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Diffstat (limited to 'libjava/classpath/vm/reference/sun/misc')
| -rw-r--r-- | libjava/classpath/vm/reference/sun/misc/Unsafe.java | 328 |
1 files changed, 328 insertions, 0 deletions
diff --git a/libjava/classpath/vm/reference/sun/misc/Unsafe.java b/libjava/classpath/vm/reference/sun/misc/Unsafe.java new file mode 100644 index 000000000..e316bdb8d --- /dev/null +++ b/libjava/classpath/vm/reference/sun/misc/Unsafe.java @@ -0,0 +1,328 @@ +/* Unsafe.java - Unsafe operations needed for concurrency + Copyright (C) 2006 Free Software Foundation + +This file is part of GNU Classpath. + +GNU Classpath is free software; you can redistribute it and/or modify +it under the terms of the GNU General Public License as published by +the Free Software Foundation; either version 2, or (at your option) +any later version. + +GNU Classpath 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 for more details. + +You should have received a copy of the GNU General Public License +along with GNU Classpath; see the file COPYING. If not, write to the +Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA +02110-1301 USA. + +Linking this library statically or dynamically with other modules is +making a combined work based on this library. Thus, the terms and +conditions of the GNU General Public License cover the whole +combination. + +As a special exception, the copyright holders of this library give you +permission to link this library with independent modules to produce an +executable, regardless of the license terms of these independent +modules, and to copy and distribute the resulting executable under +terms of your choice, provided that you also meet, for each linked +independent module, the terms and conditions of the license of that +module. An independent module is a module which is not derived from +or based on this library. If you modify this library, you may extend +this exception to your version of the library, but you are not +obligated to do so. If you do not wish to do so, delete this +exception statement from your version. */ + +package sun.misc; + +import java.lang.reflect.Field; + +/** + * This class should provide access to low-level operations and its + * use should be limited to trusted code. Fields can be accessed using + * memory addresses, with undefined behaviour occurring if invalid memory + * addresses are given. + * + * @author Tom Tromey (tromey@redhat.com) + * @author Andrew John Hughes (gnu_andrew@member.fsf.org) + */ +public class Unsafe +{ + // Singleton class. + private static Unsafe unsafe = new Unsafe(); + + /** + * Private default constructor to prevent creation of an arbitrary + * number of instances. + */ + private Unsafe() + { + } + + /** + * Retrieve the singleton instance of <code>Unsafe</code>. The calling + * method should guard this instance from untrusted code, as it provides + * access to low-level operations such as direct memory access. + * + * @throws SecurityException if a security manager exists and prevents + * access to the system properties. + */ + public static Unsafe getUnsafe() + { + SecurityManager sm = System.getSecurityManager(); + if (sm != null) + sm.checkPropertiesAccess(); + return unsafe; + } + + /** + * Returns the memory address offset of the given static field. + * The offset is merely used as a means to access a particular field + * in the other methods of this class. The value is unique to the given + * field and the same value should be returned on each subsequent call. + * + * @param field the field whose offset should be returned. + * @return the offset of the given field. + */ + public native long objectFieldOffset(Field field); + + /** + * Compares the value of the integer field at the specified offset + * in the supplied object with the given expected value, and updates + * it if they match. The operation of this method should be atomic, + * thus providing an uninterruptible way of updating an integer field. + * + * @param obj the object containing the field to modify. + * @param offset the offset of the integer field within <code>obj</code>. + * @param expect the expected value of the field. + * @param update the new value of the field if it equals <code>expect</code>. + * @return true if the field was changed. + */ + public native boolean compareAndSwapInt(Object obj, long offset, + int expect, int update); + + /** + * Compares the value of the long field at the specified offset + * in the supplied object with the given expected value, and updates + * it if they match. The operation of this method should be atomic, + * thus providing an uninterruptible way of updating a long field. + * + * @param obj the object containing the field to modify. + * @param offset the offset of the long field within <code>obj</code>. + * @param expect the expected value of the field. + * @param update the new value of the field if it equals <code>expect</code>. + * @return true if the field was changed. + */ + public native boolean compareAndSwapLong(Object obj, long offset, + long expect, long update); + + /** + * Compares the value of the object field at the specified offset + * in the supplied object with the given expected value, and updates + * it if they match. The operation of this method should be atomic, + * thus providing an uninterruptible way of updating an object field. + * + * @param obj the object containing the field to modify. + * @param offset the offset of the object field within <code>obj</code>. + * @param expect the expected value of the field. + * @param update the new value of the field if it equals <code>expect</code>. + * @return true if the field was changed. + */ + public native boolean compareAndSwapObject(Object obj, long offset, + Object expect, Object update); + + /** + * Sets the value of the integer field at the specified offset in the + * supplied object to the given value. This is an ordered or lazy + * version of <code>putIntVolatile(Object,long,int)</code>, which + * doesn't guarantee the immediate visibility of the change to other + * threads. It is only really useful where the integer field is + * <code>volatile</code>, and is thus expected to change unexpectedly. + * + * @param obj the object containing the field to modify. + * @param offset the offset of the integer field within <code>obj</code>. + * @param value the new value of the field. + * @see #putIntVolatile(Object,long,int) + */ + public native void putOrderedInt(Object obj, long offset, int value); + + /** + * Sets the value of the long field at the specified offset in the + * supplied object to the given value. This is an ordered or lazy + * version of <code>putLongVolatile(Object,long,long)</code>, which + * doesn't guarantee the immediate visibility of the change to other + * threads. It is only really useful where the long field is + * <code>volatile</code>, and