate the new bytes; the values of any bytes | |
| 104 | + * between the previous end-of-file and the newly-written bytes are | |
| 105 | + * unspecified. | |
| 106 | + * | |
| 107 | + * <p> Setting the channel's position is not recommended when connected to | |
| 108 | + * an entity, typically a file, that is opened with the {@link | |
| 109 | + * java.nio.file.StandardOpenOption#APPEND APPEND} option. When opened for | |
| 110 | + * append, the position is first advanced to the end before writing. | |
| 111 | + * | |
| 112 | + * @param newPosition | |
| 113 | + * The new position, a non-negative integer counting | |
| 114 | + * the number of bytes from the beginning of the entity | |
| 115 | + * | |
| 116 | + * @return This channel | |
| 117 | + * | |
| 118 | + * @throws ClosedChannelException | |
| 119 | + * If this channel is closed | |
| 120 | + * @throws IllegalArgumentException | |
| 121 | + * If the new position is negative | |
| 122 | + * @throws IOException | |
| 123 | + * If some other I/O error occurs | |
| 124 | + */ | |
| 125 | + SeekableByteChannel position(long newPosition) throws IOException; | |
| 126 | + | |
| 127 | + /** | |
| 128 | + * Returns the current size of entity to which this channel is connected. | |
| 129 | + * | |
| 130 | + * @return The current size, measured in bytes | |
| 131 | + * | |
| 132 | + * @throws ClosedChannelException | |
| 133 | + * If this channel is closed | |
| 134 | + * @throws IOException | |
| 135 | + * If some other I/O error occurs | |
| 136 | + */ | |
| 137 | + long size() throws IOException; | |
| 138 | + | |
| 139 | + /** | |
| 140 | + * Truncates the entity, to which this channel is connected, to the given | |
| 141 | + * size. | |
| 142 | + * | |
| 143 | + * <p> If the given size is less than the current size then the entity is | |
| 144 | + * truncated, discarding any bytes beyond the new end. If the given size is | |
| 145 | + * greater than or equal to the current size then the entity is not modified. | |
| 146 | + * In either case, if the current position is greater than the given size | |
| 147 | + * then it is set to that size. | |
| 148 | + * | |
| 149 | + * <p> An implementation of this interface may prohibit truncation when | |
| 150 | + * connected to an entity, typically a file, opened with the {@link | |
| 151 | + * java.nio.file.StandardOpenOption#APPEND APPEND} option. | |
| 152 | + * | |
| 153 | + * @param size | |
| 154 | + * The new size, a non-negative byte count | |
| 155 | + * | |
| 156 | + * @return This channel | |
| 157 | + * | |
| 158 | + * @throws NonWritableChannelException | |
| 159 | + * If this channel was not opened for writing | |
| 160 | + * @throws ClosedChannelException | |
| 161 | + * If this channel is closed | |
| 162 | + * @throws IllegalArgumentException | |
| 163 | + * If the new size is negative | |
| 164 | + * @throws IOException | |
| 165 | + * If some other I/O error occurs | |
| 166 | + */ | |
| 167 | + SeekableByteChannel truncate(long size) throws IOException; | |
| 168 | +} | |