Java example source code file (oop.hpp)

This example Java source code file (oop.hpp) 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.

Learn more about this Java project at its project page.

Java - Java tags/keywords

all_oop_oop_iterate_closures_1, all_oop_oop_iterate_closures_2, barrierset, fastscanclosure, heapword, include_all_gcs, klass, memregion, metadata, oop_iterate_decl, product, share_vm_oops_oop_hpp, vmstructs

The oop.hpp 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.
 *
 */

#ifndef SHARE_VM_OOPS_OOP_HPP
#define SHARE_VM_OOPS_OOP_HPP

#include "memory/iterator.hpp"
#include "memory/memRegion.hpp"
#include "memory/specialized_oop_closures.hpp"
#include "oops/metadata.hpp"
#include "utilities/macros.hpp"
#include "utilities/top.hpp"

// oopDesc is the top baseclass for objects classes.  The {name}Desc classes describe
// the format of Java objects so the fields can be accessed from C++.
// oopDesc is abstract.
// (see oopHierarchy for complete oop class hierarchy)
//
// no virtual functions allowed

// store into oop with store check
template <class T> void oop_store(T* p, oop v);
template <class T> void oop_store(volatile T* p, oop v);

extern bool always_do_update_barrier;

// Forward declarations.
class OopClosure;
class ScanClosure;
class FastScanClosure;
class FilteringClosure;
class BarrierSet;
class CMSIsAliveClosure;

class PSPromotionManager;
class ParCompactionManager;

class oopDesc {
  friend class VMStructs;
 private:
  volatile markOop  _mark;
  union _metadata {
    Klass*      _klass;
    narrowKlass _compressed_klass;
  } _metadata;

  // Fast access to barrier set.  Must be initialized.
  static BarrierSet* _bs;

 public:
  markOop  mark() const         { return _mark; }
  markOop* mark_addr() const    { return (markOop*) &_mark; }

  void set_mark(volatile markOop m)      { _mark = m;   }

  void    release_set_mark(markOop m);
  markOop cas_set_mark(markOop new_mark, markOop old_mark);

  // Used only to re-initialize the mark word (e.g., of promoted
  // objects during a GC) -- requires a valid klass pointer
  void init_mark();

  Klass* klass() const;
  Klass* klass_or_null() const volatile;
  Klass** klass_addr();
  narrowKlass* compressed_klass_addr();

  void set_klass(Klass* k);

  // For klass field compression
  int klass_gap() const;
  void set_klass_gap(int z);
  // For when the klass pointer is being used as a linked list "next" field.
  void set_klass_to_list_ptr(oop k);
  oop list_ptr_from_klass();

  // size of object header, aligned to platform wordSize
  static int header_size()          { return sizeof(oopDesc)/HeapWordSize; }

  // Returns whether this is an instance of k or an instance of a subclass of k
  bool is_a(Klass* k)  const;

  // Returns the actual oop size of the object
  int size();

  // Sometimes (for complicated concurrency-related reasons), it is useful
  // to be able to figure out the size of an object knowing its klass.
  int size_given_klass(Klass* klass);

  // type test operations (inlined in oop.inline.h)
  bool is_instance()           const;
  bool is_instanceMirror()     const;
  bool is_instanceRef()        const;
  bool is_array()              const;
  bool is_objArray()           const;
  bool is_typeArray()          const;

 private:
  // field addresses in oop
  void*     field_base(int offset)        const;

  jbyte*    byte_field_addr(int offset)   const;
  jchar*    char_field_addr(int offset)   const;
  jboolean* bool_field_addr(int offset)   const;
  jint*     int_field_addr(int offset)    const;
  jshort*   short_field_addr(int offset)  const;
  jlong*    long_field_addr(int offset)   const;
  jfloat*   float_field_addr(int offset)  const;
  jdouble*  double_field_addr(int offset) const;
  Metadata** metadata_field_addr(int offset) const;

 public:
  // Need this as public for garbage collection.
  template <class T> T* obj_field_addr(int offset) const;

  // Needed for javaClasses
  address*  address_field_addr(int offset) const;

  static bool is_null(oop obj);
  static bool is_null(narrowOop obj);
  static bool is_null(Klass* obj);

