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package org.jruby.runtime.opto;

import org.jruby.RubyModule;
import org.jruby.runtime.builtin.IRubyObject;

/**
 * A tuple representing the data needed to verify a cached constant:
 * 
 * <li>The value of the constant</li>
 * <li>The generation of the constant's invalidator at the time of caching</li>
 * <li>The constant's invalidator</li>
 * <li>(Optional) the hashcode of the module form which the constant was cache</li>
 */
public class ConstantCache {
    public final IRubyObject value;
    public final Object generation;
    public final Invalidator invalidator;
    public final int targetHash;

    /**
     * Construct a new ConstantCache with the given elements.
     * 
     * @param value
     * @param generation
     * @param invalidator
     * @param targetHash 
     */
    public ConstantCache(IRubyObject value, Object generation, Invalidator invalidator, int targetHash) {
        this.value = value;
        this.generation = generation;
        this.invalidator = invalidator;
        this.targetHash = targetHash;
    }

    /**
     * Construct a new ConstantCache with the given elements.
     * 
     * @param value
     * @param generation
     * @param invalidator 
     */
    public ConstantCache(IRubyObject value, Object generation, Invalidator invalidator) {
        this(value, generation, invalidator, -1);
    }

    /**
     * Check if the given ConstantCache is non-null and valid, given the target module.
     * 
     * This method is static to ensure it is inlinable as trivially as possible.
     */
    public static boolean isCachedFrom(RubyModule target, ConstantCache cache) {
        return cache != null
                && cache.value != null
                && cache.generation == cache.invalidator.getData()
                && cache.targetHash == target.hashCode();
    }

    /**
     * Check if the given ConstantCache is non-null and valid.
     * 
     * This method is static to ensure it is inlinable as trivially as possible.
     */
    public static boolean isCached(ConstantCache cache) {
        return cache != null
                && cache.value != null
                && cache.generation == cache.invalidator.getData();
    }
}
