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package org.jruby.runtime.ivars;

import com.headius.invokebinder.Binder;
import org.jruby.RubyBasicObject;
import org.jruby.RubyClass;
import org.jruby.runtime.Helpers;
import org.jruby.specialized.RubyObjectSpecializer;

import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;

A variable accessor that accesses a field directly;
/**
 * A variable accessor that accesses a field directly;
 */
public class FieldVariableAccessor extends VariableAccessor {
    private final MethodHandle getter;
    private final MethodHandle setter;
    
    
Construct a new FieldVariableAccessor for the given "real" class,
variable name, variable index, class ID, and field offset
Params:
realClass – the "real" class
name – the variable's name
index – the variable's index
classId – the class's ID
getter – the getter handle for the field
setter – the setter handle for the field/**
     * Construct a new FieldVariableAccessor for the given "real" class,
     * variable name, variable index, class ID, and field offset
     * 
     * @param realClass the "real" class
     * @param name the variable's name
     * @param index the variable's index
     * @param classId the class's ID
     * @param getter the getter handle for the field
     * @param setter the setter handle for the field
     */
    public FieldVariableAccessor(RubyClass realClass, String name, int index, int classId, MethodHandle getter, MethodHandle setter) {
        super(realClass, name, index, classId);

        this.getter = getter;

        // mix frozen check into setter
        setter = MethodHandles.foldArguments(setter, ENSURE_SETTABLE.asType(setter.type()));
        
        this.setter = setter;
    }

    public MethodHandle getGetter() {
        return getter;
    }

    public MethodHandle getSetter() {
        return setter;
    }

    
Retrieve the variable's value from the given object.
Params:
object – the object from which to retrieve this variable
Returns:
the variable's value/**
     * Retrieve the variable's value from the given object.
     *
     * @param object the object from which to retrieve this variable
     * @return the variable's value
     */
    public Object get(Object object) {
        try {
            return getter.invoke(object);
        } catch (Throwable t) {
            Helpers.throwException(t);
            return null;
        }
    }

    
Set this variable into the given object using Unsafe to ensure
safe updating of the variable table.
Params:
object – the object into which to set this variable
value – the variable's value/**
     * Set this variable into the given object using Unsafe to ensure
     * safe updating of the variable table.
     *
     * @param object the object into which to set this variable
     * @param value the variable's value
     */
    public void set(Object object, Object value) {
        try {
            setter.invoke(object, value);
        } catch (Throwable t) {
            Helpers.throwException(t);
        }
    }

    private static final MethodHandle ENSURE_SETTABLE = Binder
            .from(Object.class, Object.class, Object.class)
            .dropLast()
            .cast(void.class, RubyBasicObject.class)
            .invokeVirtualQuiet(RubyObjectSpecializer.LOOKUP, "ensureInstanceVariablesSettable");
}