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C-Struct like features for Java 6+ to improve performance.

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/*
 * Copyright (C) 2015 SoftIndex LLC.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package net.wpm.codegen;

import org.objectweb.asm.Label;
import org.objectweb.asm.Type;
import org.objectweb.asm.commons.GeneratorAdapter;

import net.wpm.codegen.Context;
import net.wpm.codegen.Expression;
import net.wpm.codegen.ExpressionCmpNull;
import net.wpm.codegen.PredicateDef;

public class ExpressionCmpNull implements PredicateDef {
	private final Expression field;

	ExpressionCmpNull(Expression field) {
		this.field = field;
	}

	@Override
	public Type type(Context ctx) {
		return Type.BOOLEAN_TYPE;
	}

	@Override
	public Type load(Context ctx) {
		GeneratorAdapter g = ctx.getGeneratorAdapter();

		Label labelNull = new Label();
		Label labelExit = new Label();

		field.load(ctx);
		g.ifNull(labelNull);
		g.push(false);
		g.goTo(labelExit);

		g.mark(labelNull);
		g.push(true);

		g.mark(labelExit);

		return Type.BOOLEAN_TYPE;
	}

	@Override
	public boolean equals(Object o) {
		if (this == o) return true;
		if (o == null || getClass() != o.getClass()) return false;

		ExpressionCmpNull that = (ExpressionCmpNull) o;

		return !(field != null ? !field.equals(that.field) : that.field != null);

	}

	@Override
	public int hashCode() {
		return field != null ? field.hashCode() : 0;
	}
}