  // Decode an oop pointer from a narrowOop if compressed.
  // These are overloaded for oop and narrowOop as are the other functions
  // below so that they can be called in template functions.
  static oop decode_heap_oop_not_null(oop v);
  static oop decode_heap_oop_not_null(narrowOop v);
  static oop decode_heap_oop(oop v);
  static oop decode_heap_oop(narrowOop v);

  // Encode an oop pointer to a narrow oop.  The or_null versions accept
  // null oop pointer, others do not in order to eliminate the
  // null checking branches.
  static narrowOop encode_heap_oop_not_null(oop v);
  static narrowOop encode_heap_oop(oop v);

  // Load an oop out of the Java heap
  static narrowOop load_heap_oop(narrowOop* p);
  static oop       load_heap_oop(oop* p);

  // Load an oop out of Java heap and decode it to an uncompressed oop.
  static oop load_decode_heap_oop_not_null(narrowOop* p);
  static oop load_decode_heap_oop_not_null(oop* p);
  static oop load_decode_heap_oop(narrowOop* p);
  static oop load_decode_heap_oop(oop* p);

  // Store an oop into the heap.
  static void store_heap_oop(narrowOop* p, narrowOop v);
  static void store_heap_oop(oop* p, oop v);

  // Encode oop if UseCompressedOops and store into the heap.
  static void encode_store_heap_oop_not_null(narrowOop* p, oop v);
  static void encode_store_heap_oop_not_null(oop* p, oop v);
  static void encode_store_heap_oop(narrowOop* p, oop v);
  static void encode_store_heap_oop(oop* p, oop v);

  static void release_store_heap_oop(volatile narrowOop* p, narrowOop v);
  static void release_store_heap_oop(volatile oop* p, oop v);

  static void release_encode_store_heap_oop_not_null(volatile narrowOop* p, oop v);
  static void release_encode_store_heap_oop_not_null(volatile oop* p, oop v);
  static void release_encode_store_heap_oop(volatile narrowOop* p, oop v);
  static void release_encode_store_heap_oop(volatile oop* p, oop v);

  static oop atomic_exchange_oop(oop exchange_value, volatile HeapWord *dest);
  static oop atomic_compare_exchange_oop(oop exchange_value,
                                         volatile HeapWord *dest,
                                         oop compare_value,
                                         bool prebarrier = false);

  // Access to fields in a instanceOop through these methods.
  oop obj_field(int offset) const;
  volatile oop obj_field_volatile(int offset) const;
  void obj_field_put(int offset, oop value);
  void obj_field_put_raw(int offset, oop value);
  void obj_field_put_volatile(int offset, oop value);

  Metadata* metadata_field(int offset) const;
  void metadata_field_put(int offset, Metadata* value);

  jbyte byte_field(int offset) const;
  void byte_field_put(int offset, jbyte contents);

  jchar char_field(int offset) const;
  void char_field_put(int offset, jchar contents);

  jboolean bool_field(int offset) const;
  void bool_field_put(int offset, jboolean contents);

  jint int_field(int offset) const;
  void int_field_put(int offset, jint contents);

  jshort short_field(int offset) const;
  void short_field_put(int offset, jshort contents);

  jlong long_field(int offset) const;
  void long_field_put(int offset, jlong contents);

  jfloat float_field(int offset) const;
  void float_field_put(int offset, jfloat contents);

  jdouble double_field(int offset) const;
  void double_field_put(int offset, jdouble contents);

  address address_field(int offset) const;
  void address_field_put(int offset, address contents);

  oop obj_field_acquire(int offset) const;
  void release_obj_field_put(int offset, oop value);

  jbyte byte_field_acquire(int offset) const;
  void release_byte_field_put(int offset, jbyte contents);

  jchar char_field_acquire(int offset) const;
  void release_char_field_put(int offset, jchar contents);

  jboolean bool_field_acquire(int offset) const;
  void release_bool_field_put(int offset, jboolean contents);

  jint int_field_acquire(int offset) const;
  void release_int_field_put(int offset, jint contents);

  jshort short_field_acquire(int offset) const;
  void release_short_field_put(int offset, jshort contents);

  jlong long_field_acquire(int offset) const;
  void release_long_field_put(int offset, jlong contents);

  jfloat float_field_acquire(int offset) const;
  void release_float_field_put(int offset, jfloat contents);

  jdouble double_field_acquire(int offset) const;
  void release_double_field_put(int offset, jdouble contents);

  address address_field_acquire(int offset) const;
  void release_address_field_put(int offset, address contents);

