runtime/mirror/class.cc

/*
 * Copyright (C) 2011 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "class.h"

#include "art_field-inl.h"
#include "art_method-inl.h"
#include "class_linker-inl.h"
#include "class_loader.h"
#include "class-inl.h"
#include "dex_cache.h"
#include "dex_file-inl.h"
#include "gc/accounting/card_table-inl.h"
#include "handle_scope-inl.h"
#include "method.h"
#include "object_array-inl.h"
#include "object-inl.h"
#include "runtime.h"
#include "thread.h"
#include "throwable.h"
#include "utils.h"
#include "well_known_classes.h"

namespace art {
namespace mirror {

GcRoot<Class> Class::java_lang_Class_;

void Class::SetClassClass(Class* java_lang_Class) {
  CHECK(java_lang_Class_.IsNull())
      << java_lang_Class_.Read()
      << " " << java_lang_Class;
  CHECK(java_lang_Class != nullptr);
  java_lang_Class->SetClassFlags(mirror::kClassFlagClass);
  java_lang_Class_ = GcRoot<Class>(java_lang_Class);
}

void Class::ResetClass() {
  CHECK(!java_lang_Class_.IsNull());
  java_lang_Class_ = GcRoot<Class>(nullptr);
}

void Class::VisitRoots(RootVisitor* visitor) {
  java_lang_Class_.VisitRootIfNonNull(visitor, RootInfo(kRootStickyClass));
}

inline void Class::SetVerifyError(mirror::Object* error) {
  CHECK(error != nullptr) << PrettyClass(this);
  if (Runtime::Current()->IsActiveTransaction()) {
    SetFieldObject<true>(OFFSET_OF_OBJECT_MEMBER(Class, verify_error_), error);
  } else {
    SetFieldObject<false>(OFFSET_OF_OBJECT_MEMBER(Class, verify_error_), error);
  }
}

void Class::SetStatus(Handle<Class> h_this, Status new_status, Thread* self) {
  Status old_status = h_this->GetStatus();
  ClassLinker* class_linker = Runtime::Current()->GetClassLinker();
  bool class_linker_initialized = class_linker != nullptr && class_linker->IsInitialized();
  if (LIKELY(class_linker_initialized)) {
    if (UNLIKELY(new_status <= old_status && new_status != kStatusError &&
                 new_status != kStatusRetired)) {
      LOG(FATAL) << "Unexpected change back of class status for " << PrettyClass(h_this.Get())
                 << " " << old_status << " -> " << new_status;
    }
    if (new_status >= kStatusResolved || old_status >= kStatusResolved) {
      // When classes are being resolved the resolution code should hold the lock.
      CHECK_EQ(h_this->GetLockOwnerThreadId(), self->GetThreadId())
            << "Attempt to change status of class while not holding its lock: "
            << PrettyClass(h_this.Get()) << " " << old_status << " -> " << new_status;
    }
  }
  if (UNLIKELY(new_status == kStatusError)) {
    CHECK_NE(h_this->GetStatus(), kStatusError)
        << "Attempt to set as erroneous an already erroneous class "
        << PrettyClass(h_this.Get());
    if (VLOG_IS_ON(class_linker)) {
      LOG(ERROR) << "Setting " << PrettyDescriptor(h_this.Get()) << " to erroneous.";
      if (self->IsExceptionPending()) {
        LOG(ERROR) << "Exception: " << self->GetException()->Dump();
      }
    }

    // Remember the current exception.
    CHECK(self->GetException() != nullptr);
    h_this->SetVerifyError(self->GetException());
  }
  static_assert(sizeof(Status) == sizeof(uint32_t), "Size of status not equal to uint32");
  if (Runtime::Current()->IsActiveTransaction()) {
    h_this->SetField32Volatile<true>(OFFSET_OF_OBJECT_MEMBER(Class, status_), new_status);
  } else {
    h_this->SetField32Volatile<false>(OFFSET_OF_OBJECT_MEMBER(Class, status_), new_status);
  }

  if (!class_linker_initialized) {
    // When the class linker is being initialized its single threaded and by definition there can be
    // no waiters. During initialization classes may appear temporary but won't be retired as their
    // size was statically computed.
  } else {
    // Classes that are being resolved or initialized need to notify waiters that the class status
    // changed. See ClassLinker::EnsureResolved and ClassLinker::WaitForInitializeClass.
    if (h_this->IsTemp()) {
      // Class is a temporary one, ensure that waiters for resolution get notified of retirement
      // so that they can grab the new version of the class from the class linker's table.
      CHECK_LT(new_status, kStatusResolved) << PrettyDescriptor(h_this.Get());
      if (new_status == kStatusRetired || new_status == kStatusError) {
        h_this->NotifyAll(self);
      }
    } else {
      CHECK_NE(new_status, kStatusRetired);
      if (old_status >= kStatusResolved || new_status >= kStatusResolved) {
        h_this->NotifyAll(self);
      }
    }
  }
}

void Class::SetDexCache(DexCache* new_dex_cache) {
  SetFieldObject<false>(OFFSET_OF_OBJECT_MEMBER(Class, dex_cache_), new_dex_cache);
  SetDexCacheStrings(new_dex_cache != nullptr ? new_dex_cache->GetStrings() : nullptr);
}

void Class::SetClassSize(uint32_t new_class_size) {
  if (kIsDebugBuild && new_class_size < GetClassSize()) {
    DumpClass(LOG(INTERNAL_FATAL), kDumpClassFullDetail);
    LOG(INTERNAL_FATAL) << new_class_size << " vs " << GetClassSize();
    LOG(FATAL) << " class=" << PrettyTypeOf(this);
  }
  // Not called within a transaction.
  SetField32<false>(OFFSET_OF_OBJECT_MEMBER(Class, class_size_), new_class_size);
}

