path: root/src/jdk/nashorn/internal/ir/Block.java

/*
 * 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.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import jdk.nashorn.internal.codegen.Label;
import jdk.nashorn.internal.ir.annotations.Immutable;
import jdk.nashorn.internal.ir.visitor.NodeVisitor;
import jdk.nashorn.internal.runtime.Source;

/**
 * IR representation for a list of statements and functions. All provides the
 * basis for script body.
 */
@Immutable
public class Block extends BreakableNode implements Flags<Block> {
    /** List of statements */
    protected final List<Node> statements;

    /** Symbol table - keys must be returned in the order they were put in. */
    protected final Map<String, Symbol> symbols;

    /** Entry label. */
    protected final Label entryLabel;

    /** Does the block/function need a new scope? */
    protected final int flags;

    /** Flag indicating that this block needs scope */
    public static final int NEEDS_SCOPE = 1 << 0;

    /**
     * Flag indicating whether this block needs
     * self symbol assignment at the start. This is used only for
     * blocks that are the bodies of function nodes who refer to themselves
     * by name. It causes codegen to insert a var [fn_name] = __callee__
     * at the start of the body
     */
    public static final int NEEDS_SELF_SYMBOL = 1 << 1;

    /**
     * Is this block tagged as terminal based on its contents
     * (usually the last statement)
     */
    public static final int IS_TERMINAL = 1 << 2;

    /**
     * Constructor
     *
     * @param source     source code
     * @param token      token
     * @param finish     finish
     * @param statements statements
     */
    public Block(final Source source, final long token, final int finish, final Node... statements) {
        super(source, token, finish, new Label("block_break"));

        this.statements = Arrays.asList(statements);
        this.symbols    = new LinkedHashMap<>();
        this.entryLabel = new Label("block_entry");
        this.flags     =  0;
    }

    /**
     * Constructor
     *
     * @param source     source code
     * @param token      token
     * @param finish     finish
     * @param statements statements
     */
    public Block(final Source source, final long token, final int finish, final List<Node> statements) {
        this(source, token, finish, statements.toArray(new Node[statements.size()]));
    }

    private Block(final Block block, final int finish, final List<Node> statements, final int flags) {
        super(block);
        this.statements = statements;
        this.flags      = flags;
        this.symbols    = block.symbols; //todo - symbols have no dependencies on any IR node and can as far as we understand it be shallow copied now
        this.entryLabel = new Label(block.entryLabel);
        this.finish = finish;
    }

    @Override
    public Node ensureUniqueLabels(final LexicalContext lc) {
        return Node.replaceInLexicalContext(lc, this, new Block(this, finish, statements, flags));
    }

    /**
     * Assist in IR navigation.
     *
     * @param visitor IR navigating visitor.
     * @return new or same node
     */
    @Override
    public Node accept(final LexicalContext lc, final NodeVisitor visitor) {
        if (visitor.enterBlock(this)) {
            return visitor.leaveBlock(setStatements(lc, Node.accept(visitor, Node.class, statements)));
        }

        return this;
    }

    /**
     * Get an iterator for all the symbols defined in this block
     * @return symbol iterator
     */
    public Iterator<Symbol> symbolIterator() {
        return symbols.values().iterator();
    }

    /**
     * Retrieves an existing symbol defined in the current block.
     * @param name the name of the symbol
     * @return an existing symbol with the specified name defined in the current block, or null if this block doesn't
     * define a symbol with this name.
     */
    public Symbol getExistingSymbol(final String name) {
        return symbols.get(name);
    }

    /**
     * Test if this block represents a <tt>catch</tt> block in a <tt>try</tt> statement.
     * This is used by the Splitter as catch blocks are not be subject to splitting.
     *
     * @return true if this block represents a catch block in a try statement.
     */
    public boolean isCatchBlock() {
        return statements.size() == 1 && statements.get(0) instanceof CatchNode;
    }

    @Override
    public void toString(final StringBuilder sb) {
        for (final Node statement : statements) {
            statement.toString(sb);
            sb.append(';');
        }
    }

