http://asm.objectweb.org/asm-tree/: A very small and fast Java bytecode manipulation framework (ObjectWeb)
  • Eric Bruneton
  • Eugene Kuleshov
  • Remi Forax 
ASM: a very small and fast Java bytecode manipulation framework
Copyright (c) 2000-2011 INRIA, France Telecom
All rights reserved.
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modification, are permitted provided that the following conditions
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   notice, this list of conditions and the following disclaimer.
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   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.
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/***
 * 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.objectweb.asm.util;

import org.objectweb.asm.Opcodes;
import org.objectweb.asm.signature.SignatureVisitor;


A SignatureVisitor that checks that its methods are properly used. 
Author:Eric Bruneton
/**
 * A {@link SignatureVisitor} that checks that its methods are properly used.
 * 
 * @author Eric Bruneton
 */
public class CheckSignatureAdapter extends SignatureVisitor {

    
Type to be used to check class signatures. See 
CheckSignatureAdapter. 
/**
     * Type to be used to check class signatures. See
     * {@link #CheckSignatureAdapter(int, SignatureVisitor)
     * CheckSignatureAdapter}.
     */
    public static final int CLASS_SIGNATURE = 0;

    
Type to be used to check method signatures. See 
CheckSignatureAdapter. 
/**
     * Type to be used to check method signatures. See
     * {@link #CheckSignatureAdapter(int, SignatureVisitor)
     * CheckSignatureAdapter}.
     */
    public static final int METHOD_SIGNATURE = 1;

    
Type to be used to check type signatures.See 
CheckSignatureAdapter. 
/**
     * Type to be used to check type signatures.See
     * {@link #CheckSignatureAdapter(int, SignatureVisitor)
     * CheckSignatureAdapter}.
     */
    public static final int TYPE_SIGNATURE = 2;

    private static final int EMPTY = 1;

    private static final int FORMAL = 2;

    private static final int BOUND = 4;

    private static final int SUPER = 8;

    private static final int PARAM = 16;

    private static final int RETURN = 32;

    private static final int SIMPLE_TYPE = 64;

    private static final int CLASS_TYPE = 128;

    private static final int END = 256;

    
Type of the signature to be checked.

/**
     * Type of the signature to be checked.
     */
    private final int type;

    
State of the automaton used to check the order of method calls.

/**
     * State of the automaton used to check the order of method calls.
     */
    private int state;

    
true if the checked type signature can be 'V'.

/**
     * <tt>true</tt> if the checked type signature can be 'V'.
     */
    private boolean canBeVoid;

    
The visitor to which this adapter must delegate calls. May be
null.

/**
     * The visitor to which this adapter must delegate calls. May be
     * <tt>null</tt>.
     */
    private final SignatureVisitor sv;

    
Creates a new CheckSignatureAdapter object. Subclasses must
not use this constructor. Instead, they must use the CheckSignatureAdapter(int, int, SignatureVisitor) version. 
Params:
/**
     * Creates a new {@link CheckSignatureAdapter} object. <i>Subclasses must
     * not use this constructor</i>. Instead, they must use the
     * {@link #CheckSignatureAdapter(int, int, SignatureVisitor)} version.
     * 
     * @param type
     *            the type of signature to be checked. See
     *            {@link #CLASS_SIGNATURE}, {@link #METHOD_SIGNATURE} and
     *            {@link #TYPE_SIGNATURE}.
     * @param sv
     *            the visitor to which this adapter must delegate calls. May be
     *            <tt>null</tt>.
     */
    public CheckSignatureAdapter(final int type, final SignatureVisitor sv) {
        this(Opcodes.ASM5, type, sv);
    }

    
Creates a new CheckSignatureAdapter object. 
Params:
/**
     * Creates a new {@link CheckSignatureAdapter} object.
     * 
     * @param api
     *            the ASM API version implemented by this visitor. Must be one
     *            of {@link Opcodes#ASM4} or {@link Opcodes#ASM5}.
     * @param type
     *            the type of signature to be checked. See
     *            {@link #CLASS_SIGNATURE}, {@link #METHOD_SIGNATURE} and
     *            {@link #TYPE_SIGNATURE}.
     * @param sv
     *            the visitor to which this adapter must delegate calls. May be
     *            <tt>null</tt>.
     */
    protected CheckSignatureAdapter(final int api, final int type,
            final SignatureVisitor sv) {
        super(api);
        this.type = type;
        this.state = EMPTY;
        this.sv = sv;
    }

    // class and method signatures

    @Override
    public void visitFormalTypeParameter(final String name) {
        if (type == TYPE_SIGNATURE
                || (state != EMPTY && state != FORMAL && state != BOUND)) {
            throw new IllegalStateException();
        }
        CheckMethodAdapter.checkIdentifier(name, "formal type parameter");
        state = FORMAL;
        if (sv != null) {
            sv.visitFormalTypeParameter(name);
        }
    }

    @Override
    public SignatureVisitor visitClassBound() {
        if (state != FORMAL) {
            throw new IllegalStateException();
        }
        state = BOUND;
        SignatureVisitor v = sv == null ? null : sv.visitClassBound();
        return new CheckSignatureAdapter(TYPE_SIGNATURE, v);
    }

