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/*

 * Licensed to the Apache Software Foundation (ASF) under one or more

 * contributor license agreements.  See the NOTICE file distributed with

 * this work for additional information regarding copyright ownership.

 * The ASF licenses this file to You 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

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package com.sun.org.apache.bcel.internal.generic;

/**

 * SWITCH - Branch depending on int value, generates either LOOKUPSWITCH or

 * TABLESWITCH instruction, depending on whether the match values (int[]) can be

 * sorted with no gaps between the numbers.

 *

 * @version $Id: SWITCH.java 1749603 2016-06-21 20:50:19Z ggregory $

 */

public final class SWITCH implements CompoundInstruction {

    private int[] match;

    private InstructionHandle[] targets;

    private Select instruction;

    private int match_length;

    /**

     * Template for switch() constructs. If the match array can be

     * sorted in ascending order with gaps no larger than max_gap

     * between the numbers, a TABLESWITCH instruction is generated, and

     * a LOOKUPSWITCH otherwise. The former may be more efficient, but

     * needs more space.

     *

     * Note, that the key array always will be sorted, though we leave

     * the original arrays unaltered.

     *

     * @param match array of match values (case 2: ... case 7: ..., etc.)

     * @param targets the instructions to be branched to for each case

     * @param target the default target

     * @param max_gap maximum gap that may between case branches

     */

    public SWITCH(final int[] match, final InstructionHandle[] targets, final InstructionHandle target, final int max_gap) {

        this.match = match.clone();

        this.targets = targets.clone();

        if ((match_length = match.length) < 2) {

            instruction = new TABLESWITCH(match, targets, target);

        } else {

            sort(0, match_length - 1);

            if (matchIsOrdered(max_gap)) {

                fillup(max_gap, target);

                instruction = new TABLESWITCH(this.match, this.targets, target);

            } else {

                instruction = new LOOKUPSWITCH(this.match, this.targets, target);

            }

        }

    }

    public SWITCH(final int[] match, final InstructionHandle[] targets, final InstructionHandle target) {

        this(match, targets, target, 1);

    }

    private void fillup( final int max_gap, final InstructionHandle target ) {

        final int max_size = match_length + match_length * max_gap;

        final int[] m_vec = new int[max_size];

        final InstructionHandle[] t_vec = new InstructionHandle[max_size];

        int count = 1;

        m_vec[0] = match[0];

        t_vec[0] = targets[0];

        for (int i = 1; i < match_length; i++) {

            final int prev = match[i - 1];

            final int gap = match[i] - prev;

            for (int j = 1; j < gap; j++) {

                m_vec[count] = prev + j;

                t_vec[count] = target;

                count++;

            }

            m_vec[count] = match[i];

            t_vec[count] = targets[i];

            count++;

        }

        match = new int[count];

        targets = new InstructionHandle[count];

        System.arraycopy(m_vec, 0, match, 0, count);

        System.arraycopy(t_vec, 0, targets, 0, count);

    }

    /**

     * Sort match and targets array with QuickSort.

     */

    private void sort( final int l, final int r ) {

        int i = l;

        int j = r;

        int h;

        final int m = match[(l + r) / 2];

        InstructionHandle h2;

        do {

            while (match[i] < m) {

                i++;

            }

            while (m < match[j]) {

                j--;

            }

            if (i <= j) {

                h = match[i];

                match[i] = match[j];

                match[j] = h; // Swap elements

                h2 = targets[i];

                targets[i] = targets[j];

                targets[j] = h2; // Swap instructions, too

                i++;

                j--;

            }

        } while (i <= j);

        if (l < j) {

            sort(l, j);

        }

        if (i < r) {

            sort(i, r);

        }

    }

    /**

     * @return match is sorted in ascending order with no gap bigger than max_gap?

     */

    private boolean matchIsOrdered( final int max_gap ) {

        for (int i = 1; i < match_length; i++) {

            if (match[i] - match[i - 1] > max_gap) {

                return false;

            }

        }

        return true;

    }

    @Override

    public final InstructionList getInstructionList() {

        return new InstructionList(instruction);

    }

    public final Instruction getInstruction() {

        return instruction;

    }

}