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| 1 | /* | ||
| 2 | * Copyright (c) 2002, 2006, 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 | package sun.misc; | ||
| 26 | |||
| 27 | import java.nio.ByteBuffer; | ||
| 28 | import java.security.Permission; | ||
| 29 | import java.security.PrivilegedAction; | ||
| 30 | import java.io.IOException; | ||
| 31 | import java.io.UnsupportedEncodingException; | ||
| 32 | |||
| 33 | /** | ||
| 34 | * The Perf class provides the ability to attach to an instrumentation | ||
| 35 | * buffer maintained by a Java virtual machine. The instrumentation | ||
| 36 | * buffer may be for the Java virtual machine running the methods of | ||
| 37 | * this class or it may be for another Java virtual machine on the | ||
| 38 | * same system. | ||
| 39 | * <p> | ||
| 40 | * In addition, this class provides methods to create instrumentation | ||
| 41 | * objects in the instrumentation buffer for the Java virtual machine | ||
| 42 | * that is running these methods. It also contains methods for acquiring | ||
| 43 | * the value of a platform specific high resolution clock for time | ||
| 44 | * stamp and interval measurement purposes. | ||
| 45 | * | ||
| 46 | * @author Brian Doherty | ||
| 47 | * @since 1.4.2 | ||
| 48 | * @see #getPerf | ||
| 49 | * @see sun.misc.Perf$GetPerfAction | ||
| 50 | * @see java.nio.ByteBuffer | ||
| 51 | */ | ||
| 52 | public final class Perf { | ||
| 53 | |||
| 54 | private static Perf instance; | ||
| 55 | |||
| 56 | private static final int PERF_MODE_RO = 0; | ||
| 57 | private static final int PERF_MODE_RW = 1; | ||
| 58 | |||
| 59 | private Perf() { } // prevent instantiation | ||
| 60 | |||
| 61 | /** | ||
| 62 | * The GetPerfAction class is a convenience class for acquiring access | ||
| 63 | * to the singleton Perf instance using the | ||
| 64 | * <code>AccessController.doPrivileged()</code> method. | ||
| 65 | * <p> | ||
| 66 | * An instance of this class can be used as the argument to | ||
| 67 | * <code>AccessController.doPrivileged(PrivilegedAction)</code>. | ||
| 68 | * <p> Here is a suggested idiom for use of this class: | ||
| 69 | * | ||
| 70 | * <blockquote><pre> | ||
| 71 | * class MyTrustedClass { | ||
| 72 | * private static final Perf perf = | ||
| 73 | * AccessController.doPrivileged(new Perf.GetPerfAction<Perf>()); | ||
| 74 | * ... | ||
| 75 | * } | ||
| 76 | * </pre></blockquote> | ||
| 77 | * <p> | ||
| 78 | * In the presence of a security manager, the <code>MyTrustedClass</code> | ||
| 79 | * class in the above example will need to be granted the | ||
| 80 | * <em>"sun.misc.Perf.getPerf"</em> <code>RuntimePermission</code> | ||
| 81 | * permission in order to successfully acquire the singleton Perf instance. | ||
| 82 | * <p> | ||
| 83 | * Please note that the <em>"sun.misc.Perf.getPerf"</em> permission | ||
| 84 | * is not a JDK specified permission. | ||
| 85 | * | ||
| 86 | * @see java.security.AccessController#doPrivileged(PrivilegedAction) | ||
| 87 | * @see java.lang.RuntimePermission | ||
| 88 | */ | ||
| 89 | public static class GetPerfAction implements PrivilegedAction<Perf> | ||
| 90 | { | ||
| 91 | /** | ||
| 92 | * Run the <code>Perf.getPerf()</code> method in a privileged context. | ||
| 93 | * | ||
| 94 | * @see #getPerf | ||
| 95 | */ | ||
| 96 | public Perf run() { | ||
| 97 | return getPerf(); | ||
| 98 | } | ||
| 99 | } | ||
| 100 | |||
| 101 | /** | ||
| 102 | * Return a reference to the singleton Perf instance. | ||
| 103 | * <p> | ||
| 104 | * The getPerf() method returns the singleton instance of the Perf | ||
