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	/*
	* Copyright (c) 1994, 2003, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code 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
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	package sun.tools.java;

	import java.util.Hashtable;
	import java.io.PrintStream;
	import java.util.Enumeration;

	/**
	* A class to represent identifiers.<p>
	*
	* An identifier instance is very similar to a String. The difference
	* is that identifier can't be instanciated directly, instead they are
	* looked up in a hash table. This means that identifiers with the same
	* name map to the same identifier object. This makes comparisons of
	* identifiers much faster.<p>
	*
	* A lot of identifiers are qualified, that is they have '.'s in them.
	* Each qualified identifier is chopped up into the qualifier and the
	* name. The qualifier is cached in the value field.<p>
	*
	* Unqualified identifiers can have a type. This type is an integer that
	* can be used by a scanner as a token value. This value has to be set
	* using the setType method.<p>
	*
	* WARNING: The contents of this source file are not part of any
	* supported API. Code that depends on them does so at its own risk:
	* they are subject to change or removal without notice.
	*
	* @author Arthur van Hoff
	*/

	public final
	class Identifier implements Constants {
	/**
	* The hashtable of identifiers
	*/
	static Hashtable hash = new Hashtable(3001, 0.5f);

	/**
	* The name of the identifier
	*/
	String name;

	/**
	* The value of the identifier, for keywords this is an
	* instance of class Integer, for qualified names this is
	* another identifier (the qualifier).
	*/
	Object value;

	/**
	* The Type which corresponds to this Identifier. This is used as
	* cache for Type.tClass() and shouldn't be used outside of that
	* context.
	*/
	Type typeObject = null;

	/**
	* The index of INNERCLASS_PREFIX in the name, or -1 if none.
	*/
	private int ipos;

	/**
	* Construct an identifier. Don't call this directly,
	* use lookup instead.
	* @see Identifier.lookup
	*/
	private Identifier(String name) {
	this.name = name;
	this.ipos = name.indexOf(INNERCLASS_PREFIX);
	}

	/**
	* Get the type of the identifier.
	*/
	int getType() {
	return ((value != null) && (value instanceof Integer)) ?
	((Integer)value).intValue() : IDENT;
	}

	/**
	* Set the type of the identifier.
	*/
	void setType(int t) {
	value = new Integer(t);
	//System.out.println("type(" + this + ")=" + t);
	}

	/**
	* Lookup an identifier.
	*/
	public static synchronized Identifier lookup(String s) {
	//System.out.println("lookup(" + s + ")");
	Identifier id = (Identifier)hash.get(s);
	if (id == null) {
	hash.put(s, id = new Identifier(s));
	}
	return id;
	}

	/**
	* Lookup a qualified identifier.
	*/
	public static Identifier lookup(Identifier q, Identifier n) {
	// lookup("", x) => x
	if (q == idNull) return n;
	// lookup(lookupInner(c, ""), n) => lookupInner(c, lookup("", n))
	if (q.name.charAt(q.name.length()-1) == INNERCLASS_PREFIX)
	return lookup(q.name+n.name);
	Identifier id = lookup(q + "." + n);
	if (!n.isQualified() && !q.isInner())
	id.value = q;
	return id;
	}

	/**
	* Lookup an inner identifier.
	* (Note: n can be idNull.)
	*/
	public static Identifier lookupInner(Identifier c, Identifier n) {
	Identifier id;
	if (c.isInner()) {
	if (c.name.charAt(c.name.length()-1) == INNERCLASS_PREFIX)
	id = lookup(c.name+n);
	else
	id = lookup(c, n);
	} else {
	id = lookup(c + "." + INNERCLASS_PREFIX + n);
	}
	id.value = c.value;
	return id;
	}

	/**
	* Convert to a string.
	*/
	public String toString() {
	return name;
	}

	/**
	* Check if the name is qualified (ie: it contains a '.').
	*/
	public boolean isQualified() {
	if (value == null) {
	int idot = ipos;
	if (idot <= 0)
	idot = name.length();
	else
	idot -= 1; // back up over previous dot
	int index = name.lastIndexOf('.', idot-1);
	value = (index < 0) ? idNull : Identifier.lookup(name.substring(0, index));
	}
	return (value instanceof Identifier) && (value != idNull);
	}

	/**
	* Return the qualifier. The null identifier is returned if
	* the name was not qualified. The qualifier does not include
	* any inner part of the name.
	*/
	public Identifier getQualifier() {
	return isQualified() ? (Identifier)value : idNull;
	}

