J. Duke | 319a3b9 | 2007-12-01 00:00:00 +0000 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright 2000-2001 Sun Microsystems, Inc. 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. Sun designates this |
| 8 | * particular file as subject to the "Classpath" exception as provided |
| 9 | * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
| 22 | * CA 95054 USA or visit www.sun.com if you need additional information or |
| 23 | * have any questions. |
| 24 | */ |
| 25 | |
| 26 | package java.nio.channels; |
| 27 | |
| 28 | import java.io.IOException; |
| 29 | import java.net.DatagramSocket; |
| 30 | import java.net.SocketAddress; |
| 31 | import java.nio.ByteBuffer; |
| 32 | import java.nio.channels.spi.*; |
| 33 | |
| 34 | |
| 35 | /** |
| 36 | * A selectable channel for datagram-oriented sockets. |
| 37 | * |
| 38 | * |
| 39 | * <p> Datagram channels are not a complete abstraction of network datagram |
| 40 | * sockets. Binding and the manipulation of socket options must be done |
| 41 | * through an associated {@link java.net.DatagramSocket} object obtained by |
| 42 | * invoking the {@link #socket() socket} method. It is not possible to create |
| 43 | * a channel for an arbitrary, pre-existing datagram socket, nor is it possible |
| 44 | * to specify the {@link java.net.DatagramSocketImpl} object to be used by a |
| 45 | * datagram socket associated with a datagram channel. |
| 46 | * |
| 47 | * <p> A datagram channel is created by invoking the {@link #open open} method |
| 48 | * of this class. A newly-created datagram channel is open but not connected. |
| 49 | * A datagram channel need not be connected in order for the {@link #send send} |
| 50 | * and {@link #receive receive} methods to be used. A datagram channel may be |
| 51 | * connected, by invoking its {@link #connect connect} method, in order to |
| 52 | * avoid the overhead of the security checks are otherwise performed as part of |
| 53 | * every send and receive operation. A datagram channel must be connected in |
| 54 | * order to use the {@link #read(java.nio.ByteBuffer) read} and {@link |
| 55 | * #write(java.nio.ByteBuffer) write} methods, since those methods do not |
| 56 | * accept or return socket addresses. |
| 57 | * |
| 58 | * <p> Once connected, a datagram channel remains connected until it is |
| 59 | * disconnected or closed. Whether or not a datagram channel is connected may |
| 60 | * be determined by invoking its {@link #isConnected isConnected} method. |
| 61 | * |
| 62 | * <p> Datagram channels are safe for use by multiple concurrent threads. They |
| 63 | * support concurrent reading and writing, though at most one thread may be |
| 64 | * reading and at most one thread may be writing at any given time. </p> |
| 65 | * |
| 66 | * |
| 67 | * @author Mark Reinhold |
| 68 | * @author JSR-51 Expert Group |
| 69 | * @since 1.4 |
| 70 | */ |
| 71 | |
| 72 | public abstract class DatagramChannel |
| 73 | extends AbstractSelectableChannel |
| 74 | implements ByteChannel, ScatteringByteChannel, GatheringByteChannel |
| 75 | { |
| 76 | |
| 77 | /** |
| 78 | * Initializes a new instance of this class. |
| 79 | */ |
| 80 | protected DatagramChannel(SelectorProvider provider) { |
| 81 | super(provider); |
| 82 | } |
| 83 | |
| 84 | /** |
| 85 | * Opens a datagram channel. |
| 86 | * |
| 87 | * <p> The new channel is created by invoking the {@link |
| 88 | * java.nio.channels.spi.SelectorProvider#openDatagramChannel() |
| 89 | * openDatagramChannel} method of the system-wide default {@link |
| 90 | * java.nio.channels.spi.SelectorProvider} object. The channel will not be |
| 91 | * connected. </p> |
| 92 | * |
| 93 | * @return A new datagram channel |
| 94 | * |
| 95 | * @throws IOException |
| 96 | * If an I/O error occurs |
| 97 | */ |
| 98 | public static DatagramChannel open() throws IOException { |