| 105 | * class. The returned object provides the caller with the capability | ||
| 106 | * for accessing the instrumentation buffer for this or another local | ||
| 107 | * Java virtual machine. | ||
| 108 | * <p> | ||
| 109 | * If a security manager is installed, its <code>checkPermission</code> | ||
| 110 | * method is called with a <code>RuntimePermission</code> with a target | ||
| 111 | * of <em>"sun.misc.Perf.getPerf"</em>. A security exception will result | ||
| 112 | * if the caller has not been granted this permission. | ||
| 113 | * <p> | ||
| 114 | * Access to the returned <code>Perf</code> object should be protected | ||
| 115 | * by its caller and not passed on to untrusted code. This object can | ||
| 116 | * be used to attach to the instrumentation buffer provided by this Java | ||
| 117 | * virtual machine or for those of other Java virtual machines running | ||
| 118 | * on the same system. The instrumentation buffer may contain senstitive | ||
| 119 | * information. API's built on top of this interface may want to provide | ||
| 120 | * finer grained access control to the contents of individual | ||
| 121 | * instrumentation objects contained within the buffer. | ||
| 122 | * <p> | ||
| 123 | * Please note that the <em>"sun.misc.Perf.getPerf"</em> permission | ||
| 124 | * is not a JDK specified permission. | ||
| 125 | * | ||
| 126 | * @return A reference to the singleton Perf instance. | ||
| 127 | * @throws AccessControlException if a security manager exists and | ||
| 128 | * its <code>checkPermission</code> method doesn't allow | ||
| 129 | * access to the <em>"sun.misc.Perf.getPerf"</em> target. | ||
| 130 | * @see java.lang.RuntimePermission | ||
| 131 | * @see #attach | ||
| 132 | */ | ||
| 133 | public static Perf getPerf() | ||
| 134 | { | ||
| 135 | SecurityManager security = System.getSecurityManager(); | ||
| 136 | if (security != null) { | ||
| 137 | Permission perm = new RuntimePermission("sun.misc.Perf.getPerf"); | ||
| 138 | security.checkPermission(perm); | ||
| 139 | } | ||
| 140 | |||
| 141 | return instance; | ||
| 142 | } | ||
| 143 | |||
| 144 | /** | ||
| 145 | * Attach to the instrumentation buffer for the specified Java virtual | ||
| 146 | * machine. | ||
| 147 | * <p> | ||
| 148 | * This method will attach to the instrumentation buffer for the | ||
| 149 | * specified virtual machine. It returns a <code>ByteBuffer</code> object | ||
| 150 | * that is initialized to access the instrumentation buffer for the | ||
| 151 | * indicated Java virtual machine. The <code>lvmid</code> parameter is | ||
| 152 | * a integer value that uniquely identifies the target local Java virtual | ||
| 153 | * machine. It is typically, but not necessarily, the process id of | ||
| 154 | * the target Java virtual machine. | ||
| 155 | * <p> | ||
| 156 | * If the <code>lvmid</code> identifies a Java virtual machine different | ||
| 157 | * from the one running this method, then the coherency characteristics | ||
| 158 | * of the buffer are implementation dependent. Implementations that do | ||
| 159 | * not support named, coherent, shared memory may return a | ||
| 160 | * <code>ByteBuffer</code> object that contains only a snap shot of the | ||
| 161 | * data in the instrumentation buffer. Implementations that support named, | ||
| 162 | * coherent, shared memory, may return a <code>ByteBuffer</code> object | ||
| 163 | * that will be changing dynamically over time as the target Java virtual | ||
| 164 | * machine updates its mapping of this buffer. | ||
| 165 | * <p> | ||
| 166 | * If the <code>lvmid</code> is 0 or equal to the actual <code>lvmid</code> | ||
