001// ASM: a very small and fast Java bytecode manipulation framework
002// Copyright (c) 2000-2011 INRIA, France Telecom
003// All rights reserved.
004//
005// Redistribution and use in source and binary forms, with or without
006// modification, are permitted provided that the following conditions
007// are met:
008// 1. Redistributions of source code must retain the above copyright
009//    notice, this list of conditions and the following disclaimer.
010// 2. Redistributions in binary form must reproduce the above copyright
011//    notice, this list of conditions and the following disclaimer in the
012//    documentation and/or other materials provided with the distribution.
013// 3. Neither the name of the copyright holders nor the names of its
014//    contributors may be used to endorse or promote products derived from
015//    this software without specific prior written permission.
016//
017// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
018// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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020// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
021// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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028package io.ebean.enhance.asm.commons;
029
030import io.ebean.enhance.asm.ClassVisitor;
031import io.ebean.enhance.asm.MethodVisitor;
032import io.ebean.enhance.asm.Opcodes;
033
034/**
035 * A {@link ClassVisitor} that merges <clinit> methods into a single one. All the existing
036 * <clinit> methods are renamed, and a new one is created, which calls all the renamed
037 * methods.
038 *
039 * @author Eric Bruneton
040 */
041public class StaticInitMerger extends ClassVisitor {
042
043  /** The internal name of the visited class. */
044  private String owner;
045
046  /** The prefix to use to rename the existing <clinit> methods. */
047  private final String renamedClinitMethodPrefix;
048
049  /** The number of <clinit> methods visited so far. */
050  private int numClinitMethods;
051
052  /** The MethodVisitor for the merged <clinit> method. */
053  private MethodVisitor mergedClinitVisitor;
054
055  /**
056   * Constructs a new {@link StaticInitMerger}. <i>Subclasses must not use this constructor</i>.
057   * Instead, they must use the {@link #StaticInitMerger(int, String, ClassVisitor)} version.
058   *
059   * @param prefix the prefix to use to rename the existing &lt;clinit&gt; methods.
060   * @param classVisitor the class visitor to which this visitor must delegate method calls. May be
061   *     null.
062   */
063  public StaticInitMerger(final String prefix, final ClassVisitor classVisitor) {
064    this(/* latest api = */ Opcodes.ASM9, prefix, classVisitor);
065  }
066
067  /**
068   * Constructs a new {@link StaticInitMerger}.
069   *
070   * @param api the ASM API version implemented by this visitor. Must be one of {@link
071   *     Opcodes#ASM4}, {@link Opcodes#ASM5}, {@link Opcodes#ASM6}, {@link Opcodes#ASM7}, {@link
072   *     Opcodes#ASM8} or {@link Opcodes#ASM9}.
073   * @param prefix the prefix to use to rename the existing &lt;clinit&gt; methods.
074   * @param classVisitor the class visitor to which this visitor must delegate method calls. May be
075   *     null.
076   */
077  protected StaticInitMerger(final int api, final String prefix, final ClassVisitor classVisitor) {
078    super(api, classVisitor);
079    this.renamedClinitMethodPrefix = prefix;
080  }
081
082  @Override
083  public void visit(
084      final int version,
085      final int access,
086      final String name,
087      final String signature,
088      final String superName,
089      final String[] interfaces) {
090    super.visit(version, access, name, signature, superName, interfaces);
091    this.owner = name;
092  }
093
094  @Override
095  public MethodVisitor visitMethod(
096      final int access,
097      final String name,
098      final String descriptor,
099      final String signature,
100      final String[] exceptions) {
101    MethodVisitor methodVisitor;
102    if ("<clinit>".equals(name)) {
103      int newAccess = Opcodes.ACC_PRIVATE + Opcodes.ACC_STATIC;
104      String newName = renamedClinitMethodPrefix + numClinitMethods++;
105      methodVisitor = super.visitMethod(newAccess, newName, descriptor, signature, exceptions);
106
107      if (mergedClinitVisitor == null) {
108        mergedClinitVisitor = super.visitMethod(newAccess, name, descriptor, null, null);
109      }
110      mergedClinitVisitor.visitMethodInsn(Opcodes.INVOKESTATIC, owner, newName, descriptor, false);
111    } else {
112      methodVisitor = super.visitMethod(access, name, descriptor, signature, exceptions);
113    }
114    return methodVisitor;
115  }
116
117  @Override
118  public void visitEnd() {
119    if (mergedClinitVisitor != null) {
120      mergedClinitVisitor.visitInsn(Opcodes.RETURN);
121      mergedClinitVisitor.visitMaxs(0, 0);
122    }
123    super.visitEnd();
124  }
125}