src/class_linker.cc

// Copyright 2011 Google Inc. All Rights Reserved.

#include "class_linker.h"

#include <deque>
#include <string>
#include <utility>
#include <vector>

#include "casts.h"
#include "class_loader.h"
#include "dex_cache.h"
#include "dex_file.h"
#include "dex_verifier.h"
#include "heap.h"
#include "intern_table.h"
#include "logging.h"
#include "monitor.h"
#include "object.h"
#include "runtime.h"
#include "space.h"
#include "thread.h"
#include "UniquePtr.h"
#include "utils.h"

namespace art {

namespace {

void ThrowNoClassDefFoundError(const char* fmt, ...) __attribute__((__format__ (__printf__, 1, 2)));
void ThrowNoClassDefFoundError(const char* fmt, ...) {
  va_list args;
  va_start(args, fmt);
  Thread::Current()->ThrowNewExceptionV("Ljava/lang/NoClassDefFoundError;", fmt, args);
  va_end(args);
}

void ThrowVirtualMachineError(const char* fmt, ...) __attribute__((__format__ (__printf__, 1, 2)));
void ThrowVirtualMachineError(const char* fmt, ...) {
  va_list args;
  va_start(args, fmt);
  UNIMPLEMENTED(FATAL) << "VirtualMachineError is abstract, throw something else";
  Thread::Current()->ThrowNewExceptionV("Ljava/lang/VirtualMachineError;", fmt, args);
  va_end(args);
}

void ThrowLinkageError(const char* fmt, ...) __attribute__((__format__ (__printf__, 1, 2)));
void ThrowLinkageError(const char* fmt, ...) {
  va_list args;
  va_start(args, fmt);
  Thread::Current()->ThrowNewExceptionV("Ljava/lang/LinkageError;", fmt, args);
  va_end(args);
}

void ThrowEarlierClassFailure(Class* c) {
  /*
   * The class failed to initialize on a previous attempt, so we want to throw
   * a NoClassDefFoundError (v2 2.17.5).  The exception to this rule is if we
   * failed in verification, in which case v2 5.4.1 says we need to re-throw
   * the previous error.
   */
  LOG(INFO) << "Rejecting re-init on previously-failed class " << PrettyClass(c);

  if (c->GetVerifyErrorClass() != NULL) {
    // TODO: change the verifier to store an _instance_, with a useful detail message?
    std::string error_descriptor(c->GetVerifyErrorClass()->GetDescriptor()->ToModifiedUtf8());
    Thread::Current()->ThrowNewException(error_descriptor.c_str(), "%s",
        PrettyDescriptor(c->GetDescriptor()).c_str());
  } else {
    ThrowNoClassDefFoundError("%s", PrettyDescriptor(c->GetDescriptor()).c_str());
  }
}

}

const char* ClassLinker::class_roots_descriptors_[] = {
  "Ljava/lang/Class;",
  "Ljava/lang/Object;",
  "[Ljava/lang/Class;",
  "[Ljava/lang/Object;",
  "Ljava/lang/String;",
  "Ljava/lang/reflect/Constructor;",
  "Ljava/lang/reflect/Field;",
  "Ljava/lang/reflect/Method;",
  "Ljava/lang/ClassLoader;",
  "Ldalvik/system/BaseDexClassLoader;",
  "Ldalvik/system/PathClassLoader;",
  "Ljava/lang/StackTraceElement;",
  "Z",
  "B",
  "C",
  "D",
  "F",
  "I",
  "J",
  "S",
  "V",
  "[Z",
  "[B",
  "[C",
  "[D",
  "[F",
  "[I",
  "[J",
  "[S",
  "[Ljava/lang/StackTraceElement;",
};

class ObjectLock {
 public:
  explicit ObjectLock(Object* object) : self_(Thread::Current()), obj_(object) {
    CHECK(object != NULL);
    obj_->MonitorEnter(self_);
  }

  ~ObjectLock() {
    obj_->MonitorExit(self_);
  }

  void Wait() {
    return Monitor::Wait(self_, obj_, 0, 0, false);
  }

  void Notify() {
    obj_->Notify();
  }

  void NotifyAll() {
    obj_->NotifyAll();
  }

 private:
  Thread* self_;
  Object* obj_;
  DISALLOW_COPY_AND_ASSIGN(ObjectLock);
};

ClassLinker* ClassLinker::Create(const std::vector<const DexFile*>& boot_class_path,
                                 const std::vector<const DexFile*>& class_path,
                                 InternTable* intern_table, bool image) {
  CHECK_NE(boot_class_path.size(), 0U);
  UniquePtr<ClassLinker> class_linker(new ClassLinker(intern_table));
  if (image) {
    class_linker->InitFromImage(boot_class_path, class_path);
  } else {
    class_linker->Init(boot_class_path, class_path);
  }
  // TODO: check for failure during initialization
  return class_linker.release();
}

ClassLinker::ClassLinker(InternTable* intern_table)
    : lock_("ClassLinker lock"),
      class_roots_(NULL),
      array_interfaces_(NULL),
      array_iftable_(NULL),
      init_done_(false),
      intern_table_(intern_table) {
  CHECK_EQ(arraysize(class_roots_descriptors_), size_t(kClassRootsMax));
}

void ClassLinker::Init(const std::vector<const DexFile*>& boot_class_path,
                       const std::vector<const DexFile*>& class_path) {
  CHECK(!init_done_);

  // java_lang_Class comes first, its needed for AllocClass
  Class* java_lang_Class = down_cast<Class*>(
      Heap::AllocObject(NULL, sizeof(ClassClass)));
  CHECK(java_lang_Class != NULL);
  java_lang_Class->SetClass(java_lang_Class);
  java_lang_Class->SetClassSize(sizeof(ClassClass));
  // AllocClass(Class*) can now be used

  // Class[] is used for reflection support.
  Class* class_array_class = AllocClass(java_lang_Class, sizeof(Class));
  class_array_class->SetComponentType(java_lang_Class);

  // java_lang_Object comes next so that object_array_class can be created
  Class* java_lang_Object = AllocClass(java_lang_Class, sizeof(Class));
  CHECK(java_lang_Object != NULL);
  // backfill Object as the super class of Class
  java_lang_Class->SetSuperClass(java_lang_Object);
  java_lang_Object->SetStatus(Class::kStatusLoaded);

  // Object[] next to hold class roots
  Class* object_array_class = AllocClass(java_lang_Class, sizeof(Class));
  object_array_class->SetComponentType(java_lang_Object);

  // Setup the char class to be used for char[]
  Class* char_class = AllocClass(java_lang_Class, sizeof(Class));

  // Setup the char[] class to be used for String
  Class* char_array_class = AllocClass(java_lang_Class, sizeof(Class));
  char_array_class->SetComponentType(char_class);
  CharArray::SetArrayClass(char_array_class);

  // Setup String
  Class* java_lang_String = AllocClass(java_lang_Class, sizeof(StringClass));
  String::SetClass(java_lang_String);
  java_lang_String->SetObjectSize(sizeof(String));
  java_lang_String->SetStatus(Class::kStatusResolved);

  // Backfill Class descriptors missing until this point
  java_lang_Class->SetDescriptor(intern_table_->InternStrong("Ljava/lang/Class;"));
  java_lang_Object->SetDescriptor(intern_table_->InternStrong("Ljava/lang/Object;"));
  class_array_class->SetDescriptor(intern_table_->InternStrong("[Ljava/lang/Class;"));
  object_array_class->SetDescriptor(intern_table_->InternStrong("[Ljava/lang/Object;"));
  java_lang_String->SetDescriptor(intern_table_->InternStrong("Ljava/lang/String;"));
  char_array_class->SetDescriptor(intern_table_->InternStrong("[C"));

  // Create storage for root classes, save away our work so far (requires
  // descriptors)
  class_roots_ = ObjectArray<Class>::Alloc(object_array_class, kClassRootsMax);
  SetClassRoot(kJavaLangClass, java_lang_Class);
  SetClassRoot(kJavaLangObject, java_lang_Object);
  SetClassRoot(kClassArrayClass, class_array_class);
  SetClassRoot(kObjectArrayClass, object_array_class);
  SetClassRoot(kCharArrayClass, char_array_class);
  SetClassRoot(kJavaLangString, java_lang_String);

  // Setup the primitive type classes.
  SetClassRoot(kPrimitiveBoolean, CreatePrimitiveClass("Z", Class::kPrimBoolean));
  SetClassRoot(kPrimitiveByte, CreatePrimitiveClass("B", Class::kPrimByte));
  SetClassRoot(kPrimitiveShort, CreatePrimitiveClass("S", Class::kPrimShort));
  SetClassRoot(kPrimitiveInt, CreatePrimitiveClass("I", Class::kPrimInt));
  SetClassRoot(kPrimitiveLong, CreatePrimitiveClass("J", Class::kPrimLong));
  SetClassRoot(kPrimitiveFloat, CreatePrimitiveClass("F", Class::kPrimFloat));
  SetClassRoot(kPrimitiveDouble, CreatePrimitiveClass("D", Class::kPrimDouble));
  SetClassRoot(kPrimitiveVoid, CreatePrimitiveClass("V", Class::kPrimVoid));

  // Create array interface entries to populate once we can load system classes
  array_interfaces_ = AllocClassArray(2);
  array_iftable_ = AllocObjectArray<InterfaceEntry>(2);

  // Create int array type for AllocDexCache (done in AppendToBootClassPath)
  Class* int_array_class = AllocClass(java_lang_Class, sizeof(Class));
  int_array_class->SetDescriptor(intern_table_->InternStrong("[I"));
  int_array_class->SetComponentType(GetClassRoot(kPrimitiveInt));
  IntArray::SetArrayClass(int_array_class);
  SetClassRoot(kIntArrayClass, int_array_class);

  // now that these are registered, we can use AllocClass() and AllocObjectArray

  // setup boot_class_path_ and register class_path now that we can
  // use AllocObjectArray to create DexCache instances
  for (size_t i = 0; i != boot_class_path.size(); ++i) {
    const DexFile* dex_file = boot_class_path[i];
    CHECK(dex_file != NULL);
    AppendToBootClassPath(*dex_file);
  }
  for (size_t i = 0; i != class_path.size(); ++i) {
    const DexFile* dex_file = class_path[i];
    CHECK(dex_file != NULL);
    RegisterDexFile(*dex_file);
  }

  // Constructor, Field, and Method are necessary so that FindClass can link members
  Class* java_lang_reflect_Constructor = AllocClass(java_lang_Class, sizeof(MethodClass));
  java_lang_reflect_Constructor->SetDescriptor(intern_table_->InternStrong("Ljava/lang/reflect/Constructor;"));
  CHECK(java_lang_reflect_Constructor != NULL);
  java_lang_reflect_Constructor->SetObjectSize(sizeof(Method));
  SetClassRoot(kJavaLangReflectConstructor, java_lang_reflect_Constructor);
  java_lang_reflect_Constructor->SetStatus(Class::kStatusResolved);

  Class* java_lang_reflect_Field = AllocClass(java_lang_Class, sizeof(FieldClass));
  CHECK(java_lang_reflect_Field != NULL);
  java_lang_reflect_Field->SetDescriptor(intern_table_->InternStrong("Ljava/lang/reflect/Field;"));
  java_lang_reflect_Field->SetObjectSize(sizeof(Field));
  SetClassRoot(kJavaLangReflectField, java_lang_reflect_Field);
  java_lang_reflect_Field->SetStatus(Class::kStatusResolved);
  Field::SetClass(java_lang_reflect_Field);

  Class* java_lang_reflect_Method = AllocClass(java_lang_Class, sizeof(MethodClass));
  java_lang_reflect_Method->SetDescriptor(intern_table_->InternStrong("Ljava/lang/reflect/Method;"));
  CHECK(java_lang_reflect_Method != NULL);
  java_lang_reflect_Method->SetObjectSize(sizeof(Method));
  SetClassRoot(kJavaLangReflectMethod, java_lang_reflect_Method);
  java_lang_reflect_Method->SetStatus(Class::kStatusResolved);
  Method::SetClasses(java_lang_reflect_Constructor, java_lang_reflect_Method);

