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Java example source code file (klass.cpp)

This example Java source code file (klass.cpp) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

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Java - Java tags/keywords

assert, check, growablearray, instanceklass, klass, klass\:\:array_klass_impl, null, resourcemark, should, systemdictionary\:\:object_klass, thread, traps, universe\:\:heap, wizardmode

The klass.cpp Java example source code

/*
 * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 *
 */

#include "precompiled.hpp"
#include "classfile/javaClasses.hpp"
#include "classfile/dictionary.hpp"
#include "classfile/systemDictionary.hpp"
#include "classfile/vmSymbols.hpp"
#include "gc_implementation/shared/markSweep.inline.hpp"
#include "gc_interface/collectedHeap.inline.hpp"
#include "memory/heapInspection.hpp"
#include "memory/metadataFactory.hpp"
#include "memory/oopFactory.hpp"
#include "memory/resourceArea.hpp"
#include "oops/instanceKlass.hpp"
#include "oops/klass.inline.hpp"
#include "oops/oop.inline2.hpp"
#include "runtime/atomic.hpp"
#include "trace/traceMacros.hpp"
#include "utilities/stack.hpp"
#include "utilities/macros.hpp"
#if INCLUDE_ALL_GCS
#include "gc_implementation/parallelScavenge/psParallelCompact.hpp"
#include "gc_implementation/parallelScavenge/psPromotionManager.hpp"
#include "gc_implementation/parallelScavenge/psScavenge.hpp"
#endif // INCLUDE_ALL_GCS

void Klass::set_name(Symbol* n) {
  _name = n;
  if (_name != NULL) _name->increment_refcount();
}

bool Klass::is_subclass_of(const Klass* k) const {
  // Run up the super chain and check
  if (this == k) return true;

  Klass* t = const_cast<Klass*>(this)->super();

  while (t != NULL) {
    if (t == k) return true;
    t = t->super();
  }
  return false;
}

bool Klass::search_secondary_supers(Klass* k) const {
  // Put some extra logic here out-of-line, before the search proper.
  // This cuts down the size of the inline method.

  // This is necessary, since I am never in my own secondary_super list.
  if (this == k)
    return true;
  // Scan the array-of-objects for a match
  int cnt = secondary_supers()->length();
  for (int i = 0; i < cnt; i++) {
    if (secondary_supers()->at(i) == k) {
      ((Klass*)this)->set_secondary_super_cache(k);
      return true;
    }
  }
  return false;
}

// Return self, except for abstract classes with exactly 1
// implementor.  Then return the 1 concrete implementation.
Klass *Klass::up_cast_abstract() {
  Klass *r = this;
  while( r->is_abstract() ) {   // Receiver is abstract?
    Klass *s = r->subklass();   // Check for exactly 1 subklass
    if( !s || s->next_sibling() ) // Oops; wrong count; give up
      return this;              // Return 'this' as a no-progress flag
    r = s;                    // Loop till find concrete class
  }
  return r;                   // Return the 1 concrete class
}

// Find LCA in class hierarchy
Klass *Klass::LCA( Klass *k2 ) {
  Klass *k1 = this;
  while( 1 ) {
    if( k1->is_subtype_of(k2) ) return k2;
    if( k2->is_subtype_of(k1) ) return k1;
    k1 = k1->super();
    k2 = k2->super();
  }
}


void Klass::check_valid_for_instantiation(bool throwError, TRAPS) {
  ResourceMark rm(THREAD);
  THROW_MSG(throwError ? vmSymbols::java_lang_InstantiationError()
            : vmSymbols::java_lang_InstantiationException(), external_name());
}


void Klass::copy_array(arrayOop s, int src_pos, arrayOop d, int dst_pos, int length, TRAPS) {
  THROW(vmSymbols::java_lang_ArrayStoreException());
}


void Klass::initialize(TRAPS) {
  ShouldNotReachHere();
}

bool Klass::compute_is_subtype_of(Klass* k) {
  assert(k->is_klass(), "argument must be a class");
  return is_subclass_of(k);
}


