/*
* @(#)NOfFunction.java
*
* Copyright 2003-2005 Sun Microsystems, Inc. All Rights Reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistribution of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* 2. Redistribution in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* Neither the name of Sun Microsystems, Inc. or the names of contributors may
* be used to endorse or promote products derived from this software without
* specific prior written permission.
*
* This software is provided "AS IS," without a warranty of any kind. ALL
* EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING
* ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
* OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN MICROSYSTEMS, INC. ("SUN")
* AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE
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package com.sun.xacml.cond;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Set;
import com.sun.xacml.EvaluationCtx;
import com.sun.xacml.attr.BooleanAttribute;
import com.sun.xacml.attr.IntegerAttribute;
/**
* A class that implements the n-of function. It requires at least one argument. The first argument
* must be an integer and the rest of the arguments must be booleans. If the number of boolean
* arguments that evaluate to true is at least the value of the first argument, the function returns
* true. Otherwise, it returns false (or indeterminate, as described in the next paragraph.
* <p>
* This function evaluates the arguments one at a time, starting with the first one. As soon as the
* result of the function can be determined, evaluation stops and that result is returned. During
* this process, if any argument evaluates to indeterminate, an indeterminate result is returned.
*
* @since 1.0
* @author Steve Hanne
* @author Seth Proctor
*
* Adding generic type support by Christian Mueller (geotools)
*/
public class NOfFunction extends FunctionBase {
/**
* Standard identifier for the n-of function.
*/
public static final String NAME_N_OF = FUNCTION_NS + "n-of";
/**
* Creates a new <code>NOfFunction</code> object.
*
* @param functionName
* the standard XACML name of the function to be handled by this object, including
* the full namespace
*
* @throws IllegalArgumentException
* if the function is unknown
*/
public NOfFunction(String functionName) {
super(NAME_N_OF, 0, BooleanAttribute.identifier, false);
if (!functionName.equals(NAME_N_OF))
throw new IllegalArgumentException("unknown nOf function: " + functionName);
}
/**
* Returns a <code>Set</code> containing all the function identifiers supported by this class.
*
* @return a <code>Set</code> of <code>String</code>s
*/
public static Set<String> getSupportedIdentifiers() {
Set<String> set = new HashSet<String>();
set.add(NAME_N_OF);
return set;
}
/**
* Evaluate the function, using the specified parameters.
*
* @param inputs
* a <code>List</code> of <code>Evaluatable</code> objects representing the arguments
* passed to the function
* @param context
* an <code>EvaluationCtx</code> so that the <code>Evaluatable</code> objects can be
* evaluated
* @return an <code>EvaluationResult</code> representing the function's result
*/
public EvaluationResult evaluate(List<? extends Expression> inputs, EvaluationCtx context) {
// Evaluate the arguments one by one. As soon as we can return
// a result, do so. Return Indeterminate if any argument
// evaluated is indeterminate.
Iterator<? extends Expression> it = inputs.iterator();
Evaluatable eval = (Evaluatable) (it.next());
// Evaluate the first argument
EvaluationResult result = eval.evaluate(context);
if (result.indeterminate())
return result;
// if there were no problems, we know 'n'
long n = ((IntegerAttribute) (result.getAttributeValue())).getValue();
// If the number of trues needed is less than zero, report an error.
if (n < 0)
return makeProcessingError("First argument to " + getFunctionName()
+ " cannot be negative.");
// If the number of trues needed is zero, return true.
if (n == 0)
return EvaluationResult.getTrueInstance();
// make sure it's possible to find n true values
long remainingArgs = inputs.size() - 1;
if (n > remainingArgs)
return makeProcessingError("not enough arguments to n-of to " + "find " + n
+ " true values");
// loop through the inputs, trying to find at least n trues
while (remainingArgs >= n) {
eval = (Evaluatable) (it.next());
// evaluate the next argument
result = eval.evaluate(context);
if (result.indeterminate())
return result;
// get the next value, and see if it's true
if (((BooleanAttribute) (result.getAttributeValue())).getValue()) {
// we're one closer to our goal...see if we met it
if (--n == 0)
return EvaluationResult.getTrueInstance();
}
// we're still looking, but we've got one fewer arguments
remainingArgs--;
}
// if we got here then we didn't meet our quota
return EvaluationResult.getFalseInstance();
}
/**
*
*/
public void checkInputs(List<? extends Expression> inputs) throws IllegalArgumentException {
// check that none of the inputs is a bag
Object[] list = inputs.toArray();
for (int i = 0; i < list.length; i++)
if (((Evaluatable) (list[i])).returnsBag())
throw new IllegalArgumentException("n-of can't use bags");
// if we got here then there were no bags, so ask the other check
// method to finish the checking
checkInputsNoBag(inputs);
}
/**
*
*/
public void checkInputsNoBag(List<? extends Expression> inputs) throws IllegalArgumentException {
Object[] list = inputs.toArray();
// check that there is at least one arg
if (list.length == 0)
throw new IllegalArgumentException("n-of requires an argument");
// check that the first element is an Integer
Evaluatable eval = (Evaluatable) (list[0]);
if (!eval.getType().toString().equals(IntegerAttribute.identifier))
throw new IllegalArgumentException("first argument to n-of must" + " be an integer");
// now check that the rest of the args are booleans
for (int i = 1; i < list.length; i++) {
if (!((Evaluatable) (list[i])).getType().toString().equals(BooleanAttribute.identifier))
throw new IllegalArgumentException("invalid parameter in n-of"
+ ": expected boolean");
}
}
}