  // now we can use FindSystemClass

  // run char class through InitializePrimitiveClass to finish init
  InitializePrimitiveClass(char_class, "C", Class::kPrimChar);
  SetClassRoot(kPrimitiveChar, char_class);  // needs descriptor

  // Object and String need to be rerun through FindSystemClass to finish init
  java_lang_Object->SetStatus(Class::kStatusNotReady);
  Class* Object_class = FindSystemClass("Ljava/lang/Object;");
  CHECK_EQ(java_lang_Object, Object_class);
  CHECK_EQ(java_lang_Object->GetObjectSize(), sizeof(Object));
  java_lang_String->SetStatus(Class::kStatusNotReady);
  Class* String_class = FindSystemClass("Ljava/lang/String;");
  CHECK_EQ(java_lang_String, String_class);
  CHECK_EQ(java_lang_String->GetObjectSize(), sizeof(String));

  // Setup the primitive array type classes - can't be done until Object has a vtable
  SetClassRoot(kBooleanArrayClass, FindSystemClass("[Z"));
  BooleanArray::SetArrayClass(GetClassRoot(kBooleanArrayClass));

  SetClassRoot(kByteArrayClass, FindSystemClass("[B"));
  ByteArray::SetArrayClass(GetClassRoot(kByteArrayClass));

  Class* found_char_array_class = FindSystemClass("[C");
  CHECK_EQ(char_array_class, found_char_array_class);

  SetClassRoot(kShortArrayClass, FindSystemClass("[S"));
  ShortArray::SetArrayClass(GetClassRoot(kShortArrayClass));

  Class* found_int_array_class = FindSystemClass("[I");
  CHECK_EQ(int_array_class, found_int_array_class);

  SetClassRoot(kLongArrayClass, FindSystemClass("[J"));
  LongArray::SetArrayClass(GetClassRoot(kLongArrayClass));

  SetClassRoot(kFloatArrayClass, FindSystemClass("[F"));
  FloatArray::SetArrayClass(GetClassRoot(kFloatArrayClass));

  SetClassRoot(kDoubleArrayClass, FindSystemClass("[D"));
  DoubleArray::SetArrayClass(GetClassRoot(kDoubleArrayClass));

  Class* found_class_array_class = FindSystemClass("[Ljava/lang/Class;");
  CHECK_EQ(class_array_class, found_class_array_class);

  Class* found_object_array_class = FindSystemClass("[Ljava/lang/Object;");
  CHECK_EQ(object_array_class, found_object_array_class);

  // Setup the single, global copies of "interfaces" and "iftable"
  Class* java_lang_Cloneable = FindSystemClass("Ljava/lang/Cloneable;");
  CHECK(java_lang_Cloneable != NULL);
  Class* java_io_Serializable = FindSystemClass("Ljava/io/Serializable;");
  CHECK(java_io_Serializable != NULL);
  CHECK(array_interfaces_ != NULL);
  array_interfaces_->Set(0, java_lang_Cloneable);
  array_interfaces_->Set(1, java_io_Serializable);
  // We assume that Cloneable/Serializable don't have superinterfaces --
  // normally we'd have to crawl up and explicitly list all of the
  // supers as well.
  array_iftable_->Set(0, AllocInterfaceEntry(array_interfaces_->Get(0)));
  array_iftable_->Set(1, AllocInterfaceEntry(array_interfaces_->Get(1)));

  // Sanity check Class[] and Object[]'s interfaces
  CHECK_EQ(java_lang_Cloneable, class_array_class->GetInterface(0));
  CHECK_EQ(java_io_Serializable, class_array_class->GetInterface(1));
  CHECK_EQ(java_lang_Cloneable, object_array_class->GetInterface(0));
  CHECK_EQ(java_io_Serializable, object_array_class->GetInterface(1));

  // run Class, Constructor, Field, and Method through FindSystemClass.
  // this initializes their dex_cache_ fields and register them in classes_.
  Class* Class_class = FindSystemClass("Ljava/lang/Class;");
  CHECK_EQ(java_lang_Class, Class_class);

  java_lang_reflect_Constructor->SetStatus(Class::kStatusNotReady);
  Class* Constructor_class = FindSystemClass("Ljava/lang/reflect/Constructor;");
  CHECK_EQ(java_lang_reflect_Constructor, Constructor_class);

  java_lang_reflect_Field->SetStatus(Class::kStatusNotReady);
  Class* Field_class = FindSystemClass("Ljava/lang/reflect/Field;");
  CHECK_EQ(java_lang_reflect_Field, Field_class);

  java_lang_reflect_Method->SetStatus(Class::kStatusNotReady);
  Class* Method_class = FindSystemClass("Ljava/lang/reflect/Method;");
  CHECK_EQ(java_lang_reflect_Method, Method_class);

  // java.lang.ref classes need to be specially flagged, but otherwise are normal classes
  Class* java_lang_ref_FinalizerReference = FindSystemClass("Ljava/lang/ref/FinalizerReference;");
  java_lang_ref_FinalizerReference->SetAccessFlags(
      java_lang_ref_FinalizerReference->GetAccessFlags() |
          kAccClassIsReference | kAccClassIsFinalizerReference);
  Class* java_lang_ref_PhantomReference = FindSystemClass("Ljava/lang/ref/PhantomReference;");
  java_lang_ref_PhantomReference->SetAccessFlags(
      java_lang_ref_PhantomReference->GetAccessFlags() |
          kAccClassIsReference | kAccClassIsPhantomReference);
  Class* java_lang_ref_SoftReference = FindSystemClass("Ljava/lang/ref/SoftReference;");
  java_lang_ref_SoftReference->SetAccessFlags(
      java_lang_ref_SoftReference->GetAccessFlags() | kAccClassIsReference);
  Class* java_lang_ref_WeakReference = FindSystemClass("Ljava/lang/ref/WeakReference;");
  java_lang_ref_WeakReference->SetAccessFlags(
      java_lang_ref_WeakReference->GetAccessFlags() |
          kAccClassIsReference | kAccClassIsWeakReference);

  // Setup the ClassLoaders, adjusting the object_size_ as necessary
  Class* java_lang_ClassLoader = FindSystemClass("Ljava/lang/ClassLoader;");
  CHECK_LT(java_lang_ClassLoader->GetObjectSize(), sizeof(ClassLoader));
  java_lang_ClassLoader->SetObjectSize(sizeof(ClassLoader));
  SetClassRoot(kJavaLangClassLoader, java_lang_ClassLoader);

  Class* dalvik_system_BaseDexClassLoader = FindSystemClass("Ldalvik/system/BaseDexClassLoader;");
  CHECK_EQ(dalvik_system_BaseDexClassLoader->GetObjectSize(), sizeof(BaseDexClassLoader));
  SetClassRoot(kDalvikSystemBaseDexClassLoader, dalvik_system_BaseDexClassLoader);

  Class* dalvik_system_PathClassLoader = FindSystemClass("Ldalvik/system/PathClassLoader;");
  CHECK_EQ(dalvik_system_PathClassLoader->GetObjectSize(), sizeof(PathClassLoader));
  SetClassRoot(kDalvikSystemPathClassLoader, dalvik_system_PathClassLoader);
  PathClassLoader::SetClass(dalvik_system_PathClassLoader);

  // Set up java.lang.StackTraceElement as a convenience
  SetClassRoot(kJavaLangStackTraceElement, FindSystemClass("Ljava/lang/StackTraceElement;"));
  SetClassRoot(kJavaLangStackTraceElementArrayClass, FindSystemClass("[Ljava/lang/StackTraceElement;"));
  StackTraceElement::SetClass(GetClassRoot(kJavaLangStackTraceElement));

  FinishInit();
}

void ClassLinker::FinishInit() {

  // Let the heap know some key offsets into java.lang.ref instances
  // NB we hard code the field indexes here rather than using FindInstanceField
  // as the types of the field can't be resolved prior to the runtime being
  // fully initialized
  Class* java_lang_ref_Reference = FindSystemClass("Ljava/lang/ref/Reference;");
  Class* java_lang_ref_FinalizerReference = FindSystemClass("Ljava/lang/ref/FinalizerReference;");

  Field* pendingNext = java_lang_ref_Reference->GetInstanceField(0);
  CHECK(pendingNext->GetName()->Equals("pendingNext"));
  CHECK_EQ(ResolveType(pendingNext->GetTypeIdx(), pendingNext), java_lang_ref_Reference);

  Field* queue = java_lang_ref_Reference->GetInstanceField(1);
  CHECK(queue->GetName()->Equals("queue"));
  CHECK_EQ(ResolveType(queue->GetTypeIdx(), queue),
           FindSystemClass("Ljava/lang/ref/ReferenceQueue;"));

  Field* queueNext = java_lang_ref_Reference->GetInstanceField(2);
  CHECK(queueNext->GetName()->Equals("queueNext"));
  CHECK_EQ(ResolveType(queueNext->GetTypeIdx(), queueNext), java_lang_ref_Reference);

  Field* referent = java_lang_ref_Reference->GetInstanceField(3);
  CHECK(referent->GetName()->Equals("referent"));
  CHECK_EQ(ResolveType(referent->GetTypeIdx(), referent), GetClassRoot(kJavaLangObject));

  Field* zombie = java_lang_ref_FinalizerReference->GetInstanceField(2);
  CHECK(zombie->GetName()->Equals("zombie"));
  CHECK_EQ(ResolveType(zombie->GetTypeIdx(), zombie), GetClassRoot(kJavaLangObject));

  Heap::SetReferenceOffsets(referent->GetOffset(),
                            queue->GetOffset(),
                            queueNext->GetOffset(),
                            pendingNext->GetOffset(),
                            zombie->GetOffset());

  // ensure all class_roots_ are initialized
  for (size_t i = 0; i < kClassRootsMax; i++) {
    ClassRoot class_root = static_cast<ClassRoot>(i);
    Class* klass = GetClassRoot(class_root);
    CHECK(klass != NULL);
    DCHECK(klass->IsArrayClass() || klass->IsPrimitive() || klass->GetDexCache() != NULL);
    // note SetClassRoot does additional validation.
    // if possible add new checks there to catch errors early
  }

  // disable the slow paths in FindClass and CreatePrimitiveClass now
  // that Object, Class, and Object[] are setup
  init_done_ = true;
}

struct ClassLinker::InitFromImageCallbackState {
  ClassLinker* class_linker;

  Class* class_roots[kClassRootsMax];

  typedef std::tr1::unordered_map<std::string, ClassRoot> Table;
  Table descriptor_to_class_root;

  typedef std::tr1::unordered_set<DexCache*, DexCacheHash> Set;
  Set dex_caches;
};

void ClassLinker::InitFromImage(const std::vector<const DexFile*>& boot_class_path,
                                const std::vector<const DexFile*>& class_path) {
  CHECK(!init_done_);

  HeapBitmap* heap_bitmap = Heap::GetLiveBits();
  DCHECK(heap_bitmap != NULL);

  InitFromImageCallbackState state;
  state.class_linker = this;
  for (size_t i = 0; i < kClassRootsMax; i++) {
    ClassRoot class_root = static_cast<ClassRoot>(i);
    state.descriptor_to_class_root[GetClassRootDescriptor(class_root)] = class_root;
  }

  // reinit clases_ table
  heap_bitmap->Walk(InitFromImageCallback, &state);

  // reinit class_roots_
  Class* object_array_class = state.class_roots[kObjectArrayClass];
  class_roots_ = ObjectArray<Class>::Alloc(object_array_class, kClassRootsMax);
  for (size_t i = 0; i < kClassRootsMax; i++) {
    ClassRoot class_root = static_cast<ClassRoot>(i);
    SetClassRoot(class_root, state.class_roots[class_root]);
  }

  // reinit array_interfaces_ from any array class instance, they should all be ==
  array_interfaces_ = GetClassRoot(kObjectArrayClass)->GetInterfaces();
  DCHECK(array_interfaces_ == GetClassRoot(kBooleanArrayClass)->GetInterfaces());

