| /******************************************************************************* |
| * Copyright (c) 2009, 2010 Cloudsmith Inc. and others. |
| * All rights reserved. This program and the accompanying materials |
| * are made available under the terms of the Eclipse Public License v1.0 |
| * which accompanies this distribution, and is available at |
| * http://www.eclipse.org/legal/epl-v10.html |
| * |
| * Contributors: |
| * Cloudsmith Inc. - initial API and implementation |
| *******************************************************************************/ |
| package org.eclipse.equinox.internal.p2.metadata.expression; |
| |
| import java.util.Iterator; |
| import org.eclipse.equinox.p2.metadata.expression.IEvaluationContext; |
| |
| /** |
| * An expression that represents a function such as filter(<expr>) or version(<expr>) |
| */ |
| public abstract class Function extends NAry { |
| |
| private Object instance; |
| |
| protected Function(Expression[] operands) { |
| super(operands); |
| } |
| |
| boolean assertSingleArgumentClass(Object v) { |
| return true; |
| } |
| |
| Object createInstance(Object arg) { |
| throw new UnsupportedOperationException(); |
| } |
| |
| final Object createInstance(String arg) { |
| throw new UnsupportedOperationException(); |
| } |
| |
| public Object evaluate(IEvaluationContext context) { |
| if (instance != null) |
| return instance; |
| |
| Expression operand = operands[0]; |
| Object arg = operand.evaluate(context); |
| if (assertSingleArgumentClass(arg)) { |
| Object result = createInstance(arg); |
| if (operand instanceof Literal || operand instanceof Parameter) |
| // operand won't change over time so we can cache this instance. |
| instance = result; |
| return result; |
| } |
| String what = arg == null ? "null" : ("a " + arg.getClass().getName()); //$NON-NLS-1$ //$NON-NLS-2$ |
| throw new IllegalArgumentException("Cannot create a " + getOperator() + " from " + what); //$NON-NLS-1$ //$NON-NLS-2$ |
| } |
| |
| public Iterator<?> evaluateAsIterator(IEvaluationContext context) { |
| Object value = evaluate(context); |
| if (!(value instanceof Iterator<?>)) |
| value = RepeatableIterator.create(value); |
| return (Iterator<?>) value; |
| } |
| |
| public int getExpressionType() { |
| return TYPE_FUNCTION; |
| } |
| |
| public int getPriority() { |
| return PRIORITY_FUNCTION; |
| } |
| |
| public void toString(StringBuffer bld, Variable rootVariable) { |
| bld.append(getOperator()); |
| bld.append('('); |
| elementsToString(bld, rootVariable, operands); |
| bld.append(')'); |
| } |
| } |