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/*
* Copyright (C) 2014-2020 Lightbend Inc.
*/
package akka.util
import java.io.{ DataInputStream, InputStream }
import java.lang.invoke.SerializedLambda
import scala.annotation.switch
import scala.util.control.NonFatal
/**
* This is a minimized byte-code parser that concentrates exclusively on line
* numbers and source file extraction. It works for all normal classes up to
* format 52:0 (JDK8), and it also works for Lambdas that are Serializable. The
* latter restriction is due to the fact that the proxy object generated by
* LambdaMetafactory otherwise contains no information about which method backs
* this particular lambda (and there might be multiple defined within a single
* class).
*/
object LineNumbers {
sealed trait Result
case object NoSourceInfo extends Result
final case class UnknownSourceFormat(explanation: String) extends Result
final case class SourceFile(filename: String) extends Result {
override def toString = filename
}
final case class SourceFileLines(filename: String, from: Int, to: Int) extends Result {
override def toString = if (from != to) s"$filename:$from-$to" else s"$filename:$from"
}
/**
* Scala API: Obtain line number information for the class defining the given object.
* This is done by reading the byte code (a potentially blocking IO operation)
* and interpreting the debug information that it may contain.
*
* This does not work for Java 8 lambdas that are not Serializable, because
* the language designers have consciously made it impossible to obtain the
* byte code for those.
*/
// FIXME: this needs memoization with an LRU cache
def apply(obj: AnyRef): Result = forObject(obj)
/**
* Java API: Obtain line number information for the class defining the given object.
* This is done by reading the byte code (a potentially blocking IO operation)
* and interpreting the debug information that it may contain.
*
* This does not work for Java 8 lambdas that are not Serializable, because
* the language designers have consciously made it impossible to obtain the
* byte code for those.
*/
def `for`(obj: AnyRef): Result = apply(obj)
/**
* Extract source information if available and format a string to identify the
* class definition in question. This will include the package name and either
* source file information or the class name.
*/
def prettyName(obj: AnyRef): String =
apply(obj) match {
case NoSourceInfo => obj.getClass.getName
case UnknownSourceFormat(msg) => s"${obj.getClass.getName}($msg)"
case SourceFile(f) => s"${obj.getClass.getName}($f)"
case l: SourceFileLines => s"${obj.getClass.getPackage.getName}/$l"
}
/*
* IMPLEMENTATION
*/
// compile-time constant; conditionals below will be elided if false
private final val debug = false
private class Constants(count: Int) {
private var _fwd = Map.empty[Int, String]
private var _rev = Map.empty[String, Int]
private var _xref = Map.empty[Int, Int]
def fwd: Map[Int, String] = _fwd
def rev: Map[String, Int] = _rev
private var nextIdx = 1
def isDone: Boolean = nextIdx >= count
def apply(idx: Int): String = _fwd(idx)
def apply(str: String): Int = _rev(str)
def resolve(): Unit = _xref.foreach(p => put(p._1, apply(p._2)))
def contains(str: String): Boolean = _rev contains str
private def put(idx: Int, str: String): Unit = {
if (!(_rev contains str)) _rev = _rev.updated(str, idx)
_fwd = _fwd.updated(idx, str)
}
def readOne(d: DataInputStream): Unit =
(d.readByte(): @switch) match {
case 1 => // Utf8
val str = d.readUTF()
