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Nashorn is an Open Source JavaScript (ECMAScript 5.1 and some 6 features) engine for the JVM.
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/*
* Copyright (c) 2010, 2015, 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
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*/
package org.openjdk.nashorn.internal.parser;
import static org.openjdk.nashorn.internal.parser.TokenKind.LITERAL;
import org.openjdk.nashorn.internal.runtime.Source;
/**
* A token is a 64 bit long value that represents a basic parse/lex unit.
* This class provides static methods to manipulate lexer tokens.
*/
public class Token {
/**
* We use 28 bits for the position and 28 bits for the length of the token.
* This limits the maximal length of code we can handle to 2 ^ 28 - 1 bytes.
*/
public final static int LENGTH_MASK = 0xfffffff;
// The first 8 bits are used for the token type, followed by length and position
private final static int LENGTH_SHIFT = 8;
private final static int POSITION_SHIFT = 36;
private Token() {
}
/**
* Create a compact form of token information.
* @param type Type of token.
* @param position Start position of the token in the source.
* @param length Length of the token.
* @return Token descriptor.
*/
public static long toDesc(final TokenType type, final int position, final int length) {
assert position <= LENGTH_MASK && length <= LENGTH_MASK;
return (long)position << POSITION_SHIFT |
(long)length << LENGTH_SHIFT |
type.ordinal();
}
/**
* Extract token position from a token descriptor.
* @param token Token descriptor.
* @return Start position of the token in the source.
*/
public static int descPosition(final long token) {
return (int)(token >>> POSITION_SHIFT);
}
/**
* Normally returns the token itself, except in case of string tokens
* which report their position past their opening delimiter and thus
* need to have position and length adjusted.
*
* @param token Token descriptor.
* @return same or adjusted token.
*/
public static long withDelimiter(final long token) {
final TokenType tokenType = Token.descType(token);
switch(tokenType) {
case STRING:
case ESCSTRING:
case EXECSTRING:
case TEMPLATE:
case TEMPLATE_TAIL: {
final int start = Token.descPosition(token) - 1;
final int len = Token.descLength(token) + 2;
return toDesc(tokenType, start, len);
}
case TEMPLATE_HEAD:
case TEMPLATE_MIDDLE: {
final int start = Token.descPosition(token) - 1;
final int len = Token.descLength(token) + 3;
return toDesc(tokenType, start, len);
}
default: {
return token;
}
}
}
/**
* Extract token length from a token descriptor.
* @param token Token descriptor.
* @return Length of the token.
*/
public static int descLength(final long token) {
return (int)((token >>> LENGTH_SHIFT) & LENGTH_MASK);
}
/**
* Extract token type from a token descriptor.
* @param token Token descriptor.
* @return Type of token.
*/
public static TokenType descType(final long token) {
return TokenType.getValues()[(int)token & 0xff];
}
/**
* Change the token to use a new type.
*
* @param token The original token.
* @param newType The new token type.
* @return The recast token.
*/
public static long recast(final long token, final TokenType newType) {
return token & ~0xFFL | newType.ordinal();
}
/**
* Return a string representation of a token.
* @param source Token source.
* @param token Token descriptor.
* @param verbose True to include details.
* @return String representation.
*/
public static String toString(final Source source, final long token, final boolean verbose) {
final TokenType type = Token.descType(token);
String result;
if (source != null && type.getKind() == LITERAL) {
result = source.getString(token);
} else {
result = type.getNameOrType();
}
if (verbose) {
final int position = Token.descPosition(token);
final int length = Token.descLength(token);
result += " (" + position + ", " + length + ")";
}
return result;
}
/**
* String conversion of token
*
* @param source the source
* @param token the token
*
* @return token as string
*/
public static String toString(final Source source, final long token) {
return Token.toString(source, token, false);
}
/**
* String conversion of token - version without source given
*
* @param token the token
*
* @return token as string
*/
public static String toString(final long token) {
return Token.toString(null, token, false);
}
/**
* Static hash code computation function token
*
* @param token a token
*
* @return hash code for token
*/
public static int hashCode(final long token) {
return (int)(token ^ token >>> 32);
}
}