  // build a map from location to DexCache to match up with DexFile::GetLocation
  std::tr1::unordered_map<std::string, DexCache*> location_to_dex_cache;
  typedef InitFromImageCallbackState::Set::const_iterator It;  // TODO: C++0x auto
  for (It it = state.dex_caches.begin(), end = state.dex_caches.end(); it != end; ++it) {
    DexCache* dex_cache = *it;
    std::string location = dex_cache->GetLocation()->ToModifiedUtf8();
    location_to_dex_cache[location] = dex_cache;
  }
  CHECK_EQ(boot_class_path.size() + class_path.size(),
           location_to_dex_cache.size());

  // reinit boot_class_path with DexFile arguments and found DexCaches
  for (size_t i = 0; i != boot_class_path.size(); ++i) {
    const DexFile* dex_file = boot_class_path[i];
    CHECK(dex_file != NULL);
    DexCache* dex_cache = location_to_dex_cache[dex_file->GetLocation()];
    CHECK(dex_cache != NULL) << dex_file->GetLocation();
    AppendToBootClassPath(*dex_file, dex_cache);
  }

  // register class_path with DexFile arguments and found DexCaches
  for (size_t i = 0; i != class_path.size(); ++i) {
    const DexFile* dex_file = class_path[i];
    CHECK(dex_file != NULL);
    DexCache* dex_cache = location_to_dex_cache[dex_file->GetLocation()];
    CHECK(dex_cache != NULL) << dex_file->GetLocation();
    RegisterDexFile(*dex_file, dex_cache);
  }

  String::SetClass(GetClassRoot(kJavaLangString));
  Field::SetClass(GetClassRoot(kJavaLangReflectField));
  Method::SetClasses(GetClassRoot(kJavaLangReflectConstructor), GetClassRoot(kJavaLangReflectMethod));
  BooleanArray::SetArrayClass(GetClassRoot(kBooleanArrayClass));
  ByteArray::SetArrayClass(GetClassRoot(kByteArrayClass));
  CharArray::SetArrayClass(GetClassRoot(kCharArrayClass));
  DoubleArray::SetArrayClass(GetClassRoot(kDoubleArrayClass));
  FloatArray::SetArrayClass(GetClassRoot(kFloatArrayClass));
  IntArray::SetArrayClass(GetClassRoot(kIntArrayClass));
  LongArray::SetArrayClass(GetClassRoot(kLongArrayClass));
  ShortArray::SetArrayClass(GetClassRoot(kShortArrayClass));
  PathClassLoader::SetClass(GetClassRoot(kDalvikSystemPathClassLoader));
  StackTraceElement::SetClass(GetClassRoot(kJavaLangStackTraceElement));

  FinishInit();
}

void ClassLinker::InitFromImageCallback(Object* obj, void* arg) {
  DCHECK(obj != NULL);
  DCHECK(arg != NULL);
  InitFromImageCallbackState* state = reinterpret_cast<InitFromImageCallbackState*>(arg);

  if (obj->IsString()) {
    state->class_linker->intern_table_->RegisterStrong(obj->AsString());
    return;
  }
  if (!obj->IsClass()) {
    return;
  }
  Class* klass = obj->AsClass();
  // TODO: restore ClassLoader's list of DexFiles after image load
  // CHECK(klass->GetClassLoader() == NULL);
  const ClassLoader* class_loader = klass->GetClassLoader();
  if (class_loader != NULL) {
    // TODO: replace this hack with something based on command line arguments
    Thread::Current()->SetClassLoaderOverride(class_loader);
  }

  std::string descriptor = klass->GetDescriptor()->ToModifiedUtf8();
  // restore class to ClassLinker::classes_ table
  state->class_linker->InsertClass(descriptor, klass);

  // note DexCache to match with DexFile later
  DexCache* dex_cache = klass->GetDexCache();
  if (dex_cache != NULL) {
    state->dex_caches.insert(dex_cache);
  } else {
    DCHECK(klass->IsArrayClass() || klass->IsPrimitive());
  }

  // check if this is a root, if so, register it
  typedef InitFromImageCallbackState::Table::const_iterator It;  // TODO: C++0x auto
  It it = state->descriptor_to_class_root.find(descriptor);
  if (it != state->descriptor_to_class_root.end()) {
    ClassRoot class_root = it->second;
    state->class_roots[class_root] = klass;
  }
}

// Keep in sync with InitCallback. Anything we visit, we need to
// reinit references to when reinitializing a ClassLinker from a
// mapped image.
void ClassLinker::VisitRoots(Heap::RootVisitor* visitor, void* arg) const {
  visitor(class_roots_, arg);

  for (size_t i = 0; i < dex_caches_.size(); i++) {
    visitor(dex_caches_[i], arg);
  }

  {
    MutexLock mu(lock_);
    typedef Table::const_iterator It;  // TODO: C++0x auto
    for (It it = classes_.begin(), end = classes_.end(); it != end; ++it) {
      visitor(it->second, arg);
    }
  }

  visitor(array_interfaces_, arg);
}

ClassLinker::~ClassLinker() {
  String::ResetClass();
  Field::ResetClass();
  Method::ResetClasses();
  BooleanArray::ResetArrayClass();
  ByteArray::ResetArrayClass();
  CharArray::ResetArrayClass();
  DoubleArray::ResetArrayClass();
  FloatArray::ResetArrayClass();
  IntArray::ResetArrayClass();
  LongArray::ResetArrayClass();
  ShortArray::ResetArrayClass();
  PathClassLoader::ResetClass();
  StackTraceElement::ResetClass();
}

DexCache* ClassLinker::AllocDexCache(const DexFile& dex_file) {
  DexCache* dex_cache = down_cast<DexCache*>(AllocObjectArray<Object>(DexCache::LengthAsArray()));
  dex_cache->Init(intern_table_->InternStrong(dex_file.GetLocation().c_str()),
                  AllocObjectArray<String>(dex_file.NumStringIds()),
                  AllocClassArray(dex_file.NumTypeIds()),
                  AllocObjectArray<Method>(dex_file.NumMethodIds()),
                  AllocObjectArray<Field>(dex_file.NumFieldIds()),
                  AllocCodeAndDirectMethods(dex_file.NumMethodIds()),
                  AllocObjectArray<StaticStorageBase>(dex_file.NumTypeIds()));
  return dex_cache;
}

CodeAndDirectMethods* ClassLinker::AllocCodeAndDirectMethods(size_t length) {
  return down_cast<CodeAndDirectMethods*>(IntArray::Alloc(CodeAndDirectMethods::LengthAsArray(length)));
}

InterfaceEntry* ClassLinker::AllocInterfaceEntry(Class* interface) {
  DCHECK(interface->IsInterface());
  ObjectArray<Object>* array = AllocObjectArray<Object>(InterfaceEntry::LengthAsArray());
  InterfaceEntry* interface_entry = down_cast<InterfaceEntry*>(array);
  interface_entry->SetInterface(interface);
  return interface_entry;
}

Class* ClassLinker::AllocClass(Class* java_lang_Class, size_t class_size) {
  DCHECK_GE(class_size, sizeof(Class));
  Class* klass = Heap::AllocObject(java_lang_Class, class_size)->AsClass();
  klass->SetPrimitiveType(Class::kPrimNot);  // default to not being primitive
  klass->SetClassSize(class_size);
  return klass;
}

Class* ClassLinker::AllocClass(size_t class_size) {
  return AllocClass(GetClassRoot(kJavaLangClass), class_size);
}

Field* ClassLinker::AllocField() {
  return down_cast<Field*>(GetClassRoot(kJavaLangReflectField)->AllocObject());
}

Method* ClassLinker::AllocMethod() {
  return down_cast<Method*>(GetClassRoot(kJavaLangReflectMethod)->AllocObject());
}

ObjectArray<StackTraceElement>* ClassLinker::AllocStackTraceElementArray(size_t length) {
  return ObjectArray<StackTraceElement>::Alloc(
      GetClassRoot(kJavaLangStackTraceElementArrayClass),
      length);
}

Class* ClassLinker::FindClass(const StringPiece& descriptor,
                              const ClassLoader* class_loader) {
  // TODO: remove this contrived parent class loader check when we have a real ClassLoader.
  if (class_loader != NULL) {
    Class* klass = FindClass(descriptor, NULL);
    if (klass != NULL) {
      return klass;
    }
    Thread::Current()->ClearException();
  }

  Thread* self = Thread::Current();
  DCHECK(self != NULL);
  CHECK(!self->IsExceptionPending()) << PrettyTypeOf(self->GetException());
  // Find the class in the loaded classes table.
  Class* klass = LookupClass(descriptor, class_loader);
  if (klass == NULL) {
    // Class is not yet loaded.
    if (descriptor[0] == '[' && descriptor[1] != '\0') {
      return CreateArrayClass(descriptor, class_loader);
    }
    const DexFile::ClassPath& class_path = ((class_loader != NULL)
                                            ? ClassLoader::GetClassPath(class_loader)
                                            : boot_class_path_);
    DexFile::ClassPathEntry pair = DexFile::FindInClassPath(descriptor, class_path);
    if (pair.second == NULL) {
      std::string name(PrintableString(descriptor));
      ThrowNoClassDefFoundError("Class %s not found in class loader %p", name.c_str(), class_loader);
      return NULL;
    }
    const DexFile& dex_file = *pair.first;
    const DexFile::ClassDef& dex_class_def = *pair.second;
    DexCache* dex_cache = FindDexCache(dex_file);
    // Load the class from the dex file.
    if (!init_done_) {
      // finish up init of hand crafted class_roots_
      if (descriptor == "Ljava/lang/Object;") {
        klass = GetClassRoot(kJavaLangObject);
      } else if (descriptor == "Ljava/lang/Class;") {
        klass = GetClassRoot(kJavaLangClass);
      } else if (descriptor == "Ljava/lang/String;") {
        klass = GetClassRoot(kJavaLangString);
      } else if (descriptor == "Ljava/lang/reflect/Constructor;") {
        klass = GetClassRoot(kJavaLangReflectConstructor);
      } else if (descriptor == "Ljava/lang/reflect/Field;") {
        klass = GetClassRoot(kJavaLangReflectField);
      } else if (descriptor == "Ljava/lang/reflect/Method;") {
        klass = GetClassRoot(kJavaLangReflectMethod);
      } else {
        klass = AllocClass(SizeOfClass(dex_file, dex_class_def));
      }
    } else {
      klass = AllocClass(SizeOfClass(dex_file, dex_class_def));
    }
    if (!klass->IsResolved()) {
      klass->SetDexCache(dex_cache);
      LoadClass(dex_file, dex_class_def, klass, class_loader);
      // Check for a pending exception during load
      if (self->IsExceptionPending()) {
        return NULL;
      }
      ObjectLock lock(klass);
      klass->SetClinitThreadId(self->GetTid());
      // Add the newly loaded class to the loaded classes table.
      bool success = InsertClass(descriptor, klass);  // TODO: just return collision
      if (!success) {
        // We may fail to insert if we raced with another thread.
        klass->SetClinitThreadId(0);
        klass = LookupClass(descriptor, class_loader);
        CHECK(klass != NULL);
        return klass;
      } else {
        // Finish loading (if necessary) by finding parents
        CHECK(!klass->IsLoaded());
        if (!LoadSuperAndInterfaces(klass, dex_file)) {
          // Loading failed.
          CHECK(self->IsExceptionPending());
          lock.NotifyAll();
          return NULL;
        }
        CHECK(klass->IsLoaded());
        // Link the class (if necessary)
        CHECK(!klass->IsResolved());
        if (!LinkClass(klass)) {
          // Linking failed.
          CHECK(self->IsExceptionPending());
          lock.NotifyAll();
          return NULL;
        }
        CHECK(klass->IsResolved());
      }
    }
  }
  // Link the class if it has not already been linked.
  if (!klass->IsResolved() && !klass->IsErroneous()) {
    ObjectLock lock(klass);
    // Check for circular dependencies between classes.
    if (!klass->IsResolved() && klass->GetClinitThreadId() == self->GetTid()) {
      self->ThrowNewException("Ljava/lang/ClassCircularityError;", "%s",
          PrettyDescriptor(klass->GetDescriptor()).c_str());
      return NULL;
    }
    // Wait for the pending initialization to complete.
    while (!klass->IsResolved() && !klass->IsErroneous()) {
      lock.Wait();
    }
  }
  if (klass->IsErroneous()) {
    ThrowEarlierClassFailure(klass);
    return NULL;
  }
  // Return the loaded class.  No exceptions should be pending.
  CHECK(klass->IsResolved());
  CHECK(!self->IsExceptionPending());
  return klass;
}