| 167 | * for the Java virtual machine running this method, then the returned | ||
| 168 | * <code>ByteBuffer</code> object will always be coherent and dynamically | ||
| 169 | * changing. | ||
| 170 | * <p> | ||
| 171 | * The attach mode specifies the access permissions requested for the | ||
| 172 | * instrumentation buffer of the target virtual machine. The permitted | ||
| 173 | * access permissions are: | ||
| 174 | * <p> | ||
| 175 | * <bl> | ||
| 176 | * <li>"r" - Read only access. This Java virtual machine has only | ||
| 177 | * read access to the instrumentation buffer for the target Java | ||
| 178 | * virtual machine. | ||
| 179 | * <li>"rw" - Read/Write access. This Java virtual machine has read and | ||
| 180 | * write access to the instrumentation buffer for the target Java virtual | ||
| 181 | * machine. This mode is currently not supported and is reserved for | ||
| 182 | * future enhancements. | ||
| 183 | * </bl> | ||
| 184 | * | ||
| 185 | * @param lvmid an integer that uniquely identifies the | ||
| 186 | * target local Java virtual machine. | ||
| 187 | * @param mode a string indicating the attach mode. | ||
| 188 | * @return ByteBuffer a direct allocated byte buffer | ||
| 189 | * @throws IllegalArgumentException The lvmid or mode was invalid. | ||
| 190 | * @throws IOException An I/O error occurred while trying to acquire | ||
| 191 | * the instrumentation buffer. | ||
| 192 | * @throws OutOfMemoryError The instrumentation buffer could not be mapped | ||
| 193 | * into the virtual machine's address space. | ||
| 194 | * @see java.nio.ByteBuffer | ||
| 195 | */ | ||
| 196 | public ByteBuffer attach(int lvmid, String mode) | ||
| 197 | throws IllegalArgumentException, IOException | ||
| 198 | { | ||
| 199 | if (mode.compareTo("r") == 0) { | ||
| 200 | return attachImpl(null, lvmid, PERF_MODE_RO); | ||
| 201 | } | ||
| 202 | else if (mode.compareTo("rw") == 0) { | ||
| 203 | return attachImpl(null, lvmid, PERF_MODE_RW); | ||
| 204 | } | ||
| 205 | else { | ||
| 206 | throw new IllegalArgumentException("unknown mode"); | ||
| 207 | } | ||
| 208 | } | ||
| 209 | |||
| 210 | /** | ||
| 211 | * Attach to the instrumentation buffer for the specified Java virtual | ||
| 212 | * machine owned by the given user. | ||
| 213 | * <p> | ||
| 214 | * This method behaves just as the <code>attach(int lvmid, String mode) | ||
| 215 | * </code> method, except that it only searches for Java virtual machines | ||
| 216 | * owned by the specified user. | ||
| 217 | * | ||
| 218 | * @param user A <code>String</code> object containing the | ||
| 219 | * name of the user that owns the target Java | ||
| 220 | * virtual machine. | ||
| 221 | * @param lvmid an integer that uniquely identifies the | ||
| 222 | * target local Java virtual machine. | ||
| 223 | * @param mode a string indicating the attach mode. | ||
| 224 | * @return ByteBuffer a direct allocated byte buffer | ||
| 225 | * @throws IllegalArgumentException The lvmid or mode was invalid. | ||
| 226 | * @throws IOException An I/O error occurred while trying to acquire | ||
| 227 | * the instrumentation buffer. | ||
| 228 | * @throws OutOfMemoryError The instrumentation buffer could not be mapped | ||
| 229 | * into the virtual machine's address space. | ||
| 230 | * @see java.nio.ByteBuffer | ||
| 231 | */ | ||
| 232 | public ByteBuffer attach(String user, int lvmid, String mode) | ||
| 233 | throws IllegalArgumentException, IOException | ||
| 234 | { | ||
| 235 | if (mode.compareTo("r") == 0) { | ||
| 236 | return attachImpl(user, lvmid, PERF_MODE_RO); | ||
