/*
* @(#)Keywords.java 1.19 07/03/21
*
* Copyright (c) 2007 Sun Microsystems, Inc. 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. Sun designates this
* particular file as subject to the "Classpath" exception as provided
* by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
* CA 95054 USA or visit www.sun.com if you need additional information or
* have any questions.
*/
package com.sun.tools.javac.parser;
import com.sun.tools.javac.util.Context;
import com.sun.tools.javac.util.Log;
import com.sun.tools.javac.util.Name;
import com.sun.tools.javac.util.Version;
import static com.sun.tools.javac.parser.Token.*;
/**
* Map from Name to Token and Token to String.
*
* <p><b>This is NOT part of any API supported by Sun Microsystems.
* If you write code that depends on this, you do so at your own risk.
* This code and its internal interfaces are subject to change or
* deletion without notice.</b>
*/
@Version("@(#)Keywords.java 1.19 07/03/21")
public class Keywords {
private static my.Debug DEBUG=new my.Debug(my.Debug.Keywords);//我加上的
public static final Context.Key<Keywords> keywordsKey =
new Context.Key<Keywords>();
public static Keywords instance(Context context) {
Keywords instance = context.get(keywordsKey);
if (instance == null)
instance = new Keywords(context);
return instance;
}
private final Log log;
private final Name.Table names;
protected Keywords(Context context) {
DEBUG.P(this,"Keywords(1)");
context.put(keywordsKey, this);
log = Log.instance(context);
names = Name.Table.instance(context);
for (Token t : Token.values()) {
/*
Token是enum类型,values()对所有enum类型都通用，并不是Token中定义的方法,
EOF,
ERROR,
IDENTIFIER,
ABSTRACT("abstract"),
对应的输出是:
Token t=EOF name=null ordina=0
Token t=ERROR name=null ordina=1
Token t=IDENTIFIER name=null ordina=2
Token t=ABSTRACT name=abstract ordina=3
*/
//DEBUG.P("ordina="+t.ordinal()+"\t\tToken t="+t+"\t\tname="+t.name);
if (t.name != null)
enterKeyword(t.name, t);
else
tokenName[t.ordinal()] = null;
DEBUG.P("tokenName["+t.ordinal()+"]="+tokenName[t.ordinal()]);
}
DEBUG.P("maxKey="+maxKey);
key = new Token[maxKey+1];
DEBUG.P("key.length="+key.length);
for (int i = 0; i <= maxKey; i++) key[i] = IDENTIFIER;
for (Token t : Token.values()) {
if (t.name != null)
key[tokenName[t.ordinal()].index] = t;
}
for (int i = 0; i <= maxKey; i++) DEBUG.P("key["+i+"]="+key[i]);
DEBUG.P(0,this,"Keywords(1)");
}
//检查Scanner当前得到的token是否是关键字
//判断思路很简单,因关键字在没开始词法分析前已加入符号表，
//并用maxKey记下所有关键字中在符号表字节数组的最大索引index
//如果当前token的index>maxKey则当前的token肯定是IDENTIFIER
//否则直接返回关键字key[name.index]
/*
Token枚举类的所有name!=null的枚举常量都被加进Name.Table类
的names字段(一个字节数组)，并且都对应一个index，maxKey记录了其中的最大index，
“Token[] key”的长度等于maxKey+1,在给“Token[] key”初始化时，
如果“Token[] key”的下标刚好等于Token枚举类的所有name!=null的枚举常量在
Name.Table类的names字段的index，那么“Token[] key”对应下标的元素值就是
这个枚举常量，否则为IDENTIFIER
*/
//这里的设计原则是:牺牲点内存空间，加快编译器的编译速度
public Token key(Name name) {
return (name.index > maxKey) ? IDENTIFIER : key[name.index];
}
/**
* Keyword array. Maps name indices to Token.
*/
private final Token[] key;//如何缩减数组的长度,见Name.Table类的构造方法
/** The number of the last entered keyword.
*/
private int maxKey = 0;
/** The names of all tokens.
*/
//这个字段是可有可无的，如果不需要这个字段，只需把enterKeyword方法的代码
//移到构造方法中即可
private Name[] tokenName = new Name[Token.values().length];
public String token2string(Token token) {
switch (token) {
case IDENTIFIER:
return log.getLocalizedString("token.identifier");
case CHARLITERAL:
return log.getLocalizedString("token.character");
case STRINGLITERAL:
return log.getLocalizedString("token.string");
case INTLITERAL:
return log.getLocalizedString("token.integer");
case LONGLITERAL:
return log.getLocalizedString("token.long-integer");
case FLOATLITERAL:
return log.getLocalizedString("token.float");
case DOUBLELITERAL:
return log.getLocalizedString("token.double");
case ERROR:
return log.getLocalizedString("token.bad-symbol");
case EOF:
return log.getLocalizedString("token.end-of-input");
case DOT: case COMMA: case SEMI: case LPAREN: case RPAREN:
case LBRACKET: case RBRACKET: case LBRACE: case RBRACE:
return "'" + token.name + "'";
default:
return token.name;
}
}
private void enterKeyword(String s, Token token) {
Name n = names.fromString(s);
tokenName[token.ordinal()] = n;
if (n.index > maxKey) maxKey = n.index;
}
}