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Diffstat (limited to 'src/actors/scala/actors/threadpool/helpers/Utils.java')
| -rw-r--r-- | src/actors/scala/actors/threadpool/helpers/Utils.java | 343 |
1 files changed, 0 insertions, 343 deletions
diff --git a/src/actors/scala/actors/threadpool/helpers/Utils.java b/src/actors/scala/actors/threadpool/helpers/Utils.java deleted file mode 100644 index d12389215d..0000000000 --- a/src/actors/scala/actors/threadpool/helpers/Utils.java +++ /dev/null @@ -1,343 +0,0 @@ -/* - * Written by Dawid Kurzyniec, based on code written by Doug Lea with assistance - * from members of JCP JSR-166 Expert Group. Released to the public domain, - * as explained at http://creativecommons.org/licenses/publicdomain. - * - * Thanks to Craig Mattocks for suggesting to use <code>sun.misc.Perf</code>. - */ - -package scala.actors.threadpool.helpers; - -//import edu.emory.mathcs.backport.java.util.*; -import scala.actors.threadpool.*; -import scala.actors.threadpool.locks.*; -import java.security.AccessController; -import java.security.PrivilegedAction; -import java.lang.reflect.Array; -import java.util.Iterator; -import java.util.Collection; - -/** - * <p> - * This class groups together the functionality of java.util.concurrent that - * cannot be fully and reliably implemented in backport, but for which some - * form of emulation is possible. - * <p> - * Currently, this class contains methods related to nanosecond-precision - * timing, particularly via the {@link #nanoTime} method. To measure time - * accurately, this method by default uses <code>java.sun.Perf</code> on - * JDK1.4.2 and it falls back to <code>System.currentTimeMillis</code> - * on earlier JDKs. - * - * @author Dawid Kurzyniec - * @version 1.0 - */ -public final class Utils { - - private final static NanoTimer nanoTimer; - private final static String providerProp = - "edu.emory.mathcs.backport.java.util.concurrent.NanoTimerProvider"; - - static { - NanoTimer timer = null; - try { - String nanoTimerClassName = - AccessController.doPrivileged(new PrivilegedAction<String>() { - public String run() { - return System.getProperty(providerProp); - } - }); - if (nanoTimerClassName != null) { - Class cls = Class.forName(nanoTimerClassName); - timer = (NanoTimer) cls.newInstance(); - } - } - catch (Exception e) { - System.err.println("WARNING: unable to load the system-property-defined " + - "nanotime provider; switching to the default"); - e.printStackTrace(); - } - - if (timer == null) { - try { - timer = new SunPerfProvider(); - } - catch (Throwable e) {} - } - - if (timer == null) { - timer = new MillisProvider(); - } - - nanoTimer = timer; - } - - private Utils() {} - - /** - * Returns the current value of the most precise available system timer, - * in nanoseconds. This method can only be used to measure elapsed time and - * is not related to any other notion of system or wall-clock time. The - * value returned represents nanoseconds since some fixed but arbitrary - * time (perhaps in the future, so values may be negative). This method - * provides nanosecond precision, but not necessarily nanosecond accuracy. - * No guarantees are made about how frequently values change. Differences - * in successive calls that span greater than approximately 292 years - * (2^63 nanoseconds) will not accurately compute elapsed time due to - * numerical overflow. - * <p> - * <em>Implementation note:</em>By default, this method uses - * <code>sun.misc.Perf</code> on Java 1.4.2, and falls back to - * System.currentTimeMillis() emulation on earlier JDKs. Custom - * timer can be provided via the system property - * <code>edu.emory.mathcs.backport.java.util.concurrent.NanoTimerProvider</code>. - * The value of the property should name a class implementing - * {@link NanoTimer} interface. - * <p> - * Note: on JDK 1.4.2, <code>sun.misc.Perf</code> timer seems to have - * resolution of the order of 1 microsecond, measured on Linux. - * - * @return The current value of the system timer, in nanoseconds. - */ - public static long nanoTime() { - return nanoTimer.nanoTime(); - } - - /** - * Causes the current thread to wait until it is signalled or interrupted, - * or the specified waiting time elapses. This method originally appears - * in the {@link