001 /*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements. See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership. The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the "License");
007 * you may not use this file except in compliance with the License.
008 * You may obtain a copy of the License at
009 *
010 * http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018 /*
019 * $Id: SlotAllocator.java 468649 2006-10-28 07:00:55Z minchau $
020 */
021
022 package org.apache.xalan.xsltc.compiler.util;
023
024 import org.apache.bcel.generic.LocalVariableGen;
025 import org.apache.bcel.generic.Type;
026
027 /**
028 * @author Jacek Ambroziak
029 */
030 final class SlotAllocator {
031
032 private int _firstAvailableSlot;
033 private int _size = 8;
034 private int _free = 0;
035 private int[] _slotsTaken = new int[_size];
036
037 public void initialize(LocalVariableGen[] vars) {
038 final int length = vars.length;
039 int slot = 0, size, index;
040
041 for (int i = 0; i < length; i++) {
042 size = vars[i].getType().getSize();
043 index = vars[i].getIndex();
044 slot = Math.max(slot, index + size);
045 }
046 _firstAvailableSlot = slot;
047 }
048
049 public int allocateSlot(Type type) {
050 final int size = type.getSize();
051 final int limit = _free;
052 int slot = _firstAvailableSlot, where = 0;
053
054 if (_free + size > _size) {
055 final int[] array = new int[_size *= 2];
056 for (int j = 0; j < limit; j++)
057 array[j] = _slotsTaken[j];
058 _slotsTaken = array;
059 }
060
061 while (where < limit) {
062 if (slot + size <= _slotsTaken[where]) {
063 // insert
064 for (int j = limit - 1; j >= where; j--)
065 _slotsTaken[j + size] = _slotsTaken[j];
066 break;
067 }
068 else {
069 slot = _slotsTaken[where++] + 1;
070 }
071 }
072
073 for (int j = 0; j < size; j++)
074 _slotsTaken[where + j] = slot + j;
075
076 _free += size;
077 return slot;
078 }
079
080 public void releaseSlot(LocalVariableGen lvg) {
081 final int size = lvg.getType().getSize();
082 final int slot = lvg.getIndex();
083 final int limit = _free;
084
085 for (int i = 0; i < limit; i++) {
086 if (_slotsTaken[i] == slot) {
087 int j = i + size;
088 while (j < limit) {
089 _slotsTaken[i++] = _slotsTaken[j++];
090 }
091 _free -= size;
092 return;
093 }
094 }
095 String state = "Variable slot allocation error"+
096 "(size="+size+", slot="+slot+", limit="+limit+")";
097 ErrorMsg err = new ErrorMsg(ErrorMsg.INTERNAL_ERR, state);
098 throw new Error(err.toString());
099 }
100 }