| 237 | } | ||
| 238 | else if (mode.compareTo("rw") == 0) { | ||
| 239 | return attachImpl(user, lvmid, PERF_MODE_RW); | ||
| 240 | } | ||
| 241 | else { | ||
| 242 | throw new IllegalArgumentException("unknown mode"); | ||
| 243 | } | ||
| 244 | } | ||
| 245 | |||
| 246 | /** | ||
| 247 | * Call the implementation specific attach method. | ||
| 248 | * <p> | ||
| 249 | * This method calls into the Java virtual machine to perform the platform | ||
| 250 | * specific attach method. Buffers returned from this method are | ||
| 251 | * internally managed as <code>PhantomRefereces</code> to provide for | ||
| 252 | * guaranteed, secure release of the native resources. | ||
| 253 | * | ||
| 254 | * @param user A <code>String</code> object containing the | ||
| 255 | * name of the user that owns the target Java | ||
| 256 | * virtual machine. | ||
| 257 | * @param lvmid an integer that uniquely identifies the | ||
| 258 | * target local Java virtual machine. | ||
| 259 | * @param mode a string indicating the attach mode. | ||
| 260 | * @return ByteBuffer a direct allocated byte buffer | ||
| 261 | * @throws IllegalArgumentException The lvmid or mode was invalid. | ||
| 262 | * @throws IOException An I/O error occurred while trying to acquire | ||
| 263 | * the instrumentation buffer. | ||
| 264 | * @throws OutOfMemoryError The instrumentation buffer could not be mapped | ||
| 265 | * into the virtual machine's address space. | ||
| 266 | */ | ||
| 267 | private ByteBuffer attachImpl(String user, int lvmid, int mode) | ||
| 268 | throws IllegalArgumentException, IOException | ||
| 269 | { | ||
| 270 | final ByteBuffer b = attach(user, lvmid, mode); | ||
| 271 | |||
| 272 | if (lvmid == 0) { | ||
| 273 | // The native instrumentation buffer for this Java virtual | ||
| 274 | // machine is never unmapped. | ||
| 275 | return b; | ||
| 276 | } | ||
| 277 | else { | ||
| 278 | // This is an instrumentation buffer for another Java virtual | ||
| 279 | // machine with native resources that need to be managed. We | ||
| 280 | // create a duplicate of the native ByteBuffer and manage it | ||
| 281 | // with a Cleaner object (PhantomReference). When the duplicate | ||
| 282 | // becomes only phantomly reachable, the native resources will | ||
| 283 | // be released. | ||
| 284 | |||
| 285 | final ByteBuffer dup = b.duplicate(); | ||
| 286 | Cleaner.create(dup, new Runnable() { | ||
| 287 | public void run() { | ||
| 288 | try { | ||
| 289 | instance.detach(b); | ||
| 290 | } | ||
| 291 | catch (Throwable th) { | ||
| 292 | // avoid crashing the reference handler thread, | ||
| 293 | // but provide for some diagnosability | ||
| 294 | assert false : th.toString(); | ||
| 295 | } | ||
| 296 | } | ||
| 297 | }); | ||
| 298 | return dup; | ||
| 299 | } | ||
| 300 | } | ||
| 301 | |||
| 302 | /** | ||
| 303 | * Native method to perform the implementation specific attach mechanism. | ||
| 304 | * <p> | ||
| 305 | * The implementation of this method may return distinct or identical | ||
| 306 | * <code>ByteBuffer</code> objects for two distinct calls requesting | ||
| 307 | * attachment to the same Java virtual machine. | ||
| 308 | * <p> | ||
| 309 | * For the Sun HotSpot JVM, two distinct calls to attach to the same | ||
| 310 | * target Java virtual machine will result in two distinct ByteBuffer | ||
| 311 | * objects returned by this method. This may change in a future release. | ||
| 312 | * | ||
| 313 | * @param user A <code>String</code> object containing the | ||
| 314 | * name of the user that owns the target Java | ||
| 315 | * virtual machine. | ||