// Precomputes size that will be needed for Class, matching LinkStaticFields
size_t ClassLinker::SizeOfClass(const DexFile& dex_file,
                                const DexFile::ClassDef& dex_class_def) {
  const byte* class_data = dex_file.GetClassData(dex_class_def);
  DexFile::ClassDataHeader header = dex_file.ReadClassDataHeader(&class_data);
  size_t num_static_fields = header.static_fields_size_;
  size_t num_ref = 0;
  size_t num_32 = 0;
  size_t num_64 = 0;
  if (num_static_fields != 0) {
    uint32_t last_idx = 0;
    for (size_t i = 0; i < num_static_fields; ++i) {
      DexFile::Field dex_field;
      dex_file.dexReadClassDataField(&class_data, &dex_field, &last_idx);
      const DexFile::FieldId& field_id = dex_file.GetFieldId(dex_field.field_idx_);
      const char* descriptor = dex_file.dexStringByTypeIdx(field_id.type_idx_);
      char c = descriptor[0];
      if (c == 'L' || c == '[') {
        num_ref++;
      } else if (c == 'J' || c == 'D') {
        num_64++;
      } else {
        num_32++;
      }
    }
  }

  // start with generic class data
  size_t size = sizeof(Class);
  // follow with reference fields which must be contiguous at start
  size += (num_ref * sizeof(uint32_t));
  // if there are 64-bit fields to add, make sure they are aligned
  if (num_64 != 0 && size != RoundUp(size, 8)) { // for 64-bit alignment
    if (num_32 != 0) {
      // use an available 32-bit field for padding
      num_32--;
    }
    size += sizeof(uint32_t);  // either way, we are adding a word
    DCHECK_EQ(size, RoundUp(size, 8));
  }
  // tack on any 64-bit fields now that alignment is assured
  size += (num_64 * sizeof(uint64_t));
  // tack on any remaining 32-bit fields
  size += (num_32 * sizeof(uint32_t));
  return size;
}

void ClassLinker::LoadClass(const DexFile& dex_file,
                            const DexFile::ClassDef& dex_class_def,
                            Class* klass,
                            const ClassLoader* class_loader) {
  CHECK(klass != NULL);
  CHECK(klass->GetDexCache() != NULL);
  CHECK_EQ(Class::kStatusNotReady, klass->GetStatus());
  const byte* class_data = dex_file.GetClassData(dex_class_def);
  DexFile::ClassDataHeader header = dex_file.ReadClassDataHeader(&class_data);

  const char* descriptor = dex_file.GetClassDescriptor(dex_class_def);
  CHECK(descriptor != NULL);

  klass->SetClass(GetClassRoot(kJavaLangClass));
  if (klass->GetDescriptor() != NULL) {
    DCHECK(klass->GetDescriptor()->Equals(descriptor));
  } else {
    klass->SetDescriptor(intern_table_->InternStrong(descriptor));
  }
  uint32_t access_flags = dex_class_def.access_flags_;
  // Make sure there aren't any "bonus" flags set, since we use them for runtime
  // state.
  CHECK_EQ(access_flags & ~kAccClassFlagsMask, 0U);
  klass->SetAccessFlags(access_flags);
  klass->SetClassLoader(class_loader);
  DCHECK(klass->GetPrimitiveType() == Class::kPrimNot);
  klass->SetStatus(Class::kStatusIdx);

  klass->SetSuperClassTypeIdx(dex_class_def.superclass_idx_);

  size_t num_static_fields = header.static_fields_size_;
  size_t num_instance_fields = header.instance_fields_size_;
  size_t num_direct_methods = header.direct_methods_size_;
  size_t num_virtual_methods = header.virtual_methods_size_;

  klass->SetSourceFile(intern_table_->InternStrong(dex_file.dexGetSourceFile(dex_class_def)));

  // Load class interfaces.
  LoadInterfaces(dex_file, dex_class_def, klass);

  // Load static fields.
  if (num_static_fields != 0) {
    klass->SetSFields(AllocObjectArray<Field>(num_static_fields));
    uint32_t last_idx = 0;
    for (size_t i = 0; i < num_static_fields; ++i) {
      DexFile::Field dex_field;
      dex_file.dexReadClassDataField(&class_data, &dex_field, &last_idx);
      Field* sfield = AllocField();
      klass->SetStaticField(i, sfield);
      LoadField(dex_file, dex_field, klass, sfield);
    }
  }

  // Load instance fields.
  if (num_instance_fields != 0) {
    klass->SetIFields(AllocObjectArray<Field>(num_instance_fields));
    uint32_t last_idx = 0;
    for (size_t i = 0; i < num_instance_fields; ++i) {
      DexFile::Field dex_field;
      dex_file.dexReadClassDataField(&class_data, &dex_field, &last_idx);
      Field* ifield = AllocField();
      klass->SetInstanceField(i, ifield);
      LoadField(dex_file, dex_field, klass, ifield);
    }
  }

  // Load direct methods.
  if (num_direct_methods != 0) {
    // TODO: append direct methods to class object
    klass->SetDirectMethods(AllocObjectArray<Method>(num_direct_methods));
    uint32_t last_idx = 0;
    for (size_t i = 0; i < num_direct_methods; ++i) {
      DexFile::Method dex_method;
      dex_file.dexReadClassDataMethod(&class_data, &dex_method, &last_idx);
      Method* meth = AllocMethod();
      klass->SetDirectMethod(i, meth);
      LoadMethod(dex_file, dex_method, klass, meth);
      // TODO: register maps
    }
  }

  // Load virtual methods.
  if (num_virtual_methods != 0) {
    // TODO: append virtual methods to class object
    klass->SetVirtualMethods(AllocObjectArray<Method>(num_virtual_methods));
    uint32_t last_idx = 0;
    for (size_t i = 0; i < num_virtual_methods; ++i) {
      DexFile::Method dex_method;
      dex_file.dexReadClassDataMethod(&class_data, &dex_method, &last_idx);
      Method* meth = AllocMethod();
      klass->SetVirtualMethod(i, meth);
      LoadMethod(dex_file, dex_method, klass, meth);
      // TODO: register maps
    }
  }
}

void ClassLinker::LoadInterfaces(const DexFile& dex_file,
                                 const DexFile::ClassDef& dex_class_def,
                                 Class* klass) {
  const DexFile::TypeList* list = dex_file.GetInterfacesList(dex_class_def);
  if (list != NULL) {
    klass->SetInterfaces(AllocClassArray(list->Size()));
    IntArray* interfaces_idx = IntArray::Alloc(list->Size());
    klass->SetInterfacesTypeIdx(interfaces_idx);
    for (size_t i = 0; i < list->Size(); ++i) {
      const DexFile::TypeItem& type_item = list->GetTypeItem(i);
      interfaces_idx->Set(i, type_item.type_idx_);
    }
  }
}

void ClassLinker::LoadField(const DexFile& dex_file,
                            const DexFile::Field& src,
                            Class* klass,
                            Field* dst) {
  const DexFile::FieldId& field_id = dex_file.GetFieldId(src.field_idx_);
  dst->SetDeclaringClass(klass);
  dst->SetName(ResolveString(dex_file, field_id.name_idx_, klass->GetDexCache()));
  dst->SetTypeIdx(field_id.type_idx_);
  dst->SetAccessFlags(src.access_flags_);

  // In order to access primitive types using GetTypeDuringLinking we need to
  // ensure they are resolved into the dex cache
  const char* descriptor = dex_file.dexStringByTypeIdx(field_id.type_idx_);
  if (descriptor[1] == '\0') {
    // only the descriptors of primitive types should be 1 character long
    Class* resolved = ResolveType(dex_file, field_id.type_idx_, klass);
    DCHECK(resolved->IsPrimitive());
  }
}

void ClassLinker::LoadMethod(const DexFile& dex_file,
                             const DexFile::Method& src,
                             Class* klass,
                             Method* dst) {
  const DexFile::MethodId& method_id = dex_file.GetMethodId(src.method_idx_);
  dst->SetDeclaringClass(klass);
  String* method_name = ResolveString(dex_file, method_id.name_idx_, klass->GetDexCache());
  dst->SetName(method_name);
  if (method_name->Equals("<init>")) {
    dst->SetClass(GetClassRoot(kJavaLangReflectConstructor));
  }
  {
    int32_t utf16_length;
    std::string utf8(dex_file.CreateMethodDescriptor(method_id.proto_idx_, &utf16_length));
    dst->SetSignature(intern_table_->InternStrong(utf16_length, utf8.c_str()));
  }
  dst->SetProtoIdx(method_id.proto_idx_);
  dst->SetCodeItemOffset(src.code_off_);
  const char* shorty = dex_file.GetShorty(method_id.proto_idx_);
  dst->SetShorty(intern_table_->InternStrong(shorty));
  dst->SetAccessFlags(src.access_flags_);
  dst->SetReturnTypeIdx(dex_file.GetProtoId(method_id.proto_idx_).return_type_idx_);

  dst->SetDexCacheStrings(klass->GetDexCache()->GetStrings());
  dst->SetDexCacheResolvedTypes(klass->GetDexCache()->GetResolvedTypes());
  dst->SetDexCacheResolvedMethods(klass->GetDexCache()->GetResolvedMethods());
  dst->SetDexCacheResolvedFields(klass->GetDexCache()->GetResolvedFields());
  dst->SetDexCacheCodeAndDirectMethods(klass->GetDexCache()->GetCodeAndDirectMethods());
  dst->SetDexCacheInitializedStaticStorage(klass->GetDexCache()->GetInitializedStaticStorage());

  // TODO: check for finalize method

  const DexFile::CodeItem* code_item = dex_file.GetCodeItem(src);
  if (code_item != NULL) {
    dst->SetNumRegisters(code_item->registers_size_);
    dst->SetNumIns(code_item->ins_size_);
    dst->SetNumOuts(code_item->outs_size_);
  } else {
    uint16_t num_args = Method::NumArgRegisters(shorty);
    if ((src.access_flags_ & kAccStatic) != 0) {
      ++num_args;
    }
    dst->SetNumRegisters(num_args);
    // TODO: native methods
  }
}

void ClassLinker::AppendToBootClassPath(const DexFile& dex_file) {
  AppendToBootClassPath(dex_file, AllocDexCache(dex_file));
}

void ClassLinker::AppendToBootClassPath(const DexFile& dex_file, DexCache* dex_cache) {
  CHECK(dex_cache != NULL) << dex_file.GetLocation();
  boot_class_path_.push_back(&dex_file);
  RegisterDexFile(dex_file, dex_cache);
}

void ClassLinker::RegisterDexFile(const DexFile& dex_file) {
  RegisterDexFile(dex_file, AllocDexCache(dex_file));
}

void ClassLinker::RegisterDexFile(const DexFile& dex_file, DexCache* dex_cache) {
  MutexLock mu(lock_);
  CHECK(dex_cache != NULL) << dex_file.GetLocation();
  CHECK(dex_cache->GetLocation()->Equals(dex_file.GetLocation()));
  dex_files_.push_back(&dex_file);
  dex_caches_.push_back(dex_cache);
}

const DexFile& ClassLinker::FindDexFile(const DexCache* dex_cache) const {
  MutexLock mu(lock_);
  for (size_t i = 0; i != dex_caches_.size(); ++i) {
    if (dex_caches_[i] == dex_cache) {
        return *dex_files_[i];
    }
  }
  CHECK(false) << "Failed to find DexFile for DexCache " << dex_cache->GetLocation()->ToModifiedUtf8();
  return *dex_files_[-1];
}