	/**
	* Return the unqualified name.
	* In the case of an inner name, the unqualified name
	* will itself contain components.
	*/
	public Identifier getName() {
	return isQualified() ?
	Identifier.lookup(name.substring(((Identifier)value).name.length() + 1)) : this;
	}

	/** A space character, which precedes the first inner class
	* name in a qualified name, and thus marks the qualification
	* as involving inner classes, instead of merely packages.<p>
	* Ex: <tt>java.util.Vector. Enumerator</tt>.
	*/
	public static final char INNERCLASS_PREFIX = ' ';

	/* Explanation:
	* Since much of the compiler's low-level name resolution code
	* operates in terms of Identifier objects. This includes the
	* code which walks around the file system and reports what
	* classes are where. It is important to get nesting information
	* right as early as possible, since it affects the spelling of
	* signatures. Thus, the low-level import and resolve code must
	* be able Identifier type must be able to report the nesting
	* of types, which implied that that information must be carried
	* by Identifiers--or that the low-level interfaces be significantly
	* changed.
	*/

	/**
	* Check if the name is inner (ie: it contains a ' ').
	*/
	public boolean isInner() {
	return (ipos > 0);
	}

	/**
	* Return the class name, without its qualifier,
	* and with any nesting flattened into a new qualfication structure.
	* If the original identifier is inner,
	* the result will be qualified, and can be further
	* decomposed by means of <tt>getQualifier</tt> and <tt>getName</tt>.
	* <p>
	* For example:
	* <pre>
	* Identifier id = Identifier.lookup("pkg.Foo. Bar");
	* id.getName().name => "Foo. Bar"
	* id.getFlatName().name => "Foo.Bar"
	* </pre>
	*/
	public Identifier getFlatName() {
	if (isQualified()) {
	return getName().getFlatName();
	}
	if (ipos > 0 && name.charAt(ipos-1) == '.') {
	if (ipos+1 == name.length()) {
	// last component is idNull
	return Identifier.lookup(name.substring(0,ipos-1));
	}
	String n = name.substring(ipos+1);
	String t = name.substring(0,ipos);
	return Identifier.lookup(t+n);
	}
	// Not inner. Just return the same as getName()
	return this;
	}

	public Identifier getTopName() {
	if (!isInner()) return this;
	return Identifier.lookup(getQualifier(), getFlatName().getHead());
	}

	/**
	* Yet another way to slice qualified identifiers:
	* The head of an identifier is its first qualifier component,
	* and the tail is the rest of them.
	*/
	public Identifier getHead() {
	Identifier id = this;
	while (id.isQualified())
	id = id.getQualifier();
	return id;
	}

	/**
	* @see getHead
	*/
	public Identifier getTail() {
	Identifier id = getHead();
	if (id == this)
	return idNull;
	else
	return Identifier.lookup(name.substring(id.name.length() + 1));
	}

	// Unfortunately, the current structure of the compiler requires
	// that the resolveName() family of methods (which appear in
	// Environment.java, Context.java, and ClassDefinition.java) raise
	// no exceptions and emit no errors. When we are in resolveName()
	// and we find a method that is ambiguous, we need to
	// unambiguously mark it as such, so that later stages of the
	// compiler realize that they should give an ambig.class rather than
	// a class.not.found error. To mark it we add a special prefix
	// which cannot occur in the program source. The routines below
	// are used to check, add, and remove this prefix.
	// (part of solution for 4059855).

	/**
	* A special prefix to add to ambiguous names.
	*/
	private static final String ambigPrefix = "<<ambiguous>>";

	/**
	* Determine whether an Identifier has been marked as ambiguous.
	*/
	public boolean hasAmbigPrefix() {
	return (name.startsWith(ambigPrefix));
	}

	/**
	* Add ambigPrefix to `this' to make a new Identifier marked as
	* ambiguous. It is important that this new Identifier not refer
	* to an existing class.
	*/
	public Identifier addAmbigPrefix() {
	return Identifier.lookup(ambigPrefix + name);
	}

	/**
	* Remove the ambigPrefix from `this' to get the original identifier.
	*/
	public Identifier removeAmbigPrefix() {
	if (hasAmbigPrefix()) {
	return Identifier.lookup(name.substring(ambigPrefix.length()));
	} else {
	return this;
	}
	}
	}

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