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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, 2013, 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.SPECIAL;
import static org.openjdk.nashorn.internal.parser.TokenType.IDENT;
/**
* Fast lookup of operators and keywords.
*
*/
public final class TokenLookup {
/**
* Lookup table for tokens.
*/
private static final TokenType[] table;
/**
* Table base character.
*/
private static final int tableBase = ' ';
/**
* Table base character.
*/
private static final int tableLimit = '~';
/**
* Table size.
*/
private static final int tableLength = tableLimit - tableBase + 1;
static {
// Construct the table.
table = new TokenType[tableLength];
// For each token type.
for (final TokenType tokenType : TokenType.getValues()) {
// Get the name.
final String name = tokenType.getName();
// Filter tokens.
if (name == null) {
continue;
}
// Ignore null and special.
if (tokenType.getKind() != SPECIAL) {
// Get the first character of the name.
final char first = name.charAt(0);
// Translate that character into a table index.
final int index = first - tableBase;
assert index < tableLength : "Token name does not fit lookup table";
// Get the length of the token so that the longest come first.
final int length = tokenType.getLength();
// Prepare for table insert.
TokenType prev = null;
TokenType next = table[index];
// Find the right spot in the table.
while(next != null && next.getLength() > length) {
prev = next;
next = next.getNext();
}
// Insert in table.
tokenType.setNext(next);
if (prev == null) {
table[index] = tokenType;
} else {
prev.setNext(tokenType);
}
}
}
}
private TokenLookup() {
}
/**
* Lookup keyword.
*
* @param content parse content char array
* @param position index of position to start looking
* @param length max length to scan
*
* @return token type for keyword
*/
public static TokenType lookupKeyword(final char[] content, final int position, final int length) {
assert table != null : "Token lookup table is not initialized";
// First character of keyword.
final char first = content[position];
// Must be lower case character.
if ('a' <= first && first <= 'z') {
// Convert to table index.
final int index = first - tableBase;
// Get first bucket entry.
TokenType tokenType = table[index];
// Search bucket list.
while (tokenType != null) {
final int tokenLength = tokenType.getLength();
// if we have a length match maybe a keyword.
if (tokenLength == length) {
// Do an exact compare of string.
final String name = tokenType.getName();
int i;
for (i = 0; i < length; i++) {
if (content[position + i] != name.charAt(i)) {
break;
}
}
if (i == length) {
// Found a match.
return tokenType;
}
} else if (tokenLength < length) {
// Rest of tokens are shorter.
break;
}
// Try next token.
tokenType = tokenType.getNext();
}
}
// Not found.
return IDENT;
}
/**
* Lookup operator.
*
* @param ch0 0th char in stream
* @param ch1 1st char in stream
* @param ch2 2nd char in stream
* @param ch3 3rd char in stream
*
* @return the token type for the operator
*/
public static TokenType lookupOperator(final char ch0, final char ch1, final char ch2, final char ch3) {
assert table != null : "Token lookup table is not initialized";
// Ignore keyword entries.
if (tableBase < ch0 && ch0 <= tableLimit && !('a' <= ch0 && ch0 <= 'z')) {
// Convert to index.
final int index = ch0 - tableBase;
// Get first bucket entry.
TokenType tokenType = table[index];
// Search bucket list.
while (tokenType != null) {
final String name = tokenType.getName();
switch (name.length()) {
case 1:
// One character entry.
return tokenType;
case 2:
// Two character entry.
if (name.charAt(1) == ch1) {
return tokenType;
}
break;
case 3:
// Three character entry.
if (name.charAt(1) == ch1 &&
name.charAt(2) == ch2) {
return tokenType;
}
break;
case 4:
// Four character entry.
if (name.charAt(1) == ch1 &&
name.charAt(2) == ch2 &&
name.charAt(3) == ch3) {
return tokenType;
}
break;
default:
break;
}
// Try next token.
tokenType = tokenType.getNext();
}
}
// Not found.
return null;
}
}