put(nextIdx, str)
nextIdx += 1
case 3 => // Integer
skip(d, 4)
nextIdx += 1
case 4 => // Float
skip(d, 4)
nextIdx += 1
case 5 => // Long
skip(d, 8)
nextIdx += 2
case 6 => // Double
skip(d, 8)
nextIdx += 2
case 7 => // Class
val other = d.readUnsignedShort()
_xref = _xref.updated(nextIdx, other)
nextIdx += 1
case 8 => // String
skip(d, 2)
nextIdx += 1
case 9 => // FieldRef
skip(d, 4) // two shorts
nextIdx += 1
case 10 => // MethodRef
skip(d, 4) // two shorts
nextIdx += 1
case 11 => // InterfaceMethodRef
skip(d, 4) // two shorts
nextIdx += 1
case 12 => // NameAndType
skip(d, 4) // two shorts
nextIdx += 1
case 15 => // MethodHandle
skip(d, 3) // a byte and a short
nextIdx += 1
case 16 => // MethodType
skip(d, 2)
nextIdx += 1
case 18 => // InvokeDynamic
skip(d, 4) // two shorts
nextIdx += 1
}
}
private def forObject(obj: AnyRef): Result =
getStreamForClass(obj.getClass).orElse(getStreamForLambda(obj)) match {
case None => NoSourceInfo
case Some((stream, filter)) => getInfo(stream, filter)
}
private def getInfo(stream: InputStream, filter: Option[String]): Result = {
val dis = new DataInputStream(stream)
try {
skipID(dis)
skipVersion(dis)
implicit val constants = getConstants(dis)
if (debug)
println(s"LNB: fwd(${constants.fwd.size}) rev(${constants.rev.size}) ${constants.fwd.keys.toList.sorted}")
skipClassInfo(dis)
skipInterfaceInfo(dis)
skipFields(dis)
val lines = readMethods(dis, filter)
val source = readAttributes(dis)
if (source.isEmpty) NoSourceInfo
else
lines match {
case None => SourceFile(source.get)
case Some((from, to)) => SourceFileLines(source.get, from, to)
}
} catch {
case NonFatal(ex) => UnknownSourceFormat(s"parse error: ${ex.getMessage}")
} finally {
try dis.close()
catch {
case ex: InterruptedException => throw ex
case NonFatal(_) => // ignore
}
}
}
private def getStreamForClass(c: Class[_]): Option[(InputStream, None.type)] = {
val resource = c.getName.replace('.', '/') + ".class"
val cl = c.getClassLoader
val r = cl.getResourceAsStream(resource)
if (debug) println(s"LNB: resource '$resource' resolved to stream $r")
Option(r).map(_ -> None)
}
private def getStreamForLambda(l: AnyRef): Option[(InputStream, Some[String])] =
try {
val c = l.getClass
val writeReplace = c.getDeclaredMethod("writeReplace")
writeReplace.setAccessible(true)
writeReplace.invoke(l) match {
case serialized: SerializedLambda =>
if (debug)
println(s"LNB: found Lambda implemented in ${serialized.getImplClass}:${serialized.getImplMethodName}")
Option(c.getClassLoader.getResourceAsStream(serialized.getImplClass + ".class"))
.map(_ -> Some(serialized.getImplMethodName))
case _ => None
}
} catch {
case NonFatal(ex) =>
if (debug) ex.printStackTrace()
None
}
private def skipID(d: DataInputStream): Unit = {
val magic = d.readInt()
if (debug) println(f"LNB: magic=0x$magic%08X")
if (magic != 0xcafebabe) throw new IllegalArgumentException("not a Java class file")
}
private def skipVersion(d: DataInputStream): Unit = {
val minor = d.readShort()
val major = d.readShort()
if (debug) println(s"LNB: version=$major:$minor")
}
private def getConstants(d: DataInputStream): Constants = {
val count = d.readUnsignedShort()
if (debug) println(s"LNB: reading $count constants")
val c = new Constants(count)
while (!c.isDone) c.readOne(d)
c.resolve()
c
}
private def skipClassInfo(d: DataInputStream)(implicit c: Constants): Unit = {
skip(d, 2) // access flags
val name = d.readUnsignedShort() // class name
skip(d, 2) // superclass name
if (debug) println(s"LNB: class name = ${c(name)}")