DexCache* ClassLinker::FindDexCache(const DexFile& dex_file) const {
  MutexLock mu(lock_);
  for (size_t i = 0; i != dex_files_.size(); ++i) {
    if (dex_files_[i] == &dex_file) {
        return dex_caches_[i];
    }
  }
  CHECK(false) << "Failed to find DexCache for DexFile " << dex_file.GetLocation();
  return NULL;
}

Class* ClassLinker::InitializePrimitiveClass(Class* primitive_class,
                                             const char* descriptor,
                                             Class::PrimitiveType type) {
  // TODO: deduce one argument from the other
  CHECK(primitive_class != NULL);
  primitive_class->SetAccessFlags(kAccPublic | kAccFinal | kAccAbstract);
  primitive_class->SetDescriptor(intern_table_->InternStrong(descriptor));
  primitive_class->SetPrimitiveType(type);
  primitive_class->SetStatus(Class::kStatusInitialized);
  bool success = InsertClass(descriptor, primitive_class);
  CHECK(success) << "InitPrimitiveClass(" << descriptor << ") failed";
  return primitive_class;
}

// Create an array class (i.e. the class object for the array, not the
// array itself).  "descriptor" looks like "[C" or "[[[[B" or
// "[Ljava/lang/String;".
//
// If "descriptor" refers to an array of primitives, look up the
// primitive type's internally-generated class object.
//
// "class_loader" is the class loader of the class that's referring to
// us.  It's used to ensure that we're looking for the element type in
// the right context.  It does NOT become the class loader for the
// array class; that always comes from the base element class.
//
// Returns NULL with an exception raised on failure.
Class* ClassLinker::CreateArrayClass(const StringPiece& descriptor,
                                     const ClassLoader* class_loader) {
  CHECK_EQ('[', descriptor[0]);

  // Identify the underlying component type
  Class* component_type = FindClass(descriptor.substr(1), class_loader);
  if (component_type == NULL) {
    DCHECK(Thread::Current()->IsExceptionPending());
    return NULL;
  }

  // See if the component type is already loaded.  Array classes are
  // always associated with the class loader of their underlying
  // element type -- an array of Strings goes with the loader for
  // java/lang/String -- so we need to look for it there.  (The
  // caller should have checked for the existence of the class
  // before calling here, but they did so with *their* class loader,
  // not the component type's loader.)
  //
  // If we find it, the caller adds "loader" to the class' initiating
  // loader list, which should prevent us from going through this again.
  //
  // This call is unnecessary if "loader" and "component_type->GetClassLoader()"
  // are the same, because our caller (FindClass) just did the
  // lookup.  (Even if we get this wrong we still have correct behavior,
  // because we effectively do this lookup again when we add the new
  // class to the hash table --- necessary because of possible races with
  // other threads.)
  if (class_loader != component_type->GetClassLoader()) {
    Class* new_class = LookupClass(descriptor, component_type->GetClassLoader());
    if (new_class != NULL) {
      return new_class;
    }
  }

  // Fill out the fields in the Class.
  //
  // It is possible to execute some methods against arrays, because
  // all arrays are subclasses of java_lang_Object_, so we need to set
  // up a vtable.  We can just point at the one in java_lang_Object_.
  //
  // Array classes are simple enough that we don't need to do a full
  // link step.

  Class* new_class = NULL;
  if (!init_done_) {
    // Classes that were hand created, ie not by FindSystemClass
    if (descriptor == "[Ljava/lang/Class;") {
      new_class = GetClassRoot(kClassArrayClass);
    } else if (descriptor == "[Ljava/lang/Object;") {
      new_class = GetClassRoot(kObjectArrayClass);
    } else if (descriptor == "[C") {
      new_class = GetClassRoot(kCharArrayClass);
    } else if (descriptor == "[I") {
      new_class = GetClassRoot(kIntArrayClass);
    }
  }
  if (new_class == NULL) {
    new_class = AllocClass(sizeof(Class));
    if (new_class == NULL) {
      return NULL;
    }
    new_class->SetComponentType(component_type);
  }
  DCHECK(new_class->GetComponentType() != NULL);
  if (new_class->GetDescriptor() != NULL) {
    DCHECK(new_class->GetDescriptor()->Equals(descriptor));
  } else {
    new_class->SetDescriptor(intern_table_->InternStrong(descriptor.ToString().c_str()));
  }
  Class* java_lang_Object = GetClassRoot(kJavaLangObject);
  new_class->SetSuperClass(java_lang_Object);
  new_class->SetVTable(java_lang_Object->GetVTable());
  new_class->SetPrimitiveType(Class::kPrimNot);
  new_class->SetClassLoader(component_type->GetClassLoader());
  new_class->SetStatus(Class::kStatusInitialized);
  // don't need to set new_class->SetObjectSize(..)
  // because Object::SizeOf delegates to Array::SizeOf


  // All arrays have java/lang/Cloneable and java/io/Serializable as
  // interfaces.  We need to set that up here, so that stuff like
  // "instanceof" works right.
  //
  // Note: The GC could run during the call to FindSystemClass,
  // so we need to make sure the class object is GC-valid while we're in
  // there.  Do this by clearing the interface list so the GC will just
  // think that the entries are null.


  // Use the single, global copies of "interfaces" and "iftable"
  // (remember not to free them for arrays).
  new_class->SetInterfaces(array_interfaces_);
  new_class->SetIfTable(array_iftable_);

  // Inherit access flags from the component type.  Arrays can't be
  // used as a superclass or interface, so we want to add "final"
  // and remove "interface".
  //
  // Don't inherit any non-standard flags (e.g., kAccFinal)
  // from component_type.  We assume that the array class does not
  // override finalize().
  new_class->SetAccessFlags(((new_class->GetComponentType()->GetAccessFlags() &
                             ~kAccInterface) | kAccFinal) & kAccJavaFlagsMask);

  if (InsertClass(descriptor, new_class)) {
    return new_class;
  }
  // Another thread must have loaded the class after we
  // started but before we finished.  Abandon what we've
  // done.
  //
  // (Yes, this happens.)

  // Grab the winning class.
  Class* other_class = LookupClass(descriptor, component_type->GetClassLoader());
  DCHECK(other_class != NULL);
  return other_class;
}

Class* ClassLinker::FindPrimitiveClass(char type) {
  switch (type) {
    case 'B':
      return GetClassRoot(kPrimitiveByte);
    case 'C':
      return GetClassRoot(kPrimitiveChar);
    case 'D':
      return GetClassRoot(kPrimitiveDouble);
    case 'F':
      return GetClassRoot(kPrimitiveFloat);
    case 'I':
      return GetClassRoot(kPrimitiveInt);
    case 'J':
      return GetClassRoot(kPrimitiveLong);
    case 'S':
      return GetClassRoot(kPrimitiveShort);
    case 'Z':
      return GetClassRoot(kPrimitiveBoolean);
    case 'V':
      return GetClassRoot(kPrimitiveVoid);
  }
  std::string printable_type(PrintableChar(type));
  ThrowNoClassDefFoundError("Not a primitive type: %s", printable_type.c_str());
  return NULL;
}

bool ClassLinker::InsertClass(const StringPiece& descriptor, Class* klass) {
  size_t hash = StringPieceHash()(descriptor);
  MutexLock mu(lock_);
  Table::iterator it = classes_.insert(std::make_pair(hash, klass));
  return ((*it).second == klass);
}

Class* ClassLinker::LookupClass(const StringPiece& descriptor, const ClassLoader* class_loader) {
  size_t hash = StringPieceHash()(descriptor);
  MutexLock mu(lock_);
  typedef Table::const_iterator It;  // TODO: C++0x auto
  for (It it = classes_.find(hash), end = classes_.end(); it != end; ++it) {
    Class* klass = it->second;
    if (klass->GetDescriptor()->Equals(descriptor) && klass->GetClassLoader() == class_loader) {
      return klass;
    }
  }
  return NULL;
}

void ClassLinker::VerifyClass(Class* klass) {
  if (klass->IsVerified()) {
    return;
  }

  CHECK_EQ(klass->GetStatus(), Class::kStatusResolved);

  klass->SetStatus(Class::kStatusVerifying);
  if (!DexVerifier::VerifyClass(klass)) {
    LOG(ERROR) << "Verification failed on class "
               << klass->GetDescriptor()->ToModifiedUtf8();
    Object* exception = Thread::Current()->GetException();
    // CHECK(exception != NULL) << PrettyClass(klass);
    if (exception == NULL) {
      UNIMPLEMENTED(ERROR) << "null verification exception for " << PrettyClass(klass);
    } else {
      klass->SetVerifyErrorClass(exception->GetClass());
    }
    klass->SetStatus(Class::kStatusError);
    return;
  }

  klass->SetStatus(Class::kStatusVerified);
}

bool ClassLinker::InitializeClass(Class* klass, bool can_run_clinit) {
  CHECK(klass->GetStatus() == Class::kStatusResolved ||
      klass->GetStatus() == Class::kStatusVerified ||
      klass->GetStatus() == Class::kStatusInitializing ||
      klass->GetStatus() == Class::kStatusError)
          << PrettyClass(klass) << " is " << klass->GetStatus();

  Thread* self = Thread::Current();

  Method* clinit = NULL;
  {
    ObjectLock lock(klass);

    if (klass->GetStatus() < Class::kStatusVerified) {
      if (klass->IsErroneous()) {
        ThrowEarlierClassFailure(klass);
        return false;
      }

      VerifyClass(klass);
      if (klass->GetStatus() != Class::kStatusVerified) {
        return false;
      }
    }

    if (klass->GetStatus() == Class::kStatusInitialized) {
      return true;
    }

    clinit = klass->FindDeclaredDirectMethod("<clinit>", "()V");
    if (clinit != NULL && !can_run_clinit) {
      // if the class has a <clinit>, don't bother going to initializing
      return false;
    }

    while (klass->GetStatus() == Class::kStatusInitializing) {
      // We caught somebody else in the act; was it us?
      if (klass->GetClinitThreadId() == self->GetTid()) {
        // Yes. That's fine.
        return true;
      }

      CHECK(!self->IsExceptionPending());
      lock.Wait();
      CHECK(!self->IsExceptionPending());

      // When we wake up, repeat the test for init-in-progress.  If
      // there's an exception pending (only possible if
      // "interruptShouldThrow" was set), bail out.
      if (self->IsExceptionPending()) {
        self->ThrowNewException("Ljava/lang/ExceptionInInitializerError;",
            "Exception %s thrown while initializing class %s",
            PrettyTypeOf(self->GetException()).c_str(),
            PrettyDescriptor(klass->GetDescriptor()).c_str());
        klass->SetStatus(Class::kStatusError);
        return false;
      }
      if (klass->GetStatus() == Class::kStatusInitializing) {
        continue;
      }
      DCHECK(klass->GetStatus() == Class::kStatusInitialized ||
             klass->GetStatus() == Class::kStatusError);
      if (klass->IsErroneous()) {
        // The caller wants an exception, but it was thrown in a
        // different thread.  Synthesize one here.
        self->ThrowNewException("Ljava/lang/UnsatisfiedLinkError;",
            "<clinit> failed for class %s; see exception in other thread",
            PrettyDescriptor(klass->GetDescriptor()).c_str());
        return false;
      }
      return true;  // otherwise, initialized
    }

    // see if we failed previously
    if (klass->IsErroneous()) {
      // might be wise to unlock before throwing; depends on which class
      // it is that we have locked
      ThrowEarlierClassFailure(klass);
      return false;
    }

    if (!ValidateSuperClassDescriptors(klass)) {
      klass->SetStatus(Class::kStatusError);
      return false;
    }