// Return the class' name. The exact format is bizarre, but it's the specified behavior for
// Class.getName: keywords for primitive types, regular "[I" form for primitive arrays (so "int"
// but "[I"), and arrays of reference types written between "L" and ";" but with dots rather than
// slashes (so "java.lang.String" but "[Ljava.lang.String;"). Madness.
String* Class::ComputeName(Handle<Class> h_this) {
  String* name = h_this->GetName();
  if (name != nullptr) {
    return name;
  }
  std::string temp;
  const char* descriptor = h_this->GetDescriptor(&temp);
  Thread* self = Thread::Current();
  if ((descriptor[0] != 'L') && (descriptor[0] != '[')) {
    // The descriptor indicates that this is the class for
    // a primitive type; special-case the return value.
    const char* c_name = nullptr;
    switch (descriptor[0]) {
    case 'Z': c_name = "boolean"; break;
    case 'B': c_name = "byte";    break;
    case 'C': c_name = "char";    break;
    case 'S': c_name = "short";   break;
    case 'I': c_name = "int";     break;
    case 'J': c_name = "long";    break;
    case 'F': c_name = "float";   break;
    case 'D': c_name = "double";  break;
    case 'V': c_name = "void";    break;
    default:
      LOG(FATAL) << "Unknown primitive type: " << PrintableChar(descriptor[0]);
    }
    name = String::AllocFromModifiedUtf8(self, c_name);
  } else {
    // Convert the UTF-8 name to a java.lang.String. The name must use '.' to separate package
    // components.
    name = String::AllocFromModifiedUtf8(self, DescriptorToDot(descriptor).c_str());
  }
  h_this->SetName(name);
  return name;
}

void Class::DumpClass(std::ostream& os, int flags) {
  if ((flags & kDumpClassFullDetail) == 0) {
    os << PrettyClass(this);
    if ((flags & kDumpClassClassLoader) != 0) {
      os << ' ' << GetClassLoader();
    }
    if ((flags & kDumpClassInitialized) != 0) {
      os << ' ' << GetStatus();
    }
    os << "\n";
    return;
  }

  Thread* const self = Thread::Current();
  StackHandleScope<2> hs(self);
  Handle<mirror::Class> h_this(hs.NewHandle(this));
  Handle<mirror::Class> h_super(hs.NewHandle(GetSuperClass()));
  auto image_pointer_size = Runtime::Current()->GetClassLinker()->GetImagePointerSize();

  std::string temp;
  os << "----- " << (IsInterface() ? "interface" : "class") << " "
     << "'" << GetDescriptor(&temp) << "' cl=" << GetClassLoader() << " -----\n",
  os << "  objectSize=" << SizeOf() << " "
     << "(" << (h_super.Get() != nullptr ? h_super->SizeOf() : -1) << " from super)\n",
  os << StringPrintf("  access=0x%04x.%04x\n",
      GetAccessFlags() >> 16, GetAccessFlags() & kAccJavaFlagsMask);
  if (h_super.Get() != nullptr) {
    os << "  super='" << PrettyClass(h_super.Get()) << "' (cl=" << h_super->GetClassLoader()
       << ")\n";
  }
  if (IsArrayClass()) {
    os << "  componentType=" << PrettyClass(GetComponentType()) << "\n";
  }
  const size_t num_direct_interfaces = NumDirectInterfaces();
  if (num_direct_interfaces > 0) {
    os << "  interfaces (" << num_direct_interfaces << "):\n";
    for (size_t i = 0; i < num_direct_interfaces; ++i) {
      Class* interface = GetDirectInterface(self, h_this, i);
      if (interface == nullptr) {
        os << StringPrintf("    %2zd: nullptr!\n", i);
      } else {
        const ClassLoader* cl = interface->GetClassLoader();
        os << StringPrintf("    %2zd: %s (cl=%p)\n", i, PrettyClass(interface).c_str(), cl);
      }
    }
  }
  if (!IsLoaded()) {
    os << "  class not yet loaded";
  } else {
    // After this point, this may have moved due to GetDirectInterface.
    os << "  vtable (" << h_this->NumVirtualMethods() << " entries, "
        << (h_super.Get() != nullptr ? h_super->NumVirtualMethods() : 0) << " in super):\n";
    for (size_t i = 0; i < NumVirtualMethods(); ++i) {
      os << StringPrintf("    %2zd: %s\n", i, PrettyMethod(
          h_this->GetVirtualMethodDuringLinking(i, image_pointer_size)).c_str());
    }
    os << "  direct methods (" << h_this->NumDirectMethods() << " entries):\n";
    for (size_t i = 0; i < h_this->NumDirectMethods(); ++i) {
      os << StringPrintf("    %2zd: %s\n", i, PrettyMethod(
          h_this->GetDirectMethod(i, image_pointer_size)).c_str());
    }
    if (h_this->NumStaticFields() > 0) {
      os << "  static fields (" << h_this->NumStaticFields() << " entries):\n";
      if (h_this->IsResolved() || h_this->IsErroneous()) {
        for (size_t i = 0; i < h_this->NumStaticFields(); ++i) {
          os << StringPrintf("    %2zd: %s\n", i, PrettyField(h_this->GetStaticField(i)).c_str());
        }
      } else {
        os << "    <not yet available>";
      }
    }
    if (h_this->NumInstanceFields() > 0) {
      os << "  instance fields (" << h_this->NumInstanceFields() << " entries):\n";
      if (h_this->IsResolved() || h_this->IsErroneous()) {
        for (size_t i = 0; i < h_this->NumInstanceFields(); ++i) {
          os << StringPrintf("    %2zd: %s\n", i, PrettyField(h_this->GetInstanceField(i)).c_str());
        }
      } else {
        os << "    <not yet available>";
      }
    }
  }
}

