/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.catalina.ssi;
/**
* Parses an expression string to return the individual tokens. This is patterned similar to the StreamTokenizer in the
* JDK but customized for SSI conditional expression parsing.
*/
public class ExpressionTokenizer {
public static final int TOKEN_STRING = 0;
public static final int TOKEN_AND = 1;
public static final int TOKEN_OR = 2;
public static final int TOKEN_NOT = 3;
public static final int TOKEN_EQ = 4;
public static final int TOKEN_NOT_EQ = 5;
public static final int TOKEN_RBRACE = 6;
public static final int TOKEN_LBRACE = 7;
public static final int TOKEN_GE = 8;
public static final int TOKEN_LE = 9;
public static final int TOKEN_GT = 10;
public static final int TOKEN_LT = 11;
public static final int TOKEN_END = 12;
private final char[] expr;
private String tokenVal = null;
private int index;
private final int length;
/**
* Creates a new parser for the specified expression.
*
* @param expr The expression
*/
public ExpressionTokenizer(String expr) {
this.expr = expr.trim().toCharArray();
this.length = this.expr.length;
}
/**
* @return <code>true</code> if there are more tokens.
*/
public boolean hasMoreTokens() {
return index < length;
}
/**
* @return the current index for error reporting purposes.
*/
public int getIndex() {
return index;
}
protected boolean isMetaChar(char c) {
return Character.isWhitespace(c) || c == '(' || c == ')' || c == '!' || c == '<' || c == '>' || c == '|' ||
c == '&' || c == '=';
}
/**
* @return the next token type and initializes any state variables accordingly.
*/
public int nextToken() {
// Skip any leading white space
while (index < length && Character.isWhitespace(expr[index])) {
index++;
}
// Clear the current token val
tokenVal = null;
if (index == length) {
return TOKEN_END; // End of string
}
int start = index;
char currentChar = expr[index];
char nextChar = (char) 0;
index++;
if (index < length) {
nextChar = expr[index];
}
// Check for a known token start
switch (currentChar) {
case '(':
return TOKEN_LBRACE;
case ')':
return TOKEN_RBRACE;
case '=':
return TOKEN_EQ;
case '!':
if (nextChar == '=') {
index++;
return TOKEN_NOT_EQ;
}
return TOKEN_NOT;
case '|':
if (nextChar == '|') {
index++;
return TOKEN_OR;
}
break;
case '&':
if (nextChar == '&') {
index++;
return TOKEN_AND;
}
break;
case '>':
if (nextChar == '=') {
index++;
return TOKEN_GE; // Greater than or equal
}
return TOKEN_GT; // Greater than
case '<':
if (nextChar == '=') {
index++;
return TOKEN_LE; // Less than or equal
}
return TOKEN_LT; // Less than
default:
// Otherwise it's a string
break;
}
int end;
if (currentChar == '"' || currentChar == '\'') {
// It's a quoted string and the end is the next unescaped quote
boolean escaped = false;
start++;
for (; index < length; index++) {
if (expr[index] == '\\' && !escaped) {
escaped = true;
continue;
}
if (expr[index] == currentChar && !escaped) {
break;
}
escaped = false;
}
end = index;
index++; // Skip the end quote
} else if (currentChar == '/') {
// It's a regular expression and the end is the next unescaped /
boolean escaped = false;
for (; index < length; index++) {
if (expr[index] == '\\' && !escaped) {
escaped = true;
continue;
}
if (expr[index] == currentChar && !escaped) {
break;
}
escaped = false;
}
end = ++index;
} else {
// End is the next whitespace character
for (; index < length; index++) {
if (isMetaChar(expr[index])) {
break;
}
}
end = index;
}
// Extract the string from the array
this.tokenVal = new String(expr, start, end - start);
return TOKEN_STRING;
}
/**
* @return the String value of the token if it was type TOKEN_STRING. Otherwise null is returned.
*/
public String getTokenValue() {
return tokenVal;
}
}