plastic/src/external/java/org/apache/tapestry5/internal/plastic/asm/util/TraceSignatureVisitor.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
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package org.apache.tapestry5.internal.plastic.asm.util;

import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import org.apache.tapestry5.internal.plastic.asm.Opcodes;
import org.apache.tapestry5.internal.plastic.asm.signature.SignatureVisitor;

/**
 * A {@link SignatureVisitor} that builds the Java generic type declaration corresponding to the
 * signature it visits.
 *
 * @author Eugene Kuleshov
 * @author Eric Bruneton
 */
public final class TraceSignatureVisitor extends SignatureVisitor {

  private static final String COMMA_SEPARATOR = ", ";
  private static final String EXTENDS_SEPARATOR = " extends ";
  private static final String IMPLEMENTS_SEPARATOR = " implements ";

  private static final Map<Character, String> BASE_TYPES;

  static {
    HashMap<Character, String> baseTypes = new HashMap<>();
    baseTypes.put('Z', "boolean");
    baseTypes.put('B', "byte");
    baseTypes.put('C', "char");
    baseTypes.put('S', "short");
    baseTypes.put('I', "int");
    baseTypes.put('J', "long");
    baseTypes.put('F', "float");
    baseTypes.put('D', "double");
    baseTypes.put('V', "void");
    BASE_TYPES = Collections.unmodifiableMap(baseTypes);
  }

  /** Whether the visited signature is a class signature of a Java interface. */
  private final boolean isInterface;

  /** The Java generic type declaration corresponding to the visited signature. */
  private final StringBuilder declaration;

  /** The Java generic method return type declaration corresponding to the visited signature. */
  private StringBuilder returnType;

  /** The Java generic exception types declaration corresponding to the visited signature. */
  private StringBuilder exceptions;

  /** Whether {@link #visitFormalTypeParameter} has been called. */
  private boolean formalTypeParameterVisited;

  /** Whether {@link #visitInterfaceBound} has been called. */
  private boolean interfaceBoundVisited;

  /** Whether {@link #visitParameterType} has been called. */
  private boolean parameterTypeVisited;

  /** Whether {@link #visitInterface} has been called. */
  private boolean interfaceVisited;

  /**
   * 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.
   */
  private int argumentStack;

  /**
   * The stack used to keep track of array class types. 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 arrayStack;

  /** The separator to append before the next visited class or inner class type. */
  private String separator = "";

  /**
   * Constructs a new {@link TraceSignatureVisitor}.
   *
   * @param accessFlags for class type signatures, the access flags of the class.
   */
  public TraceSignatureVisitor(final int accessFlags) {
    super(/* latest api = */ Opcodes.ASM8);
    this.isInterface = (accessFlags & Opcodes.ACC_INTERFACE) != 0;
    this.declaration = new StringBuilder();
  }

  private TraceSignatureVisitor(final StringBuilder stringBuilder) {
    super(/* latest api = */ Opcodes.ASM8);
    this.isInterface = false;
    this.declaration = stringBuilder;
  }

  @Override
  public void visitFormalTypeParameter(final String name) {
    declaration.append(formalTypeParameterVisited ? COMMA_SEPARATOR : "<").append(name);
    formalTypeParameterVisited = true;
    interfaceBoundVisited = false;
  }

  @Override
  public SignatureVisitor visitClassBound() {
    separator = EXTENDS_SEPARATOR;
    startType();
    return this;
  }

  @Override
  public SignatureVisitor visitInterfaceBound() {
    separator = interfaceBoundVisited ? COMMA_SEPARATOR : EXTENDS_SEPARATOR;
    interfaceBoundVisited = true;
    startType();
    return this;
  }

  @Override
  public SignatureVisitor visitSuperclass() {
    endFormals();
    separator = EXTENDS_SEPARATOR;
    startType();
    return this;
  }

  @Override
  public SignatureVisitor visitInterface() {
    if (interfaceVisited) {
      separator = COMMA_SEPARATOR;
    } else {
      separator = isInterface ? EXTENDS_SEPARATOR : IMPLEMENTS_SEPARATOR;
      interfaceVisited = true;
    }
    startType();
    return this;
  }

