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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
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// THE POSSIBILITY OF SUCH DAMAGE.
package net.hasor.utils.asm.signature;
import net.hasor.utils.asm.Opcodes;

/**
 * A SignatureVisitor that generates signature literals, as defined in the Java Virtual Machine
 * Specification (JVMS).
 *
 * @see JVMS 4.7.9.1
 * @author Thomas Hallgren
 * @author Eric Bruneton
 */
public class SignatureWriter extends SignatureVisitor {
    /** The builder used to construct the visited signature. */
    private final StringBuilder stringBuilder = new StringBuilder();
    /** Whether the visited signature contains formal type parameters. */
    private       boolean       hasFormals;
    /** Whether the visited signature contains method parameter types. */
    private       boolean       hasParameters;
    /**
     * The 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 least significant bit. Pushing false
     * = *2, pushing true = *2+1, popping = /2.
     *
     * 

Class type arguments must be surrounded with '<' and '>' and, because * *

    *
  1. class types can be nested (because type arguments can themselves be class types), *
  2. SignatureWriter always returns 'this' in each visit* method (to avoid allocating new * SignatureWriter instances), *
* *

we need a stack to properly balance these 'parentheses'. A new element is pushed on this * stack for each new visited type, and popped when the visit of this type ends (either is * visitEnd, or because visitInnerClassType is called). */ private int argumentStack; /** Constructs a new {@link SignatureWriter}. */ public SignatureWriter() { super(Opcodes.ASM7); } // ----------------------------------------------------------------------------------------------- // Implementation of the SignatureVisitor interface // ----------------------------------------------------------------------------------------------- @Override public void visitFormalTypeParameter(final String name) { if (!hasFormals) { hasFormals = true; stringBuilder.append('<'); } stringBuilder.append(name); stringBuilder.append(':'); } @Override public SignatureVisitor visitClassBound() { return this; } @Override public SignatureVisitor visitInterfaceBound() { stringBuilder.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; stringBuilder.append('('); } return this; } @Override public SignatureVisitor visitReturnType() { endFormals(); if (!hasParameters) { stringBuilder.append('('); } stringBuilder.append(')'); return this; } @Override public SignatureVisitor visitExceptionType() { stringBuilder.append('^'); return this; } @Override public void visitBaseType(final char descriptor) { stringBuilder.append(descriptor); } @Override public void visitTypeVariable(final String name) { stringBuilder.append('T'); stringBuilder.append(name); stringBuilder.append(';'); } @Override public SignatureVisitor visitArrayType() { stringBuilder.append('['); return this; } @Override public void visitClassType(final String name) { stringBuilder.append('L'); stringBuilder.append(name); // Pushes 'false' on the stack, meaning that this type does not have type arguments (as far as // we can tell at this point). argumentStack *= 2; } @Override public void visitInnerClassType(final String name) { endArguments(); stringBuilder.append('.'); stringBuilder.append(name); // Pushes 'false' on the stack, meaning that this type does not have type arguments (as far as // we can tell at this point). argumentStack *= 2; } @Override public void visitTypeArgument() { // If the top of the stack is 'false', this means we are visiting the first type argument of the // currently visited type. We therefore need to append a '<', and to replace the top stack // element with 'true' (meaning that the current type does have type arguments). if (argumentStack % 2 == 0) { argumentStack |= 1; stringBuilder.append('<'); } stringBuilder.append('*'); } @Override public SignatureVisitor visitTypeArgument(final char wildcard) { // If the top of the stack is 'false', this means we are visiting the first type argument of the // currently visited type. We therefore need to append a '<', and to replace the top stack // element with 'true' (meaning that the current type does have type arguments). if (argumentStack % 2 == 0) { argumentStack |= 1; stringBuilder.append('<'); } if (wildcard != '=') { stringBuilder.append(wildcard); } return this; } @Override public void visitEnd() { endArguments(); stringBuilder.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 stringBuilder.toString(); } // ----------------------------------------------------------------------------------------------- // Utility methods // ----------------------------------------------------------------------------------------------- /** Ends the formal type parameters section of the signature. */ private void endFormals() { if (hasFormals) { hasFormals = false; stringBuilder.append('>'); } } /** Ends the type arguments of a class or inner class type. */ private void endArguments() { // If the top of the stack is 'true', this means that some type arguments have been visited for // the type whose visit is now ending. We therefore need to append a '>', and to pop one element // from the stack. if (argumentStack % 2 == 1) { stringBuilder.append('>'); } argumentStack /= 2; } }





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