Java example source code file (PrintVisitor.java)

This example Java source code file (PrintVisitor.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

block, expressionstatement, fornode, functionnode, goto, labelnode, list, node, override, printvisitor, splitnode, stringbuilder, tabwidth, util, varnode

The PrintVisitor.java Java example source code

/*
 * 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.debug;

import java.util.List;
import jdk.nashorn.internal.ir.BinaryNode;
import jdk.nashorn.internal.ir.Block;
import jdk.nashorn.internal.ir.BlockStatement;
import jdk.nashorn.internal.ir.CaseNode;
import jdk.nashorn.internal.ir.CatchNode;
import jdk.nashorn.internal.ir.ExpressionStatement;
import jdk.nashorn.internal.ir.ForNode;
import jdk.nashorn.internal.ir.FunctionNode;
import jdk.nashorn.internal.ir.IfNode;
import jdk.nashorn.internal.ir.LabelNode;
import jdk.nashorn.internal.ir.LexicalContext;
import jdk.nashorn.internal.ir.Node;
import jdk.nashorn.internal.ir.SplitNode;
import jdk.nashorn.internal.ir.Statement;
import jdk.nashorn.internal.ir.SwitchNode;
import jdk.nashorn.internal.ir.TryNode;
import jdk.nashorn.internal.ir.UnaryNode;
import jdk.nashorn.internal.ir.VarNode;
import jdk.nashorn.internal.ir.WhileNode;
import jdk.nashorn.internal.ir.WithNode;
import jdk.nashorn.internal.ir.visitor.NodeVisitor;

/**
 * Print out the AST as human readable source code.
 * This works both on lowered and unlowered ASTs
 *
 * see the flags --print-parse and --print-lower-parse
 */
public final class PrintVisitor extends NodeVisitor<LexicalContext> {
    /** Tab width */
    private static final int TABWIDTH = 4;

    /** Composing buffer. */
    private final StringBuilder sb;

    /** Indentation factor. */
    private int indent;

    /** Line separator. */
    private final String EOLN;

    /** Print line numbers */
    private final boolean printLineNumbers;

    private int lastLineNumber = -1;

    /**
     * Constructor.
     */
    public PrintVisitor() {
        this(true);
    }

    /**
     * Constructor
     *
     * @param printLineNumbers  should line number nodes be included in the output?
     */
    public PrintVisitor(final boolean printLineNumbers) {
        super(new LexicalContext());
        this.EOLN             = System.lineSeparator();
        this.sb               = new StringBuilder();
        this.printLineNumbers = printLineNumbers;
    }

    /**
     * Constructor
     *
     * @param root  a node from which to start printing code
     */
    public PrintVisitor(final Node root) {
        this(root, true);
    }

    /**
     * Constructor
     *
     * @param root              a node from which to start printing code
     * @param printLineNumbers  should line numbers nodes be included in the output?
     */
    public PrintVisitor(final Node root, final boolean printLineNumbers) {
        this(printLineNumbers);
        visit(root);
    }

    private void visit(final Node root) {
        root.accept(this);
    }

    @Override
    public String toString() {
        return sb.append(EOLN).toString();
    }

    /**
     * Insert spaces before a statement.
     */
    private void indent() {
        for (int i = indent; i > 0; i--) {
            sb.append(' ');
        }
    }

    /*
     * Visits.
     */

    @Override
    public boolean enterDefault(final Node node) {
        node.toString(sb);
        return false;
    }

    @Override
    public boolean enterBlock(final Block block) {
        sb.append(' ');
        sb.append('{');

        indent += TABWIDTH;

        final List<Statement> statements = block.getStatements();

        for (final Node statement : statements) {
            if (printLineNumbers && (statement instanceof Statement)) {
                final int lineNumber = ((Statement)statement).getLineNumber();
                sb.append('\n');
                if (lineNumber != lastLineNumber) {
                    indent();
                    sb.append("[|").append(lineNumber).append("|];").append('\n');
                }
                lastLineNumber = lineNumber;
            }
            indent();

            statement.accept(this);

            if (statement instanceof FunctionNode) {
                continue;
            }

            int  lastIndex = sb.length() - 1;
            char lastChar  = sb.charAt(lastIndex);
            while (Character.isWhitespace(lastChar) && lastIndex >= 0) {
                lastChar = sb.charAt(--lastIndex);
            }

            if (lastChar != '}' && lastChar != ';') {
                sb.append(';');
            }

            if (statement.hasGoto()) {
                sb.append(" [GOTO]");
            }

            if (statement.isTerminal()) {
                sb.append(" [TERMINAL]");
            }
        }

        indent -= TABWIDTH;

        sb.append(EOLN);
        indent();
        sb.append('}');

        return false;
    }

    @Override
    public boolean enterBlockStatement(final BlockStatement statement) {
        statement.getBlock().accept(this);
        return false;
    }

