org.openjdk.jmc.common.item.CachingAccessor Maven / Gradle / Ivy

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package org.openjdk.jmc.common.item;

import java.util.HashMap;
import java.util.Map;

/**
 * An accessor that can be used for multiple types. It keeps a cache of accessors for the types of
 * the items that {@link #getMember} is called with.
 * 
 * Note that this class is not thread safe.
 *
 * @param 
 *            the type of member values returned by this accessor
 */
class CachingAccessor implements IMemberAccessor {

	private final IAccessorFactory attribute;
	private final Map, IMemberAccessor> fieldsToMerge = new HashMap<>();

	private IType lastType;
	private IMemberAccessor lastField;

	CachingAccessor(IAccessorFactory attribute) {
		this.attribute = attribute;
	}

	@Override
	public T getMember(IItem inObject) {
		if (inObject != null) {
			if (lastType != inObject.getType()) {
				lastType = ItemToolkit.getItemType(inObject);
				lastField = fieldsToMerge.get(lastType);
				if (lastField == null) {
					if (!fieldsToMerge.containsKey(lastType)) {
						lastField = attribute.getAccessor(lastType);
						fieldsToMerge.put(lastType, lastField);
					}
				}
			}
			return lastField == null ? null : lastField.getMember(inObject);
		}
		return null;
	}
}