mirror of git://gcc.gnu.org/git/gcc.git
94 lines
3.3 KiB
Java
94 lines
3.3 KiB
Java
/* VMString.java -- VM Specific String methods
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Copyright (C) 2003, 2010 Free Software Foundation, Inc.
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING. If not, write to the
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Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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02110-1301 USA.
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Linking this library statically or dynamically with other modules is
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making a combined work based on this library. Thus, the terms and
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conditions of the GNU General Public License cover the whole
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combination.
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As a special exception, the copyright holders of this library give you
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permission to link this library with independent modules to produce an
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executable, regardless of the license terms of these independent
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modules, and to copy and distribute the resulting executable under
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terms of your choice, provided that you also meet, for each linked
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independent module, the terms and conditions of the license of that
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module. An independent module is a module which is not derived from
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or based on this library. If you modify this library, you may extend
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this exception to your version of the library, but you are not
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obligated to do so. If you do not wish to do so, delete this
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exception statement from your version. */
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package java.lang;
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import java.lang.ref.WeakReference;
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import java.util.WeakHashMap;
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/*
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* This class is a reference version, mainly for compiling a class library
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* jar. It is likely that VM implementers replace this with their own
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* version that can communicate effectively with the VM.
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*/
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/**
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* Code relocated from java.lang.String by
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* @author Dave Grove <groved@us.ibm.com>
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*/
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final class VMString
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{
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/**
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* Holds the references for each intern()'d String. If all references to
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* the string disappear, and the VM properly supports weak references,
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* the String will be GC'd.
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*/
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private static final WeakHashMap internTable = new WeakHashMap();
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private VMString() {} // Prohibits instantiation.
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/**
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* Fetches this String from the intern hashtable. If two Strings are
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* considered equal, by the equals() method, then intern() will return the
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* same String instance. ie. if (s1.equals(s2)) then
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* (s1.intern() == s2.intern()). All string literals and string-valued
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* constant expressions are already interned.
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*
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* @param str the String to intern
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* @return the interned String
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*/
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static String intern(String str)
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{
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synchronized (internTable)
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{
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WeakReference ref = (WeakReference) internTable.get(str);
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if (ref != null)
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{
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String s = (String) ref.get();
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// If s is null, then no strong references exist to the String;
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// the weak hash map will soon delete the key.
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if (s != null)
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return s;
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}
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internTable.put(str, new WeakReference(str));
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}
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return str;
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}
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} // class VMString
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