Condition} interface, but it was moved to here since it - * can only be emulated, with very little accuracy guarantees: the - * efficient implementation requires accurate nanosecond timer and native - * support for nanosecond-precision wait queues, which are not usually - * present in JVMs prior to 1.5. Loss of precision may cause total waiting - * times to be systematically shorter than specified when re-waits occur. - * - * <p>The lock associated with this condition is atomically - * released and the current thread becomes disabled for thread scheduling - * purposes and lies dormant until <em>one</em> of five things happens: - * <ul> - * <li>Some other thread invokes the {@link - * edu.emory.mathcs.backport.java.util.concurrent.locks.Condition#signal} - * method for this - * <tt>Condition</tt> and the current thread happens to be chosen as the - * thread to be awakened; or - * <li>Some other thread invokes the {@link - * edu.emory.mathcs.backport.java.util.concurrent.locks.Condition#signalAll} - * method for this - * <tt>Condition</tt>; or - * <li>Some other thread {@link Thread#interrupt interrupts} the current - * thread, and interruption of thread suspension is supported; or - * <li>The specified waiting time elapses; or - * <li>A "<em>spurious wakeup</em>" occurs. - * </ul> - * - * <p>In all cases, before this method can return the current thread must - * re-acquire the lock associated with this condition. When the - * thread returns it is <em>guaranteed</em> to hold this lock. - * - * <p>If the current thread: - * <ul> - * <li>has its interrupted status set on entry to this method; or - * <li>is {@link Thread#interrupt interrupted} while waiting - * and interruption of thread suspension is supported, - * </ul> - * then {@link InterruptedException} is thrown and the current thread's - * interrupted status is cleared. It is not specified, in the first - * case, whether or not the test for interruption occurs before the lock - * is released. - * - * <p>The method returns an estimate of the number of nanoseconds - * remaining to wait given the supplied <tt>nanosTimeout</tt> - * value upon return, or a value less than or equal to zero if it - * timed out. Accuracy of this estimate is directly dependent on the - * accuracy of {@link #nanoTime}. This value can be used to determine - * whether and how long to re-wait in cases where the wait returns but an - * awaited condition still does not hold. Typical uses of this method take - * the following form: - * - * <pre> - * synchronized boolean aMethod(long timeout, TimeUnit unit) { - * long nanosTimeout = unit.toNanos(timeout); - * while (!conditionBeingWaitedFor) { - * if (nanosTimeout > 0) - * nanosTimeout = theCondition.awaitNanos(nanosTimeout); - * else - * return false; - * } - * // ... - * } - * </pre> - * - * <p><b>Implementation Considerations</b> - * <p>The current thread is assumed to hold the lock associated with this - * <tt>Condition</tt> when this method is called. - * It is up to the implementation to determine if this is - * the case and if not, how to respond. Typically, an exception will be - * thrown (such as {@link IllegalMonitorStateException}) and the - * implementation must document that fact. - * - * <p>A condition implementation can favor responding to an interrupt over - * normal method return in response to a signal, or over indicating the - * elapse of the specified waiting time. In either case the implementation - * must ensure that the signal is redirected to another waiting thread, if - * there is one. - * - * @param cond the condition to wait for - * @param nanosTimeout the maximum time to wait, in nanoseconds - * @return A value less than or equal to zero if the wait has - * timed out; otherwise an estimate, that - * is strictly less than the <tt>nanosTimeout</tt> argument, - * of the time still remaining when this method returned. - * - * @throws InterruptedException if the current thread is interrupted (and - * interruption of thread suspension is supported). - */ - public static long awaitNanos(Condition cond, long nanosTimeout) - throws InterruptedException - { - if (nanosTimeout <= 0) return nanosTimeout; - long now = nanoTime(); - cond.await(nanosTimeout, TimeUnit.NANOSECONDS); - return nanosTimeout - (nanoTime() - now); - } - - private static final