src/main/java/org/luaj/vm3/UpValue.java

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package org.luaj.vm3;

/** Upvalue used with Closure formulation
 * <p>
 * @see LuaClosure
 * @see Prototype
 */
public final class UpValue {

	LuaValue[] array; // initially the stack, becomes a holder 
	int index;

	/**
	 *  Create an upvalue relative to a stack
	 * @param stack the stack
	 * @param index the index on the stack for the upvalue
	 */
	public UpValue(LuaValue[] stack, int index) {
		this.array = stack;
		this.index = index;
	}

	public String toString() {
		return index + "/" + array.length + " " + array[index];
	}

	/** 
	 * Convert this upvalue to a Java String
	 * @return the Java String for this upvalue.
	 * @see LuaValue#tojstring()
	 */
	public String tojstring() {
		return array[index].tojstring();
	}

	/**
	 * Get the value of the upvalue
	 * @return the {@link LuaValue} for this upvalue
	 */
	public final LuaValue getValue() {
		return array[index];
	}

	/**
	 * Set the value of the upvalue
	 * @param the {@link LuaValue} to set it to
	 */
	public final void setValue(LuaValue value) {
		array[index] = value;
	}

	/**
	 * Close this upvalue so it is no longer on the stack
	 */
	public final void close() {
		LuaValue[] old = array;
		array = new LuaValue[] { old[index] };
		old[index] = null;
		index = 0;
	}
}