}
private def skipInterfaceInfo(d: DataInputStream)(implicit c: Constants): Unit = {
val count = d.readUnsignedShort()
for (_ <- 1 to count) {
val intf = d.readUnsignedShort()
if (debug) println(s"LNB: implements ${c(intf)}")
}
}
private def skipFields(d: DataInputStream)(implicit c: Constants): Unit = {
val count = d.readUnsignedShort()
if (debug) println(s"LNB: reading $count fields:")
for (_ <- 1 to count) skipMethodOrField(d)
}
private def skipMethodOrField(d: DataInputStream)(implicit c: Constants): Unit = {
skip(d, 2) // access flags
val name = d.readUnsignedShort() // name
skip(d, 2) // signature
val attributes = d.readUnsignedShort()
for (_ <- 1 to attributes) skipAttribute(d)
if (debug) println(s"LNB: ${c(name)} ($attributes attributes)")
}
private def skipAttribute(d: DataInputStream): Unit = {
skip(d, 2) // tag
val length = d.readInt()
skip(d, length)
}
private def readMethods(d: DataInputStream, filter: Option[String])(implicit c: Constants): Option[(Int, Int)] = {
val count = d.readUnsignedShort()
if (debug) println(s"LNB: reading $count methods")
if (c.contains("Code") && c.contains("LineNumberTable")) {
(1 to count)
.map(_ => readMethod(d, c("Code"), c("LineNumberTable"), filter))
.flatten
.foldLeft(Int.MaxValue -> 0) {
case ((low, high), (start, end)) => (Math.min(low, start), Math.max(high, end))
} match {
case (Int.MaxValue, 0) => None
case other => Some(other)
}
} else {
if (debug) println(s"LNB: (skipped)")
for (_ <- 1 to count) skipMethodOrField(d)
None
}
}
private def readMethod(d: DataInputStream, codeTag: Int, lineNumberTableTag: Int, filter: Option[String])(
implicit c: Constants): Option[(Int, Int)] = {
skip(d, 2) // access flags
val name = d.readUnsignedShort() // name
skip(d, 2) // signature
if (debug) println(s"LNB: ${c(name)}")
val attributes =
for (_ <- 1 to d.readUnsignedShort()) yield {
val tag = d.readUnsignedShort()
val length = d.readInt()
if (tag != codeTag || (filter.isDefined && c(name) != filter.get)) {
skip(d, length)
None
} else {
skip(d, 4) // shorts: max stack, max locals
skip(d, d.readInt()) // skip byte-code
// skip exception table: N records of 4 shorts (start PC, end PC, handler PC, catch type)
skip(d, 8 * d.readUnsignedShort())
val possibleLines =
for (_ <- 1 to d.readUnsignedShort()) yield {
val tag = d.readUnsignedShort()
val length = d.readInt()
if (tag != lineNumberTableTag) {
skip(d, length)
None
} else {
val lines =
for (_ <- 1 to d.readUnsignedShort()) yield {
skip(d, 2) // start PC
d.readUnsignedShort() // finally: the line number
}
Some(lines.min -> lines.max)
}
}
if (debug) println(s"LNB: nested attributes yielded: $possibleLines")
possibleLines.flatten.headOption
}
}
attributes.flatten.headOption
}
private def readAttributes(d: DataInputStream)(implicit c: Constants): Option[String] = {
val count = d.readUnsignedShort()
if (debug) println(s"LNB: reading $count attributes")
if (c contains "SourceFile") {
val s = c("SourceFile")
val attributes =
for (_ <- 1 to count) yield {
val tag = d.readUnsignedShort()
val length = d.readInt()
if (debug) println(s"LNB: tag ${c(tag)} ($length bytes)")
if (tag != s) {
skip(d, length)
None
} else {
val name = d.readUnsignedShort()
Some(c(name))
}
}
if (debug) println(s"LNB: yielded $attributes")
attributes.flatten.headOption
} else {
if (debug) println(s"LNB: (skipped)")
None
}
}
private def skip(d: DataInputStream, length: Int): Unit =
if (d.skipBytes(length) != length) throw new IllegalArgumentException("class file ends prematurely")
}
