SignatureWriter.java

/***
 * ASM: a very small and fast Java bytecode manipulation framework
 * Copyright (c) 2000-2011 INRIA, France Telecom
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the copyright holders nor the names of its
 *    contributors may be used to endorse or promote products derived from
 *    this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
 * THE POSSIBILITY OF SUCH DAMAGE.
 */
package org.eclipse.persistence.internal.libraries.asm.signature;

import org.eclipse.persistence.internal.libraries.asm.Opcodes;

/**
 * A signature visitor that generates signatures in string format.
 * 
 * @author Thomas Hallgren
 * @author Eric Bruneton
 */
public class SignatureWriter extends SignatureVisitor {

    /**
     * Builder used to construct the signature.
     */
    private final StringBuilder buf = new StringBuilder();

    /**
     * Indicates if the signature contains formal type parameters.
     */
    private boolean hasFormals;

    /**
     * Indicates if the signature contains method parameter types.
     */
    private boolean hasParameters;

    /**
     * Stack used to keep track of class types that have arguments. Each element
     * of this stack is a boolean encoded in one bit. The top of the stack is
     * the lowest order bit. Pushing false = *2, pushing true = *2+1, popping =
     * /2.
     */
    private int argumentStack;

    /**
     * Constructs a new {@link SignatureWriter} object.
     */
    public SignatureWriter() {
        super(Opcodes.ASM5);
    }

    // ------------------------------------------------------------------------
    // Implementation of the SignatureVisitor interface
    // ------------------------------------------------------------------------

    @Override
    public void visitFormalTypeParameter(final String name) {
        if (!hasFormals) {
            hasFormals = true;
            buf.append('<');
        }
        buf.append(name);
        buf.append(':');
    }

    @Override
    public SignatureVisitor visitClassBound() {
        return this;
    }

    @Override
    public SignatureVisitor visitInterfaceBound() {
        buf.append(':');
        return this;
    }

    @Override
    public SignatureVisitor visitSuperclass() {
        endFormals();
        return this;
    }

    @Override
    public SignatureVisitor visitInterface() {
        return this;
    }

    @Override
    public SignatureVisitor visitParameterType() {
        endFormals();
        if (!hasParameters) {
            hasParameters = true;
            buf.append('(');
        }
        return this;
    }

    @Override
    public SignatureVisitor visitReturnType() {
        endFormals();
        if (!hasParameters) {
            buf.append('(');
        }
        buf.append(')');
        return this;
    }

    @Override
    public SignatureVisitor visitExceptionType() {
        buf.append('^');
        return this;
    }

    @Override
    public void visitBaseType(final char descriptor) {
        buf.append(descriptor);
    }

    @Override
    public void visitTypeVariable(final String name) {
        buf.append('T');
        buf.append(name);
        buf.append(';');
    }

    @Override
    public SignatureVisitor visitArrayType() {
        buf.append('[');
        return this;
    }

    @Override
    public void visitClassType(final String name) {
        buf.append('L');
        buf.append(name);
        argumentStack *= 2;
    }

    @Override
    public void visitInnerClassType(final String name) {
        endArguments();
        buf.append('.');
        buf.append(name);
        argumentStack *= 2;
    }

    @Override
    public void visitTypeArgument() {
        if (argumentStack % 2 == 0) {
            ++argumentStack;
            buf.append('<');
        }
        buf.append('*');
    }

    @Override
    public SignatureVisitor visitTypeArgument(final char wildcard) {
        if (argumentStack % 2 == 0) {
            ++argumentStack;
            buf.append('<');
        }
        if (wildcard != '=') {
            buf.append(wildcard);
        }
        return this;
    }

    @Override
    public void visitEnd() {
        endArguments();
        buf.append(';');
    }

    /**
     * Returns the signature that was built by this signature writer.
     * 
     * @return the signature that was built by this signature writer.
     */
    @Override
    public String toString() {
        return buf.toString();
    }

    // ------------------------------------------------------------------------
    // Utility methods
    // ------------------------------------------------------------------------

    /**
     * Ends the formal type parameters section of the signature.
     */
    private void endFormals() {
        if (hasFormals) {
            hasFormals = false;
            buf.append('>');
        }
    }

    /**
     * Ends the type arguments of a class or inner class type.
     */
    private void endArguments() {
        if (argumentStack % 2 != 0) {
            buf.append('>');
        }
        argumentStack /= 2;
    }
}