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| 1 | /* | ||
| 2 | * Copyright (c) 2000, 2008, 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.io.IOException; | ||
| 29 | import java.nio.channels.spi.AbstractInterruptibleChannel; | ||
| 30 | import java.nio.channels.spi.SelectorProvider; | ||
| 31 | |||
| 32 | |||
| 33 | /** | ||
| 34 | * A channel that can be multiplexed via a {@link Selector}. | ||
| 35 | * | ||
| 36 | * <p> In order to be used with a selector, an instance of this class must | ||
| 37 | * first be <i>registered</i> via the {@link #register(Selector,int,Object) | ||
| 38 | * register} method. This method returns a new {@link SelectionKey} object | ||
| 39 | * that represents the channel's registration with the selector. | ||
| 40 | * | ||
| 41 | * <p> Once registered with a selector, a channel remains registered until it | ||
| 42 | * is <i>deregistered</i>. This involves deallocating whatever resources were | ||
| 43 | * allocated to the channel by the selector. | ||
| 44 | * | ||
| 45 | * <p> A channel cannot be deregistered directly; instead, the key representing | ||
| 46 | * its registration must be <i>cancelled</i>. Cancelling a key requests that | ||
| 47 | * the channel be deregistered during the selector's next selection operation. | ||
| 48 | * A key may be cancelled explicitly by invoking its {@link | ||
| 49 | * SelectionKey#cancel() cancel} method. All of a channel's keys are cancelled | ||
| 50 | * implicitly when the channel is closed, whether by invoking its {@link | ||
| 51 | * Channel#close close} method or by interrupting a thread blocked in an I/O | ||
| 52 | * operation upon the channel. | ||
| 53 | * | ||
| 54 | * <p> If the selector itself is closed then the channel will be deregistered, | ||
| 55 | * and the key representing its registration will be invalidated, without | ||
| 56 | * further delay. | ||
| 57 | * | ||
| 58 | * <p> A channel may be registered at most once with any particular selector. | ||
| 59 | * | ||
| 60 | * <p> Whether or not a channel is registered with one or more selectors may be | ||
| 61 | * determined by invoking the {@link #isRegistered isRegistered} method. | ||
| 62 | * | ||
| 63 | * <p> Selectable channels are safe for use by multiple concurrent | ||
| 64 | * threads. </p> | ||
| 65 | * | ||
| 66 | * | ||
| 67 | * <a name="bm"> | ||
| 68 | * <h4>Blocking mode</h4> | ||
| 69 | * | ||
| 70 | * A selectable channel is either in <i>blocking</i> mode or in | ||
| 71 | * <i>non-blocking</i> mode. In blocking mode, every I/O operation invoked | ||
| 72 | * upon the channel will block until it completes. In non-blocking mode an I/O | ||
| 73 | * operation will never block and may transfer fewer bytes than were requested | ||
| 74 | * or possibly no bytes at all. The blocking mode of a selectable channel may | ||
| 75 | * be determined by invoking its {@link #isBlocking isBlocking} method. | ||
| 76 | * | ||
| 77 | * <p> Newly-created selectable channels are always in blocking mode. | ||
| 78 | * Non-blocking mode is most useful in conjunction with selector-based | ||
| 79 | * multiplexing. A channel must be placed into non-blocking mode before being | ||
| 80 | * registered with a selector, and may not be returned to blocking mode until | ||
| 81 | * it has been deregistered. | ||
| 82 | * | ||
| 83 | * | ||
| 84 | * @author Mark Reinhold | ||
| 85 | * @author JSR-51 Expert Group | ||
| 86 | * @since 1.4 | ||
| 87 | * | ||
| 88 | * @see SelectionKey | ||
| 89 | * @see Selector | ||
| 90 | */ | ||
| 91 | |||
| 92 | public abstract class SelectableChannel | ||
| 93 | extends AbstractInterruptibleChannel | ||
| 94 | implements Channel | ||
| 95 | { | ||
| 96 | |||
| 97 | /** | ||
