Unpickle "privateWith", aka "package private"

Anything which is package private is now excluded from the problem
analysis MiMa does.  This includes:

* classes/traits/objects,
* methods/fields,
* method overloads,
* as well as classes becoming private/public.

core/src/main/scala/com/typesafe/tools/mima/core/BufferReader.scala

@@ -18,10 +18,12 @@ private[core] sealed class BytesReader(buf: Array[Byte]) {
   final def getDouble(idx: Int): Double = longBitsToDouble(getLong(idx))
 
   final def getString(idx: Int, len: Int): String = new String(buf, idx, len, StandardCharsets.UTF_8)
+
+  final def getBytes(idx: Int, bytes: Array[Byte]): Unit = System.arraycopy(buf, idx, bytes, 0, bytes.length)
 }
 
 /** A BytesReader which also holds a mutable pointer to where it will read next. */
-private[core] final class BufferReader(buf: Array[Byte]) extends BytesReader(buf) {
+private[core] final class BufferReader(buf: Array[Byte], val path: String) extends BytesReader(buf) {
   /** the buffer pointer */
   var bp: Int = 0
 

core/src/main/scala/com/typesafe/tools/mima/core/ByteCodecs.scala

@@ -0,0 +1,125 @@
+package com.typesafe.tools.mima.core
+
+/**
+ * Helper methods to serialize a byte array as String
+ * that can be written as "modified" UTF-8 to classfiles.
+ *
+ * Modified UTF-8 is the same as UTF-8, except for 0x00,
+ * which is represented as the "overlong" 0xC0 0x80.
+ * Constant strings in classfiles use this encoding.
+ *
+ * Encoding (according to SID-10):
+ *   - The 8-bit bytes are split into 7-bit bytes, e.g., 0xff 0x0f becomes 0x7f 0x1f 0x00
+ *   - Every bit is incremented by 1 (modulo 0x80), in the example we get  0x00, 0x20 0x01
+ *   - 0x00 is mapped to the overlong encoding, so we get                  0xC0 0x80 0x20 0x01
+ *
+ * The +1 increment should reduce the number of (overlong) zeros in the resulting string,
+ * as 0x7f is (hoped to be) more common than 0x00.
+ */
+object ByteCodecs {
+  /** Map 0xC0 0x80 to 0x00, then subtract 1 from each element. In-place. */
+  def regenerateZero(src: Array[Byte]): Int = {
+    var i = 0
+    val srclen = src.length
+    var j = 0
+    while (i < srclen) {
+      val in: Int = src(i) & 0xff
+      if (in == 0xc0 && (src(i + 1) & 0xff) == 0x80) {
+        src(j) = 0x7f
+        i += 2
+      } else if (in == 0) {
+        src(j) = 0x7f
+        i += 1
+      } else {
+        src(j) = (in - 1).toByte
+        i += 1
+      }
+      j += 1
+    }
+    j
+  }
+
+  def decode7to8(src: Array[Byte], srclen: Int): Int = {
+    var i = 0
+    var j = 0
+    val dstlen = (srclen * 7 + 7) / 8
+    while (i + 7 < srclen) {
+      var out: Int = src(i).toInt
+      var in: Byte = src(i + 1)
+      src(j) = (out | (in & 0x01) << 7).toByte
+      out = in >>> 1
+      in = src(i + 2)
+      src(j + 1) = (out | (in & 0x03) << 6).toByte
+      out = in >>> 2
+      in = src(i + 3)
+      src(j + 2) = (out | (in & 0x07) << 5).toByte
+      out = in >>> 3
+      in = src(i + 4)
+      src(j + 3) = (out | (in & 0x0f) << 4).toByte
+      out = in >>> 4
+      in = src(i + 5)
+      src(j + 4) = (out | (in & 0x1f) << 3).toByte
+      out = in >>> 5
+      in = src(i + 6)
+      src(j + 5) = (out | (in & 0x3f) << 2).toByte
+      out = in >>> 6
+      in = src(i + 7)
+      src(j + 6) = (out | in << 1).toByte
+      i += 8
+      j += 7
+    }
+    if (i < srclen) {
+      var out: Int = src(i).toInt
+      if (i + 1 < srclen) {
+        var in: Byte = src(i + 1)
+        src(j) = (out | (in & 0x01) << 7).toByte; j += 1
+        out = in >>> 1
+        if (i + 2 < srclen) {
+          in = src(i + 2)
+          src(j) = (out | (in & 0x03) << 6).toByte; j += 1
+          out = in >>> 2
+          if (i + 3 < srclen) {
+            in = src(i + 3)
+            src(j) = (out | (in & 0x07) << 5).toByte; j += 1
+            out = in >>> 3
+            if (i + 4 < srclen) {
+              in = src(i + 4)
+              src(j) = (out | (in & 0x0f) << 4).toByte; j += 1
+              out = in >>> 4
+              if (i + 5 < srclen) {
+                in = src(i + 5)
+                src(j) = (out | (in & 0x1f) << 3).toByte; j += 1
+                out = in >>> 5
+                if (i + 6 < srclen) {
+                  in = src(i + 6)
+                  src(j) = (out | (in & 0x3f) << 2).toByte; j += 1
+                  out = in >>> 6
+                }
+              }
+            }
+          }
+        }
+      }
+      if (j < dstlen) src(j) = out.toByte
+    }
+    dstlen
+  }
+
+  /**
+   * Destructively decodes array xs and returns the length of the decoded array.
+   *
+   * Sometimes returns (length+1) of the decoded array. Example:
+   *
+   *   scala> val enc = scala.reflect.internal.pickling.ByteCodecs.encode(Array(1,2,3))
+   *   enc: Array[Byte] = Array(2, 5, 13, 1)
+   *
+   *   scala> scala.reflect.internal.pickling.ByteCodecs.decode(enc)
+   *   res43: Int = 4
+   *
+   *   scala> enc
+   *   res44: Array[Byte] = Array(1, 2, 3, 0)
+   *
+   * However, this does not always happen.
+   */
+  def decode(xs: Array[Byte]): Int = decode7to8(xs, regenerateZero(xs))
+}

