    001/*
    002 *  Licensed to the Apache Software Foundation (ASF) under one or more
    003 *  contributor license agreements.  See the NOTICE file distributed with
    004 *  this work for additional information regarding copyright ownership.
    005 *  The ASF licenses this file to You under the Apache License, Version 2.0
    006 *  (the "License"); you may not use this file except in compliance with
    007 *  the License.  You may obtain a copy of the License at
    008 *
    009 *     http://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 *  Unless required by applicable law or agreed to in writing, software
    012 *  distributed under the License is distributed on an "AS IS" BASIS,
    013 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 *  See the License for the specific language governing permissions and
    015 *  limitations under the License.
    016 */
    017package org.apache.commons.compress.harmony.unpack200.bytecode.forms;
    018
    019import java.util.Arrays;
    020
    021import org.apache.commons.compress.harmony.unpack200.bytecode.ByteCode;
    022import org.apache.commons.compress.harmony.unpack200.bytecode.OperandManager;
    023
    024public class LookupSwitchForm extends SwitchForm {
    025
    026    public LookupSwitchForm(final int opcode, final String name) {
    027        super(opcode, name);
    028    }
    029
    030    @Override
    031    public void setByteCodeOperands(final ByteCode byteCode, final OperandManager operandManager, final int codeLength) {
    032        final int caseCount = operandManager.nextCaseCount();
    033        final int defaultPc = operandManager.nextLabel();
    034        final int[] caseValues = new int[caseCount];
    035        Arrays.setAll(caseValues, i -> operandManager.nextCaseValues());
    036        final int[] casePcs = new int[caseCount];
    037        Arrays.setAll(casePcs, i -> operandManager.nextLabel());
    038
    039        final int[] labelsArray = new int[caseCount + 1];
    040        labelsArray[0] = defaultPc;
    041        System.arraycopy(casePcs, 0, labelsArray, 1, caseCount + 1 - 1);
    042        byteCode.setByteCodeTargets(labelsArray);
    043
    044        // All this gets dumped into the rewrite bytes of the
    045        // poor bytecode.
    046
    047        // Unlike most byte codes, the LookupSwitch is a
    048        // variable-sized bytecode. Because of this, the
    049        // rewrite array has to be defined here individually
    050        // for each bytecode, rather than in the ByteCodeForm
    051        // class.
    052
    053        // First, there's the bytecode. Then there are 0-3
    054        // bytes of padding so that the first (default)
    055        // label is on a 4-byte offset.
    056        final int padLength = 3 - codeLength % 4;
    057        final int rewriteSize = 1 + padLength + 4 // defaultbytes
    058                + 4 // npairs
    059                + 4 * caseValues.length + 4 * casePcs.length;
    060
    061        final int[] newRewrite = new int[rewriteSize];
    062        int rewriteIndex = 0;
    063
    064        // Fill in what we can now
    065        // opcode
    066        newRewrite[rewriteIndex++] = byteCode.getOpcode();
    067
    068        // padding
    069        for (int index = 0; index < padLength; index++) {
    070            newRewrite[rewriteIndex++] = 0;
    071        }
    072
    073        // defaultbyte
    074        // This gets overwritten by fixUpByteCodeTargets
    075        newRewrite[rewriteIndex++] = -1;
    076        newRewrite[rewriteIndex++] = -1;
    077        newRewrite[rewriteIndex++] = -1;
    078        newRewrite[rewriteIndex++] = -1;
    079
    080        // npairs
    081        final int npairsIndex = rewriteIndex;
    082        setRewrite4Bytes(caseValues.length, npairsIndex, newRewrite);
    083        rewriteIndex += 4;
    084
    085        // match-offset pairs
    086        // The caseValues aren't overwritten, but the
    087        // casePcs will get overwritten by fixUpByteCodeTargets
    088        for (final int caseValue : caseValues) {
    089            // match
    090            setRewrite4Bytes(caseValue, rewriteIndex, newRewrite);
    091            rewriteIndex += 4;
    092            // offset
    093            newRewrite[rewriteIndex++] = -1;
    094            newRewrite[rewriteIndex++] = -1;
    095            newRewrite[rewriteIndex++] = -1;
    096            newRewrite[rewriteIndex++] = -1;
    097        }
    098        byteCode.setRewrite(newRewrite);
    099    }
    100}