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/* gnu.classpath.tools.gjdoc.expr.Evaluator
Copyright (C) 2004 Free Software Foundation, Inc.
This file is part of GNU Classpath.
GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
GNU Classpath 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 for more details.
You should have received a copy of the GNU General Public License
along with GNU Classpath; see the file COPYING. If not, write to the
Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA. */
package gnu.classpath.tools.gjdoc.expr;
import java.io.StringReader;
import java.math.BigInteger;
import antlr.RecognitionException;
import antlr.TokenStreamException;
import java.util.Set;
public class Evaluator
{
/**
* Try to evaluate the given Java expression in the context of the
* given environment.
*
* @param expression the Java expression to evaluate. The
* expression string must not include a terminating semicolon.
*
* @param source the FieldDoc (part of) whose constant field value
* expression is being evaluated. Used to prevent circular
* references.
*
* @param environment callback hook used by the Evaluator to query
* the value of static fields referenced in the expression.
*
* @return a Java object representing the value of the expression,
* or <code>null</code> if the expression evaluates to
* <code>null</code>.
*
* @throws IllegalExpressionException if the expression is
* invalid, uses unsupported syntax constructs (e.g. method calls,
* array access) or references unknown static fields.
*/
public static Object evaluate(String expression,
Set visitedFields,
EvaluatorEnvironment environment)
throws IllegalExpressionException
{
try {
JavaLexer lexer = new JavaLexer(new StringReader(expression));
JavaRecognizer recognizer = new JavaRecognizer(lexer);
Expression e = recognizer.expression();
ConstantExpression value = e.evaluate(new Context(environment, visitedFields));
return value.asObject();
}
catch (RecognitionException e) {
throw new IllegalExpressionException(e);
}
catch (TokenStreamException e) {
throw new IllegalExpressionException(e);
}
}
static int parseInt(String stringValue)
{
int base = 10;
if (stringValue.startsWith("0x")) {
base = 16;
stringValue = stringValue.substring(2);
}
else if (stringValue.length() > 1 && stringValue.startsWith("0")) {
base = 8;
stringValue = stringValue.substring(1);
}
while (stringValue.length() > 1 && stringValue.startsWith("0")) {
stringValue = stringValue.substring(1);
}
if (10 == base) {
return Integer.parseInt(stringValue);
}
else {
long result = Long.parseLong(stringValue, base);
if (result > Integer.MAX_VALUE) {
result -= 0x100000000L;
}
if (result > Integer.MAX_VALUE) {
throw new NumberFormatException(result + " > " + Integer.MAX_VALUE);
}
else if (result < Integer.MIN_VALUE) {
throw new NumberFormatException(result + " < " + Integer.MIN_VALUE);
}
else {
return (int)result;
}
}
}
static long parseLong(String stringValue)
{
int base = 10;
if (stringValue.startsWith("0x")) {
base = 16;
stringValue = stringValue.substring(2);
}
else if (stringValue.length() > 1 && stringValue.startsWith("0")) {
base = 8;
stringValue = stringValue.substring(1);
}
while (stringValue.length() > 1 && stringValue.startsWith("0")) {
stringValue = stringValue.substring(1);
}
BigInteger bigInt = new BigInteger(stringValue, base);
long result = bigInt.longValue();
return result;
}
}
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