  @Override
  public SignatureVisitor visitParameterType() {
    endFormals();
    if (parameterTypeVisited) {
      declaration.append(COMMA_SEPARATOR);
    } else {
      declaration.append('(');
      parameterTypeVisited = true;
    }
    startType();
    return this;
  }

  @Override
  public SignatureVisitor visitReturnType() {
    endFormals();
    if (parameterTypeVisited) {
      parameterTypeVisited = false;
    } else {
      declaration.append('(');
    }
    declaration.append(')');
    returnType = new StringBuilder();
    return new TraceSignatureVisitor(returnType);
  }

  @Override
  public SignatureVisitor visitExceptionType() {
    if (exceptions == null) {
      exceptions = new StringBuilder();
    } else {
      exceptions.append(COMMA_SEPARATOR);
    }
    return new TraceSignatureVisitor(exceptions);
  }

  @Override
  public void visitBaseType(final char descriptor) {
    String baseType = BASE_TYPES.get(descriptor);
    if (baseType == null) {
      throw new IllegalArgumentException();
    }
    declaration.append(baseType);
    endType();
  }

  @Override
  public void visitTypeVariable(final String name) {
    declaration.append(separator).append(name);
    separator = "";
    endType();
  }

  @Override
  public SignatureVisitor visitArrayType() {
    startType();
    arrayStack |= 1;
    return this;
  }

  @Override
  public void visitClassType(final String name) {
    if ("java/lang/Object".equals(name)) {
      // 'Map<java.lang.Object,java.util.List>' or 'abstract public V get(Object key);' should have
      // Object 'but java.lang.String extends java.lang.Object' is unnecessary.
      boolean needObjectClass = argumentStack % 2 != 0 || parameterTypeVisited;
      if (needObjectClass) {
        declaration.append(separator).append(name.replace('/', '.'));
      }
    } else {
      declaration.append(separator).append(name.replace('/', '.'));
    }
    separator = "";
    argumentStack *= 2;
  }

  @Override
  public void visitInnerClassType(final String name) {
    if (argumentStack % 2 != 0) {
      declaration.append('>');
    }
    argumentStack /= 2;
    declaration.append('.');
    declaration.append(separator).append(name.replace('/', '.'));
    separator = "";
    argumentStack *= 2;
  }

  @Override
  public void visitTypeArgument() {
    if (argumentStack % 2 == 0) {
      ++argumentStack;
      declaration.append('<');
    } else {
      declaration.append(COMMA_SEPARATOR);
    }
    declaration.append('?');
  }

  @Override
  public SignatureVisitor visitTypeArgument(final char tag) {
    if (argumentStack % 2 == 0) {
      ++argumentStack;
      declaration.append('<');
    } else {
      declaration.append(COMMA_SEPARATOR);
    }

    if (tag == EXTENDS) {
      declaration.append("? extends ");
    } else if (tag == SUPER) {
      declaration.append("? super ");
    }

    startType();
    return this;
  }

  @Override
  public void visitEnd() {
    if (argumentStack % 2 != 0) {
      declaration.append('>');
    }
    argumentStack /= 2;
    endType();
  }

  // -----------------------------------------------------------------------------------------------

  /**
   * Returns the Java generic type declaration corresponding to the visited signature.
   *
   * @return the Java generic type declaration corresponding to the visited signature.
   */
  public String getDeclaration() {
    return declaration.toString();
  }

  /**
   * Returns the Java generic method return type declaration corresponding to the visited signature.
   *
   * @return the Java generic method return type declaration corresponding to the visited signature.
   */
  public String getReturnType() {
    return returnType == null ? null : returnType.toString();
  }

  /**
   * Returns the Java generic exception types declaration corresponding to the visited signature.
   *
   * @return the Java generic exception types declaration corresponding to the visited signature.
   */
  public String getExceptions() {
    return exceptions == null ? null : exceptions.toString();
  }

  // -----------------------------------------------------------------------------------------------

  private void endFormals() {
    if (formalTypeParameterVisited) {
      declaration.append('>');
      formalTypeParameterVisited = false;
    }
  }

  private void startType() {
    arrayStack *= 2;
  }

  private void endType() {
    if (arrayStack % 2 == 0) {
      arrayStack /= 2;
    } else {
      while (arrayStack % 2 != 0) {
        arrayStack /= 2;
        declaration.append("[]");
      }
    }
  }
}