| 316 | * @param lvmid an integer that uniquely identifies the | ||
| 317 | * target local Java virtual machine. | ||
| 318 | * @param mode a string indicating the attach mode. | ||
| 319 | * @return ByteBuffer a direct allocated byte buffer | ||
| 320 | * @throws IllegalArgumentException The lvmid or mode was invalid. | ||
| 321 | * @throws IOException An I/O error occurred while trying to acquire | ||
| 322 | * the instrumentation buffer. | ||
| 323 | * @throws OutOfMemoryError The instrumentation buffer could not be mapped | ||
| 324 | * into the virtual machine's address space. | ||
| 325 | */ | ||
| 326 | private native ByteBuffer attach(String user, int lvmid, int mode) | ||
| 327 | throws IllegalArgumentException, IOException; | ||
| 328 | |||
| 329 | /** | ||
| 330 | * Native method to perform the implementation specific detach mechanism. | ||
| 331 | * <p> | ||
| 332 | * If this method is passed a <code>ByteBuffer</code> object that is | ||
| 333 | * not created by the <code>attach</code> method, then the results of | ||
| 334 | * this method are undefined, with unpredictable and potentially damaging | ||
| 335 | * effects to the Java virtual machine. To prevent accidental or malicious | ||
| 336 | * use of this method, all native ByteBuffer created by the <code> | ||
| 337 | * attach</code> method are managed internally as PhantomReferences | ||
| 338 | * and resources are freed by the system. | ||
| 339 | * <p> | ||
| 340 | * If this method is passed a <code>ByteBuffer</code> object created | ||
| 341 | * by the <code>attach</code> method with a lvmid for the Java virtual | ||
| 342 | * machine running this method (lvmid=0, for example), then the detach | ||
| 343 | * request is silently ignored. | ||
| 344 | * | ||
| 345 | * @param ByteBuffer A direct allocated byte buffer created by the | ||
| 346 | * <code>attach</code> method. | ||
| 347 | * @see java.nio.ByteBuffer | ||
| 348 | * @see #attach | ||
| 349 | */ | ||
| 350 | private native void detach(ByteBuffer bb); | ||
| 351 | |||
| 352 | /** | ||
| 353 | * Create a <code>long</code> scalar entry in the instrumentation buffer | ||
| 354 | * with the given variability characteristic, units, and initial value. | ||
| 355 | * <p> | ||
| 356 | * Access to the instrument is provided through the returned <code> | ||
| 357 | * ByteBuffer</code> object. Typically, this object should be wrapped | ||
| 358 | * with <code>LongBuffer</code> view object. | ||
| 359 | * | ||
| 360 | * @param variability the variability characteristic for this entry. | ||
| 361 | * @param units the units for this entry. | ||
| 362 | * @param name the name of this entry. | ||
| 363 | * @param value the initial value for this entry. | ||
| 364 | * @return ByteBuffer a direct allocated ByteBuffer object that | ||
| 365 | * allows write access to a native memory location | ||
| 366 | * containing a <code>long</code> value. | ||
| 367 | * | ||
| 368 | * see sun.misc.perf.Variability | ||
| 369 | * see sun.misc.perf.Units | ||
| 370 | * @see java.nio.ByteBuffer | ||
| 371 | */ | ||
| 372 | public native ByteBuffer createLong(String name, int variability, | ||
| 373 | int units, long value); | ||
| 374 | |||
| 375 | /** | ||
| 376 | * Create a <code>String</code> entry in the instrumentation buffer with | ||
| 377 | * the given variability characteristic, units, and initial value. | ||
| 378 | * <p> | ||
| 379 | * The maximum length of the <code>String</code> stored in this string | ||
| 380 | * instrument is given in by <code>maxLength</code> parameter. Updates | ||
| 381 | * to this instrument with <code>String</code> values with lengths greater | ||
