From 554fd8c5195424bdbcabf5de30fdc183aba391bd Mon Sep 17 00:00:00 2001 From: upstream source tree Date: Sun, 15 Mar 2015 20:14:05 -0400 Subject: obtained gcc-4.6.4.tar.bz2 from upstream website; verified gcc-4.6.4.tar.bz2.sig; imported gcc-4.6.4 source tree from verified upstream tarball. downloading a git-generated archive based on the 'upstream' tag should provide you with a source tree that is binary identical to the one extracted from the above tarball. if you have obtained the source via the command 'git clone', however, do note that line-endings of files in your working directory might differ from line-endings of the respective files in the upstream repository. --- libjava/classpath/java/lang/ThreadLocalMap.java | 325 ++++++++++++++++++++++++ 1 file changed, 325 insertions(+) create mode 100644 libjava/classpath/java/lang/ThreadLocalMap.java (limited to 'libjava/classpath/java/lang/ThreadLocalMap.java') diff --git a/libjava/classpath/java/lang/ThreadLocalMap.java b/libjava/classpath/java/lang/ThreadLocalMap.java new file mode 100644 index 000000000..7f67b1311 --- /dev/null +++ b/libjava/classpath/java/lang/ThreadLocalMap.java @@ -0,0 +1,325 @@ +/* ThreadLocal -- a variable with a unique value per thread + Copyright (C) 2000, 2002, 2003, 2004, 2005, 2006 Free Software Foundation, Inc. + +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 java.lang; + +import java.lang.ref.WeakReference; + +/** + * ThreadLocalMap is the basic storage for the map of ThreadLocal instance + * to a thread's current value. + * + * Some applications really work out ThreadLocals, leading to this + * optimized implementation. + */ +final class ThreadLocalMap +{ + /** + * The log (base 2) of the initial size of the map + */ + private static final int LOG_INITIAL_SIZE = 3; + + /** + * The maximum occupancy rate (after which we grow) + */ + private static final float MAX_OCCUPANCY = 0.7f; + + /** + * The target occupancy rate. + */ + private static final float TARGET_OCCUPANCY = 0.5f; + + /** + * The deleted entry sentinel value. + */ + private static final Entry deletedEntry = new Entry(null); + + /** + * Constructor + */ + ThreadLocalMap() + { + /* Dummy value to ensure fast path can be optimized */ + entries = new Entry[1]; + hashMask = 0; + count = 0; + } + + /** + * The map entries + */ + private Entry[] entries; + + /** + * Used for start index computation + */ + private int hashMask; + + /** + * The number of entries currently in the map + */ + private int count; + + /** + * Create or grow the table to the specified size. The size must be a + * power of two for the efficient mask/hash computation. + * + * @param newSize The new table size. + */ + private void newEntryArray(int newSize) + { + int mask = newSize - 1; + Entry[] oldEntries = this.entries; + this.entries = new Entry[newSize]; + this.hashMask = mask; + + /* Copy old entries to new table */ + count = 0; + if (oldEntries != null) + { + for(Entry e: oldEntries) + { + if (e != null) + { + ThreadLocal key = e.get(); + if (e != deletedEntry && key != null) + { + for(int i = key.fastHash & mask;; i = (i + 1) & mask) + { + if (entries[i] == null) + { + entries[i] = e; + count++; + break; + } + } + } + } + } + } + } + + /** + * We have run out of space in our locals. We use this as the + * trigger to attempt to find unused slots as ThreadLocals have + * died. If we recover any slots this way then we do not grow. + */ + private void overflow() + { + /* First 'actual' use */ + if (entries.length == 1) + { + newEntryArray(1 << LOG_INITIAL_SIZE); + return; + } + + /* Attempt to recover unused slots */ + int deleted = 0; + for(int i=0; i < entries.length; i++) + { + Entry e = entries[i]; + if (e != null) + { + if (e == deletedEntry) + { + deleted++; + } + else if (e.get() == null) + { + entries[i] = deletedEntry; + deleted++; + } + } + } + + if ((count-deleted) <= (TARGET_OCCUPANCY * entries.length)) + { + /* We currently rehash by simple reallocating into a same-sized table. + * An alternative would be to implement a clever hashing algorithm but + * as this happens infrequently this seems preferred */ + newEntryArray(entries.length); + return; + } + + /* Double the size */ + newEntryArray(entries.length << 1); + } + + /** + * This is the class that is used to refer to a thread local weakly. + * + * As we want to minimize indirections we extend WeakReference. + */ + static final class Entry extends WeakReference> { + /** + * The value stored in this slot + */ + Object value; + + /** + * Constructor + */ + Entry(ThreadLocal threadLocal) { + super(threadLocal); + } + } + + /** + * Gets the value associated with the ThreadLocal object for the currently + * executing Thread. If this is the first time the current thread has called + * get(), and it has not already called set(), the sentinel value is returned. + * + * @return the value of the variable in this thread, or sentinel if not present. + */ + public Object get(ThreadLocal key) + { + int mask = this.hashMask; + for(int i = key.fastHash & mask;; i = (i + 1) & mask) { + Entry e = entries[i]; + if (e != null) { + if (e.get() == key) { + return e.value; + } + } else { + return ThreadLocal.sentinel; + } + } + } + + /** + * Sets the value associated with the ThreadLocal object for the currently + * executing Thread. This overrides any existing value associated with the + * current Thread and prevents initialValue() from being + * called if this is the first access to this ThreadLocal in this Thread. + * + * @param value the value to set this thread's view of the variable to + */ + public void set(ThreadLocal key, Object value) + { + /* Overflow ? */ + if ((count+1) >= (MAX_OCCUPANCY * entries.length)) + { + overflow(); + } + + /* Set the entry */ + int mask = this.hashMask; + for(int i = key.fastHash & mask;; i = (i + 1) & mask) + { + Entry e = entries[i]; + if (e == null || e == deletedEntry) + { + /* Create entry */ + if (e == null) count++; + entries[i] = e = new Entry(key); + e.value = value; + return; + } + else + { + ThreadLocal entryKey = e.get(); + if (entryKey == null) + { + entries[i] = deletedEntry; + } + else if (entryKey == key) + { + /* Update entry */ + e.value = value; + return; + } + } + } + } + + /** + * Removes the value associated with the ThreadLocal object for the + * currently executing Thread. + * @since 1.5 + */ + public void remove(ThreadLocal key) + { + int mask = this.hashMask; + for(int i = key.fastHash & mask;; i = (i + 1) & mask) + { + Entry e = entries[i]; + if (e != null) + { + ThreadLocal entryKey = e.get(); + if (entryKey != key) + { + if (entryKey == null) { + entries[i] = deletedEntry; + } + continue; + } + else + { + /* Remove from the table */ + entries[i] = deletedEntry; + } + } + return; + } + } + + /** + * Clear out the map. Done once during thread death. + */ + void clear() { + entries = null; + } + + /** + * Inherit all the InheritableThreadLocal instances from the given parent. + * + * @param parentMap The map to inherit from. + */ + public void inherit(ThreadLocalMap parentMap) { + for(Entry e: parentMap.entries) + { + if (e != null && e != deletedEntry) + { + ThreadLocal key = e.get(); + if (key instanceof InheritableThreadLocal) + { + set(key, ((InheritableThreadLocal)key).childValue(e.value)); + } + } + } + } +} -- cgit v1.2.3