Source code

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
019// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
020// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
021// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
022// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
023// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
024// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
025// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
026// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
027// THE POSSIBILITY OF SUCH DAMAGE.
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 &lt;clinit&gt; methods into a single one. All the existing
036 * &lt;clinit&gt; 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 &lt;clinit&gt; methods. */
047  private final String renamedClinitMethodPrefix;
048
049  /** The number of &lt;clinit&gt; methods visited so far. */
050  private int numClinitMethods;
051
052  /** The MethodVisitor for the merged &lt;clinit&gt; 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 the {@code
071   *     ASM}<i>x</i> values in {@link Opcodes}.
072   * @param prefix the prefix to use to rename the existing &lt;clinit&gt; methods.
073   * @param classVisitor the class visitor to which this visitor must delegate method calls. May be
074   *     null.
075   */
076  protected StaticInitMerger(final int api, final String prefix, final ClassVisitor classVisitor) {
077    super(api, classVisitor);
078    this.renamedClinitMethodPrefix = prefix;
079  }
080
081  @Override
082  public void visit(
083      final int version,
084      final int access,
085      final String name,
086      final String signature,
087      final String superName,
088      final String[] interfaces) {
089    super.visit(version, access, name, signature, superName, interfaces);
090    this.owner = name;
091  }
092
093  @Override
094  public MethodVisitor visitMethod(
095      final int access,
096      final String name,
097      final String descriptor,
098      final String signature,
099      final String[] exceptions) {
100    MethodVisitor methodVisitor;
101    if ("<clinit>".equals(name)) {
102      int newAccess = Opcodes.ACC_PRIVATE + Opcodes.ACC_STATIC;
103      String newName = renamedClinitMethodPrefix + numClinitMethods++;
104      methodVisitor = super.visitMethod(newAccess, newName, descriptor, signature, exceptions);
105
106      if (mergedClinitVisitor == null) {
107        mergedClinitVisitor = super.visitMethod(newAccess, name, descriptor, null, null);
108      }
109      mergedClinitVisitor.visitMethodInsn(Opcodes.INVOKESTATIC, owner, newName, descriptor, false);
110    } else {
111      methodVisitor = super.visitMethod(access, name, descriptor, signature, exceptions);
112    }
113    return methodVisitor;
114  }
115
116  @Override
117  public void visitEnd() {
118    if (mergedClinitVisitor != null) {
119      mergedClinitVisitor.visitInsn(Opcodes.RETURN);
120      mergedClinitVisitor.visitMaxs(0, 0);
121    }
122    super.visitEnd();
123  }
124}