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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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package java.lang.invoke;

import java.util.*;

import jdk.internal.vm.annotation.Stable;

import static java.lang.invoke.MethodHandleStatics.rangeCheck1;

import static java.lang.invoke.MethodHandleStatics.rangeCheck2;

/** Utility class for implementing ConstantGroup. */

/*non-public*/

abstract class AbstractConstantGroup implements ConstantGroup {

    /** The size of this constant group, set permanently by the constructor. */

    protected final int size;

    /** The constructor requires the size of the constant group being represented.

     * @param size the size of this constant group, set permanently by the constructor

     */

    AbstractConstantGroup(int size) {

        this.size = size;

    }

    @Override public final int size() {

        return size;

    }

    public abstract Object get(int index) throws LinkageError;

    public abstract Object get(int index, Object ifNotPresent);

    public abstract boolean isPresent(int index);

    // Do not override equals or hashCode, since this type is stateful.

    /**

     * Produce a string using the non-resolving list view,

     * where unresolved elements are presented as asterisks.

     * @return {@code this.asList("*").toString()}

     */

    @Override public String toString() {

        return asList("*").toString();

    }

    static class AsIterator implements Iterator<Object> {

        private final ConstantGroup self;

        private final int end;

        private final boolean resolving;

        private final Object ifNotPresent;

        // Mutable state:

        private int index;

        private AsIterator(ConstantGroup self, int start, int end,

                         boolean resolving, Object ifNotPresent) {

            this.self = self;

            this.end = end;

            this.index = start;

            this.resolving = resolving;

            this.ifNotPresent = ifNotPresent;

        }

        AsIterator(ConstantGroup self, int start, int end) {

            this(self, start, end, true, null);

        }

        AsIterator(ConstantGroup self, int start, int end,

                 Object ifNotPresent) {

            this(self, start, end, false, ifNotPresent);

        }

        @Override

        public boolean hasNext() {

            return index < end;

        }

        @Override

        public Object next() {

            int i = bumpIndex();

            if (resolving)

                return self.get(i);

            else

                return self.get(i, ifNotPresent);

        }

        private int bumpIndex() {

            int i = index;

            if (i >= end)  throw new NoSuchElementException();

            index = i+1;

            return i;

        }

    }

    static class SubGroup extends AbstractConstantGroup {

        private final ConstantGroup self;  // the real CG

        private final int offset;  // offset within myself

        SubGroup(ConstantGroup self, int start, int end) {

            super(end - start);

            this.self = self;

            this.offset = start;

            rangeCheck2(start, end, size);

        }

        private int mapIndex(int index) {

            return rangeCheck1(index, size) + offset;

        }

        @Override

        public Object get(int index) {

            return self.get(mapIndex(index));

        }

        @Override

        public Object get(int index, Object ifNotPresent) {

            return self.get(mapIndex(index), ifNotPresent);

        }

        @Override

        public boolean isPresent(int index) {

            return self.isPresent(mapIndex(index));

        }

        @Override

        public ConstantGroup subGroup(int start, int end) {

            rangeCheck2(start, end, size);

            return new SubGroup(self, offset + start, offset + end);

        }

        @Override

        public List<Object> asList() {

            return new AsList(self, offset, offset + size);

        }

        @Override

        public List<Object> asList(Object ifNotPresent) {

            return new AsList(self, offset, offset + size, ifNotPresent);

        }

        @Override

        public int copyConstants(int start, int end,

                                  Object[] buf, int pos) throws LinkageError {

            rangeCheck2(start, end, size);

            return self.copyConstants(offset + start, offset + end,

                                      buf, pos);

        }

        @Override

        public int copyConstants(int start, int end,

                                  Object[] buf, int pos,

                                  Object ifNotPresent) {

            rangeCheck2(start, end, size);

            return self.copyConstants(offset + start, offset + end,

                                      buf, pos, ifNotPresent);

        }

    }

    static class AsList extends AbstractList<Object> {

        private final ConstantGroup self;

        private final int size;

        private final int offset;

        private final boolean resolving;

        private final Object ifNotPresent;

        private AsList(ConstantGroup self, int start, int end,

                       boolean resolving, Object ifNotPresent) {

            this.self = self;

            this.size = end - start;

            this.offset = start;

            this.resolving = resolving;

            this.ifNotPresent = ifNotPresent;

            rangeCheck2(start, end, self.size());

