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 * ASM: a very small and fast Java bytecode manipulation framework
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package jdk.internal.org.objectweb.asm.commons;

import jdk.internal.org.objectweb.asm.ClassVisitor;
import jdk.internal.org.objectweb.asm.MethodVisitor;
import jdk.internal.org.objectweb.asm.Opcodes;

A ClassVisitor that merges <clinit> methods into a single one. All the existing <clinit> methods are renamed, and a new one is created, which calls all the renamed methods.
Author:Eric Bruneton
/** * A {@link ClassVisitor} that merges &lt;clinit&gt; methods into a single one. All the existing * &lt;clinit&gt; methods are renamed, and a new one is created, which calls all the renamed * methods. * * @author Eric Bruneton */
public class StaticInitMerger extends ClassVisitor {
The internal name of the visited class.
/** The internal name of the visited class. */
private String owner;
The prefix to use to rename the existing <clinit> methods.
/** The prefix to use to rename the existing &lt;clinit&gt; methods. */
private final String renamedClinitMethodPrefix;
The number of <clinit> methods visited so far.
/** The number of &lt;clinit&gt; methods visited so far. */
private int numClinitMethods;
The MethodVisitor for the merged <clinit> method.
/** The MethodVisitor for the merged &lt;clinit&gt; method. */
private MethodVisitor mergedClinitVisitor;
Constructs a new StaticInitMerger. Subclasses must not use this constructor. Instead, they must use the StaticInitMerger(int, String, ClassVisitor) version.
Params:
  • prefix – the prefix to use to rename the existing <clinit> methods.
  • classVisitor – the class visitor to which this visitor must delegate method calls. May be null.
/** * Constructs a new {@link StaticInitMerger}. <i>Subclasses must not use this constructor</i>. * Instead, they must use the {@link #StaticInitMerger(int, String, ClassVisitor)} version. * * @param prefix the prefix to use to rename the existing &lt;clinit&gt; methods. * @param classVisitor the class visitor to which this visitor must delegate method calls. May be * null. */
public StaticInitMerger(final String prefix, final ClassVisitor classVisitor) { this(/* latest api = */ Opcodes.ASM8, prefix, classVisitor); }
Constructs a new StaticInitMerger.
Params:
  • api – the ASM API version implemented by this visitor. Must be one of Opcodes.ASM4, Opcodes.ASM5, Opcodes.ASM6, Opcodes.ASM7 or Opcodes.ASM8.
  • prefix – the prefix to use to rename the existing <clinit> methods.
  • classVisitor – the class visitor to which this visitor must delegate method calls. May be null.
/** * Constructs a new {@link StaticInitMerger}. * * @param api the ASM API version implemented by this visitor. Must be one of {@link * Opcodes#ASM4}, {@link Opcodes#ASM5}, {@link Opcodes#ASM6}, {@link Opcodes#ASM7} or {@link * Opcodes#ASM8}. * @param prefix the prefix to use to rename the existing &lt;clinit&gt; methods. * @param classVisitor the class visitor to which this visitor must delegate method calls. May be * null. */
protected StaticInitMerger(final int api, final String prefix, final ClassVisitor classVisitor) { super(api, classVisitor); this.renamedClinitMethodPrefix = prefix; } @Override public void visit( final int version, final int access, final String name, final String signature, final String superName, final String[] interfaces) { super.visit(version, access, name, signature, superName, interfaces); this.owner = name; } @Override public MethodVisitor visitMethod( final int access, final String name, final String descriptor, final String signature, final String[] exceptions) { MethodVisitor methodVisitor; if ("<clinit>".equals(name)) { int newAccess = Opcodes.ACC_PRIVATE + Opcodes.ACC_STATIC; String newName = renamedClinitMethodPrefix + numClinitMethods++; methodVisitor = super.visitMethod(newAccess, newName, descriptor, signature, exceptions); if (mergedClinitVisitor == null) { mergedClinitVisitor = super.visitMethod(newAccess, name, descriptor, null, null); } mergedClinitVisitor.visitMethodInsn(Opcodes.INVOKESTATIC, owner, newName, descriptor, false); } else { methodVisitor = super.visitMethod(access, name, descriptor, signature, exceptions); } return methodVisitor; } @Override public void visitEnd() { if (mergedClinitVisitor != null) { mergedClinitVisitor.visitInsn(Opcodes.RETURN); mergedClinitVisitor.visitMaxs(0, 0); } super.visitEnd(); } }