    @Override
    public SignatureVisitor visitInterfaceBound() {
        if (state != FORMAL && state != BOUND) {
            throw new IllegalArgumentException();
        }
        SignatureVisitor v = sv == null ? null : sv.visitInterfaceBound();
        return new CheckSignatureAdapter(TYPE_SIGNATURE, v);
    }

    // class signatures

    @Override
    public SignatureVisitor visitSuperclass() {
        if (type != CLASS_SIGNATURE || (state & (EMPTY | FORMAL | BOUND)) == 0) {
            throw new IllegalArgumentException();
        }
        state = SUPER;
        SignatureVisitor v = sv == null ? null : sv.visitSuperclass();
        return new CheckSignatureAdapter(TYPE_SIGNATURE, v);
    }

    @Override
    public SignatureVisitor visitInterface() {
        if (state != SUPER) {
            throw new IllegalStateException();
        }
        SignatureVisitor v = sv == null ? null : sv.visitInterface();
        return new CheckSignatureAdapter(TYPE_SIGNATURE, v);
    }

    // method signatures

    @Override
    public SignatureVisitor visitParameterType() {
        if (type != METHOD_SIGNATURE
                || (state & (EMPTY | FORMAL | BOUND | PARAM)) == 0) {
            throw new IllegalArgumentException();
        }
        state = PARAM;
        SignatureVisitor v = sv == null ? null : sv.visitParameterType();
        return new CheckSignatureAdapter(TYPE_SIGNATURE, v);
    }

    @Override
    public SignatureVisitor visitReturnType() {
        if (type != METHOD_SIGNATURE
                || (state & (EMPTY | FORMAL | BOUND | PARAM)) == 0) {
            throw new IllegalArgumentException();
        }
        state = RETURN;
        SignatureVisitor v = sv == null ? null : sv.visitReturnType();
        CheckSignatureAdapter cv = new CheckSignatureAdapter(TYPE_SIGNATURE, v);
        cv.canBeVoid = true;
        return cv;
    }

    @Override
    public SignatureVisitor visitExceptionType() {
        if (state != RETURN) {
            throw new IllegalStateException();
        }
        SignatureVisitor v = sv == null ? null : sv.visitExceptionType();
        return new CheckSignatureAdapter(TYPE_SIGNATURE, v);
    }

    // type signatures

    @Override
    public void visitBaseType(final char descriptor) {
        if (type != TYPE_SIGNATURE || state != EMPTY) {
            throw new IllegalStateException();
        }
        if (descriptor == 'V') {
            if (!canBeVoid) {
                throw new IllegalArgumentException();
            }
        } else {
            if ("ZCBSIFJD".indexOf(descriptor) == -1) {
                throw new IllegalArgumentException();
            }
        }
        state = SIMPLE_TYPE;
        if (sv != null) {
            sv.visitBaseType(descriptor);
        }
    }

    @Override
    public void visitTypeVariable(final String name) {
        if (type != TYPE_SIGNATURE || state != EMPTY) {
            throw new IllegalStateException();
        }
        CheckMethodAdapter.checkIdentifier(name, "type variable");
        state = SIMPLE_TYPE;
        if (sv != null) {
            sv.visitTypeVariable(name);
        }
    }

    @Override
    public SignatureVisitor visitArrayType() {
        if (type != TYPE_SIGNATURE || state != EMPTY) {
            throw new IllegalStateException();
        }
        state = SIMPLE_TYPE;
        SignatureVisitor v = sv == null ? null : sv.visitArrayType();
        return new CheckSignatureAdapter(TYPE_SIGNATURE, v);
    }

    @Override
    public void visitClassType(final String name) {
        if (type != TYPE_SIGNATURE || state != EMPTY) {
            throw new IllegalStateException();
        }
        CheckMethodAdapter.checkInternalName(name, "class name");
        state = CLASS_TYPE;
        if (sv != null) {
            sv.visitClassType(name);
        }
    }

    @Override
    public void visitInnerClassType(final String name) {
        if (state != CLASS_TYPE) {
            throw new IllegalStateException();
        }
        CheckMethodAdapter.checkIdentifier(name, "inner class name");
        if (sv != null) {
            sv.visitInnerClassType(name);
        }
    }

    @Override
    public void visitTypeArgument() {
        if (state != CLASS_TYPE) {
            throw new IllegalStateException();
        }
        if (sv != null) {
            sv.visitTypeArgument();
        }
    }

    @Override
    public SignatureVisitor visitTypeArgument(final char wildcard) {
        if (state != CLASS_TYPE) {
            throw new IllegalStateException();
        }
        if ("+-=".indexOf(wildcard) == -1) {
            throw new IllegalArgumentException();
        }
        SignatureVisitor v = sv == null ? null : sv.visitTypeArgument(wildcard);
        return new CheckSignatureAdapter(TYPE_SIGNATURE, v);
    }

    @Override
    public void visitEnd() {
        if (state != CLASS_TYPE) {
            throw new IllegalStateException();
        }
        state = END;
        if (sv != null) {
            sv.visitEnd();
        }
    }
}