Method* Klass::uncached_lookup_method(Symbol* name, Symbol* signature) const {
#ifdef ASSERT
  tty->print_cr("Error: uncached_lookup_method called on a klass oop."
                " Likely error: reflection method does not correctly"
                " wrap return value in a mirror object.");
#endif
  ShouldNotReachHere();
  return NULL;
}

void* Klass::operator new(size_t size, ClassLoaderData* loader_data, size_t word_size, TRAPS) throw() {
  return Metaspace::allocate(loader_data, word_size, /*read_only*/false,
                             MetaspaceObj::ClassType, CHECK_NULL);
}

Klass::Klass() {
  Klass* k = this;

  // Preinitialize supertype information.
  // A later call to initialize_supers() may update these settings:
  set_super(NULL);
  for (juint i = 0; i < Klass::primary_super_limit(); i++) {
    _primary_supers[i] = NULL;
  }
  set_secondary_supers(NULL);
  set_secondary_super_cache(NULL);
  _primary_supers[0] = k;
  set_super_check_offset(in_bytes(primary_supers_offset()));

  set_java_mirror(NULL);
  set_modifier_flags(0);
  set_layout_helper(Klass::_lh_neutral_value);
  set_name(NULL);
  AccessFlags af;
  af.set_flags(0);
  set_access_flags(af);
  set_subklass(NULL);
  set_next_sibling(NULL);
  set_next_link(NULL);
  TRACE_INIT_ID(this);

  set_prototype_header(markOopDesc::prototype());
  set_biased_lock_revocation_count(0);
  set_last_biased_lock_bulk_revocation_time(0);

  // The klass doesn't have any references at this point.
  clear_modified_oops();
  clear_accumulated_modified_oops();
}

jint Klass::array_layout_helper(BasicType etype) {
  assert(etype >= T_BOOLEAN && etype <= T_OBJECT, "valid etype");
  // Note that T_ARRAY is not allowed here.
  int  hsize = arrayOopDesc::base_offset_in_bytes(etype);
  int  esize = type2aelembytes(etype);
  bool isobj = (etype == T_OBJECT);
  int  tag   =  isobj ? _lh_array_tag_obj_value : _lh_array_tag_type_value;
  int lh = array_layout_helper(tag, hsize, etype, exact_log2(esize));

  assert(lh < (int)_lh_neutral_value, "must look like an array layout");
  assert(layout_helper_is_array(lh), "correct kind");
  assert(layout_helper_is_objArray(lh) == isobj, "correct kind");
  assert(layout_helper_is_typeArray(lh) == !isobj, "correct kind");
  assert(layout_helper_header_size(lh) == hsize, "correct decode");
  assert(layout_helper_element_type(lh) == etype, "correct decode");
  assert(1 << layout_helper_log2_element_size(lh) == esize, "correct decode");

  return lh;
}

bool Klass::can_be_primary_super_slow() const {
  if (super() == NULL)
    return true;
  else if (super()->super_depth() >= primary_super_limit()-1)
    return false;
  else
    return true;
}

void Klass::initialize_supers(Klass* k, TRAPS) {
  if (FastSuperclassLimit == 0) {
    // None of the other machinery matters.
    set_super(k);
    return;
  }
  if (k == NULL) {
    set_super(NULL);
    _primary_supers[0] = this;
    assert(super_depth() == 0, "Object must already be initialized properly");
  } else if (k != super() || k == SystemDictionary::Object_klass()) {
    assert(super() == NULL || super() == SystemDictionary::Object_klass(),
           "initialize this only once to a non-trivial value");
    set_super(k);
    Klass* sup = k;
    int sup_depth = sup->super_depth();
    juint my_depth  = MIN2(sup_depth + 1, (int)primary_super_limit());
    if (!can_be_primary_super_slow())
      my_depth = primary_super_limit();
    for (juint i = 0; i < my_depth; i++) {
      _primary_supers[i] = sup->_primary_supers[i];
    }
    Klass* *super_check_cell;
    if (my_depth < primary_super_limit()) {
      _primary_supers[my_depth] = this;
      super_check_cell = &_primary_supers[my_depth];
    } else {
      // Overflow of the primary_supers array forces me to be secondary.
      super_check_cell = &_secondary_super_cache;
    }
    set_super_check_offset((address)super_check_cell - (address) this);