| 99 | return SelectorProvider.provider().openDatagramChannel(); |
| 100 | } |
| 101 | |
| 102 | /** |
| 103 | * Returns an operation set identifying this channel's supported |
| 104 | * operations. |
| 105 | * |
| 106 | * <p> Datagram channels support reading and writing, so this method |
| 107 | * returns <tt>(</tt>{@link SelectionKey#OP_READ} <tt>|</tt> {@link |
| 108 | * SelectionKey#OP_WRITE}<tt>)</tt>. </p> |
| 109 | * |
| 110 | * @return The valid-operation set |
| 111 | */ |
| 112 | public final int validOps() { |
| 113 | return (SelectionKey.OP_READ |
| 114 | | SelectionKey.OP_WRITE); |
| 115 | } |
| 116 | |
| 117 | |
| 118 | // -- Socket-specific operations -- |
| 119 | |
| 120 | /** |
| 121 | * Retrieves a datagram socket associated with this channel. |
| 122 | * |
| 123 | * <p> The returned object will not declare any public methods that are not |
| 124 | * declared in the {@link java.net.DatagramSocket} class. </p> |
| 125 | * |
| 126 | * @return A datagram socket associated with this channel |
| 127 | */ |
| 128 | public abstract DatagramSocket socket(); |
| 129 | |
| 130 | /** |
| 131 | * Tells whether or not this channel's socket is connected. </p> |
| 132 | * |
| 133 | * @return <tt>true</tt> if, and only if, this channel's socket |
| 134 | * is connected |
| 135 | */ |
| 136 | public abstract boolean isConnected(); |
| 137 | |
| 138 | /** |
| 139 | * Connects this channel's socket. |
| 140 | * |
| 141 | * <p> The channel's socket is configured so that it only receives |
| 142 | * datagrams from, and sends datagrams to, the given remote <i>peer</i> |
| 143 | * address. Once connected, datagrams may not be received from or sent to |
| 144 | * any other address. A datagram socket remains connected until it is |
| 145 | * explicitly disconnected or until it is closed. |
| 146 | * |
| 147 | * <p> This method performs exactly the same security checks as the {@link |
| 148 | * java.net.DatagramSocket#connect connect} method of the {@link |
| 149 | * java.net.DatagramSocket} class. That is, if a security manager has been |
| 150 | * installed then this method verifies that its {@link |
| 151 | * java.lang.SecurityManager#checkAccept checkAccept} and {@link |
| 152 | * java.lang.SecurityManager#checkConnect checkConnect} methods permit |
| 153 | * datagrams to be received from and sent to, respectively, the given |
| 154 | * remote address. |
| 155 | * |
| 156 | * <p> This method may be invoked at any time. It will not have any effect |
| 157 | * on read or write operations that are already in progress at the moment |
| 158 | * that it is invoked. </p> |
| 159 | * |
| 160 | * @param remote |
| 161 | * The remote address to which this channel is to be connected |
| 162 | * |
| 163 | * @return This datagram channel |
| 164 | * |
| 165 | * @throws ClosedChannelException |
| 166 | * If this channel is closed |
| 167 | * |
| 168 | * @throws AsynchronousCloseException |
| 169 | * If another thread closes this channel |
| 170 | * while the connect operation is in progress |
| 171 | * |
| 172 | * @throws ClosedByInterruptException |
| 173 | * If another thread interrupts the current thread |
| 174 | * while the connect operation is in progress, thereby |
| 175 | * closing the channel and setting the current thread's |
| 176 | * interrupt status |
| 177 | * |
| 178 | * @throws SecurityException |
| 179 | * If a security manager has been installed |
| 180 | * and it does not permit access to the given remote address |
| 181 | * |
| 182 | * @throws IOException |
| 183 | * If some other I/O error occurs |
| 184 | */ |
| 185 | public abstract DatagramChannel connect(SocketAddress remote) |
| 186 | throws IOException; |
| 187 | |
| 188 | /** |
| 189 | * Disconnects this channel's socket. |
| 190 | * |
| 191 | * <p> The channel's socket is configured so that it can receive datagrams |
| 192 | * from, and sends datagrams to, any remote address so long as the security |