    DCHECK_LT(klass->GetStatus(), Class::kStatusInitializing);

    klass->SetClinitThreadId(self->GetTid());
    klass->SetStatus(Class::kStatusInitializing);
  }

  if (!InitializeSuperClass(klass, can_run_clinit)) {
    return false;
  }

  InitializeStaticFields(klass);

  if (clinit != NULL) {
    clinit->Invoke(self, NULL, NULL, NULL);
  }

  {
    ObjectLock lock(klass);

    if (self->IsExceptionPending()) {
      klass->SetStatus(Class::kStatusError);
    } else {
      ++Runtime::Current()->GetStats()->class_init_count;
      ++self->GetStats()->class_init_count;
      // TODO: class_init_time_ns
      klass->SetStatus(Class::kStatusInitialized);
    }
    lock.NotifyAll();
  }

  return true;
}

bool ClassLinker::ValidateSuperClassDescriptors(const Class* klass) {
  if (klass->IsInterface()) {
    return true;
  }
  // begin with the methods local to the superclass
  if (klass->HasSuperClass() &&
      klass->GetClassLoader() != klass->GetSuperClass()->GetClassLoader()) {
    const Class* super = klass->GetSuperClass();
    for (int i = super->NumVirtualMethods() - 1; i >= 0; --i) {
      const Method* method = super->GetVirtualMethod(i);
      if (method != super->GetVirtualMethod(i) &&
          !HasSameMethodDescriptorClasses(method, super, klass)) {
        ThrowLinkageError("Classes resolve differently in superclass");
        return false;
      }
    }
  }
  for (int32_t i = 0; i < klass->GetIfTableCount(); ++i) {
    InterfaceEntry* interface_entry = klass->GetIfTable()->Get(i);
    Class* interface = interface_entry->GetInterface();
    if (klass->GetClassLoader() != interface->GetClassLoader()) {
      for (size_t j = 0; j < interface->NumVirtualMethods(); ++j) {
        const Method* method = interface_entry->GetMethodArray()->Get(j);
        if (!HasSameMethodDescriptorClasses(method, interface,
                                            method->GetDeclaringClass())) {
          ThrowLinkageError("Classes resolve differently in interface");
          return false;
        }
      }
    }
  }
  return true;
}

bool ClassLinker::HasSameMethodDescriptorClasses(const Method* method,
                                                 const Class* klass1,
                                                 const Class* klass2) {
  const DexFile& dex_file = FindDexFile(method->GetDeclaringClass()->GetDexCache());
  const DexFile::ProtoId& proto_id = dex_file.GetProtoId(method->GetProtoIdx());
  DexFile::ParameterIterator *it;
  for (it = dex_file.GetParameterIterator(proto_id); it->HasNext(); it->Next()) {
    const char* descriptor = it->GetDescriptor();
    if (descriptor == NULL) {
      break;
    }
    if (descriptor[0] == 'L' || descriptor[0] == '[') {
      // Found a non-primitive type.
      if (!HasSameDescriptorClasses(descriptor, klass1, klass2)) {
        return false;
      }
    }
  }
  // Check the return type
  const char* descriptor = dex_file.GetReturnTypeDescriptor(proto_id);
  if (descriptor[0] == 'L' || descriptor[0] == '[') {
    if (HasSameDescriptorClasses(descriptor, klass1, klass2)) {
      return false;
    }
  }
  return true;
}

// Returns true if classes referenced by the descriptor are the
// same classes in klass1 as they are in klass2.
bool ClassLinker::HasSameDescriptorClasses(const char* descriptor,
                                           const Class* klass1,
                                           const Class* klass2) {
  CHECK(descriptor != NULL);
  CHECK(klass1 != NULL);
  CHECK(klass2 != NULL);
  Class* found1 = FindClass(descriptor, klass1->GetClassLoader());
  // TODO: found1 == NULL
  Class* found2 = FindClass(descriptor, klass2->GetClassLoader());
  // TODO: found2 == NULL
  // TODO: lookup found1 in initiating loader list
  if (found1 == NULL || found2 == NULL) {
    Thread::Current()->ClearException();
    if (found1 == found2) {
      return true;
    } else {
      return false;
    }
  }
  return true;
}

bool ClassLinker::InitializeSuperClass(Class* klass, bool can_run_clinit) {
  CHECK(klass != NULL);
  if (!klass->IsInterface() && klass->HasSuperClass()) {
    Class* super_class = klass->GetSuperClass();
    if (super_class->GetStatus() != Class::kStatusInitialized) {
      CHECK(!super_class->IsInterface());
      Thread* self = Thread::Current();
      klass->MonitorEnter(self);
      bool super_initialized = InitializeClass(super_class, can_run_clinit);
      klass->MonitorExit(self);
      // TODO: check for a pending exception
      if (!super_initialized) {
        if (!can_run_clinit) {
         // Don't set status to error when we can't run <clinit>.
         CHECK_EQ(klass->GetStatus(), Class::kStatusInitializing);
         klass->SetStatus(Class::kStatusVerified);
         return false;
        }
        klass->SetStatus(Class::kStatusError);
        klass->NotifyAll();
        return false;
      }
    }
  }
  return true;
}

bool ClassLinker::EnsureInitialized(Class* c, bool can_run_clinit) {
  CHECK(c != NULL);
  if (c->IsInitialized()) {
    return true;
  }

  Thread* self = Thread::Current();
  c->MonitorEnter(self);
  InitializeClass(c, can_run_clinit);
  c->MonitorExit(self);
  return !self->IsExceptionPending();
}

StaticStorageBase* ClassLinker::InitializeStaticStorageFromCode(uint32_t type_idx,
                                                                const Method* referrer) {
  ClassLinker* class_linker = Runtime::Current()->GetClassLinker();
  Class* klass = class_linker->ResolveType(type_idx, referrer);
  if (klass == NULL) {
    CHECK(Thread::Current()->IsExceptionPending());
    return NULL;  // Failure - Indicate to caller to deliver exception
  }
  // If we are the <clinit> of this class, just return our storage.
  //
  // Do not set the DexCache InitializedStaticStorage, since that
  // implies <clinit> has finished running.
  if (klass == referrer->GetDeclaringClass() && referrer->GetName()->Equals("<clinit>")) {
    return klass;
  }
  if (!class_linker->EnsureInitialized(klass, true)) {
    CHECK(Thread::Current()->IsExceptionPending());
    return NULL;  // Failure - Indicate to caller to deliver exception
  }
  referrer->GetDexCacheInitializedStaticStorage()->Set(type_idx, klass);
  return klass;
}

void ClassLinker::ConstructFieldMap(const DexFile& dex_file, const DexFile::ClassDef& dex_class_def,
    Class* c, std::map<int, Field*>& field_map) {
  const ClassLoader* cl = c->GetClassLoader();
  const byte* class_data = dex_file.GetClassData(dex_class_def);
  DexFile::ClassDataHeader header = dex_file.ReadClassDataHeader(&class_data);
  uint32_t last_idx = 0;
  for (size_t i = 0; i < header.static_fields_size_; ++i) {
    DexFile::Field dex_field;
    dex_file.dexReadClassDataField(&class_data, &dex_field, &last_idx);
    field_map[i] = ResolveField(dex_file, dex_field.field_idx_, c->GetDexCache(), cl, true);
  }
}

void ClassLinker::InitializeStaticFields(Class* klass) {
  size_t num_static_fields = klass->NumStaticFields();
  if (num_static_fields == 0) {
    return;
  }
  DexCache* dex_cache = klass->GetDexCache();
  // TODO: this seems like the wrong check. do we really want !IsPrimitive && !IsArray?
  if (dex_cache == NULL) {
    return;
  }
  const std::string descriptor(klass->GetDescriptor()->ToModifiedUtf8());
  const DexFile& dex_file = FindDexFile(dex_cache);
  const DexFile::ClassDef* dex_class_def = dex_file.FindClassDef(descriptor);
  CHECK(dex_class_def != NULL);

  // We reordered the fields, so we need to be able to map the field indexes to the right fields.
  std::map<int, Field*> field_map;
  ConstructFieldMap(dex_file, *dex_class_def, klass, field_map);

  const byte* addr = dex_file.GetEncodedArray(*dex_class_def);
  if (addr == NULL) {
    // All this class' static fields have default values.
    return;
  }
  size_t array_size = DecodeUnsignedLeb128(&addr);
  for (size_t i = 0; i < array_size; ++i) {
    Field* field = field_map[i];
    JValue value;
    DexFile::ValueType type = dex_file.ReadEncodedValue(&addr, &value);
    switch (type) {
      case DexFile::kByte:
        field->SetByte(NULL, value.b);
        break;
      case DexFile::kShort:
        field->SetShort(NULL, value.s);
        break;
      case DexFile::kChar:
        field->SetChar(NULL, value.c);
        break;
      case DexFile::kInt:
        field->SetInt(NULL, value.i);
        break;
      case DexFile::kLong:
        field->SetLong(NULL, value.j);
        break;
      case DexFile::kFloat:
        field->SetFloat(NULL, value.f);
        break;
      case DexFile::kDouble:
        field->SetDouble(NULL, value.d);
        break;
      case DexFile::kString: {
        uint32_t string_idx = value.i;
        const String* resolved = ResolveString(dex_file, string_idx, klass->GetDexCache());
        field->SetObject(NULL, resolved);
        break;
      }
      case DexFile::kBoolean:
        field->SetBoolean(NULL, value.z);
        break;
      case DexFile::kNull:
        field->SetObject(NULL, value.l);
        break;
      default:
        LOG(FATAL) << "Unknown type " << static_cast<int>(type);
    }
  }
}

bool ClassLinker::LinkClass(Class* klass) {
  CHECK_EQ(Class::kStatusLoaded, klass->GetStatus());
  if (!LinkSuperClass(klass)) {
    return false;
  }
  if (!LinkMethods(klass)) {
    return false;
  }
  if (!LinkInstanceFields(klass)) {
    return false;
  }
  if (!LinkStaticFields(klass)) {
    return false;
  }
  CreateReferenceInstanceOffsets(klass);
  CreateReferenceStaticOffsets(klass);
  CHECK_EQ(Class::kStatusLoaded, klass->GetStatus());
  klass->SetStatus(Class::kStatusResolved);
  return true;
}

bool ClassLinker::LoadSuperAndInterfaces(Class* klass, const DexFile& dex_file) {
  CHECK_EQ(Class::kStatusIdx, klass->GetStatus());
  if (klass->GetSuperClassTypeIdx() != DexFile::kDexNoIndex) {
    Class* super_class = ResolveType(dex_file, klass->GetSuperClassTypeIdx(), klass);
    if (super_class == NULL) {
      DCHECK(Thread::Current()->IsExceptionPending());
      // TODO: can't ThrowVirtualMachineError, its abstract
      // ThrowVirtualMachineError("Failed to resolve superclass with type index %d for class %s",
      //     klass->GetSuperClassTypeIdx(), PrettyDescriptor(klass->GetDescriptor()).c_str());
      return false;
    }
    klass->SetSuperClass(super_class);
  }
  for (size_t i = 0; i < klass->NumInterfaces(); ++i) {
    uint32_t idx = klass->GetInterfacesTypeIdx()->Get(i);
    Class *interface = ResolveType(dex_file, idx, klass);
    klass->SetInterface(i, interface);
    if (interface == NULL) {
      ThrowVirtualMachineError("Failed to resolve interface with type index %d for class %s",
          idx, PrettyDescriptor(klass->GetDescriptor()).c_str());
      return false;
    }
    // Verify
    if (!klass->CanAccess(interface)) {
      ThrowVirtualMachineError("Inaccessible interface %s implemented by class %s",
          PrettyDescriptor(interface->GetDescriptor()).c_str(),
          PrettyDescriptor(klass->GetDescriptor()).c_str());
      return false;
    }
  }
  // Mark the class as loaded.
  klass->SetStatus(Class::kStatusLoaded);
  return true;
}

bool ClassLinker::LinkSuperClass(Class* klass) {
  CHECK(!klass->IsPrimitive());
  Class* super = klass->GetSuperClass();
  if (klass->GetDescriptor()->Equals("Ljava/lang/Object;")) {
    if (super != NULL) {
      Thread::Current()->ThrowNewException("Ljava/lang/ClassFormatError;",
          "java.lang.Object must not have a superclass");
      return false;
    }
    // TODO: clear finalize attribute
    return true;
  }
  if (super == NULL) {
    ThrowLinkageError("No superclass defined for class %s",
        PrettyDescriptor(klass->GetDescriptor()).c_str());
    return false;
  }
  // Verify
  if (super->IsFinal() || super->IsInterface()) {
    Thread::Current()->ThrowNewException("Ljava/lang/IncompatibleClassChangeError;",
        "Superclass %s is %s", PrettyDescriptor(super->GetDescriptor()).c_str(),
        super->IsFinal() ? "declared final" : "an interface");
    return false;
  }
  if (!klass->CanAccess(super)) {
    Thread::Current()->ThrowNewException("Ljava/lang/IllegalAccessError;",
        "Superclass %s is inaccessible", PrettyDescriptor(super->GetDescriptor()).c_str());
    return false;
  }
#ifndef NDEBUG
  // Ensure super classes are fully resolved prior to resolving fields..
  while (super != NULL) {
    CHECK(super->IsResolved());
    super = super->GetSuperClass();
  }
#endif
  return true;
}