void Class::SetReferenceInstanceOffsets(uint32_t new_reference_offsets) {
  if (kIsDebugBuild && new_reference_offsets != kClassWalkSuper) {
    // Sanity check that the number of bits set in the reference offset bitmap
    // agrees with the number of references
    uint32_t count = 0;
    for (Class* c = this; c != nullptr; c = c->GetSuperClass()) {
      count += c->NumReferenceInstanceFieldsDuringLinking();
    }
    // +1 for the Class in Object.
    CHECK_EQ(static_cast<uint32_t>(POPCOUNT(new_reference_offsets)) + 1, count);
  }
  // Not called within a transaction.
  SetField32<false>(OFFSET_OF_OBJECT_MEMBER(Class, reference_instance_offsets_),
                    new_reference_offsets);
}

bool Class::IsInSamePackage(const StringPiece& descriptor1, const StringPiece& descriptor2) {
  size_t i = 0;
  size_t min_length = std::min(descriptor1.size(), descriptor2.size());
  while (i < min_length && descriptor1[i] == descriptor2[i]) {
    ++i;
  }
  if (descriptor1.find('/', i) != StringPiece::npos ||
      descriptor2.find('/', i) != StringPiece::npos) {
    return false;
  } else {
    return true;
  }
}

bool Class::IsInSamePackage(Class* that) {
  Class* klass1 = this;
  Class* klass2 = that;
  if (klass1 == klass2) {
    return true;
  }
  // Class loaders must match.
  if (klass1->GetClassLoader() != klass2->GetClassLoader()) {
    return false;
  }
  // Arrays are in the same package when their element classes are.
  while (klass1->IsArrayClass()) {
    klass1 = klass1->GetComponentType();
  }
  while (klass2->IsArrayClass()) {
    klass2 = klass2->GetComponentType();
  }
  // trivial check again for array types
  if (klass1 == klass2) {
    return true;
  }
  // Compare the package part of the descriptor string.
  std::string temp1, temp2;
  return IsInSamePackage(klass1->GetDescriptor(&temp1), klass2->GetDescriptor(&temp2));
}

bool Class::IsThrowableClass() {
  return WellKnownClasses::ToClass(WellKnownClasses::java_lang_Throwable)->IsAssignableFrom(this);
}

void Class::SetClassLoader(ClassLoader* new_class_loader) {
  if (Runtime::Current()->IsActiveTransaction()) {
    SetFieldObject<true>(OFFSET_OF_OBJECT_MEMBER(Class, class_loader_), new_class_loader);
  } else {
    SetFieldObject<false>(OFFSET_OF_OBJECT_MEMBER(Class, class_loader_), new_class_loader);
  }
}

ArtMethod* Class::FindInterfaceMethod(const StringPiece& name, const StringPiece& signature,
                                      size_t pointer_size) {
  // Check the current class before checking the interfaces.
  ArtMethod* method = FindDeclaredVirtualMethod(name, signature, pointer_size);
  if (method != nullptr) {
    return method;
  }

  int32_t iftable_count = GetIfTableCount();
  IfTable* iftable = GetIfTable();
  for (int32_t i = 0; i < iftable_count; ++i) {
    method = iftable->GetInterface(i)->FindDeclaredVirtualMethod(name, signature, pointer_size);
    if (method != nullptr) {
      return method;
    }
  }
  return nullptr;
}

ArtMethod* Class::FindInterfaceMethod(const StringPiece& name, const Signature& signature,
                                      size_t pointer_size) {
  // Check the current class before checking the interfaces.
  ArtMethod* method = FindDeclaredVirtualMethod(name, signature, pointer_size);
  if (method != nullptr) {
    return method;
  }

  int32_t iftable_count = GetIfTableCount();
  IfTable* iftable = GetIfTable();
  for (int32_t i = 0; i < iftable_count; ++i) {
    method = iftable->GetInterface(i)->FindDeclaredVirtualMethod(name, signature, pointer_size);
    if (method != nullptr) {
      return method;
    }
  }
  return nullptr;
}

ArtMethod* Class::FindInterfaceMethod(const DexCache* dex_cache, uint32_t dex_method_idx,
                                      size_t pointer_size) {
  // Check the current class before checking the interfaces.
  ArtMethod* method = FindDeclaredVirtualMethod(dex_cache, dex_method_idx, pointer_size);
  if (method != nullptr) {
    return method;
  }

  int32_t iftable_count = GetIfTableCount();
  IfTable* iftable = GetIfTable();
  for (int32_t i = 0; i < iftable_count; ++i) {
    method = iftable->GetInterface(i)->FindDeclaredVirtualMethod(
        dex_cache, dex_method_idx, pointer_size);
    if (method != nullptr) {
      return method;
    }
  }
  return nullptr;
}

