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/*
 * Copyright (C) 2008 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.dx.util;

import java.util.NoSuchElementException;

/**
 * A set of integers, represented by a bit set
 */
public class BitIntSet implements IntSet {

    /** also accessed in ListIntSet */
    int[] bits;

    /**
     * Constructs an instance.
     *
     * @param max the maximum value of ints in this set.
     */
    public BitIntSet(int max) {
        bits = Bits.makeBitSet(max);
    }

    /** {@inheritDoc} */
    @Override
    public void add(int value) {
        ensureCapacity(value);
        Bits.set(bits, value, true);
    }

    /**
     * Ensures that the bit set has the capacity to represent the given value.
     *
     * @param value {@code >= 0;} value to represent
     */
    private void ensureCapacity(int value) {
        if (value >= Bits.getMax(bits)) {
            int[] newBits = Bits.makeBitSet(
                    Math.max(value + 1, 2 * Bits.getMax(bits)));
            System.arraycopy(bits, 0, newBits, 0, bits.length);
            bits = newBits;
        }
    }

    /** {@inheritDoc} */
    @Override
    public void remove(int value) {
        if (value < Bits.getMax(bits)) {
            Bits.set(bits, value, false);
        }
    }

    /** {@inheritDoc} */
    @Override
    public boolean has(int value) {
        return (value < Bits.getMax(bits)) && Bits.get(bits, value);
    }

    /** {@inheritDoc} */
    @Override
    public void merge(IntSet other) {
        if (other instanceof BitIntSet) {
            BitIntSet o = (BitIntSet) other;
            ensureCapacity(Bits.getMax(o.bits) + 1);
            Bits.or(bits, o.bits);
        } else if (other instanceof ListIntSet) {
            ListIntSet o = (ListIntSet) other;
            int sz = o.ints.size();

            if (sz > 0) {
                ensureCapacity(o.ints.get(sz - 1));
            }
            for (int i = 0; i < o.ints.size(); i++) {
                Bits.set(bits, o.ints.get(i), true);
            }
        } else {
            IntIterator iter = other.iterator();
            while (iter.hasNext()) {
                add(iter.next());
            }
        }
    }

    /** {@inheritDoc} */
    @Override
    public int elements() {
        return Bits.bitCount(bits);
    }

    /** {@inheritDoc} */
    @Override
    public IntIterator iterator() {
        return new IntIterator() {
            private int idx = Bits.findFirst(bits, 0);

            /** {@inheritDoc} */
            @Override
            public boolean hasNext() {
                return idx >= 0;
            }

            /** {@inheritDoc} */
            @Override
            public int next() {
                if (!hasNext()) {
                    throw new NoSuchElementException();
                }

                int ret = idx;

                idx = Bits.findFirst(bits, idx+1);

                return ret;
            }
        };
    }

    /** {@inheritDoc} */
    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder();

        sb.append('{');

        boolean first = true;
        for (int i = Bits.findFirst(bits, 0)
                ; i >= 0
                ; i = Bits.findFirst(bits, i + 1)) {
            if (!first) {
                sb.append(", ");
            }
            first = false;
            sb.append(i);
        }

        sb.append('}');

        return sb.toString();
    }
}