lubomir@221: /**
lubomir@221:  * Back 2 Browser Bytecode Translator
lubomir@221:  * Copyright (C) 2012 Jaroslav Tulach <jaroslav.tulach@apidesign.org>
lubomir@221:  *
lubomir@221:  * This program is free software: you can redistribute it and/or modify
lubomir@221:  * it under the terms of the GNU General Public License as published by
lubomir@221:  * the Free Software Foundation, version 2 of the License.
lubomir@221:  *
lubomir@221:  * This program is distributed in the hope that it will be useful,
lubomir@221:  * but WITHOUT ANY WARRANTY; without even the implied warranty of
lubomir@221:  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
lubomir@221:  * GNU General Public License for more details.
lubomir@221:  *
lubomir@221:  * You should have received a copy of the GNU General Public License
lubomir@221:  * along with this program. Look for COPYING file in the top folder.
lubomir@221:  * If not, see http://opensource.org/licenses/GPL-2.0.
lubomir@221:  */
lubomir@221: package org.apidesign.vm4brwsr;
lubomir@221: 
lubomir@221: public final class StackToVariableMapper {
lubomir@221:     private static final String VAR_NAME_PREFIX = "stack";
lubomir@221: 
lubomir@221:     private int stackSize;
lubomir@221:     private StringBuilder varNameBuilder;
lubomir@221: 
lubomir@221:     private int maxStackSize;
lubomir@221: 
lubomir@221:     public StackToVariableMapper() {
lubomir@221:         varNameBuilder = new StringBuilder(VAR_NAME_PREFIX);
lubomir@221:     }
lubomir@221: 
lubomir@221:     public void reset(final int newStackSize) {
lubomir@221:         stackSize = newStackSize;
lubomir@221:         if (maxStackSize < stackSize) {
lubomir@221:             maxStackSize = stackSize;
lubomir@221:         }
lubomir@221:     }
lubomir@221: 
lubomir@221:     public void push(final int numOfElements) {
lubomir@221:         stackSize += numOfElements;
lubomir@221:         if (maxStackSize < stackSize) {
lubomir@221:             maxStackSize = stackSize;
lubomir@221:         }
lubomir@221:     }
lubomir@221: 
lubomir@221:     public String push() {
lubomir@221:         push(1);
lubomir@221:         return get(0);
lubomir@221:     }
lubomir@221: 
lubomir@221:     public void pop(final int numOfElements) {
lubomir@221:         if (numOfElements > stackSize) {
lubomir@221:             throw new IllegalStateException("Stack underflow");
lubomir@221:         }
lubomir@221:         stackSize -= numOfElements;
lubomir@221:     }
lubomir@221: 
lubomir@221:     public String pop() {
lubomir@221:         final String variableName = get(0);
lubomir@221:         pop(1);
lubomir@221:         return variableName;
lubomir@221:     }
lubomir@221: 
lubomir@221:     public String get(final int indexFromTop) {
lubomir@221:         if (indexFromTop >= stackSize) {
lubomir@221:             throw new IllegalStateException("Stack underflow");
lubomir@221:         }
lubomir@221: 
lubomir@221:         return constructVariableName(stackSize - indexFromTop - 1);
lubomir@221:     }
lubomir@221: 
lubomir@221:     public String top() {
lubomir@221:         return get(0);
lubomir@221:     }
lubomir@221: 
lubomir@221:     public String bottom() {
lubomir@221:         if (stackSize == 0) {
lubomir@221:             throw new IllegalStateException("Stack underflow");
lubomir@221:         }
lubomir@221: 
lubomir@221:         return constructVariableName(0);
lubomir@221:     }
lubomir@221: 
lubomir@221:     public int getMaxStackSize() {
lubomir@221:         return maxStackSize;
lubomir@221:     }
lubomir@221: 
lubomir@221:     public String constructVariableName(final int index) {
lubomir@221:         varNameBuilder.setLength(VAR_NAME_PREFIX.length());
lubomir@221:         varNameBuilder.append(index);
lubomir@221:         return varNameBuilder.toString();
lubomir@221:     }
lubomir@221: }