#ifdef ASSERT
    {
      juint j = super_depth();
      assert(j == my_depth, "computed accessor gets right answer");
      Klass* t = this;
      while (!t->can_be_primary_super()) {
        t = t->super();
        j = t->super_depth();
      }
      for (juint j1 = j+1; j1 < primary_super_limit(); j1++) {
        assert(primary_super_of_depth(j1) == NULL, "super list padding");
      }
      while (t != NULL) {
        assert(primary_super_of_depth(j) == t, "super list initialization");
        t = t->super();
        --j;
      }
      assert(j == (juint)-1, "correct depth count");
    }
#endif
  }

  if (secondary_supers() == NULL) {
    KlassHandle this_kh (THREAD, this);

    // Now compute the list of secondary supertypes.
    // Secondaries can occasionally be on the super chain,
    // if the inline "_primary_supers" array overflows.
    int extras = 0;
    Klass* p;
    for (p = super(); !(p == NULL || p->can_be_primary_super()); p = p->super()) {
      ++extras;
    }

    ResourceMark rm(THREAD);  // need to reclaim GrowableArrays allocated below

    // Compute the "real" non-extra secondaries.
    GrowableArray<Klass*>* secondaries = compute_secondary_supers(extras);
    if (secondaries == NULL) {
      // secondary_supers set by compute_secondary_supers
      return;
    }

    GrowableArray<Klass*>* primaries = new GrowableArray(extras);

    for (p = this_kh->super(); !(p == NULL || p->can_be_primary_super()); p = p->super()) {
      int i;                    // Scan for overflow primaries being duplicates of 2nd'arys

      // This happens frequently for very deeply nested arrays: the
      // primary superclass chain overflows into the secondary.  The
      // secondary list contains the element_klass's secondaries with
      // an extra array dimension added.  If the element_klass's
      // secondary list already contains some primary overflows, they
      // (with the extra level of array-ness) will collide with the
      // normal primary superclass overflows.
      for( i = 0; i < secondaries->length(); i++ ) {
        if( secondaries->at(i) == p )
          break;
      }
      if( i < secondaries->length() )
        continue;               // It's a dup, don't put it in
      primaries->push(p);
    }
    // Combine the two arrays into a metadata object to pack the array.
    // The primaries are added in the reverse order, then the secondaries.
    int new_length = primaries->length() + secondaries->length();
    Array<Klass*>* s2 = MetadataFactory::new_array(
                                       class_loader_data(), new_length, CHECK);
    int fill_p = primaries->length();
    for (int j = 0; j < fill_p; j++) {
      s2->at_put(j, primaries->pop());  // add primaries in reverse order.
    }
    for( int j = 0; j < secondaries->length(); j++ ) {
      s2->at_put(j+fill_p, secondaries->at(j));  // add secondaries on the end.
    }

  #ifdef ASSERT
      // We must not copy any NULL placeholders left over from bootstrap.
    for (int j = 0; j < s2->length(); j++) {
      assert(s2->at(j) != NULL, "correct bootstrapping order");
    }
  #endif

    this_kh->set_secondary_supers(s2);
  }
}

GrowableArray<Klass*>* Klass::compute_secondary_supers(int num_extra_slots) {
  assert(num_extra_slots == 0, "override for complex klasses");
  set_secondary_supers(Universe::the_empty_klass_array());
  return NULL;
}


Klass* Klass::subklass() const {
  return _subklass == NULL ? NULL : _subklass;
}