  // printing functions for VM debugging
  void print_on(outputStream* st) const;         // First level print
  void print_value_on(outputStream* st) const;   // Second level print.
  void print_address_on(outputStream* st) const; // Address printing

  // printing on default output stream
  void print();
  void print_value();
  void print_address();

  // return the print strings
  char* print_string();
  char* print_value_string();

  // verification operations
  void verify_on(outputStream* st);
  void verify();

  // locking operations
  bool is_locked()   const;
  bool is_unlocked() const;
  bool has_bias_pattern() const;

  // asserts
  bool is_oop(bool ignore_mark_word = false) const;
  bool is_oop_or_null(bool ignore_mark_word = false) const;
#ifndef PRODUCT
  bool is_unlocked_oop() const;
#endif

  // garbage collection
  bool is_gc_marked() const;
  // Apply "MarkSweep::mark_and_push" to (the address of) every non-NULL
  // reference field in "this".
  void follow_contents(void);

#if INCLUDE_ALL_GCS
  // Parallel Scavenge
  void push_contents(PSPromotionManager* pm);

  // Parallel Old
  void update_contents(ParCompactionManager* cm);

  void follow_contents(ParCompactionManager* cm);
#endif // INCLUDE_ALL_GCS

  bool is_scavengable() const;

  // Forward pointer operations for scavenge
  bool is_forwarded() const;

  void forward_to(oop p);
  bool cas_forward_to(oop p, markOop compare);

#if INCLUDE_ALL_GCS
  // Like "forward_to", but inserts the forwarding pointer atomically.
  // Exactly one thread succeeds in inserting the forwarding pointer, and
  // this call returns "NULL" for that thread; any other thread has the
  // value of the forwarding pointer returned and does not modify "this".
  oop forward_to_atomic(oop p);
#endif // INCLUDE_ALL_GCS

  oop forwardee() const;

  // Age of object during scavenge
  uint age() const;
  void incr_age();

  // Adjust all pointers in this object to point at it's forwarded location and
  // return the size of this oop.  This is used by the MarkSweep collector.
  int adjust_pointers();

  // mark-sweep support
  void follow_body(int begin, int end);

  // Fast access to barrier set
  static BarrierSet* bs()            { return _bs; }
  static void set_bs(BarrierSet* bs) { _bs = bs; }

  // iterators, returns size of object
#define OOP_ITERATE_DECL(OopClosureType, nv_suffix)                      \
  int oop_iterate(OopClosureType* blk);                                  \
  int oop_iterate(OopClosureType* blk, MemRegion mr);  // Only in mr.

  ALL_OOP_OOP_ITERATE_CLOSURES_1(OOP_ITERATE_DECL)
  ALL_OOP_OOP_ITERATE_CLOSURES_2(OOP_ITERATE_DECL)

#if INCLUDE_ALL_GCS

#define OOP_ITERATE_BACKWARDS_DECL(OopClosureType, nv_suffix)            \
  int oop_iterate_backwards(OopClosureType* blk);

  ALL_OOP_OOP_ITERATE_CLOSURES_1(OOP_ITERATE_BACKWARDS_DECL)
  ALL_OOP_OOP_ITERATE_CLOSURES_2(OOP_ITERATE_BACKWARDS_DECL)
#endif

  int oop_iterate_no_header(OopClosure* bk);
  int oop_iterate_no_header(OopClosure* bk, MemRegion mr);

  // identity hash; returns the identity hash key (computes it if necessary)
  // NOTE with the introduction of UseBiasedLocking that identity_hash() might reach a
  // safepoint if called on a biased object. Calling code must be aware of that.
  intptr_t identity_hash();
  intptr_t slow_identity_hash();

  // Alternate hashing code if string table is rehashed
  unsigned int new_hash(jint seed);

  // marks are forwarded to stack when object is locked
  bool     has_displaced_mark() const;
  markOop  displaced_mark() const;
  void     set_displaced_mark(markOop m);

  // for code generation
  static int mark_offset_in_bytes()    { return offset_of(oopDesc, _mark); }
  static int klass_offset_in_bytes()   { return offset_of(oopDesc, _metadata._klass); }
  static int klass_gap_offset_in_bytes();
};

#endif // SHARE_VM_OOPS_OOP_HPP