core/src/main/scala/com/typesafe/tools/mima/core/ClassInfo.scala

@@ -60,7 +60,9 @@ private[mima] sealed abstract class ClassInfo(val owner: PackageInfo) extends In
   final var _fields: Members[FieldInfo]   = NoMembers
   final var _methods: Members[MethodInfo] = NoMembers
   final var _flags: Int                   = 0
+  final var _packagePrivate: Boolean      = false
   final var _implClass: ClassInfo         = NoClass
+  final var _module: ClassInfo            = NoClass
 
   protected def afterLoading[A](x: => A): A
 
@@ -72,18 +74,20 @@ private[mima] sealed abstract class ClassInfo(val owner: PackageInfo) extends In
   final def fields: Members[FieldInfo]   = afterLoading(_fields)
   final def methods: Members[MethodInfo] = afterLoading(_methods)
   final def flags: Int                   = afterLoading(_flags)
+  final def isPackagePrivate: Boolean    = afterLoading(_packagePrivate)
   final def implClass: ClassInfo         = { owner.setImplClasses; _implClass } // returns NoClass if this is not a trait
+  final def module: ClassInfo            = { owner.setModules; _module }
 
-  final def isTrait: Boolean     = implClass ne NoClass // trait with some concrete methods or fields
-  final def isModule: Boolean    = bytecodeName.endsWith("$") // super scuffed
-  final def isImplClass: Boolean = bytecodeName.endsWith("$class")
-  final def isInterface: Boolean = ClassfileParser.isInterface(flags) // java interface or trait w/o impl methods
-  final def isClass: Boolean     = !isTrait && !isInterface // class, object or trait's impl class
+  final def isTrait: Boolean          = implClass ne NoClass // trait with some concrete methods or fields
+  final def isModuleClass: Boolean    = bytecodeName.endsWith("$") // super scuffed
+  final def isImplClass: Boolean      = bytecodeName.endsWith("$class")
+  final def isInterface: Boolean      = ClassfileParser.isInterface(flags) // java interface or trait w/o impl methods
+  final def isClass: Boolean          = !isTrait && !isInterface // class, object or trait's impl class
 
   final def accessModifier: String    = if (isProtected) "protected" else if (isPrivate) "private" else ""
-  final def declarationPrefix: String = if (isModule) "object" else if (isTrait) "trait" else if (isInterface) "interface" else "class"
+  final def declarationPrefix: String = if (isModuleClass) "object" else if (isTrait) "trait" else if (isInterface) "interface" else "class"
   final lazy val fullName: String     = if (owner.isRoot) bytecodeName else s"${owner.fullName}.$bytecodeName"
-  final def formattedFullName: String = formatClassName(if (isModule) fullName.init else fullName)
+  final def formattedFullName: String = formatClassName(if (isModuleClass) fullName.init else fullName)
   final def description: String       = s"$declarationPrefix $formattedFullName"
   final def classString: String       = s"$accessModifier $declarationPrefix $formattedFullName".trim
 

core/src/main/scala/com/typesafe/tools/mima/core/ClassfileConstants.scala

@@ -43,4 +43,8 @@ private[core] object ClassfileConstants {
   final val VOID_TAG       = 'V'
   final val OBJECT_TAG     = 'L'
   final val ANNOTATION_TAG = '@'
+
+  final val STRING_TAG = 's'
+  final val ENUM_TAG   = 'e'
+  final val CLASS_TAG  = 'c'
 }