VarArgSignature.java

package eu.stratosphere.util.reflect;

import java.lang.reflect.Array;

/**
 * Signature with a number of fixed arguments followed by a variable number of arguments of a specific type.
 * 
 * @author Arvid Heise
 */
public class VarArgSignature extends Signature {
	/**
	 * 
	 */
	private static final long serialVersionUID = -3584806055121932031L;

	/**
	 * Initializes VarArgSignature with the given argument types. In an actual invocation of the associated method, the
	 * may occur 0 to n instances of the last parameter type.
	 * 
	 * @param parameterTypes
	 *        the parameter types
	 */
	public VarArgSignature(final Class<?>[] parameterTypes) {
		super(parameterTypes);
	}

	@Override
	public int getDistance(final Signature actualSignature) {
		final Class<?>[] actualParamTypes = actualSignature.getParameterTypes();
		final int nonVarArgs = this.getParameterTypes().length - 1;
		if (nonVarArgs > actualParamTypes.length)
			return INCOMPATIBLE;

		int distance = 0;
		for (int index = 0; index < nonVarArgs; index++) {
			final int actualDistance =
				ReflectUtil.getDistance(this.getParameterTypes()[index], actualParamTypes[index]);
			if (actualDistance < 0)
				return INCOMPATIBLE;
			distance += actualDistance;
		}

		if (nonVarArgs < actualParamTypes.length)
			if (actualParamTypes.length > nonVarArgs + 1
				|| !this.getParameterTypes()[nonVarArgs].isAssignableFrom(actualParamTypes[nonVarArgs])) {
				final Class<?> varargType = this.getParameterTypes()[nonVarArgs].getComponentType();
				for (int index = nonVarArgs; index < actualParamTypes.length; index++) {
					final int actualDistance = ReflectUtil.getDistance(varargType, actualParamTypes[index]);
					if (actualDistance < 0)
						return INCOMPATIBLE;
					distance += actualDistance + 1;
				}
			}

		return distance;
	}

	@Override
	public Object[] adjustParameters(final Object[] params) {
		final Class<?>[] parameterTypes = this.getParameterTypes();
		final int varArgIndex = parameterTypes.length - 1;
		final int varArgCount = params.length - varArgIndex;

		if (varArgCount == 1 && parameterTypes[varArgIndex].isInstance(params[varArgIndex]))
			return params;

		final Object vararg = Array.newInstance(parameterTypes[varArgIndex].getComponentType(), varArgCount);
		for (int index = 0; index < varArgCount; index++)
			Array.set(vararg, index, params[varArgIndex + index]);

		final Object[] actualParams = new Object[parameterTypes.length];
		System.arraycopy(params, 0, actualParams, 0, varArgIndex);
		actualParams[varArgIndex] = vararg;
		return actualParams;
	}
}