| 98 | * Initializes a new instance of this class. | ||
| 99 | */ | ||
| 100 | protected SelectableChannel() { } | ||
| 101 | |||
| 102 | /** | ||
| 103 | * Returns the provider that created this channel. | ||
| 104 | * | ||
| 105 | * @return The provider that created this channel | ||
| 106 | */ | ||
| 107 | public abstract SelectorProvider provider(); | ||
| 108 | |||
| 109 | /** | ||
| 110 | * Returns an <a href="SelectionKey.html#opsets">operation set</a> | ||
| 111 | * identifying this channel's supported operations. The bits that are set | ||
| 112 | * in this integer value denote exactly the operations that are valid for | ||
| 113 | * this channel. This method always returns the same value for a given | ||
| 114 | * concrete channel class. </p> | ||
| 115 | * | ||
| 116 | * @return The valid-operation set | ||
| 117 | */ | ||
| 118 | public abstract int validOps(); | ||
| 119 | |||
| 120 | // Internal state: | ||
| 121 | // keySet, may be empty but is never null, typ. a tiny array | ||
| 122 | // boolean isRegistered, protected by key set | ||
| 123 | // regLock, lock object to prevent duplicate registrations | ||
| 124 | // boolean isBlocking, protected by regLock | ||
| 125 | |||
| 126 | /** | ||
| 127 | * Tells whether or not this channel is currently registered with any | ||
| 128 | * selectors. A newly-created channel is not registered. | ||
| 129 | * | ||
| 130 | * <p> Due to the inherent delay between key cancellation and channel | ||
| 131 | * deregistration, a channel may remain registered for some time after all | ||
| 132 | * of its keys have been cancelled. A channel may also remain registered | ||
| 133 | * for some time after it is closed. </p> | ||
| 134 | * | ||
| 135 | * @return <tt>true</tt> if, and only if, this channel is registered | ||
| 136 | */ | ||
| 137 | public abstract boolean isRegistered(); | ||
| 138 | // | ||
| 139 | // sync(keySet) { return isRegistered; } | ||
| 140 | |||
| 141 | /** | ||
| 142 | * Retrieves the key representing the channel's registration with the given | ||
| 143 | * selector. </p> | ||
| 144 | * | ||
| 145 | * @return The key returned when this channel was last registered with the | ||
| 146 | * given selector, or <tt>null</tt> if this channel is not | ||
| 147 | * currently registered with that selector | ||
| 148 | */ | ||
| 149 | public abstract SelectionKey keyFor(Selector sel); | ||
| 150 | // | ||
| 151 | // sync(keySet) { return findKey(sel); } | ||
| 152 | |||
| 153 | /** | ||
| 154 | * Registers this channel with the given selector, returning a selection | ||
| 155 | * key. | ||
| 156 | * | ||
| 157 | * <p> If this channel is currently registered with the given selector then | ||
| 158 | * the selection key representing that registration is returned. The key's | ||
| 159 | * interest set will have been changed to <tt>ops</tt>, as if by invoking | ||
| 160 | * the {@link SelectionKey#interestOps(int) interestOps(int)} method. If | ||
| 161 | * the <tt>att</tt> argument is not <tt>null</tt> then the key's attachment | ||
| 162 | * will have been set to that value. A {@link CancelledKeyException} will | ||
| 163 | * be thrown if the key has already been cancelled. | ||
| 164 | * | ||
| 165 | * <p> Otherwise this channel has not yet been registered with the given | ||
| 166 | * selector, so it is registered and the resulting new key is returned. | ||
| 167 | * The key's initial interest set will be <tt>ops</tt> and its attachment | ||
| 168 | * will be <tt>att</tt>. | ||
| 169 | * | ||
| 170 | * <p> This method may be invoked at any time. If this method is invoked | ||
| 171 | * while another invocation of this method or of the {@link | ||
| 172 | * #configureBlocking(boolean) configureBlocking} method is in progress | ||