is thus expected to change unexpectedly. + * + * @param obj the object containing the field to modify. + * @param offset the offset of the long field within <code>obj</code>. + * @param value the new value of the field. + * @see #putLongVolatile(Object,long,long) + */ + public native void putOrderedLong(Object obj, long offset, long value); + + /** + * Sets the value of the object field at the specified offset in the + * supplied object to the given value. This is an ordered or lazy + * version of <code>putObjectVolatile(Object,long,Object)</code>, which + * doesn't guarantee the immediate visibility of the change to other + * threads. It is only really useful where the object field is + * <code>volatile</code>, and is thus expected to change unexpectedly. + * + * @param obj the object containing the field to modify. + * @param offset the offset of the object field within <code>obj</code>. + * @param value the new value of the field. + */ + public native void putOrderedObject(Object obj, long offset, Object value); + + /** + * Sets the value of the integer field at the specified offset in the + * supplied object to the given value, with volatile store semantics. + * + * @param obj the object containing the field to modify. + * @param offset the offset of the integer field within <code>obj</code>. + * @param value the new value of the field. + */ + public native void putIntVolatile(Object obj, long offset, int value); + + /** + * Retrieves the value of the integer field at the specified offset in the + * supplied object with volatile load semantics. + * + * @param obj the object containing the field to read. + * @param offset the offset of the integer field within <code>obj</code>. + */ + public native int getIntVolatile(Object obj, long offset); + + /** + * Sets the value of the long field at the specified offset in the + * supplied object to the given value, with volatile store semantics. + * + * @param obj the object containing the field to modify. + * @param offset the offset of the long field within <code>obj</code>. + * @param value the new value of the field. + * @see #putLong(Object,long,long) + */ + public native void putLongVolatile(Object obj, long offset, long value); + + /** + * Sets the value of the long field at the specified offset in the + * supplied object to the given value. + * + * @param obj the object containing the field to modify. + * @param offset the offset of the long field within <code>obj</code>. + * @param value the new value of the field. + * @see #putLongVolatile(Object,long,long) + */ + public native void putLong(Object obj, long offset, long value); + + /** + * Retrieves the value of the long field at the specified offset in the + * supplied object with volatile load semantics. + * + * @param obj the object containing the field to read. + * @param offset the offset of the long field within <code>obj</code>. + * @see #getLong(Object,long) + */ + public native long getLongVolatile(Object obj, long offset); + + /** + * Retrieves the value of the long field at the specified offset in the + * supplied object. + * + * @param obj the object containing the field to read. + * @param offset the offset of the long field within <code>obj</code>. + * @see #getLongVolatile(Object,long) + */ + public native long getLong(Object obj, long offset); + + /** + * Sets the value of the object field at the specified offset in the + * supplied object to the given value, with volatile store semantics. + * + * @param obj the object containing the field to modify. + * @param offset the offset of the object field within <code>obj</code>. + * @param value the new value of the field. + * @see #putObject(Object,long,Object) + */ + public native void putObjectVolatile(Object obj, long offset, Object value); + + /** + * Sets the value of the object field at the specified offset in the + * supplied object to the given value. + * + * @param obj the object containing the field to modify. + * @param offset the offset of the object field within <code>obj</code>. + * @param value the new value of the field. + * @see #putObjectVolatile(Object,long,Object) + */ + public native void putObject(Object obj, long offset, Object value); + + /** + * Retrieves the value of the object field at the specified offset in the + * supplied object with volatile load semantics. + * + * @param obj the object containing the field to read. + * @param offset the offset of the object field within <code>obj</code>. + */ + public native Object getObjectVolatile(Object obj, long offset); + + /** + * Returns the offset of the first element for a given array class. + * To access elements of the array class, this value may be used along + * with that returned by + * <a href="#arrayIndexScale"><code>arrayIndexScale</code></a>, + * if non-zero. + * + * @param arrayClass the class for which the first element's address should + * be obtained. + * @return the offset of the first element of the array class. + * @see arrayIndexScale(Class) + */ + public native int arrayBaseOffset(Class arrayClass); + + /** + * Returns the scale factor used for addressing elements of the supplied + * array class. Where a suitable scale factor can not be returned (e.g. + * for primitive types), zero should be returned. The returned value + * can be used with + * <a href="#arrayBaseOffset"><code>arrayBaseOffset</code></a> + * to access elements of the class. + * + * @param arrayClass the class whose scale factor should be returned. + * @return the scale factor, or zero if not supported for this array class. + */ + public native int arrayIndexScale(Class arrayClass); + + /** + * Releases the block on a thread created by + * <a href="#park"><code>park</code></a>. This method can also be used + * to terminate a blockage caused by a prior call to <code>park</code>. + * This operation is unsafe, as the thread must be guaranteed to be + * live. This is true of Java, but not native code. + * + * @param thread the thread to unblock. + */ + public native void unpark(Object thread); + + /** + * Blocks the thread until a matching + * <a href="#unpark"><code>unpark</code></a> occurs, the thread is + * interrupted or the optional timeout expires. If an <code>unpark</code> + * call has already occurred, this also counts. A timeout value of zero + * is defined as no timeout. When <code>isAbsolute</code> is + * <code>true</code>, the timeout is in milliseconds relative to the + * epoch. Otherwise, the value is the number of nanoseconds which must + * occur before timeout. This call may also return spuriously (i.e. + * for no apparent reason). + * + * @param isAbsolute true if the timeout is specified in milliseconds from + * the epoch. + * @param time either the number of nanoseconds to wait, or a time in + * milliseconds from the epoch to wait for. + */ + public native void park(boolean isAbsolute, long time); + +} |