    @Override
    public boolean enterBinaryNode(final BinaryNode binaryNode) {
        binaryNode.lhs().accept(this);
        sb.append(' ');
        sb.append(binaryNode.tokenType());
        sb.append(' ');
        binaryNode.rhs().accept(this);
        return false;
    }

    @Override
    public boolean enterUnaryNode(final UnaryNode unaryNode) {
        unaryNode.toString(sb, new Runnable() {
            @Override
            public void run() {
                unaryNode.rhs().accept(PrintVisitor.this);
            }
        });
        return false;
    }

    @Override
    public boolean enterExpressionStatement(final ExpressionStatement expressionStatement) {
        expressionStatement.getExpression().accept(this);
        return false;
    }

    @Override
    public boolean enterForNode(final ForNode forNode) {
        forNode.toString(sb);
        forNode.getBody().accept(this);
        return false;
    }

    @Override
    public boolean enterFunctionNode(final FunctionNode functionNode) {
        functionNode.toString(sb);
        enterBlock(functionNode.getBody());
        return false;
    }

    @Override
    public boolean enterIfNode(final IfNode ifNode) {
        ifNode.toString(sb);
        ifNode.getPass().accept(this);

        final Block fail = ifNode.getFail();

        if (fail != null) {
            sb.append(" else ");
            fail.accept(this);
        }

        return false;
    }

    @Override
    public boolean enterLabelNode(final LabelNode labeledNode) {
        indent -= TABWIDTH;
        indent();
        indent += TABWIDTH;
        labeledNode.toString(sb);
        labeledNode.getBody().accept(this);

        return false;
    }

    @Override
    public boolean enterSplitNode(final SplitNode splitNode) {
        splitNode.toString(sb);
        sb.append(EOLN);
        indent += TABWIDTH;
        indent();
        return true;
    }

    @Override
    public Node leaveSplitNode(final SplitNode splitNode) {
        sb.append("</split>");
        sb.append(EOLN);
        indent -= TABWIDTH;
        indent();
        return splitNode;
    }

    @Override
    public boolean enterSwitchNode(final SwitchNode switchNode) {
        switchNode.toString(sb);
        sb.append(" {");

        final List<CaseNode> cases = switchNode.getCases();

        for (final CaseNode caseNode : cases) {
            sb.append(EOLN);
            indent();
            caseNode.toString(sb);
            indent += TABWIDTH;
            caseNode.getBody().accept(this);
            indent -= TABWIDTH;
            sb.append(EOLN);
        }

        sb.append(EOLN);
        indent();
        sb.append("}");

        return false;
    }

    @Override
    public boolean enterTryNode(final TryNode tryNode) {
        tryNode.toString(sb);
        tryNode.getBody().accept(this);

        final List<Block> catchBlocks = tryNode.getCatchBlocks();

        for (final Block catchBlock : catchBlocks) {
            final CatchNode catchNode = (CatchNode)catchBlock.getStatements().get(0);
            catchNode.toString(sb);
            catchNode.getBody().accept(this);
        }

        final Block finallyBody = tryNode.getFinallyBody();

        if (finallyBody != null) {
            sb.append(" finally ");
            finallyBody.accept(this);
        }

        return false;
    }

    @Override
    public boolean enterVarNode(final VarNode varNode) {
        sb.append("var ");
        varNode.getName().toString(sb);
        final Node init = varNode.getInit();
        if (init != null) {
            sb.append(" = ");
            init.accept(this);
        }

        return false;
    }

    @Override
    public boolean enterWhileNode(final WhileNode whileNode) {
        if (whileNode.isDoWhile()) {
            sb.append("do");
            whileNode.getBody().accept(this);
            sb.append(' ');
            whileNode.toString(sb);
        } else {
            whileNode.toString(sb);
            whileNode.getBody().accept(this);
        }

        return false;
    }

    @Override
    public boolean enterWithNode(final WithNode withNode) {
        withNode.toString(sb);
        withNode.getBody().accept(this);

        return false;
    }

}