| 173 | * then it will first block until the other operation is complete. This | ||
| 174 | * method will then synchronize on the selector's key set and therefore may | ||
| 175 | * block if invoked concurrently with another registration or selection | ||
| 176 | * operation involving the same selector. </p> | ||
| 177 | * | ||
| 178 | * <p> If this channel is closed while this operation is in progress then | ||
| 179 | * the key returned by this method will have been cancelled and will | ||
| 180 | * therefore be invalid. </p> | ||
| 181 | * | ||
| 182 | * @param sel | ||
| 183 | * The selector with which this channel is to be registered | ||
| 184 | * | ||
| 185 | * @param ops | ||
| 186 | * The interest set for the resulting key | ||
| 187 | * | ||
| 188 | * @param att | ||
| 189 | * The attachment for the resulting key; may be <tt>null</tt> | ||
| 190 | * | ||
| 191 | * @throws ClosedChannelException | ||
| 192 | * If this channel is closed | ||
| 193 | * | ||
| 194 | * @throws ClosedSelectorException | ||
| 195 | * If the selector is closed | ||
| 196 | * | ||
| 197 | * @throws IllegalBlockingModeException | ||
| 198 | * If this channel is in blocking mode | ||
| 199 | * | ||
| 200 | * @throws IllegalSelectorException | ||
| 201 | * If this channel was not created by the same provider | ||
| 202 | * as the given selector | ||
| 203 | * | ||
| 204 | * @throws CancelledKeyException | ||
| 205 | * If this channel is currently registered with the given selector | ||
| 206 | * but the corresponding key has already been cancelled | ||
| 207 | * | ||
| 208 | * @throws IllegalArgumentException | ||
| 209 | * If a bit in the <tt>ops</tt> set does not correspond to an | ||
| 210 | * operation that is supported by this channel, that is, if | ||
| 211 | * <tt>set & ~validOps() != 0</tt> | ||
| 212 | * | ||
| 213 | * @return A key representing the registration of this channel with | ||
| 214 | * the given selector | ||
| 215 | */ | ||
| 216 | public abstract SelectionKey register(Selector sel, int ops, Object att) | ||
| 217 | throws ClosedChannelException; | ||
| 218 | // | ||
| 219 | // sync(regLock) { | ||
| 220 | // sync(keySet) { look for selector } | ||
| 221 | // if (channel found) { set interest ops -- may block in selector; | ||
| 222 | // return key; } | ||
| 223 | // create new key -- may block somewhere in selector; | ||
| 224 | // sync(keySet) { add key; } | ||
| 225 | // attach(attachment); | ||
| 226 | // return key; | ||
| 227 | // } | ||
| 228 | |||
| 229 | /** | ||
| 230 | * Registers this channel with the given selector, returning a selection | ||
| 231 | * key. | ||
| 232 | * | ||
| 233 | * <p> An invocation of this convenience method of the form | ||
| 234 | * | ||
| 235 | * <blockquote><tt>sc.register(sel, ops)</tt></blockquote> | ||
| 236 | * | ||
| 237 | * behaves in exactly the same way as the invocation | ||
| 238 | * | ||
| 239 | * <blockquote><tt>sc.{@link | ||
| 240 | * #register(java.nio.channels.Selector,int,java.lang.Object) | ||
| 241 | * register}(sel, ops, null)</tt></blockquote> | ||
| 242 | * | ||
| 243 | * @param sel | ||
| 244 | * The selector with which this channel is to be registered | ||
| 245 | * | ||
| 246 | * @param ops | ||
| 247 | * The interest set for the resulting key | ||
| 248 | * | ||
| 249 | * @throws ClosedChannelException | ||
| 250 | * If this channel is closed | ||
| 251 | * | ||
| 252 | * @throws ClosedSelectorException | ||
| 253 | * If the selector is closed | ||
| 254 | * | ||
| 255 | * @throws IllegalBlockingModeException | ||
| 256 | * If this channel is in blocking mode | ||
| 257 | * | ||
| 258 | * @throws IllegalSelectorException | ||
| 259 | * If this channel was not created by the same provider | ||