ArtMethod* Class::FindDeclaredDirectMethod(const StringPiece& name, const StringPiece& signature,
                                           size_t pointer_size) {
  for (auto& method : GetDirectMethods(pointer_size)) {
    if (name == method.GetName() && method.GetSignature() == signature) {
      return &method;
    }
  }
  return nullptr;
}

ArtMethod* Class::FindDeclaredDirectMethod(const StringPiece& name, const Signature& signature,
                                           size_t pointer_size) {
  for (auto& method : GetDirectMethods(pointer_size)) {
    if (name == method.GetName() && signature == method.GetSignature()) {
      return &method;
    }
  }
  return nullptr;
}

ArtMethod* Class::FindDeclaredDirectMethod(const DexCache* dex_cache, uint32_t dex_method_idx,
                                           size_t pointer_size) {
  if (GetDexCache() == dex_cache) {
    for (auto& method : GetDirectMethods(pointer_size)) {
      if (method.GetDexMethodIndex() == dex_method_idx) {
        return &method;
      }
    }
  }
  return nullptr;
}

ArtMethod* Class::FindDirectMethod(const StringPiece& name, const StringPiece& signature,
                                   size_t pointer_size) {
  for (Class* klass = this; klass != nullptr; klass = klass->GetSuperClass()) {
    ArtMethod* method = klass->FindDeclaredDirectMethod(name, signature, pointer_size);
    if (method != nullptr) {
      return method;
    }
  }
  return nullptr;
}

ArtMethod* Class::FindDirectMethod(const StringPiece& name, const Signature& signature,
                                   size_t pointer_size) {
  for (Class* klass = this; klass != nullptr; klass = klass->GetSuperClass()) {
    ArtMethod* method = klass->FindDeclaredDirectMethod(name, signature, pointer_size);
    if (method != nullptr) {
      return method;
    }
  }
  return nullptr;
}

ArtMethod* Class::FindDirectMethod(
    const DexCache* dex_cache, uint32_t dex_method_idx, size_t pointer_size) {
  for (Class* klass = this; klass != nullptr; klass = klass->GetSuperClass()) {
    ArtMethod* method = klass->FindDeclaredDirectMethod(dex_cache, dex_method_idx, pointer_size);
    if (method != nullptr) {
      return method;
    }
  }
  return nullptr;
}

ArtMethod* Class::FindDeclaredDirectMethodByName(const StringPiece& name, size_t pointer_size) {
  for (auto& method : GetDirectMethods(pointer_size)) {
    ArtMethod* const np_method = method.GetInterfaceMethodIfProxy(pointer_size);
    if (name == np_method->GetName()) {
      return &method;
    }
  }
  return nullptr;
}

// TODO These should maybe be changed to be named FindOwnedVirtualMethod or something similar
// because they do not only find 'declared' methods and will return copied methods. This behavior is
// desired and correct but the naming can lead to confusion because in the java language declared
// excludes interface methods which might be found by this.
ArtMethod* Class::FindDeclaredVirtualMethod(const StringPiece& name, const StringPiece& signature,
                                            size_t pointer_size) {
  for (auto& method : GetVirtualMethods(pointer_size)) {
    ArtMethod* const np_method = method.GetInterfaceMethodIfProxy(pointer_size);
    if (name == np_method->GetName() && np_method->GetSignature() == signature) {
      return &method;
    }
  }
  return nullptr;
}

ArtMethod* Class::FindDeclaredVirtualMethod(const StringPiece& name, const Signature& signature,
                                            size_t pointer_size) {
  for (auto& method : GetVirtualMethods(pointer_size)) {
    ArtMethod* const np_method = method.GetInterfaceMethodIfProxy(pointer_size);
    if (name == np_method->GetName() && signature == np_method->GetSignature()) {
      return &method;
    }
  }
  return nullptr;
}

ArtMethod* Class::FindDeclaredVirtualMethod(const DexCache* dex_cache, uint32_t dex_method_idx,
                                            size_t pointer_size) {
  if (GetDexCache() == dex_cache) {
    for (auto& method : GetDeclaredVirtualMethods(pointer_size)) {
      if (method.GetDexMethodIndex() == dex_method_idx) {
        return &method;
      }
    }
  }
  return nullptr;
}

ArtMethod* Class::FindDeclaredVirtualMethodByName(const StringPiece& name, size_t pointer_size) {
  for (auto& method : GetVirtualMethods(pointer_size)) {
    ArtMethod* const np_method = method.GetInterfaceMethodIfProxy(pointer_size);
    if (name == np_method->GetName()) {
      return &method;
    }
  }
  return nullptr;
}

ArtMethod* Class::FindVirtualMethod(
    const StringPiece& name, const StringPiece& signature, size_t pointer_size) {
  for (Class* klass = this; klass != nullptr; klass = klass->GetSuperClass()) {
    ArtMethod* method = klass->FindDeclaredVirtualMethod(name, signature, pointer_size);
    if (method != nullptr) {
      return method;
    }
  }
  return nullptr;
}

ArtMethod* Class::FindVirtualMethod(
    const StringPiece& name, const Signature& signature, size_t pointer_size) {
  for (Class* klass = this; klass != nullptr; klass = klass->GetSuperClass()) {
    ArtMethod* method = klass->FindDeclaredVirtualMethod(name, signature, pointer_size);
    if (method != nullptr) {
      return method;
    }
  }
  return nullptr;
}