// Populate the class vtable and itable. Compute return type indices.
bool ClassLinker::LinkMethods(Class* klass) {
  if (klass->IsInterface()) {
    // No vtable.
    size_t count = klass->NumVirtualMethods();
    if (!IsUint(16, count)) {
      ThrowVirtualMachineError("Too many methods on interface: %d", count);
      return false;
    }
    for (size_t i = 0; i < count; ++i) {
      klass->GetVirtualMethodDuringLinking(i)->SetMethodIndex(i);
    }
    // Link interface method tables
    LinkInterfaceMethods(klass);
  } else {
    // Link virtual method tables
    LinkVirtualMethods(klass);

    // Link interface method tables
    LinkInterfaceMethods(klass);
  }
  return true;
}

bool ClassLinker::LinkVirtualMethods(Class* klass) {
  if (klass->HasSuperClass()) {
    uint32_t max_count = klass->NumVirtualMethods() + klass->GetSuperClass()->GetVTable()->GetLength();
    size_t actual_count = klass->GetSuperClass()->GetVTable()->GetLength();
    CHECK_LE(actual_count, max_count);
    // TODO: do not assign to the vtable field until it is fully constructed.
    ObjectArray<Method>* vtable = klass->GetSuperClass()->GetVTable()->CopyOf(max_count);
    // See if any of our virtual methods override the superclass.
    for (size_t i = 0; i < klass->NumVirtualMethods(); ++i) {
      Method* local_method = klass->GetVirtualMethodDuringLinking(i);
      size_t j = 0;
      for (; j < actual_count; ++j) {
        Method* super_method = vtable->Get(j);
        if (local_method->HasSameNameAndDescriptor(super_method)) {
          // Verify
          if (super_method->IsFinal()) {
            ThrowVirtualMachineError("Method %s.%s overrides final method in class %s",
                PrettyDescriptor(klass->GetDescriptor()).c_str(),
                local_method->GetName()->ToModifiedUtf8().c_str(),
                PrettyDescriptor(super_method->GetDeclaringClass()->GetDescriptor()).c_str());
            return false;
          }
          vtable->Set(j, local_method);
          local_method->SetMethodIndex(j);
          break;
        }
      }
      if (j == actual_count) {
        // Not overriding, append.
        vtable->Set(actual_count, local_method);
        local_method->SetMethodIndex(actual_count);
        actual_count += 1;
      }
    }
    if (!IsUint(16, actual_count)) {
      ThrowVirtualMachineError("Too many methods defined on class: %d", actual_count);
      return false;
    }
    // Shrink vtable if possible
    CHECK_LE(actual_count, max_count);
    if (actual_count < max_count) {
      vtable = vtable->CopyOf(actual_count);
    }
    klass->SetVTable(vtable);
  } else {
    CHECK(klass->GetDescriptor()->Equals("Ljava/lang/Object;"));
    uint32_t num_virtual_methods = klass->NumVirtualMethods();
    if (!IsUint(16, num_virtual_methods)) {
      ThrowVirtualMachineError("Too many methods: %d", num_virtual_methods);
      return false;
    }
    ObjectArray<Method>* vtable = AllocObjectArray<Method>(num_virtual_methods);
    for (size_t i = 0; i < num_virtual_methods; ++i) {
      Method* virtual_method = klass->GetVirtualMethodDuringLinking(i);
      vtable->Set(i, virtual_method);
      virtual_method->SetMethodIndex(i & 0xFFFF);
    }
    klass->SetVTable(vtable);
  }
  return true;
}

bool ClassLinker::LinkInterfaceMethods(Class* klass) {
  int miranda_count = 0;
  int miranda_alloc = 0;
  size_t super_ifcount;
  if (klass->HasSuperClass()) {
    super_ifcount = klass->GetSuperClass()->GetIfTableCount();
  } else {
    super_ifcount = 0;
  }
  size_t ifcount = super_ifcount;
  ifcount += klass->NumInterfaces();
  for (size_t i = 0; i < klass->NumInterfaces(); i++) {
    ifcount += klass->GetInterface(i)->GetIfTableCount();
  }
  if (ifcount == 0) {
    // TODO: enable these asserts with klass status validation
    // DCHECK(klass->GetIfTableCount() == 0);
    // DCHECK(klass->GetIfTable() == NULL);
    return true;
  }
  ObjectArray<InterfaceEntry>* iftable = AllocObjectArray<InterfaceEntry>(ifcount);
  if (super_ifcount != 0) {
    ObjectArray<InterfaceEntry>* super_iftable = klass->GetSuperClass()->GetIfTable();
    for (size_t i = 0; i < super_ifcount; i++) {
      iftable->Set(i, AllocInterfaceEntry(super_iftable->Get(i)->GetInterface()));
    }
  }
  // Flatten the interface inheritance hierarchy.
  size_t idx = super_ifcount;
  for (size_t i = 0; i < klass->NumInterfaces(); i++) {
    Class* interface = klass->GetInterface(i);
    DCHECK(interface != NULL);
    if (!interface->IsInterface()) {
      Thread::Current()->ThrowNewException("Ljava/lang/IncompatibleClassChangeError;",
          "Class %s implements non-interface class %s",
          PrettyDescriptor(klass->GetDescriptor()).c_str(),
          PrettyDescriptor(interface->GetDescriptor()).c_str());
      return false;
    }
    iftable->Set(idx++, AllocInterfaceEntry(interface));
    for (int32_t j = 0; j < interface->GetIfTableCount(); j++) {
      iftable->Set(idx++, AllocInterfaceEntry(interface->GetIfTable()->Get(j)->GetInterface()));
    }
  }
  klass->SetIfTable(iftable);
  CHECK_EQ(idx, ifcount);
  if (klass->IsInterface()) {
    return true;
  }
  std::vector<Method*> miranda_list;
  for (size_t i = 0; i < ifcount; ++i) {
    InterfaceEntry* interface_entry = iftable->Get(i);
    Class* interface = interface_entry->GetInterface();
    ObjectArray<Method>* method_array = AllocObjectArray<Method>(interface->NumVirtualMethods());
    interface_entry->SetMethodArray(method_array);
    ObjectArray<Method>* vtable = klass->GetVTableDuringLinking();
    for (size_t j = 0; j < interface->NumVirtualMethods(); ++j) {
      Method* interface_method = interface->GetVirtualMethod(j);
      int32_t k;
      for (k = vtable->GetLength() - 1; k >= 0; --k) {
        Method* vtable_method = vtable->Get(k);
        if (interface_method->HasSameNameAndDescriptor(vtable_method)) {
          if (!vtable_method->IsPublic()) {
            Thread::Current()->ThrowNewException("Ljava/lang/IllegalAccessError;",
                "Implementation not public: %s", PrettyMethod(vtable_method).c_str());
            return false;
          }
          method_array->Set(j, vtable_method);
          break;
        }
      }
      if (k < 0) {
        if (miranda_count == miranda_alloc) {
          miranda_alloc += 8;
          if (miranda_list.empty()) {
            miranda_list.resize(miranda_alloc);
          } else {
            miranda_list.resize(miranda_alloc);
          }
        }
        Method* miranda_method = NULL;
        int mir;
        for (mir = 0; mir < miranda_count; mir++) {
          miranda_method = miranda_list[mir];
          if (miranda_method->HasSameNameAndDescriptor(interface_method)) {
            break;
          }
        }
        // point the interface table at a phantom slot
        method_array->Set(j, miranda_method);
        if (mir == miranda_count) {
          miranda_list[miranda_count++] = interface_method;
        }
      }
    }
  }
  if (miranda_count != 0) {
    int old_method_count = klass->NumVirtualMethods();
    int new_method_count = old_method_count + miranda_count;
    klass->SetVirtualMethods((old_method_count == 0)
                             ? AllocObjectArray<Method>(new_method_count)
                             : klass->GetVirtualMethods()->CopyOf(new_method_count));

    ObjectArray<Method>* vtable = klass->GetVTableDuringLinking();
    CHECK(vtable != NULL);
    int old_vtable_count = vtable->GetLength();
    int new_vtable_count = old_vtable_count + miranda_count;
    vtable = vtable->CopyOf(new_vtable_count);
    for (int i = 0; i < miranda_count; i++) {
      Method* meth = AllocMethod();
      // TODO: this shouldn't be a memcpy
      memcpy(meth, miranda_list[i], sizeof(Method));
      meth->SetDeclaringClass(klass);
      meth->SetAccessFlags(meth->GetAccessFlags() | kAccMiranda);
      meth->SetMethodIndex(0xFFFF & (old_vtable_count + i));
      klass->SetVirtualMethod(old_method_count + i, meth);
      vtable->Set(old_vtable_count + i, meth);
    }
    // TODO: do not assign to the vtable field until it is fully constructed.
    klass->SetVTable(vtable);
  }
  return true;
}

bool ClassLinker::LinkInstanceFields(Class* klass) {
  CHECK(klass != NULL);
  return LinkFields(klass, true);
}

bool ClassLinker::LinkStaticFields(Class* klass) {
  CHECK(klass != NULL);
  size_t allocated_class_size = klass->GetClassSize();
  bool success = LinkFields(klass, false);
  CHECK_EQ(allocated_class_size, klass->GetClassSize());
  return success;
}

struct LinkFieldsComparator {
  bool operator()(const Field* field1, const Field* field2){

    // First come reference fields, then 64-bit, and finally 32-bit
    const Class* type1 = field1->GetTypeDuringLinking();
    const Class* type2 = field2->GetTypeDuringLinking();
    bool isPrimitive1 = type1 != NULL && type1->IsPrimitive();
    bool isPrimitive2 = type2 != NULL && type2->IsPrimitive();
    bool is64bit1 = isPrimitive1 && (type1->IsPrimitiveLong() || type1->IsPrimitiveDouble());
    bool is64bit2 = isPrimitive2 && (type2->IsPrimitiveLong() || type2->IsPrimitiveDouble());
    int order1 = (!isPrimitive1 ? 0 : (is64bit1 ? 1 : 2));
    int order2 = (!isPrimitive2 ? 0 : (is64bit2 ? 1 : 2));
    if (order1 != order2) {
      return order1 < order2;
    }

    // same basic group? then sort by string.
    std::string name1 = field1->GetName()->ToModifiedUtf8();
    std::string name2 = field2->GetName()->ToModifiedUtf8();
    return name1 < name2;
  }
};

bool ClassLinker::LinkFields(Class* klass, bool instance) {
  size_t num_fields =
      instance ? klass->NumInstanceFields() : klass->NumStaticFields();

  ObjectArray<Field>* fields =
      instance ? klass->GetIFields() : klass->GetSFields();

  // Initialize size and field_offset
  size_t size;
  MemberOffset field_offset(0);
  if (instance) {
    Class* super_class = klass->GetSuperClass();
    if (super_class != NULL) {
      CHECK(super_class->IsResolved());
      field_offset = MemberOffset(super_class->GetObjectSize());
    }
    size = field_offset.Uint32Value();
  } else {
    size = klass->GetClassSize();
    field_offset = Class::FieldsOffset();
  }

