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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.ir;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Deque;
import java.util.List;
/**
* This is a subclass of lexical context used for filling
* blocks (and function nodes) with statements. When popping
* a block from the lexical context, any statements that have
* been generated in it are commited to the block. This saves
* unnecessary object mutations and lexical context replacement
*/
public class BlockLexicalContext extends LexicalContext {
/** statement stack, each block on the lexical context maintains one of these, which is
* committed to the block on pop */
private final Deque<List<Statement>> sstack = new ArrayDeque<>();
/** Last non debug statement emitted in this context */
protected Statement lastStatement;
@Override
public <T extends LexicalContextNode> T push(final T node) {
final T pushed = super.push(node);
if (node instanceof Block) {
sstack.push(new ArrayList<Statement>());
}
return pushed;
}
/**
* Get the statement list from the stack, possibly filtered
* @return statement list
*/
protected List<Statement> popStatements() {
return sstack.pop();
}
/**
* Override this method to perform some additional processing on the block after its statements have been set. By
* default does nothing and returns the original block.
* @param block the block to operate on
* @return a modified block.
*/
protected Block afterSetStatements(final Block block) {
return block;
}
@SuppressWarnings("unchecked")
@Override
public <T extends LexicalContextNode> T pop(final T node) {
T expected = node;
if (node instanceof Block) {
final List<Statement> newStatements = popStatements();
expected = (T)((Block)node).setStatements(this, newStatements);
expected = (T)afterSetStatements((Block)expected);
if (!sstack.isEmpty()) {
lastStatement = lastStatement(sstack.peek());
}
}
return super.pop(expected);
}
/**
* Append a statement to the block being generated
* @param statement statement to add
*/
public void appendStatement(final Statement statement) {
assert statement != null;
sstack.peek().add(statement);
lastStatement = statement;
}
/**
* Prepend a statement to the block being generated
* @param statement statement to prepend
* @return the prepended statement
*/
public Node prependStatement(final Statement statement) {
assert statement != null;
sstack.peek().add(0, statement);
return statement;
}
/**
* Prepend a list of statement to the block being generated
* @param statements a list of statements to prepend
*/
public void prependStatements(final List<Statement> statements) {
assert statements != null;
sstack.peek().addAll(0, statements);
}
/**
* Get the last statement that was emitted into a block
* @return the last statement emitted
*/
public Statement getLastStatement() {
return lastStatement;
}
private static Statement lastStatement(final List<Statement> statements) {
final int s = statements.size();
return s == 0 ? null : statements.get(s - 1);
}
}
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