ArtMethod* Class::FindVirtualMethod(
    const DexCache* dex_cache, uint32_t dex_method_idx, size_t pointer_size) {
  for (Class* klass = this; klass != nullptr; klass = klass->GetSuperClass()) {
    ArtMethod* method = klass->FindDeclaredVirtualMethod(dex_cache, dex_method_idx, pointer_size);
    if (method != nullptr) {
      return method;
    }
  }
  return nullptr;
}

ArtMethod* Class::FindVirtualMethodForInterfaceSuper(ArtMethod* method, size_t pointer_size) {
  DCHECK(method->GetDeclaringClass()->IsInterface());
  DCHECK(IsInterface()) << "Should only be called on a interface class";
  // Check if we have one defined on this interface first. This includes searching copied ones to
  // get any conflict methods. Conflict methods are copied into each subtype from the supertype. We
  // don't do any indirect method checks here.
  for (ArtMethod& iface_method : GetVirtualMethods(pointer_size)) {
    if (method->HasSameNameAndSignature(&iface_method)) {
      return &iface_method;
    }
  }

  std::vector<ArtMethod*> abstract_methods;
  // Search through the IFTable for a working version. We don't need to check for conflicts
  // because if there was one it would appear in this classes virtual_methods_ above.

  Thread* self = Thread::Current();
  StackHandleScope<2> hs(self);
  MutableHandle<mirror::IfTable> iftable(hs.NewHandle(GetIfTable()));
  MutableHandle<mirror::Class> iface(hs.NewHandle<mirror::Class>(nullptr));
  size_t iftable_count = GetIfTableCount();
  // Find the method. We don't need to check for conflicts because they would have been in the
  // copied virtuals of this interface.  Order matters, traverse in reverse topological order; most
  // subtypiest interfaces get visited first.
  for (size_t k = iftable_count; k != 0;) {
    k--;
    DCHECK_LT(k, iftable->Count());
    iface.Assign(iftable->GetInterface(k));
    // Iterate through every declared method on this interface. Each direct method's name/signature
    // is unique so the order of the inner loop doesn't matter.
    for (auto& method_iter : iface->GetDeclaredVirtualMethods(pointer_size)) {
      ArtMethod* current_method = &method_iter;
      if (current_method->HasSameNameAndSignature(method)) {
        if (current_method->IsDefault()) {
          // Handle JLS soft errors, a default method from another superinterface tree can
          // "override" an abstract method(s) from another superinterface tree(s).  To do this,
          // ignore any [default] method which are dominated by the abstract methods we've seen so
          // far. Check if overridden by any in abstract_methods. We do not need to check for
          // default_conflicts because we would hit those before we get to this loop.
          bool overridden = false;
          for (ArtMethod* possible_override : abstract_methods) {
            DCHECK(possible_override->HasSameNameAndSignature(current_method));
            if (iface->IsAssignableFrom(possible_override->GetDeclaringClass())) {
              overridden = true;
              break;
            }
          }
          if (!overridden) {
            return current_method;
          }
        } else {
          // Is not default.
          // This might override another default method. Just stash it for now.
          abstract_methods.push_back(current_method);
        }
      }
    }
  }
  // If we reach here we either never found any declaration of the method (in which case
  // 'abstract_methods' is empty or we found no non-overriden default methods in which case
  // 'abstract_methods' contains a number of abstract implementations of the methods. We choose one
  // of these arbitrarily.
  return abstract_methods.empty() ? nullptr : abstract_methods[0];
}

ArtMethod* Class::FindClassInitializer(size_t pointer_size) {
  for (ArtMethod& method : GetDirectMethods(pointer_size)) {
    if (method.IsClassInitializer()) {
      DCHECK_STREQ(method.GetName(), "<clinit>");
      DCHECK_STREQ(method.GetSignature().ToString().c_str(), "()V");
      return &method;
    }
  }
  return nullptr;
}

// Custom binary search to avoid double comparisons from std::binary_search.
static ArtField* FindFieldByNameAndType(LengthPrefixedArray<ArtField>* fields,
                                        const StringPiece& name,
                                        const StringPiece& type)
    SHARED_REQUIRES(Locks::mutator_lock_) {
  if (fields == nullptr) {
    return nullptr;
  }
  size_t low = 0;
  size_t high = fields->size();
  ArtField* ret = nullptr;
  while (low < high) {
    size_t mid = (low + high) / 2;
    ArtField& field = fields->At(mid);
    // Fields are sorted by class, then name, then type descriptor. This is verified in dex file
    // verifier. There can be multiple fields with the same in the same class name due to proguard.
    int result = StringPiece(field.GetName()).Compare(name);
    if (result == 0) {
      result = StringPiece(field.GetTypeDescriptor()).Compare(type);
    }
    if (result < 0) {
      low = mid + 1;
    } else if (result > 0) {
      high = mid;
    } else {
      ret = &field;
      break;
    }
  }
  if (kIsDebugBuild) {
    ArtField* found = nullptr;
    for (ArtField& field : MakeIterationRangeFromLengthPrefixedArray(fields)) {
      if (name == field.GetName() && type == field.GetTypeDescriptor()) {
        found = &field;
        break;
      }
    }
    CHECK_EQ(found, ret) << "Found " << PrettyField(found) << " vs  " << PrettyField(ret);
  }
  return ret;
}