| 382 | * than <code>maxLength</code> will be truncated to <code>maxLength</code>. | ||
| 383 | * The truncated value will be terminated by a null character. | ||
| 384 | * <p> | ||
| 385 | * The underlying implementation may further limit the length of the | ||
| 386 | * value, but will continue to preserve the null terminator. | ||
| 387 | * <p> | ||
| 388 | * Access to the instrument is provided through the returned <code> | ||
| 389 | * ByteBuffer</code> object. | ||
| 390 | * | ||
| 391 | * @param variability the variability characteristic for this entry. | ||
| 392 | * @param units the units for this entry. | ||
| 393 | * @param name the name of this entry. | ||
| 394 | * @param value the initial value for this entry. | ||
| 395 | * @param maxLength the maximum string length for this string | ||
| 396 | * instrument. | ||
| 397 | * @return ByteBuffer a direct allocated ByteBuffer that allows | ||
| 398 | * write access to a native memory location | ||
| 399 | * containing a <code>long</code> value. | ||
| 400 | * | ||
| 401 | * see sun.misc.perf.Variability | ||
| 402 | * see sun.misc.perf.Units | ||
| 403 | * @see java.nio.ByteBuffer | ||
| 404 | */ | ||
| 405 | public ByteBuffer createString(String name, int variability, | ||
| 406 | int units, String value, int maxLength) | ||
| 407 | { | ||
| 408 | byte[] v = getBytes(value); | ||
| 409 | byte[] v1 = new byte[v.length+1]; | ||
| 410 | System.arraycopy(v, 0, v1, 0, v.length); | ||
| 411 | v1[v.length] = '\0'; | ||
| 412 | return createByteArray(name, variability, units, v1, Math.max(v1.length, maxLength)); | ||
| 413 | } | ||
| 414 | |||
| 415 | /** | ||
| 416 | * Create a <code>String</code> entry in the instrumentation buffer with | ||
| 417 | * the given variability characteristic, units, and initial value. | ||
| 418 | * <p> | ||
| 419 | * The maximum length of the <code>String</code> stored in this string | ||
| 420 | * instrument is implied by the length of the <code>value</code> parameter. | ||
| 421 | * Subsequent updates to the value of this instrument will be truncated | ||
| 422 | * to this implied maximum length. The truncated value will be terminated | ||
| 423 | * by a null character. | ||
| 424 | * <p> | ||
| 425 | * The underlying implementation may further limit the length of the | ||
| 426 | * initial or subsequent value, but will continue to preserve the null | ||
| 427 | * terminator. | ||
| 428 | * <p> | ||
| 429 | * Access to the instrument is provided through the returned <code> | ||
| 430 | * ByteBuffer</code> object. | ||
| 431 | * | ||
| 432 | * @param variability the variability characteristic for this entry. | ||
| 433 | * @param units the units for this entry. | ||
| 434 | * @param name the name of this entry. | ||
| 435 | * @param value the initial value for this entry. | ||
| 436 | * @return ByteBuffer a direct allocated ByteBuffer that allows | ||
| 437 | * write access to a native memory location | ||
| 438 | * containing a <code>long</code> value. | ||
| 439 | * | ||
| 440 | * see sun.misc.perf.Variability | ||
| 441 | * see sun.misc.perf.Units | ||
| 442 | * @see java.nio.ByteBuffer | ||
| 443 | */ | ||
| 444 | public ByteBuffer createString(String name, int variability, | ||
| 445 | int units, String value) | ||
| 446 | { | ||
| 447 | byte[] v = getBytes(value); | ||
| 448 | byte[] v1 = new byte[v.length+1]; | ||
| 449 | System.arraycopy(v, 0, v1, 0, v.length); | ||
| 450 | v1[v.length] = '\0'; | ||
| 451 | return createByteArray(name, variability, units, v1, v1.length); | ||
| 452 | } | ||
| 453 | |||
| 454 | /** | ||
