| /* |
| * Copyright (c) 2007, 2011, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. Oracle designates this |
| * particular file as subject to the "Classpath" exception as provided |
| * by Oracle in the LICENSE file that accompanied this code. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| */ |
| |
| package java.nio.channels; |
| |
| import java.nio.ByteBuffer; |
| import java.io.IOException; |
| |
| /** |
| * A byte channel that maintains a current <i>position</i> and allows the |
| * position to be changed. |
| * |
| * <p> A seekable byte channel is connected to an entity, typically a file, |
| * that contains a variable-length sequence of bytes that can be read and |
| * written. The current position can be {@link #position() <i>queried</i>} and |
| * {@link #position(long) <i>modified</i>}. The channel also provides access to |
| * the current <i>size</i> of the entity to which the channel is connected. The |
| * size increases when bytes are written beyond its current size; the size |
| * decreases when it is {@link #truncate <i>truncated</i>}. |
| * |
| * <p> The {@link #position(long) position} and {@link #truncate truncate} methods |
| * which do not otherwise have a value to return are specified to return the |
| * channel upon which they are invoked. This allows method invocations to be |
| * chained. Implementations of this interface should specialize the return type |
| * so that method invocations on the implementation class can be chained. |
| * |
| * @since 1.7 |
| * @see java.nio.file.Files#newByteChannel |
| */ |
| |
| public interface SeekableByteChannel |
| extends ByteChannel |
| { |
| /** |
| * Reads a sequence of bytes from this channel into the given buffer. |
| * |
| * <p> Bytes are read starting at this channel's current position, and |
| * then the position is updated with the number of bytes actually read. |
| * Otherwise this method behaves exactly as specified in the {@link |
| * ReadableByteChannel} interface. |
| */ |
| @Override |
| int read(ByteBuffer dst) throws IOException; |
| |
| /** |
| * Writes a sequence of bytes to this channel from the given buffer. |
| * |
| * <p> Bytes are written starting at this channel's current position, unless |
| * the channel is connected to an entity such as a file that is opened with |
| * the {@link java.nio.file.StandardOpenOption#APPEND APPEND} option, in |
| * which case the position is first advanced to the end. The entity to which |
| * the channel is connected is grown, if necessary, to accommodate the |
| * written bytes, and then the position is updated with the number of bytes |
| * actually written. Otherwise this method behaves exactly as specified by |
| * the {@link WritableByteChannel} interface. |
| */ |
| @Override |
| int write(ByteBuffer src) throws IOException; |
| |
| /** |
| * Returns this channel's position. |
| * |
| * @return This channel's position, |
| * a non-negative integer counting the number of bytes |
| * from the beginning of the entity to the current position |
| * |
| * @throws ClosedChannelException |
| * If this channel is closed |
| * @throws IOException |
| * If some other I/O error occurs |
| */ |
| long position() throws IOException; |
| |
| /** |
| * Sets this channel's position. |
| * |
| * <p> Setting the position to a value that is greater than the current size |
| * is legal but does not change the size of the entity. A later attempt to |
| * read bytes at such a position will immediately return an end-of-file |
| * indication. A later attempt to write bytes at such a position will cause |
| * the entity to grow to accommodate the new bytes; the values of any bytes |
| * between the previous end-of-file and the newly-written bytes are |
| * unspecified. |
| * |
| * <p> Setting the channel's position is not recommended when connected to |
| * an entity, typically a file, that is opened with the {@link |
| * java.nio.file.StandardOpenOption#APPEND APPEND} option. When opened for |
| * append, the position is first advanced to the end before writing. |
| * |
| * @param newPosition |
| * The new position, a non-negative integer counting |
| * the number of bytes from the beginning of the entity |
| * |
| * @return This channel |
| * |
| * @throws ClosedChannelException |
| * If this channel is closed |
| * @throws IllegalArgumentException |
| * If the new position is negative |
| * @throws IOException |
| * If some other I/O error occurs |
| */ |
| SeekableByteChannel position(long newPosition) throws IOException; |
| |
| /** |
| * Returns the current size of entity to which this channel is connected. |
| * |
| * @return The current size, measured in bytes |
| * |
| * @throws ClosedChannelException |
| * If this channel is closed |
| * @throws IOException |
| * If some other I/O error occurs |
| */ |
| long size() throws IOException; |
| |
| /** |
| * Truncates the entity, to which this channel is connected, to the given |
| * size. |
| * |
| * <p> If the given size is less than the current size then the entity is |
| * truncated, discarding any bytes beyond the new end. If the given size is |
| * greater than or equal to the current size then the entity is not modified. |
| * In either case, if the current position is greater than the given size |
| * then it is set to that size. |
| * |
| * <p> An implementation of this interface may prohibit truncation when |
| * connected to an entity, typically a file, opened with the {@link |
| * java.nio.file.StandardOpenOption#APPEND APPEND} option. |
| * |
| * @param size |
| * The new size, a non-negative byte count |
| * |
| * @return This channel |
| * |
| * @throws NonWritableChannelException |
| * If this channel was not opened for writing |
| * @throws ClosedChannelException |
| * If this channel is closed |
| * @throws IllegalArgumentException |
| * If the new size is negative |
| * @throws IOException |
| * If some other I/O error occurs |
| */ |
| SeekableByteChannel truncate(long size) throws IOException; |
| } |