ArtField* Class::FindDeclaredInstanceField(const StringPiece& name, const StringPiece& type) {
  // Binary search by name. Interfaces are not relevant because they can't contain instance fields.
  return FindFieldByNameAndType(GetIFieldsPtr(), name, type);
}

ArtField* Class::FindDeclaredInstanceField(const DexCache* dex_cache, uint32_t dex_field_idx) {
  if (GetDexCache() == dex_cache) {
    for (ArtField& field : GetIFields()) {
      if (field.GetDexFieldIndex() == dex_field_idx) {
        return &field;
      }
    }
  }
  return nullptr;
}

ArtField* Class::FindInstanceField(const StringPiece& name, const StringPiece& type) {
  // Is the field in this class, or any of its superclasses?
  // Interfaces are not relevant because they can't contain instance fields.
  for (Class* c = this; c != nullptr; c = c->GetSuperClass()) {
    ArtField* f = c->FindDeclaredInstanceField(name, type);
    if (f != nullptr) {
      return f;
    }
  }
  return nullptr;
}

ArtField* Class::FindInstanceField(const DexCache* dex_cache, uint32_t dex_field_idx) {
  // Is the field in this class, or any of its superclasses?
  // Interfaces are not relevant because they can't contain instance fields.
  for (Class* c = this; c != nullptr; c = c->GetSuperClass()) {
    ArtField* f = c->FindDeclaredInstanceField(dex_cache, dex_field_idx);
    if (f != nullptr) {
      return f;
    }
  }
  return nullptr;
}

ArtField* Class::FindDeclaredStaticField(const StringPiece& name, const StringPiece& type) {
  DCHECK(type != nullptr);
  return FindFieldByNameAndType(GetSFieldsPtr(), name, type);
}

ArtField* Class::FindDeclaredStaticField(const DexCache* dex_cache, uint32_t dex_field_idx) {
  if (dex_cache == GetDexCache()) {
    for (ArtField& field : GetSFields()) {
      if (field.GetDexFieldIndex() == dex_field_idx) {
        return &field;
      }
    }
  }
  return nullptr;
}

ArtField* Class::FindStaticField(Thread* self, Handle<Class> klass, const StringPiece& name,
                                 const StringPiece& type) {
  // Is the field in this class (or its interfaces), or any of its
  // superclasses (or their interfaces)?
  for (Class* k = klass.Get(); k != nullptr; k = k->GetSuperClass()) {
    // Is the field in this class?
    ArtField* f = k->FindDeclaredStaticField(name, type);
    if (f != nullptr) {
      return f;
    }
    // Wrap k incase it moves during GetDirectInterface.
    StackHandleScope<1> hs(self);
    HandleWrapper<mirror::Class> h_k(hs.NewHandleWrapper(&k));
    // Is this field in any of this class' interfaces?
    for (uint32_t i = 0; i < h_k->NumDirectInterfaces(); ++i) {
      StackHandleScope<1> hs2(self);
      Handle<mirror::Class> interface(hs2.NewHandle(GetDirectInterface(self, h_k, i)));
      f = FindStaticField(self, interface, name, type);
      if (f != nullptr) {
        return f;
      }
    }
  }
  return nullptr;
}

ArtField* Class::FindStaticField(Thread* self, Handle<Class> klass, const DexCache* dex_cache,
                                 uint32_t dex_field_idx) {
  for (Class* k = klass.Get(); k != nullptr; k = k->GetSuperClass()) {
    // Is the field in this class?
    ArtField* f = k->FindDeclaredStaticField(dex_cache, dex_field_idx);
    if (f != nullptr) {
      return f;
    }
    // Wrap k incase it moves during GetDirectInterface.
    StackHandleScope<1> hs(self);
    HandleWrapper<mirror::Class> h_k(hs.NewHandleWrapper(&k));
    // Is this field in any of this class' interfaces?
    for (uint32_t i = 0; i < h_k->NumDirectInterfaces(); ++i) {
      StackHandleScope<1> hs2(self);
      Handle<mirror::Class> interface(hs2.NewHandle(GetDirectInterface(self, h_k, i)));
      f = FindStaticField(self, interface, dex_cache, dex_field_idx);
      if (f != nullptr) {
        return f;
      }
    }
  }
  return nullptr;
}

ArtField* Class::FindField(Thread* self, Handle<Class> klass, const StringPiece& name,
                           const StringPiece& type) {
  // Find a field using the JLS field resolution order
  for (Class* k = klass.Get(); k != nullptr; k = k->GetSuperClass()) {
    // Is the field in this class?
    ArtField* f = k->FindDeclaredInstanceField(name, type);
    if (f != nullptr) {
      return f;
    }
    f = k->FindDeclaredStaticField(name, type);
    if (f != nullptr) {
      return f;
    }
    // Is this field in any of this class' interfaces?
    StackHandleScope<1> hs(self);
    HandleWrapper<mirror::Class> h_k(hs.NewHandleWrapper(&k));
    for (uint32_t i = 0; i < h_k->NumDirectInterfaces(); ++i) {
      StackHandleScope<1> hs2(self);
      Handle<mirror::Class> interface(hs2.NewHandle(GetDirectInterface(self, h_k, i)));
      f = interface->FindStaticField(self, interface, name, type);
      if (f != nullptr) {
        return f;
      }
    }
  }
  return nullptr;
}