InstanceKlass* Klass::superklass() const {
  assert(super() == NULL || super()->oop_is_instance(), "must be instance klass");
  return _super == NULL ? NULL : InstanceKlass::cast(_super);
}

Klass* Klass::next_sibling() const {
  return _next_sibling == NULL ? NULL : _next_sibling;
}

void Klass::set_subklass(Klass* s) {
  assert(s != this, "sanity check");
  _subklass = s;
}

void Klass::set_next_sibling(Klass* s) {
  assert(s != this, "sanity check");
  _next_sibling = s;
}

void Klass::append_to_sibling_list() {
  debug_only(verify();)
  // add ourselves to superklass' subklass list
  InstanceKlass* super = superklass();
  if (super == NULL) return;        // special case: class Object
  assert((!super->is_interface()    // interfaces cannot be supers
          && (super->superklass() == NULL || !is_interface())),
         "an interface can only be a subklass of Object");
  Klass* prev_first_subklass = super->subklass_oop();
  if (prev_first_subklass != NULL) {
    // set our sibling to be the superklass' previous first subklass
    set_next_sibling(prev_first_subklass);
  }
  // make ourselves the superklass' first subklass
  super->set_subklass(this);
  debug_only(verify();)
}

bool Klass::is_loader_alive(BoolObjectClosure* is_alive) {
  assert(ClassLoaderDataGraph::contains((address)this), "is in the metaspace");

#ifdef ASSERT
  // The class is alive iff the class loader is alive.
  oop loader = class_loader();
  bool loader_alive = (loader == NULL) || is_alive->do_object_b(loader);
#endif // ASSERT

  // The class is alive if it's mirror is alive (which should be marked if the
  // loader is alive) unless it's an anoymous class.
  bool mirror_alive = is_alive->do_object_b(java_mirror());
  assert(!mirror_alive || loader_alive, "loader must be alive if the mirror is"
                        " but not the other way around with anonymous classes");
  return mirror_alive;
}

void Klass::clean_weak_klass_links(BoolObjectClosure* is_alive) {
  if (!ClassUnloading) {
    return;
  }

  Klass* root = SystemDictionary::Object_klass();
  Stack<Klass*, mtGC> stack;

  stack.push(root);
  while (!stack.is_empty()) {
    Klass* current = stack.pop();

    assert(current->is_loader_alive(is_alive), "just checking, this should be live");

    // Find and set the first alive subklass
    Klass* sub = current->subklass_oop();
    while (sub != NULL && !sub->is_loader_alive(is_alive)) {
#ifndef PRODUCT
      if (TraceClassUnloading && WizardMode) {
        ResourceMark rm;
        tty->print_cr("[Unlinking class (subclass) %s]", sub->external_name());
      }
#endif
      sub = sub->next_sibling_oop();
    }
    current->set_subklass(sub);
    if (sub != NULL) {
      stack.push(sub);
    }

    // Find and set the first alive sibling
    Klass* sibling = current->next_sibling_oop();
    while (sibling != NULL && !sibling->is_loader_alive(is_alive)) {
      if (TraceClassUnloading && WizardMode) {
        ResourceMark rm;
        tty->print_cr("[Unlinking class (sibling) %s]", sibling->external_name());
      }
      sibling = sibling->next_sibling_oop();
    }
    current->set_next_sibling(sibling);
    if (sibling != NULL) {
      stack.push(sibling);
    }

    // Clean the implementors list and method data.
    if (current->oop_is_instance()) {
      InstanceKlass* ik = InstanceKlass::cast(current);
      ik->clean_implementors_list(is_alive);
      ik->clean_method_data(is_alive);
    }
  }
}

void Klass::klass_update_barrier_set(oop v) {
  record_modified_oops();
}

void Klass::klass_update_barrier_set_pre(void* p, oop v) {
  // This barrier used by G1, where it's used remember the old oop values,
  // so that we don't forget any objects that were live at the snapshot at
  // the beginning. This function is only used when we write oops into
  // Klasses. Since the Klasses are used as roots in G1, we don't have to
  // do anything here.
}

void Klass::klass_oop_store(oop* p, oop v) {
  assert(!Universe::heap()->is_in_reserved((void*)p), "Should store pointer into metadata");
  assert(v == NULL || Universe::heap()->is_in_reserved((void*)v), "Should store pointer to an object");

