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/*******************************************************************************
* Copyright (c) 2009 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 org.eclipse.equinox.p2.metadata.expression.IEvaluationContext;
import org.eclipse.equinox.p2.metadata.expression.IExpression;
/**
* Highly specialized evaluation contexts optimized for misc purposes
*/
public class EvaluationContext implements IEvaluationContext {
public static class Parameters extends EvaluationContext {
private static final Object[] noParameters = new Object[0];
private final Object[] parameters;
public Parameters(IEvaluationContext parentContext, Object[] parameters) {
super(parentContext);
this.parameters = parameters == null ? noParameters : parameters;
}
public Object getParameter(int position) {
return position >= 0 && position < parameters.length ? parameters[position] : super.getParameter(position);
}
}
public static class SingleVariableContext implements IEvaluationContext {
private final IEvaluationContext parentContext;
private Object value;
private final IExpression variable;
public SingleVariableContext(IEvaluationContext parentContext, IExpression variable) {
this.parentContext = parentContext;
this.variable = variable;
}
public Object getParameter(int position) {
return parentContext.getParameter(position);
}
public Object getValue(IExpression var) {
return variable == var ? value : parentContext.getValue(var);
}
public void setValue(IExpression var, Object val) {
if (variable == var)
value = val;
else
parentContext.setValue(var, val);
}
}
static class MultiVariableContext implements IEvaluationContext {
private final IEvaluationContext parentContext;
private final Object[] values;
public MultiVariableContext(IEvaluationContext parentContext, IExpression[] variables) {
this.parentContext = parentContext;
values = new Object[variables.length * 2];
for (int idx = 0, ndx = 0; ndx < variables.length; ++ndx, idx += 2)
values[idx] = variables[ndx];
}
public Object getParameter(int position) {
return parentContext.getParameter(position);
}
public Object getValue(IExpression variable) {
for (int idx = 0; idx < values.length; ++idx)
if (values[idx++] == variable)
return values[idx];
return parentContext.getValue(variable);
}
public void setValue(IExpression variable, Object value) {
for (int idx = 0; idx < values.length; ++idx)
if (values[idx++] == variable) {
values[idx] = value;
return;
}
parentContext.setValue(variable, value);
}
}
public static final EvaluationContext INSTANCE = new EvaluationContext(null);
public static IEvaluationContext create() {
return INSTANCE;
}
public static IEvaluationContext create(IEvaluationContext parent, IExpression variable) {
return new SingleVariableContext(parent, variable);
}
public static IEvaluationContext create(IEvaluationContext parent, IExpression[] variables) {
return variables.length == 1 ? new SingleVariableContext(parent, variables[0]) : new MultiVariableContext(parent, variables);
}
public static IEvaluationContext create(IEvaluationContext parent, Object[] parameters) {
return new Parameters(parent, parameters);
}
public static IEvaluationContext create(IExpression variable) {
return new SingleVariableContext(null, variable);
}
public static IEvaluationContext create(IExpression[] variables) {
if (variables == null || variables.length == 0)
return INSTANCE;
return variables.length == 1 ? create(variables[0]) : new MultiVariableContext(INSTANCE, variables);
}
public static IEvaluationContext create(Object[] parameters, IExpression variable) {
return parameters == null || parameters.length == 0 ? create(variable) : new SingleVariableContext(new Parameters(null, parameters), variable);
}
public static IEvaluationContext create(Object[] parameters, IExpression[] variables) {
if (parameters == null || parameters.length == 0)
return create(variables);
Parameters pctx = new Parameters(null, parameters);
if (variables == null || variables.length == 0)
return pctx;
return create(pctx, variables);
}
protected EvaluationContext(IEvaluationContext parentContext) {
this.parentContext = parentContext;
}
private final IEvaluationContext parentContext;
public Object getParameter(int position) {
if (parentContext == null)
throw new IllegalArgumentException("No such parameter: $" + position); //$NON-NLS-1$
return parentContext.getParameter(position);
}
public Object getValue(IExpression variable) {
if (parentContext == null)
throw new IllegalArgumentException("No such variable: " + variable); //$NON-NLS-1$
return parentContext.getValue(variable);
}
public void setValue(IExpression variable, Object value) {
if (parentContext == null)
throw new IllegalArgumentException("No such variable: " + variable); //$NON-NLS-1$
parentContext.setValue(variable, value);
}
}
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