| 193 | * manager, if installed, permits it. |
| 194 | * |
| 195 | * <p> This method may be invoked at any time. It will not have any effect |
| 196 | * on read or write operations that are already in progress at the moment |
| 197 | * that it is invoked. |
| 198 | * |
| 199 | * <p> If this channel's socket is not connected, or if the channel is |
| 200 | * closed, then invoking this method has no effect. </p> |
| 201 | * |
| 202 | * @return This datagram channel |
| 203 | * |
| 204 | * @throws IOException |
| 205 | * If some other I/O error occurs |
| 206 | */ |
| 207 | public abstract DatagramChannel disconnect() throws IOException; |
| 208 | |
| 209 | /** |
| 210 | * Receives a datagram via this channel. |
| 211 | * |
| 212 | * <p> If a datagram is immediately available, or if this channel is in |
| 213 | * blocking mode and one eventually becomes available, then the datagram is |
| 214 | * copied into the given byte buffer and its source address is returned. |
| 215 | * If this channel is in non-blocking mode and a datagram is not |
| 216 | * immediately available then this method immediately returns |
| 217 | * <tt>null</tt>. |
| 218 | * |
| 219 | * <p> The datagram is transferred into the given byte buffer starting at |
| 220 | * its current position, as if by a regular {@link |
| 221 | * ReadableByteChannel#read(java.nio.ByteBuffer) read} operation. If there |
| 222 | * are fewer bytes remaining in the buffer than are required to hold the |
| 223 | * datagram then the remainder of the datagram is silently discarded. |
| 224 | * |
| 225 | * <p> This method performs exactly the same security checks as the {@link |
| 226 | * java.net.DatagramSocket#receive receive} method of the {@link |
| 227 | * java.net.DatagramSocket} class. That is, if the socket is not connected |
| 228 | * to a specific remote address and a security manager has been installed |
| 229 | * then for each datagram received this method verifies that the source's |
| 230 | * address and port number are permitted by the security manager's {@link |
| 231 | * java.lang.SecurityManager#checkAccept checkAccept} method. The overhead |
| 232 | * of this security check can be avoided by first connecting the socket via |
| 233 | * the {@link #connect connect} method. |
| 234 | * |
| 235 | * <p> This method may be invoked at any time. If another thread has |
| 236 | * already initiated a read operation upon this channel, however, then an |
| 237 | * invocation of this method will block until the first operation is |
| 238 | * complete. </p> |
| 239 | * |
| 240 | * @param dst |
| 241 | * The buffer into which the datagram is to be transferred |
| 242 | * |
| 243 | * @return The datagram's source address, |
| 244 | * or <tt>null</tt> if this channel is in non-blocking mode |
| 245 | * and no datagram was immediately available |
| 246 | * |
| 247 | * @throws ClosedChannelException |
| 248 | * If this channel is closed |
| 249 | * |
| 250 | * @throws AsynchronousCloseException |
| 251 | * If another thread closes this channel |
| 252 | * while the read operation is in progress |
| 253 | * |
| 254 | * @throws ClosedByInterruptException |
| 255 | * If another thread interrupts the current thread |
| 256 | * while the read operation is in progress, thereby |
| 257 | * closing the channel and setting the current thread's |
| 258 | * interrupt status |
| 259 | * |
| 260 | * @throws SecurityException |
| 261 | * If a security manager has been installed |
| 262 | * and it does not permit datagrams to be accepted |
| 263 | * from the datagram's sender |
| 264 | * |
| 265 | * @throws IOException |
| 266 | * If some other I/O error occurs |
| 267 | */ |
| 268 | public abstract SocketAddress receive(ByteBuffer dst) throws IOException; |
| 269 | |
| 270 | /** |
| 271 | * Sends a datagram via this channel. |
| 272 | * |