class SunPerfProvider implements NanoTimer { - final Perf perf; - final long multiplier, divisor; - SunPerfProvider() { - perf = - AccessController.doPrivileged(new PrivilegedAction<Perf>() { - public Perf run() { - return Perf.getPerf(); - } - }); - // trying to avoid BOTH overflow and rounding errors - long numerator = 1000000000; - long denominator = perf.highResFrequency(); - long gcd = gcd(numerator, denominator); - this.multiplier = numerator / gcd; - this.divisor = denominator / gcd; - } - public long nanoTime() { - long ctr = perf.highResCounter(); - - // anything less sophisticated suffers either from rounding errors - // (FP arithmetics, backport v1.0) or overflow, when gcd is small - // (a bug in backport v1.0_01 reported by Ramesh Nethi) - - return ((ctr / divisor) * multiplier) + - (ctr % divisor) * multiplier / divisor; - - // even the above can theoretically cause problems if your JVM is - // running for sufficiently long time, but "sufficiently" means 292 - // years (worst case), or 30,000 years (common case). - - // Details: when the ticks ctr overflows, there is no way to avoid - // discontinuity in computed nanos, even in infinite arithmetics, - // unless we count number of overflows that the ctr went through - // since the JVM started. This follows from the fact that - // (2^64*multiplier/divisor) mod (2^64) > 0 in general case. - // Theoretically we could find out the number of overflows by - // checking System.currentTimeMillis(), but this is unreliable - // since the system time can unpredictably change during the JVM - // lifetime. - // The time to overflow is 2^63 / ticks frequency. With current - // ticks frequencies of several MHz, it gives about 30,000 years - // before the problem happens. If ticks frequency reaches 1 GHz, the - // time to overflow is 292 years. It is unlikely that the frequency - // ever exceeds 1 GHz. We could double the time to overflow - // (to 2^64 / frequency) by using unsigned arithmetics, e.g. by - // adding the following correction whenever the ticks is negative: - // -2*((Long.MIN_VALUE / divisor) * multiplier + - // (Long.MIN_VALUE % divisor) * multiplier / divisor) - // But, with the worst case of as much as 292 years, it does not - // seem justified. - } - } - - private static final class MillisProvider implements NanoTimer { - MillisProvider() {} - public long nanoTime() { - return System.currentTimeMillis() * 1000000; - } - } - - private static long gcd(long a, long b) { - long r; - while (b>0) { r = a % b; a = b; b = r; } - return a; - } - - - public static Object[] collectionToArray(Collection c) { - // guess the array size; expect to possibly be different - int len = c.size(); - Object[] arr = new Object[len]; - Iterator itr = c.iterator(); - int idx = 0; - while (true) { - while (idx < len && itr.hasNext()) { - arr[idx++] = itr.next(); - } - if (!itr.hasNext()) { - if (idx == len) return arr; - // otherwise have to trim - return Arrays.copyOf(arr, idx, Object[].class); - } - // otherwise, have to grow - int newcap = ((arr.length/2)+1)*3; - if (newcap < arr.length) { - // overflow - if (arr.length < Integer.MAX_VALUE) { - newcap = Integer.MAX_VALUE; - } - else { - throw new OutOfMemoryError("required array size too large"); - } - } - arr = Arrays.copyOf(arr, newcap, Object[].class); - len = newcap; - } - } - - public static Object[] collectionToArray(Collection c, Object[] a) { - Class aType = a.getClass(); - // guess the array size; expect to possibly be different - int len = c.size(); - Object[] arr = (a.length >= len ? a : - (Object[])Array.newInstance(aType.getComponentType(), len)); - Iterator itr = c.iterator(); - int idx = 0; - while (true) { - while (idx < len && itr.hasNext()) { - arr[idx++] = itr.next(); - } - if (!itr.hasNext()) { - if (idx == len) return arr; - if (arr == a) { - // orig array -> null terminate - a[idx] = null; - return a; - } - else { - // have to trim - return Arrays.copyOf(arr, idx, aType); - } - } - // otherwise, have to grow - int newcap = ((arr.length/2)+1)*3; - if (newcap < arr.length) { - // overflow - if (arr.length < Integer.MAX_VALUE) { - newcap = Integer.MAX_VALUE; - } - else { - throw new OutOfMemoryError("required array size too large"); - } - } - arr = Arrays.copyOf(arr, newcap, aType); - len = newcap; - } - } -} |