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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 | } | ||