src/compiler/scala/tools/nsc/backend/jvm/AsmUtils.scala


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/* NSC -- new Scala compiler
 * Copyright 2005-2014 LAMP/EPFL
 * @author  Martin Odersky
 */

package scala.tools.nsc.backend.jvm

import scala.tools.asm.tree.{ClassNode, MethodNode}
import java.io.PrintWriter
import scala.tools.asm.util.{TraceClassVisitor, TraceMethodVisitor, Textifier}
import scala.tools.asm.ClassReader

object AsmUtils {

  /**
   * Print the bytecode of methods generated by GenBCode to the standard output. Only methods
   * whose name contains `traceMethodPattern` are traced.
   */
  final val traceMethodEnabled = false
  final val traceMethodPattern = ""

  /**
   * Print the bytecode of classes generated by GenBCode to the standard output.
   */
  final val traceClassEnabled = false
  final val traceClassPattern = ""

  /**
   * Print the bytedcode of classes as they are serialized by the ASM library. The serialization
   * performed by `asm.ClassWriter` can change the code generated by GenBCode. For example, it
   * introduces stack map frames, it computes the maximal stack sizes, and it replaces dead
   * code by NOPs (see also https://github.com/scala/scala/pull/3726#issuecomment-42861780).
   */
  final val traceSerializedClassEnabled = false
  final val traceSerializedClassPattern = ""

  def traceMethod(mnode: MethodNode): Unit = {
    println(s"Bytecode for method ${mnode.name}")
    val p = new Textifier
    val tracer = new TraceMethodVisitor(p)
    mnode.accept(tracer)
    val w = new PrintWriter(System.out)
    p.print(w)
    w.flush()
  }

  def traceClass(cnode: ClassNode): Unit = {
    println(s"Bytecode for class ${cnode.name}")
    val w = new PrintWriter(System.out)
    cnode.accept(new TraceClassVisitor(w))
    w.flush()
  }

  def traceClass(bytes: Array[Byte]): Unit = traceClass(readClass(bytes))

  def readClass(bytes: Array[Byte]): ClassNode = {
    val node = new ClassNode()
    new ClassReader(bytes).accept(node, 0)
    node
  }
}