  // do the store
  if (always_do_update_barrier) {
    klass_oop_store((volatile oop*)p, v);
  } else {
    klass_update_barrier_set_pre((void*)p, v);
    *p = v;
    klass_update_barrier_set(v);
  }
}

void Klass::klass_oop_store(volatile oop* p, oop v) {
  assert(!Universe::heap()->is_in_reserved((void*)p), "Should store pointer into metadata");
  assert(v == NULL || Universe::heap()->is_in_reserved((void*)v), "Should store pointer to an object");

  klass_update_barrier_set_pre((void*)p, v);
  OrderAccess::release_store_ptr(p, v);
  klass_update_barrier_set(v);
}

void Klass::oops_do(OopClosure* cl) {
  cl->do_oop(&_java_mirror);
}

void Klass::remove_unshareable_info() {
  if (!DumpSharedSpaces) {
    // Clean up after OOM during class loading
    if (class_loader_data() != NULL) {
      class_loader_data()->remove_class(this);
    }
  }
  set_subklass(NULL);
  set_next_sibling(NULL);
  // Clear the java mirror
  set_java_mirror(NULL);
  set_next_link(NULL);

  // Null out class_loader_data because we don't share that yet.
  set_class_loader_data(NULL);
}

void Klass::restore_unshareable_info(TRAPS) {
  ClassLoaderData* loader_data = ClassLoaderData::the_null_class_loader_data();
  // Restore class_loader_data to the null class loader data
  set_class_loader_data(loader_data);

  // Add to null class loader list first before creating the mirror
  // (same order as class file parsing)
  loader_data->add_class(this);

  // Recreate the class mirror.  The protection_domain is always null for
  // boot loader, for now.
  java_lang_Class::create_mirror(this, Handle(NULL), CHECK);
}

Klass* Klass::array_klass_or_null(int rank) {
  EXCEPTION_MARK;
  // No exception can be thrown by array_klass_impl when called with or_null == true.
  // (In anycase, the execption mark will fail if it do so)
  return array_klass_impl(true, rank, THREAD);
}


Klass* Klass::array_klass_or_null() {
  EXCEPTION_MARK;
  // No exception can be thrown by array_klass_impl when called with or_null == true.
  // (In anycase, the execption mark will fail if it do so)
  return array_klass_impl(true, THREAD);
}


Klass* Klass::array_klass_impl(bool or_null, int rank, TRAPS) {
  fatal("array_klass should be dispatched to InstanceKlass, ObjArrayKlass or TypeArrayKlass");
  return NULL;
}


Klass* Klass::array_klass_impl(bool or_null, TRAPS) {
  fatal("array_klass should be dispatched to InstanceKlass, ObjArrayKlass or TypeArrayKlass");
  return NULL;
}

oop Klass::class_loader() const { return class_loader_data()->class_loader(); }

const char* Klass::external_name() const {
  if (oop_is_instance()) {
    InstanceKlass* ik = (InstanceKlass*) this;
    if (ik->is_anonymous()) {
      assert(EnableInvokeDynamic, "");
      intptr_t hash = 0;
      if (ik->java_mirror() != NULL) {
        // java_mirror might not be created yet, return 0 as hash.
        hash = ik->java_mirror()->identity_hash();
      }
      char     hash_buf[40];
      sprintf(hash_buf, "/" UINTX_FORMAT, (uintx)hash);
      size_t   hash_len = strlen(hash_buf);

      size_t result_len = name()->utf8_length();
      char*  result     = NEW_RESOURCE_ARRAY(char, result_len + hash_len + 1);
      name()->as_klass_external_name(result, (int) result_len + 1);
      assert(strlen(result) == result_len, "");
      strcpy(result + result_len, hash_buf);
      assert(strlen(result) == result_len + hash_len, "");
      return result;
    }
  }
  if (name() == NULL)  return "<unknown>";
  return name()->as_klass_external_name();
}


const char* Klass::signature_name() const {
  if (name() == NULL)  return "<unknown>";
  return name()->as_C_string();
}