| 273 | * <p> If this channel is in non-blocking mode and there is sufficient room |
| 274 | * in the underlying output buffer, or if this channel is in blocking mode |
| 275 | * and sufficient room becomes available, then the remaining bytes in the |
| 276 | * given buffer are transmitted as a single datagram to the given target |
| 277 | * address. |
| 278 | * |
| 279 | * <p> The datagram is transferred from the byte buffer as if by a regular |
| 280 | * {@link WritableByteChannel#write(java.nio.ByteBuffer) write} operation. |
| 281 | * |
| 282 | * <p> This method performs exactly the same security checks as the {@link |
| 283 | * java.net.DatagramSocket#send send} method of the {@link |
| 284 | * java.net.DatagramSocket} class. That is, if the socket is not connected |
| 285 | * to a specific remote address and a security manager has been installed |
| 286 | * then for each datagram sent this method verifies that the target address |
| 287 | * and port number are permitted by the security manager's {@link |
| 288 | * java.lang.SecurityManager#checkConnect checkConnect} method. The |
| 289 | * overhead of this security check can be avoided by first connecting the |
| 290 | * socket via the {@link #connect connect} method. |
| 291 | * |
| 292 | * <p> This method may be invoked at any time. If another thread has |
| 293 | * already initiated a write operation upon this channel, however, then an |
| 294 | * invocation of this method will block until the first operation is |
| 295 | * complete. </p> |
| 296 | * |
| 297 | * @param src |
| 298 | * The buffer containing the datagram to be sent |
| 299 | * |
| 300 | * @param target |
| 301 | * The address to which the datagram is to be sent |
| 302 | * |
| 303 | * @return The number of bytes sent, which will be either the number |
| 304 | * of bytes that were remaining in the source buffer when this |
| 305 | * method was invoked or, if this channel is non-blocking, may be |
| 306 | * zero if there was insufficient room for the datagram in the |
| 307 | * underlying output buffer |
| 308 | * |
| 309 | * @throws ClosedChannelException |
| 310 | * If this channel is closed |
| 311 | * |
| 312 | * @throws AsynchronousCloseException |
| 313 | * If another thread closes this channel |
| 314 | * while the read operation is in progress |
| 315 | * |
| 316 | * @throws ClosedByInterruptException |
| 317 | * If another thread interrupts the current thread |
| 318 | * while the read operation is in progress, thereby |
| 319 | * closing the channel and setting the current thread's |
| 320 | * interrupt status |
| 321 | * |
| 322 | * @throws SecurityException |
| 323 | * If a security manager has been installed |
| 324 | * and it does not permit datagrams to be sent |
| 325 | * to the given address |
| 326 | * |
| 327 | * @throws IOException |
| 328 | * If some other I/O error occurs |
| 329 | */ |
| 330 | public abstract int send(ByteBuffer src, SocketAddress target) |
| 331 | throws IOException; |
| 332 | |
| 333 | |
| 334 | // -- ByteChannel operations -- |
| 335 | |
| 336 | /** |
| 337 | * Reads a datagram from this channel. |
| 338 | * |
| 339 | * <p> This method may only be invoked if this channel's socket is |
| 340 | * connected, and it only accepts datagrams from the socket's peer. If |
| 341 | * there are more bytes in the datagram than remain in the given buffer |
| 342 | * then the remainder of the datagram is silently discarded. Otherwise |
| 343 | * this method behaves exactly as specified in the {@link |
| 344 | * ReadableByteChannel} interface. </p> |
| 345 | * |
| 346 | * @throws NotYetConnectedException |
| 347 | * If this channel's socket is not connected |
| 348 | */ |
| 349 | public abstract int read(ByteBuffer dst) throws IOException; |
| 350 | |
| 351 | /** |
| 352 | * Reads a datagram from this channel. |
| 353 | * |
| 354 | * <p> This method may only be invoked if this channel's socket is |