| 455 | * Create a <code>byte</code> vector entry in the instrumentation buffer | ||
| 456 | * with the given variability characteristic, units, and initial value. | ||
| 457 | * <p> | ||
| 458 | * The <code>maxLength</code> parameter limits the size of the byte | ||
| 459 | * array instrument such that the initial or subsequent updates beyond | ||
| 460 | * this length are silently ignored. No special handling of truncated | ||
| 461 | * updates is provided. | ||
| 462 | * <p> | ||
| 463 | * The underlying implementation may further limit the length of the | ||
| 464 | * length of the initial or subsequent value. | ||
| 465 | * <p> | ||
| 466 | * Access to the instrument is provided through the returned <code> | ||
| 467 | * ByteBuffer</code> object. | ||
| 468 | * | ||
| 469 | * @param variability the variability characteristic for this entry. | ||
| 470 | * @param units the units for this entry. | ||
| 471 | * @param name the name of this entry. | ||
| 472 | * @param value the initial value for this entry. | ||
| 473 | * @param maxLength the maximum length of this byte array. | ||
| 474 | * @return ByteBuffer a direct allocated byte buffer that allows | ||
| 475 | * write access to a native memory location | ||
| 476 | * containing a <code>long</code> value. | ||
| 477 | * | ||
| 478 | * see sun.misc.perf.Variability | ||
| 479 | * see sun.misc.perf.Units | ||
| 480 | * @see java.nio.ByteBuffer | ||
| 481 | */ | ||
| 482 | public native ByteBuffer createByteArray(String name, int variability, | ||
| 483 | int units, byte[] value, | ||
| 484 | int maxLength); | ||
| 485 | |||
| 486 | |||
| 487 | /** | ||
| 488 | * convert string to an array of UTF-8 bytes | ||
| 489 | */ | ||
| 490 | private static byte[] getBytes(String s) | ||
| 491 | { | ||
| 492 | byte[] bytes = null; | ||
| 493 | |||
| 494 | try { | ||
| 495 | bytes = s.getBytes("UTF-8"); | ||
| 496 | } | ||
| 497 | catch (UnsupportedEncodingException e) { | ||
| 498 | // ignore, UTF-8 encoding is always known | ||
| 499 | } | ||
| 500 | |||
| 501 | return bytes; | ||
| 502 | } | ||
| 503 | |||
| 504 | /** | ||
| 505 | * Return the value of the High Resolution Counter. | ||
| 506 | * | ||
| 507 | * The High Resolution Counter returns the number of ticks since | ||
| 508 | * since the start of the Java virtual machine. The resolution of | ||
| 509 | * the counter is machine dependent and can be determined from the | ||
| 510 | * value return by the {@link #highResFrequency} method. | ||
| 511 | * | ||
| 512 | * @return the number of ticks of machine dependent resolution since | ||
| 513 | * the start of the Java virtual machine. | ||
| 514 | * | ||
| 515 | * @see #highResFrequency | ||
| 516 | * @see java.lang.System#currentTimeMillis() | ||
| 517 | */ | ||
| 518 | public native long highResCounter(); | ||
| 519 | |||
| 520 | /** | ||
| 521 | * Returns the frequency of the High Resolution Counter, in ticks per | ||
| 522 | * second. | ||
| 523 | * | ||
| 524 | * This value can be used to convert the value of the High Resolution | ||
| 525 | * Counter, as returned from a call to the {@link #highResCounter} method, | ||
| 526 | * into the number of seconds since the start of the Java virtual machine. | ||
| 527 | * | ||
| 528 | * @return the frequency of the High Resolution Counter. | ||
| 529 | * @see #highResCounter | ||
| 530 | */ | ||
| 531 | public native long highResFrequency(); | ||
| 532 | |||
| 533 | private static native void registerNatives(); | ||
| 534 | |||
| 535 | static { | ||
| 536 | registerNatives(); | ||
| 537 | instance = new Perf(); | ||
| 538 | } | ||
| 539 | } | ||