void Class::SetSkipAccessChecksFlagOnAllMethods(size_t pointer_size) {
  DCHECK(IsVerified());
  for (auto& m : GetMethods(pointer_size)) {
    if (!m.IsNative() && m.IsInvokable()) {
      m.SetSkipAccessChecks();
    }
  }
}

const char* Class::GetDescriptor(std::string* storage) {
  if (IsPrimitive()) {
    return Primitive::Descriptor(GetPrimitiveType());
  } else if (IsArrayClass()) {
    return GetArrayDescriptor(storage);
  } else if (IsProxyClass()) {
    *storage = Runtime::Current()->GetClassLinker()->GetDescriptorForProxy(this);
    return storage->c_str();
  } else {
    const DexFile& dex_file = GetDexFile();
    const DexFile::TypeId& type_id = dex_file.GetTypeId(GetClassDef()->class_idx_);
    return dex_file.GetTypeDescriptor(type_id);
  }
}

const char* Class::GetArrayDescriptor(std::string* storage) {
  std::string temp;
  const char* elem_desc = GetComponentType()->GetDescriptor(&temp);
  *storage = "[";
  *storage += elem_desc;
  return storage->c_str();
}

const DexFile::ClassDef* Class::GetClassDef() {
  uint16_t class_def_idx = GetDexClassDefIndex();
  if (class_def_idx == DexFile::kDexNoIndex16) {
    return nullptr;
  }
  return &GetDexFile().GetClassDef(class_def_idx);
}

uint16_t Class::GetDirectInterfaceTypeIdx(uint32_t idx) {
  DCHECK(!IsPrimitive());
  DCHECK(!IsArrayClass());
  return GetInterfaceTypeList()->GetTypeItem(idx).type_idx_;
}

mirror::Class* Class::GetDirectInterface(Thread* self, Handle<mirror::Class> klass,
                                         uint32_t idx) {
  DCHECK(klass.Get() != nullptr);
  DCHECK(!klass->IsPrimitive());
  if (klass->IsArrayClass()) {
    ClassLinker* class_linker = Runtime::Current()->GetClassLinker();
    if (idx == 0) {
      return class_linker->FindSystemClass(self, "Ljava/lang/Cloneable;");
    } else {
      DCHECK_EQ(1U, idx);
      return class_linker->FindSystemClass(self, "Ljava/io/Serializable;");
    }
  } else if (klass->IsProxyClass()) {
    mirror::ObjectArray<mirror::Class>* interfaces = klass.Get()->GetInterfaces();
    DCHECK(interfaces != nullptr);
    return interfaces->Get(idx);
  } else {
    uint16_t type_idx = klass->GetDirectInterfaceTypeIdx(idx);
    mirror::Class* interface = klass->GetDexCache()->GetResolvedType(type_idx);
    if (interface == nullptr) {
      interface = Runtime::Current()->GetClassLinker()->ResolveType(klass->GetDexFile(), type_idx,
                                                                    klass.Get());
      CHECK(interface != nullptr || self->IsExceptionPending());
    }
    return interface;
  }
}

mirror::Class* Class::GetCommonSuperClass(Handle<Class> klass) {
  DCHECK(klass.Get() != nullptr);
  DCHECK(!klass->IsInterface());
  DCHECK(!IsInterface());
  mirror::Class* common_super_class = this;
  while (!common_super_class->IsAssignableFrom(klass.Get())) {
    common_super_class = common_super_class->GetSuperClass();
  }
  DCHECK(common_super_class != nullptr);
  return common_super_class;
}

const char* Class::GetSourceFile() {
  const DexFile& dex_file = GetDexFile();
  const DexFile::ClassDef* dex_class_def = GetClassDef();
  if (dex_class_def == nullptr) {
    // Generated classes have no class def.
    return nullptr;
  }
  return dex_file.GetSourceFile(*dex_class_def);
}

std::string Class::GetLocation() {
  mirror::DexCache* dex_cache = GetDexCache();
  if (dex_cache != nullptr && !IsProxyClass()) {
    return dex_cache->GetLocation()->ToModifiedUtf8();
  }
  // Arrays and proxies are generated and have no corresponding dex file location.
  return "generated class";
}

const DexFile::TypeList* Class::GetInterfaceTypeList() {
  const DexFile::ClassDef* class_def = GetClassDef();
  if (class_def == nullptr) {
    return nullptr;
  }
  return GetDexFile().GetInterfacesList(*class_def);
}

void Class::PopulateEmbeddedImtAndVTable(ArtMethod* const (&methods)[kImtSize],
                                         size_t pointer_size) {
  for (size_t i = 0; i < kImtSize; i++) {
    auto method = methods[i];
    DCHECK(method != nullptr);
    SetEmbeddedImTableEntry(i, method, pointer_size);
  }
  PointerArray* table = GetVTableDuringLinking();
  CHECK(table != nullptr) << PrettyClass(this);
  const size_t table_length = table->GetLength();
  SetEmbeddedVTableLength(table_length);
  for (size_t i = 0; i < table_length; i++) {
    SetEmbeddedVTableEntry(i, table->GetElementPtrSize<ArtMethod*>(i, pointer_size), pointer_size);
  }
  // Keep java.lang.Object class's vtable around for since it's easier
  // to be reused by array classes during their linking.
  if (!IsObjectClass()) {
    SetVTable(nullptr);
  }
}