| 355 | * connected, and it only accepts datagrams from the socket's peer. If |
| 356 | * there are more bytes in the datagram than remain in the given buffers |
| 357 | * then the remainder of the datagram is silently discarded. Otherwise |
| 358 | * this method behaves exactly as specified in the {@link |
| 359 | * ScatteringByteChannel} interface. </p> |
| 360 | * |
| 361 | * @throws NotYetConnectedException |
| 362 | * If this channel's socket is not connected |
| 363 | */ |
| 364 | public abstract long read(ByteBuffer[] dsts, int offset, int length) |
| 365 | throws IOException; |
| 366 | |
| 367 | /** |
| 368 | * Reads a datagram from this channel. |
| 369 | * |
| 370 | * <p> This method may only be invoked if this channel's socket is |
| 371 | * connected, and it only accepts datagrams from the socket's peer. If |
| 372 | * there are more bytes in the datagram than remain in the given buffers |
| 373 | * then the remainder of the datagram is silently discarded. Otherwise |
| 374 | * this method behaves exactly as specified in the {@link |
| 375 | * ScatteringByteChannel} interface. </p> |
| 376 | * |
| 377 | * @throws NotYetConnectedException |
| 378 | * If this channel's socket is not connected |
| 379 | */ |
| 380 | public final long read(ByteBuffer[] dsts) throws IOException { |
| 381 | return read(dsts, 0, dsts.length); |
| 382 | } |
| 383 | |
| 384 | /** |
| 385 | * Writes a datagram to this channel. |
| 386 | * |
| 387 | * <p> This method may only be invoked if this channel's socket is |
| 388 | * connected, in which case it sends datagrams directly to the socket's |
| 389 | * peer. Otherwise it behaves exactly as specified in the {@link |
| 390 | * WritableByteChannel} interface. </p> |
| 391 | * |
| 392 | * @throws NotYetConnectedException |
| 393 | * If this channel's socket is not connected |
| 394 | */ |
| 395 | public abstract int write(ByteBuffer src) throws IOException; |
| 396 | |
| 397 | /** |
| 398 | * Writes a datagram to this channel. |
| 399 | * |
| 400 | * <p> This method may only be invoked if this channel's socket is |
| 401 | * connected, in which case it sends datagrams directly to the socket's |
| 402 | * peer. Otherwise it behaves exactly as specified in the {@link |
| 403 | * GatheringByteChannel} interface. </p> |
| 404 | * |
| 405 | * @return The number of bytes sent, which will be either the number |
| 406 | * of bytes that were remaining in the source buffer when this |
| 407 | * method was invoked or, if this channel is non-blocking, may be |
| 408 | * zero if there was insufficient room for the datagram in the |
| 409 | * underlying output buffer |
| 410 | * |
| 411 | * @throws NotYetConnectedException |
| 412 | * If this channel's socket is not connected |
| 413 | */ |
| 414 | public abstract long write(ByteBuffer[] srcs, int offset, int length) |
| 415 | throws IOException; |
| 416 | |
| 417 | /** |
| 418 | * Writes a datagram to this channel. |
| 419 | * |
| 420 | * <p> This method may only be invoked if this channel's socket is |
| 421 | * connected, in which case it sends datagrams directly to the socket's |
| 422 | * peer. Otherwise it behaves exactly as specified in the {@link |
| 423 | * GatheringByteChannel} interface. </p> |
| 424 | * |
| 425 | * @return The number of bytes sent, which will be either the number |
| 426 | * of bytes that were remaining in the source buffer when this |
| 427 | * method was invoked or, if this channel is non-blocking, may be |
| 428 | * zero if there was insufficient room for the datagram in the |
| 429 | * underlying output buffer |
| 430 | * |
| 431 | * @throws NotYetConnectedException |
| 432 | * If this channel's socket is not connected |
| 433 | */ |
| 434 | public final long write(ByteBuffer[] srcs) throws IOException { |
| 435 | return write(srcs, 0, srcs.length); |
| 436 | } |
| 437 | |
| 438 | } |