    /**
     * Print symbols in block in alphabetical order, sorted on name
     * Used for debugging, see the --print-symbols flag
     *
     * @param stream print writer to output symbols to
     *
     * @return true if symbols were found
     */
    public boolean printSymbols(final PrintWriter stream) {
        final List<Symbol> values = new ArrayList<>(symbols.values());

        Collections.sort(values, new Comparator<Symbol>() {
            @Override
            public int compare(final Symbol s0, final Symbol s1) {
                return s0.getName().compareTo(s1.getName());
            }
        });

        for (final Symbol symbol : values) {
            symbol.print(stream);
        }

        return !values.isEmpty();
    }

    /**
     * Tag block as terminal or non terminal
     * @param lc          lexical context
     * @param isTerminal is block terminal
     * @return same block, or new if flag changed
     */
    public Block setIsTerminal(final LexicalContext lc, final boolean isTerminal) {
        return isTerminal ? setFlag(lc, IS_TERMINAL) : clearFlag(lc, IS_TERMINAL);
    }

    @Override
    public boolean isTerminal() {
        return getFlag(IS_TERMINAL);
    }

    /**
     * Get the entry label for this block
     * @return the entry label
     */
    public Label getEntryLabel() {
        return entryLabel;
    }

    /**
     * Get the list of statements in this block
     *
     * @return a list of statements
     */
    public List<Node> getStatements() {
        return Collections.unmodifiableList(statements);
    }

    /**
     * Reset the statement list for this block
     *
     * @param lc lexical context
     * @param statements new statement list
     * @return new block if statements changed, identity of statements == block.statements
     */
    public Block setStatements(final LexicalContext lc, final List<Node> statements) {
        if (this.statements == statements) {
            return this;
        }
        int lastFinish = 0;
        if (!statements.isEmpty()) {
            lastFinish = statements.get(statements.size() - 1).getFinish();
        }
        return Node.replaceInLexicalContext(lc, this, new Block(this, Math.max(finish, lastFinish), statements, flags));
    }

    /**
     * Add or overwrite an existing symbol in the block
     *
     * @param name   name of symbol
     * @param symbol symbol
     */
    public void putSymbol(final String name, final Symbol symbol) {
        symbols.put(name, symbol);
    }

    /**
     * Check whether scope is necessary for this Block
     *
     * @return true if this function needs a scope
     */
    public boolean needsScope() {
        return (flags & NEEDS_SCOPE) == NEEDS_SCOPE;
    }

    @Override
    public Block setFlags(final LexicalContext lc, int flags) {
        if (this.flags == flags) {
            return this;
        }
        return Node.replaceInLexicalContext(lc, this, new Block(this, finish, statements, flags));
    }

    @Override
    public Block clearFlag(final LexicalContext lc, int flag) {
        return setFlags(lc, flags & ~flag);
    }

    @Override
    public Block setFlag(final LexicalContext lc, int flag) {
        return setFlags(lc, flags | flag);
    }

    @Override
    public boolean getFlag(final int flag) {
        return (flags & flag) == flag;
    }

    /**
     * Set the needs scope flag.
     * @param lc lexicalContext
     * @return new block if state changed, otherwise this
     */
    public Block setNeedsScope(final LexicalContext lc) {
        if (needsScope()) {
            return this;
        }

        return Node.replaceInLexicalContext(lc, this, new Block(this, finish, statements, flags | NEEDS_SCOPE));
    }

    /**
     * Computationally determine the next slot for this block,
     * indexed from 0. Use this as a relative base when computing
     * frames
     * @return next slot
     */
    public int nextSlot() {
        final Iterator<Symbol> iter = symbolIterator();
        int next = 0;
        while (iter.hasNext()) {
        final Symbol symbol = iter.next();
        if (symbol.hasSlot()) {
            next += symbol.slotCount();
        }
        }
        return next;
    }

    @Override
    protected boolean isBreakableWithoutLabel() {
        return false;
    }
}