        }

        AsList(ConstantGroup self, int start, int end) {

            this(self, start, end, true, null);

        }

        AsList(ConstantGroup self, int start, int end,

               Object ifNotPresent) {

            this(self, start, end, false, ifNotPresent);

        }

        private int mapIndex(int index) {

            return rangeCheck1(index, size) + offset;

        }

        @Override public final int size() {

            return size;

        }

        @Override public Object get(int index) {

            if (resolving)

                return self.get(mapIndex(index));

            else

                return self.get(mapIndex(index), ifNotPresent);

        }

        @Override

        public Iterator<Object> iterator() {

            if (resolving)

                return new AsIterator(self, offset, offset + size);

            else

                return new AsIterator(self, offset, offset + size, ifNotPresent);

        }

        @Override public List<Object> subList(int start, int end) {

            rangeCheck2(start, end, size);

            return new AsList(self, offset + start, offset + end,

                              resolving, ifNotPresent);

        }

        @Override public Object[] toArray() {

            return toArray(new Object[size]);

        }

        @Override public <T> T[] toArray(T[] a) {

            int pad = a.length - size;

            if (pad < 0) {

                pad = 0;

                a = Arrays.copyOf(a, size);

            }

            if (resolving)

                self.copyConstants(offset, offset + size, a, 0);

            else

                self.copyConstants(offset, offset + size, a, 0,

                                   ifNotPresent);

            if (pad > 0)  a[size] = null;

            return a;

        }

    }

    static abstract

    class WithCache extends AbstractConstantGroup {

        @Stable final Object[] cache;

        WithCache(int size) {

            super(size);

            // It is caller's responsibility to initialize the cache.

            // Initial contents are all-null, which means nothing is present.

            cache = new Object[size];

        }

        void initializeCache(List<Object> cacheContents, Object ifNotPresent) {

            // Replace ifNotPresent with NOT_PRESENT,

            // and null with RESOLVED_TO_NULL.

            // Then forget about the user-provided ifNotPresent.

            for (int i = 0; i < cache.length; i++) {

                Object x = cacheContents.get(i);

                if (x == ifNotPresent)

                    continue;  // leave the null in place

                if (x == null)

                    x = RESOLVED_TO_NULL;

                cache[i] = x;

            }

        }

        @Override public Object get(int i) {

            Object x = cache[i];

            // @Stable array must use null for sentinel

            if (x == null)  x = fillCache(i);

            return unwrapNull(x);

        }

        @Override public Object get(int i, Object ifNotAvailable) {

            Object x = cache[i];

            // @Stable array must use null for sentinel

            if (x == null)  return ifNotAvailable;

            return unwrapNull(x);

        }

        @Override

        public boolean isPresent(int i) {

            return cache[i] != null;

        }

        /** hook for local subclasses */

        Object fillCache(int i) {

            throw new NoSuchElementException("constant group does not contain element #"+i);

        }

        /// routines for mapping between null sentinel and true resolved null

        static Object wrapNull(Object x) {

            return x == null ? RESOLVED_TO_NULL : x;

        }

        static Object unwrapNull(Object x) {

            assert(x != null);

            return x == RESOLVED_TO_NULL ? null : x;

        }

        // secret sentinel for an actual null resolved value, in the cache

        static final Object RESOLVED_TO_NULL = new Object();

        // secret sentinel for a "hole" in the cache:

        static final Object NOT_PRESENT = new Object();

    }

    /** Skeleton implementation of BootstrapCallInfo. */

    static

    class BSCIWithCache<T> extends WithCache implements BootstrapCallInfo<T> {

        private final MethodHandle bsm;

        private final String name;

        private final T type;

        @Override public String toString() {

            return bsm+"/"+name+":"+type+super.toString();

        }

        BSCIWithCache(MethodHandle bsm, String name, T type, int size) {

            super(size);

            this.type = type;

            this.bsm = bsm;

            this.name = name;

            assert(type instanceof Class || type instanceof MethodType);

        }

        @Override public MethodHandle bootstrapMethod() { return bsm; }

        @Override public String invocationName() { return name; }

        @Override public T invocationType() { return type; }

    }

}