ModifierContributor.java

package net.bytebuddy.description.modifier;

import lombok.EqualsAndHashCode;
import org.objectweb.asm.Opcodes;

import java.util.Arrays;
import java.util.Collection;

/**
 * An element that describes a type modifier as described in the
 * <a href="http://docs.oracle.com/javase/specs/jvms/se7/html/jvms-4.html">JVMS</a>.
 * <p> </p>
 * This allows for a more expressive and type safe alternative of defining a type's or type member's modifiers.
 * However, note that modifier's that apply competing modifiers (such as {@code private} and {@code protected}
 * should not be combined and will result in invalid types. An exception is thrown when built-in modifiers that
 * cannot be combined are used together.
 */
public interface ModifierContributor {

    /**
     * The empty modifier.
     */
    int EMPTY_MASK = 0;

    /**
     * Returns the mask of this modifier.
     *
     * @return The modifier mask that is to be applied to the target type or type member.
     */
    int getMask();

    /**
     * Returns the entire range of modifiers that address this contributor's property.
     *
     * @return The range of this contributor's property.
     */
    int getRange();

    /**
     * Determines if this is the default modifier.
     *
     * @return {@code true} if this contributor represents the default modifier.
     */
    boolean isDefault();

    /**
     * A marker interface for modifiers that can be applied to types.
     */
    interface ForType extends ModifierContributor {

        /**
         * A mask for all legal modifiers of a Java type.
         */
        int MASK = Opcodes.ACC_PUBLIC | Opcodes.ACC_PROTECTED | Opcodes.ACC_PRIVATE | Opcodes.ACC_SYNTHETIC
                | Opcodes.ACC_ABSTRACT | Opcodes.ACC_INTERFACE | Opcodes.ACC_ANNOTATION | Opcodes.ACC_DEPRECATED
                | Opcodes.ACC_ENUM | Opcodes.ACC_FINAL | Opcodes.ACC_STATIC;
    }

    /**
     * A marker interface for modifiers that can be applied to fields.
     */
    interface ForField extends ModifierContributor {

        /**
         * A mask for all legal modifiers of a Java field.
         */
        int MASK = Opcodes.ACC_PUBLIC | Opcodes.ACC_PROTECTED | Opcodes.ACC_PRIVATE | Opcodes.ACC_SYNTHETIC
                | Opcodes.ACC_DEPRECATED | Opcodes.ACC_ENUM | Opcodes.ACC_FINAL | Opcodes.ACC_STATIC
                | Opcodes.ACC_SYNTHETIC | Opcodes.ACC_TRANSIENT | Opcodes.ACC_VOLATILE;
    }

    /**
     * A marker interface for modifiers that can be applied to methods.
     */
    interface ForMethod extends ModifierContributor {

        /**
         * A mask for all legal modifiers of a Java method.
         */
        int MASK = Opcodes.ACC_PUBLIC | Opcodes.ACC_PROTECTED | Opcodes.ACC_PRIVATE | Opcodes.ACC_SYNTHETIC
                | Opcodes.ACC_BRIDGE | Opcodes.ACC_FINAL | Opcodes.ACC_NATIVE | Opcodes.ACC_ABSTRACT
                | Opcodes.ACC_STATIC | Opcodes.ACC_STRICT | Opcodes.ACC_SYNCHRONIZED | Opcodes.ACC_SYNTHETIC
                | Opcodes.ACC_VARARGS;
    }

    /**
     * A marker interface for modifiers that can be applied to method parameters.
     */
    interface ForParameter extends ModifierContributor {

        /**
         * A mask for all legal modifiers of a Java parameter.
         */
        int MASK = Opcodes.ACC_MANDATED | Opcodes.ACC_FINAL | Opcodes.ACC_SYNTHETIC;

    }

    /**
     * A resolver for Java modifiers represented by {@link ModifierContributor}s.
     *
     * @param <T> The type of the {@link ModifierContributor}s being resolved.
     */
    @EqualsAndHashCode
    class Resolver<T extends ModifierContributor> {

        /**
         * The modifier contributors to resolve.
         */
        private final Collection<? extends T> modifierContributors;

        /**
         * Creates a new resolver.
         *
         * @param modifierContributors The modifier contributors to resolve.
         */
        protected Resolver(Collection<? extends T> modifierContributors) {
            this.modifierContributors = modifierContributors;
        }

        /**
         * Creates a new resolver for modifier contributors to a type.
         *
         * @param modifierContributor The modifier contributors to resolve.
         * @return A resolver for the provided modifier contributors.
         */
        public static Resolver<ForType> of(ForType... modifierContributor) {
            return of(Arrays.asList(modifierContributor));
        }

        /**
         * Creates a new resolver for modifier contributors to a field.
         *
         * @param modifierContributor The modifier contributors to resolve.
         * @return A resolver for the provided modifier contributors.
         */
        public static Resolver<ForField> of(ForField... modifierContributor) {
            return of(Arrays.asList(modifierContributor));
        }

        /**
         * Creates a new resolver for modifier contributors to a method.
         *
         * @param modifierContributor The modifier contributors to resolve.
         * @return A resolver for the provided modifier contributors.
         */
        public static Resolver<ForMethod> of(ForMethod... modifierContributor) {
            return of(Arrays.asList(modifierContributor));
        }

        /**
         * Creates a new resolver for modifier contributors to a parameter.
         *
         * @param modifierContributor The modifier contributors to resolve.
         * @return A resolver for the provided modifier contributors.
         */
        public static Resolver<ForParameter> of(ForParameter... modifierContributor) {
            return Resolver.of(Arrays.asList(modifierContributor));
        }

        /**
         * Creates a new resolver for any modifier contributor of a given type.
         *
         * @param modifierContributors The modifier contributors to resolve.
         * @param <S>                  The modifier contributors type.
         * @return A resolver for the provided modifier contributors.
         */
        public static <S extends ModifierContributor> Resolver<S> of(Collection<? extends S> modifierContributors) {
            return new Resolver<S>(modifierContributors);
        }

        /**
         * Resolves the modifier contributors based on a zero modifier.
         *
         * @return The resolved modifiers.
         */
        public int resolve() {
            return resolve(EMPTY_MASK);
        }

        /**
         * Resolves the modifier contributors based on a given modifier.
         *
         * @param modifiers The base modifiers.
         * @return The resolved modifiers.
         */
        public int resolve(int modifiers) {
            for (T modifierContributor : modifierContributors) {
                modifiers = (modifiers & ~modifierContributor.getRange()) | modifierContributor.getMask();
            }
            return modifiers;
        }
    }
}