  CHECK_EQ(num_fields == 0, fields == NULL);

  // we want a relatively stable order so that adding new fields
  // minimizes distruption of C++ version such as Class and Method.
  std::deque<Field*> grouped_and_sorted_fields;
  for (size_t i = 0; i < num_fields; i++) {
    grouped_and_sorted_fields.push_back(fields->Get(i));
  }
  std::sort(grouped_and_sorted_fields.begin(),
            grouped_and_sorted_fields.end(),
            LinkFieldsComparator());

  // References should be at the front.
  size_t current_field = 0;
  size_t num_reference_fields = 0;
  for (; current_field < num_fields; current_field++) {
    Field* field = grouped_and_sorted_fields.front();
    const Class* type = field->GetTypeDuringLinking();
    // if a field's type at this point is NULL it isn't primitive
    bool isPrimitive = type != NULL && type->IsPrimitive();
    if (isPrimitive) {
      break; // past last reference, move on to the next phase
    }
    grouped_and_sorted_fields.pop_front();
    num_reference_fields++;
    fields->Set(current_field, field);
    field->SetOffset(field_offset);
    field_offset = MemberOffset(field_offset.Uint32Value() + sizeof(uint32_t));
  }

  // Now we want to pack all of the double-wide fields together.  If
  // we're not aligned, though, we want to shuffle one 32-bit field
  // into place.  If we can't find one, we'll have to pad it.
  if (current_field != num_fields && !IsAligned(field_offset.Uint32Value(), 8)) {
    for (size_t i = 0; i < grouped_and_sorted_fields.size(); i++) {
      Field* field = grouped_and_sorted_fields[i];
      const Class* type = field->GetTypeDuringLinking();
      CHECK(type != NULL);  // should only be working on primitive types
      DCHECK(type->IsPrimitive());
      if (type->IsPrimitiveLong() || type->IsPrimitiveDouble()) {
        continue;
      }
      fields->Set(current_field++, field);
      field->SetOffset(field_offset);
      // drop the consumed field
      grouped_and_sorted_fields.erase(grouped_and_sorted_fields.begin() + i);
      break;
    }
    // whether we found a 32-bit field for padding or not, we advance
    field_offset = MemberOffset(field_offset.Uint32Value() + sizeof(uint32_t));
  }

  // Alignment is good, shuffle any double-wide fields forward, and
  // finish assigning field offsets to all fields.
  DCHECK(current_field == num_fields || IsAligned(field_offset.Uint32Value(), 8));
  while (!grouped_and_sorted_fields.empty()) {
    Field* field = grouped_and_sorted_fields.front();
    grouped_and_sorted_fields.pop_front();
    const Class* type = field->GetTypeDuringLinking();
    CHECK(type != NULL);  // should only be working on primitive types
    DCHECK(type->IsPrimitive());
    fields->Set(current_field, field);
    field->SetOffset(field_offset);
    field_offset = MemberOffset(field_offset.Uint32Value() +
                                ((type->IsPrimitiveLong() || type->IsPrimitiveDouble())
                                 ? sizeof(uint64_t)
                                 : sizeof(uint32_t)));
    current_field++;
  }

#ifndef NDEBUG
  // Make sure that all reference fields appear before
  // non-reference fields, and all double-wide fields are aligned.
  bool seen_non_ref = false;
  for (size_t i = 0; i < num_fields; i++) {
    Field* field = fields->Get(i);
    if (false) {  // enable to debug field layout
      LOG(INFO) << "LinkFields: " << (instance ? "instance" : "static")
                << " class=" << PrettyClass(klass)
                << " field=" << PrettyField(field)
                << " offset=" << field->GetField32(MemberOffset(Field::OffsetOffset()), false);
    }
    const Class* type = field->GetTypeDuringLinking();
    if (type != NULL && type->IsPrimitive()) {
      if (!seen_non_ref) {
        seen_non_ref = true;
        DCHECK_EQ(num_reference_fields, i);
      }
    } else {
      DCHECK(!seen_non_ref);
    }
  }
  if (!seen_non_ref) {
    DCHECK_EQ(num_fields, num_reference_fields);
  }
#endif
  size = field_offset.Uint32Value();
  // Update klass
  if (instance) {
    klass->SetNumReferenceInstanceFields(num_reference_fields);
    if (!klass->IsVariableSize()) {
      klass->SetObjectSize(size);
    }
  } else {
    klass->SetNumReferenceStaticFields(num_reference_fields);
    klass->SetClassSize(size);
  }
  return true;
}

//  Set the bitmap of reference offsets, refOffsets, from the ifields
//  list.
void ClassLinker::CreateReferenceInstanceOffsets(Class* klass) {
  uint32_t reference_offsets = 0;
  Class* super_class = klass->GetSuperClass();
  if (super_class != NULL) {
    reference_offsets = super_class->GetReferenceInstanceOffsets();
    // If our superclass overflowed, we don't stand a chance.
    if (reference_offsets == CLASS_WALK_SUPER) {
      klass->SetReferenceInstanceOffsets(reference_offsets);
      return;
    }
  }
  CreateReferenceOffsets(klass, true, reference_offsets);
}

void ClassLinker::CreateReferenceStaticOffsets(Class* klass) {
  CreateReferenceOffsets(klass, false, 0);
}

void ClassLinker::CreateReferenceOffsets(Class* klass, bool instance,
                                         uint32_t reference_offsets) {
  size_t num_reference_fields =
      instance ? klass->NumReferenceInstanceFieldsDuringLinking()
               : klass->NumReferenceStaticFieldsDuringLinking();
  const ObjectArray<Field>* fields =
      instance ? klass->GetIFields() : klass->GetSFields();
  // All of the fields that contain object references are guaranteed
  // to be at the beginning of the fields list.
  for (size_t i = 0; i < num_reference_fields; ++i) {
    // Note that byte_offset is the offset from the beginning of
    // object, not the offset into instance data
    const Field* field = fields->Get(i);
    MemberOffset byte_offset = field->GetOffsetDuringLinking();
    CHECK_EQ(byte_offset.Uint32Value() & (CLASS_OFFSET_ALIGNMENT - 1), 0U);
    if (CLASS_CAN_ENCODE_OFFSET(byte_offset.Uint32Value())) {
      uint32_t new_bit = CLASS_BIT_FROM_OFFSET(byte_offset.Uint32Value());
      CHECK_NE(new_bit, 0U);
      reference_offsets |= new_bit;
    } else {
      reference_offsets = CLASS_WALK_SUPER;
      break;
    }
  }
  // Update fields in klass
  if (instance) {
    klass->SetReferenceInstanceOffsets(reference_offsets);
  } else {
    klass->SetReferenceStaticOffsets(reference_offsets);
  }
}

String* ClassLinker::ResolveString(const DexFile& dex_file,
    uint32_t string_idx, DexCache* dex_cache) {
  String* resolved = dex_cache->GetResolvedString(string_idx);
  if (resolved != NULL) {
    return resolved;
  }
  const DexFile::StringId& string_id = dex_file.GetStringId(string_idx);
  int32_t utf16_length = dex_file.GetStringLength(string_id);
  const char* utf8_data = dex_file.GetStringData(string_id);
  // TODO: remote the const_cast below
  String* string = const_cast<String*>(intern_table_->InternStrong(utf16_length, utf8_data));
  dex_cache->SetResolvedString(string_idx, string);
  return string;
}

Class* ClassLinker::ResolveType(const DexFile& dex_file,
                                uint32_t type_idx,
                                DexCache* dex_cache,
                                const ClassLoader* class_loader) {
  Class* resolved = dex_cache->GetResolvedType(type_idx);
  if (resolved == NULL) {
    const char* descriptor = dex_file.dexStringByTypeIdx(type_idx);
    if (descriptor[1] == '\0') {
      // only the descriptors of primitive types should be 1 character long
      resolved = FindPrimitiveClass(descriptor[0]);
    } else {
      resolved = FindClass(descriptor, class_loader);
    }
    if (resolved != NULL) {
      Class* check = resolved->IsArrayClass() ? resolved->GetComponentType() : resolved;
      if (dex_cache != check->GetDexCache()) {
        if (check->GetClassLoader() != NULL) {
          Thread::Current()->ThrowNewException("Ljava/lang/IllegalAccessError;",
              "Class with type index %d resolved by unexpected .dex", type_idx);
          resolved = NULL;
        }
      }
    }
    if (resolved != NULL) {
      dex_cache->SetResolvedType(type_idx, resolved);
    } else {
      DCHECK(Thread::Current()->IsExceptionPending());
    }
  }
  return resolved;
}

Method* ClassLinker::ResolveMethod(const DexFile& dex_file,
                                   uint32_t method_idx,
                                   DexCache* dex_cache,
                                   const ClassLoader* class_loader,
                                   bool is_direct) {
  Method* resolved = dex_cache->GetResolvedMethod(method_idx);
  if (resolved != NULL) {
    return resolved;
  }
  const DexFile::MethodId& method_id = dex_file.GetMethodId(method_idx);
  Class* klass = ResolveType(dex_file, method_id.class_idx_, dex_cache, class_loader);
  if (klass == NULL) {
    return NULL;
  }

  const char* name = dex_file.dexStringById(method_id.name_idx_);
  std::string signature(dex_file.CreateMethodDescriptor(method_id.proto_idx_, NULL));
  if (is_direct) {
    resolved = klass->FindDirectMethod(name, signature);
  } else if (klass->IsInterface()) {
    resolved = klass->FindInterfaceMethod(name, signature);
  } else {
    resolved = klass->FindVirtualMethod(name, signature);
  }
  if (resolved != NULL) {
    dex_cache->SetResolvedMethod(method_idx, resolved);
  } else {
    DCHECK(Thread::Current()->IsExceptionPending());
  }
  return resolved;
}

Field* ClassLinker::ResolveField(const DexFile& dex_file,
                                 uint32_t field_idx,
                                 DexCache* dex_cache,
                                 const ClassLoader* class_loader,
                                 bool is_static) {
  Field* resolved = dex_cache->GetResolvedField(field_idx);
  if (resolved != NULL) {
    return resolved;
  }
  const DexFile::FieldId& field_id = dex_file.GetFieldId(field_idx);
  Class* klass = ResolveType(dex_file, field_id.class_idx_, dex_cache, class_loader);
  if (klass == NULL) {
    return NULL;
  }

  const char* name = dex_file.dexStringById(field_id.name_idx_);
  Class* field_type = ResolveType(dex_file, field_id.type_idx_, dex_cache, class_loader);
  if (field_type == NULL) {
    // TODO: LinkageError?
    UNIMPLEMENTED(WARNING) << "Failed to resolve type of field " << name
                           << " in " << PrettyClass(klass);
    return NULL;
}
  if (is_static) {
    resolved = klass->FindStaticField(name, field_type);
  } else {
    resolved = klass->FindInstanceField(name, field_type);
  }
  if (resolved != NULL) {
    dex_cache->SetResolvedField(field_idx, resolved);
  } else {
    DCHECK(Thread::Current()->IsExceptionPending());
  }
  return resolved;
}

void ClassLinker::DumpAllClasses(int flags) const {
  // TODO: at the time this was written, it wasn't safe to call PrettyField with the ClassLinker
  // lock held, because it might need to resolve a field's type, which would try to take the lock.
  std::vector<Class*> all_classes;
  {
    MutexLock mu(lock_);
    typedef Table::const_iterator It;  // TODO: C++0x auto
    for (It it = classes_.begin(), end = classes_.end(); it != end; ++it) {
      all_classes.push_back(it->second);
    }
  }

  for (size_t i = 0; i < all_classes.size(); ++i) {
    all_classes[i]->DumpClass(std::cerr, flags);
  }
}

size_t ClassLinker::NumLoadedClasses() const {
  MutexLock mu(lock_);
  return classes_.size();
}

}  // namespace art