| 260 | * as the given selector | ||
| 261 | * | ||
| 262 | * @throws CancelledKeyException | ||
| 263 | * If this channel is currently registered with the given selector | ||
| 264 | * but the corresponding key has already been cancelled | ||
| 265 | * | ||
| 266 | * @throws IllegalArgumentException | ||
| 267 | * If a bit in <tt>ops</tt> does not correspond to an operation | ||
| 268 | * that is supported by this channel, that is, if <tt>set & | ||
| 269 | * ~validOps() != 0</tt> | ||
| 270 | * | ||
| 271 | * @return A key representing the registration of this channel with | ||
| 272 | * the given selector | ||
| 273 | */ | ||
| 274 | public final SelectionKey register(Selector sel, int ops) | ||
| 275 | throws ClosedChannelException | ||
| 276 | { | ||
| 277 | return register(sel, ops, null); | ||
| 278 | } | ||
| 279 | |||
| 280 | /** | ||
| 281 | * Adjusts this channel's blocking mode. | ||
| 282 | * | ||
| 283 | * <p> If this channel is registered with one or more selectors then an | ||
| 284 | * attempt to place it into blocking mode will cause an {@link | ||
| 285 | * IllegalBlockingModeException} to be thrown. | ||
| 286 | * | ||
| 287 | * <p> This method may be invoked at any time. The new blocking mode will | ||
| 288 | * only affect I/O operations that are initiated after this method returns. | ||
| 289 | * For some implementations this may require blocking until all pending I/O | ||
| 290 | * operations are complete. | ||
| 291 | * | ||
| 292 | * <p> If this method is invoked while another invocation of this method or | ||
| 293 | * of the {@link #register(Selector, int) register} method is in progress | ||
| 294 | * then it will first block until the other operation is complete. </p> | ||
| 295 | * | ||
| 296 | * @param block If <tt>true</tt> then this channel will be placed in | ||
| 297 | * blocking mode; if <tt>false</tt> then it will be placed | ||
| 298 | * non-blocking mode | ||
| 299 | * | ||
| 300 | * @return This selectable channel | ||
| 301 | * | ||
| 302 | * @throws ClosedChannelException | ||
| 303 | * If this channel is closed | ||
| 304 | * | ||
| 305 | * @throws IllegalBlockingModeException | ||
| 306 | * If <tt>block</tt> is <tt>true</tt> and this channel is | ||
| 307 | * registered with one or more selectors | ||
| 308 | * | ||
| 309 | * @throws IOException | ||
| 310 | * If an I/O error occurs | ||
| 311 | */ | ||
| 312 | public abstract SelectableChannel configureBlocking(boolean block) | ||
| 313 | throws IOException; | ||
| 314 | // | ||
| 315 | // sync(regLock) { | ||
| 316 | // sync(keySet) { throw IBME if block && isRegistered; } | ||
| 317 | // change mode; | ||
| 318 | // } | ||
| 319 | |||
| 320 | /** | ||
| 321 | * Tells whether or not every I/O operation on this channel will block | ||
| 322 | * until it completes. A newly-created channel is always in blocking mode. | ||
| 323 | * | ||
| 324 | * <p> If this channel is closed then the value returned by this method is | ||
| 325 | * not specified. </p> | ||
| 326 | * | ||
| 327 | * @return <tt>true</tt> if, and only if, this channel is in blocking mode | ||
| 328 | */ | ||
| 329 | public abstract boolean isBlocking(); | ||
| 330 | |||
| 331 | /** | ||
| 332 | * Retrieves the object upon which the {@link #configureBlocking | ||
| 333 | * configureBlocking} and {@link #register register} methods synchronize. | ||
| 334 | * This is often useful in the implementation of adaptors that require a | ||
| 335 | * specific blocking mode to be maintained for a short period of time. | ||
| 336 | * </p> | ||
| 337 | * | ||
| 338 | * @return The blocking-mode lock object | ||
| 339 | */ | ||
| 340 | public abstract Object blockingLock(); | ||
| 341 | |||
| 342 | } | ||