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/*
* Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package jdk.nashorn.internal.codegen;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import jdk.nashorn.internal.ir.Symbol;
/**
* Tracks the variable area state.
*
*/
public final class Frame {
/** Previous frame. */
private Frame previous;
/** Current variables. */
private final ArrayList<Symbol> symbols;
/** Number of slots in previous frame. */
private int baseCount;
/** Number of slots in this frame. */
private int count;
/**
* Constructor.
*
* @param previous frame, the parent variable frame
*/
public Frame(final Frame previous) {
this.previous = previous;
this.symbols = new ArrayList<>();
this.baseCount = getBaseCount();
this.count = 0;
}
/**
* Copy constructor
* @param frame
* @param symbols
*/
private Frame(final Frame frame, final List<Symbol> symbols) {
this.previous = frame.getPrevious() == null ? null : new Frame(frame.getPrevious(), frame.getPrevious().getSymbols());
this.symbols = new ArrayList<>(frame.getSymbols());
this.baseCount = frame.getBaseCount();
this.count = frame.getCount();
}
/**
* Copy the frame
*
* @return a new frame with the identical contents
*/
public Frame copy() {
return new Frame(this, getSymbols());
}
/**
* Add a new variable to the frame.
* @param symbol Symbol representing variable.
*/
public void addSymbol(final Symbol symbol) {
final int slot = symbol.getSlot();
if (slot < 0) {
symbols.add(symbol);
count += symbol.slotCount();
}
}
/**
* Realign slot numbering prior to code generation.
* @return Number of slots in frame.
*/
public int realign() {
baseCount = getBaseCount();
count = 0;
for (final Symbol symbol : symbols) {
if (symbol.hasSlot()) {
symbol.setSlot(baseCount + count);
count += symbol.slotCount();
}
}
return count;
}
/**
* Return the slot count of previous frames.
* @return Number of slots in previous frames.
*/
private int getBaseCount() {
return previous != null ? previous.getSlotCount() : 0;
}
/**
* Determine the number of slots to top of frame.
* @return Number of slots in total.
*/
public int getSlotCount() {
return baseCount + count;
}
@Override
public String toString() {
final StringBuilder sb = new StringBuilder();
Frame f = this;
boolean hasPrev = false;
int pos = 0;
do {
if (hasPrev) {
sb.append("\n");
}
sb.append("#").
append(pos++).
append(" {baseCount:").
append(baseCount).
append(", ").
append("count:").
append(count).
append("} ");
for (final Symbol var : f.getSymbols()) {
sb.append('[').
append(var.toString()).
append(' ').
append(var.hashCode()).
append("] ");
}
f = f.getPrevious();
hasPrev = true;
} while (f != null);
return sb.toString();
}
/**
* Get variable count for this frame
* @return variable count
*/
public int getCount() {
return count;
}
/**
* Get previous frame
* @return previous frame
*/
public Frame getPrevious() {
return previous;
}
/**
* Set previous frame
* @param previous previous frame
*/
public void setPrevious(final Frame previous) {
this.previous = previous;
}
/**
* Get symbols in frame
* @return a list of symbols in this frame
*/
public List<Symbol> getSymbols() {
return Collections.unmodifiableList(symbols);
}
}
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