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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.
*
* @version $Revision: 1.2 $
* @author Paul Speed
*/
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 char[] expr;
private String tokenVal = null;
private int index;
private int length;
/**
* Creates a new parser for the specified expression.
*/
public ExpressionTokenizer(String expr) {
this.expr = expr.trim().toCharArray();
this.length = this.expr.length;
}
/**
* Returns true if there are more tokens.
*/
public boolean hasMoreTokens() {
return index < length;
}
/**
* Returns 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 == '=';
}
/**
* Returns 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;
} else {
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
} else {
return TOKEN_GT; // Greater than
}
case '<' :
if (nextChar == '=') {
index++;
return TOKEN_LE; // Less than or equal
} else {
return TOKEN_LT; // Less than
}
default :
// Otherwise it's a string
break;
}
int end = index;
// If it's a quoted string then end is the next unescaped quote
if (currentChar == '"' || currentChar == '\'') {
char endChar = currentChar;
boolean escaped = false;
start++;
for (; index < length; index++) {
if (expr[index] == '\\' && !escaped) {
escaped = true;
continue;
}
if (expr[index] == endChar && !escaped) break;
escaped = false;
}
end = index;
index++; // Skip the end quote
} 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;
}
/**
* Returns the String value of the token if it was type TOKEN_STRING.
* Otherwise null is returned.
*/
public String getTokenValue() {
return tokenVal;
}
}