// Unless overridden, modifier_flags is 0.
jint Klass::compute_modifier_flags(TRAPS) const {
  return 0;
}

int Klass::atomic_incr_biased_lock_revocation_count() {
  return (int) Atomic::add(1, &_biased_lock_revocation_count);
}

// Unless overridden, jvmti_class_status has no flags set.
jint Klass::jvmti_class_status() const {
  return 0;
}


// Printing

void Klass::print_on(outputStream* st) const {
  ResourceMark rm;
  // print title
  st->print("%s", internal_name());
  print_address_on(st);
  st->cr();
}

void Klass::oop_print_on(oop obj, outputStream* st) {
  ResourceMark rm;
  // print title
  st->print_cr("%s ", internal_name());
  obj->print_address_on(st);

  if (WizardMode) {
     // print header
     obj->mark()->print_on(st);
  }

  // print class
  st->print(" - klass: ");
  obj->klass()->print_value_on(st);
  st->cr();
}

void Klass::oop_print_value_on(oop obj, outputStream* st) {
  // print title
  ResourceMark rm;              // Cannot print in debug mode without this
  st->print("%s", internal_name());
  obj->print_address_on(st);
}

#if INCLUDE_SERVICES
// Size Statistics
void Klass::collect_statistics(KlassSizeStats *sz) const {
  sz->_klass_bytes = sz->count(this);
  sz->_mirror_bytes = sz->count(java_mirror());
  sz->_secondary_supers_bytes = sz->count_array(secondary_supers());

  sz->_ro_bytes += sz->_secondary_supers_bytes;
  sz->_rw_bytes += sz->_klass_bytes + sz->_mirror_bytes;
}
#endif // INCLUDE_SERVICES

// Verification

void Klass::verify_on(outputStream* st, bool check_dictionary) {

  // This can be expensive, but it is worth checking that this klass is actually
  // in the CLD graph but not in production.
  assert(ClassLoaderDataGraph::contains((address)this), "Should be");

  guarantee(this->is_klass(),"should be klass");

  if (super() != NULL) {
    guarantee(super()->is_klass(), "should be klass");
  }
  if (secondary_super_cache() != NULL) {
    Klass* ko = secondary_super_cache();
    guarantee(ko->is_klass(), "should be klass");
  }
  for ( uint i = 0; i < primary_super_limit(); i++ ) {
    Klass* ko = _primary_supers[i];
    if (ko != NULL) {
      guarantee(ko->is_klass(), "should be klass");
    }
  }

  if (java_mirror() != NULL) {
    guarantee(java_mirror()->is_oop(), "should be instance");
  }
}

void Klass::oop_verify_on(oop obj, outputStream* st) {
  guarantee(obj->is_oop(),  "should be oop");
  guarantee(obj->klass()->is_klass(), "klass field is not a klass");
}

#ifndef PRODUCT

bool Klass::verify_vtable_index(int i) {
  if (oop_is_instance()) {
    int limit = ((InstanceKlass*)this)->vtable_length()/vtableEntry::size();
    assert(i >= 0 && i < limit, err_msg("index %d out of bounds %d", i, limit));
  } else {
    assert(oop_is_array(), "Must be");
    int limit = ((ArrayKlass*)this)->vtable_length()/vtableEntry::size();
    assert(i >= 0 && i < limit, err_msg("index %d out of bounds %d", i, limit));
  }
  return true;
}

bool Klass::verify_itable_index(int i) {
  assert(oop_is_instance(), "");
  int method_count = klassItable::method_count_for_interface(this);
  assert(i >= 0 && i < method_count, "index out of bounds");
  return true;
}

#endif

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