class ReadBarrierOnNativeRootsVisitor {
 public:
  void operator()(mirror::Object* obj ATTRIBUTE_UNUSED,
                  MemberOffset offset ATTRIBUTE_UNUSED,
                  bool is_static ATTRIBUTE_UNUSED) const {}

  void VisitRootIfNonNull(mirror::CompressedReference<mirror::Object>* root) const
      SHARED_REQUIRES(Locks::mutator_lock_) {
    if (!root->IsNull()) {
      VisitRoot(root);
    }
  }

  void VisitRoot(mirror::CompressedReference<mirror::Object>* root) const
      SHARED_REQUIRES(Locks::mutator_lock_) {
    mirror::Object* old_ref = root->AsMirrorPtr();
    mirror::Object* new_ref = ReadBarrier::BarrierForRoot(root);
    if (old_ref != new_ref) {
      // Update the field atomically. This may fail if mutator updates before us, but it's ok.
      auto* atomic_root =
          reinterpret_cast<Atomic<mirror::CompressedReference<mirror::Object>>*>(root);
      atomic_root->CompareExchangeStrongSequentiallyConsistent(
          mirror::CompressedReference<mirror::Object>::FromMirrorPtr(old_ref),
          mirror::CompressedReference<mirror::Object>::FromMirrorPtr(new_ref));
    }
  }
};

// The pre-fence visitor for Class::CopyOf().
class CopyClassVisitor {
 public:
  CopyClassVisitor(Thread* self, Handle<mirror::Class>* orig, size_t new_length,
                   size_t copy_bytes, ArtMethod* const (&imt)[mirror::Class::kImtSize],
                   size_t pointer_size)
      : self_(self), orig_(orig), new_length_(new_length),
        copy_bytes_(copy_bytes), imt_(imt), pointer_size_(pointer_size) {
  }

  void operator()(mirror::Object* obj, size_t usable_size ATTRIBUTE_UNUSED) const
      SHARED_REQUIRES(Locks::mutator_lock_) {
    StackHandleScope<1> hs(self_);
    Handle<mirror::Class> h_new_class_obj(hs.NewHandle(obj->AsClass()));
    mirror::Object::CopyObject(self_, h_new_class_obj.Get(), orig_->Get(), copy_bytes_);
    mirror::Class::SetStatus(h_new_class_obj, Class::kStatusResolving, self_);
    h_new_class_obj->PopulateEmbeddedImtAndVTable(imt_, pointer_size_);
    h_new_class_obj->SetClassSize(new_length_);
    // Visit all of the references to make sure there is no from space references in the native
    // roots.
    static_cast<mirror::Object*>(h_new_class_obj.Get())->VisitReferences(
        ReadBarrierOnNativeRootsVisitor(), VoidFunctor());
  }

 private:
  Thread* const self_;
  Handle<mirror::Class>* const orig_;
  const size_t new_length_;
  const size_t copy_bytes_;
  ArtMethod* const (&imt_)[mirror::Class::kImtSize];
  const size_t pointer_size_;
  DISALLOW_COPY_AND_ASSIGN(CopyClassVisitor);
};

Class* Class::CopyOf(Thread* self, int32_t new_length,
                     ArtMethod* const (&imt)[mirror::Class::kImtSize], size_t pointer_size) {
  DCHECK_GE(new_length, static_cast<int32_t>(sizeof(Class)));
  // We may get copied by a compacting GC.
  StackHandleScope<1> hs(self);
  Handle<mirror::Class> h_this(hs.NewHandle(this));
  gc::Heap* heap = Runtime::Current()->GetHeap();
  // The num_bytes (3rd param) is sizeof(Class) as opposed to SizeOf()
  // to skip copying the tail part that we will overwrite here.
  CopyClassVisitor visitor(self, &h_this, new_length, sizeof(Class), imt, pointer_size);
  mirror::Object* new_class = kMovingClasses ?
      heap->AllocObject<true>(self, java_lang_Class_.Read(), new_length, visitor) :
      heap->AllocNonMovableObject<true>(self, java_lang_Class_.Read(), new_length, visitor);
  if (UNLIKELY(new_class == nullptr)) {
    self->AssertPendingOOMException();
    return nullptr;
  }
  return new_class->AsClass();
}

bool Class::ProxyDescriptorEquals(const char* match) {
  DCHECK(IsProxyClass());
  return Runtime::Current()->GetClassLinker()->GetDescriptorForProxy(this) == match;
}

// TODO: Move this to java_lang_Class.cc?
ArtMethod* Class::GetDeclaredConstructor(
    Thread* self, Handle<mirror::ObjectArray<mirror::Class>> args) {
  for (auto& m : GetDirectMethods(sizeof(void*))) {
    // Skip <clinit> which is a static constructor, as well as non constructors.
    if (m.IsStatic() || !m.IsConstructor()) {
      continue;
    }
    // May cause thread suspension and exceptions.
    if (m.GetInterfaceMethodIfProxy(sizeof(void*))->EqualParameters(args)) {
      return &m;
    }
    if (UNLIKELY(self->IsExceptionPending())) {
      return nullptr;
    }
  }
  return nullptr;
}

uint32_t Class::Depth() {
  uint32_t depth = 0;
  for (Class* klass = this; klass->GetSuperClass() != nullptr; klass = klass->GetSuperClass()) {
    depth++;
  }
  return depth;
}

}  // namespace mirror
}  // namespace art