handles.hpp revision 0:a61af66fc99e
1/* 2 * Copyright 1997-2007 Sun Microsystems, Inc. All Rights Reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, 20 * CA 95054 USA or visit www.sun.com if you need additional information or 21 * have any questions. 22 * 23 */ 24 25//------------------------------------------------------------------------------------------------------------------------ 26// In order to preserve oops during garbage collection, they should be 27// allocated and passed around via Handles within the VM. A handle is 28// simply an extra indirection allocated in a thread local handle area. 29// 30// A handle is a ValueObj, so it can be passed around as a value, can 31// be used as a parameter w/o using &-passing, and can be returned as a 32// return value. 33// 34// oop parameters and return types should be Handles whenever feasible. 35// 36// Handles are declared in a straight-forward manner, e.g. 37// 38// oop obj = ...; 39// Handle h1(obj); // allocate new handle 40// Handle h2(thread, obj); // faster allocation when current thread is known 41// Handle h3; // declare handle only, no allocation occurs 42// ... 43// h3 = h1; // make h3 refer to same indirection as h1 44// oop obj2 = h2(); // get handle value 45// h1->print(); // invoking operation on oop 46// 47// Handles are specialized for different oop types to provide extra type 48// information and avoid unnecessary casting. For each oop type xxxOop 49// there is a corresponding handle called xxxHandle, e.g. 50// 51// oop Handle 52// methodOop methodHandle 53// instanceOop instanceHandle 54// 55// For klassOops, it is often useful to model the Klass hierarchy in order 56// to get access to the klass_part without casting. For each xxxKlass there 57// is a corresponding handle called xxxKlassHandle, e.g. 58// 59// klassOop Klass KlassHandle 60// klassOop methodKlass methodKlassHandle 61// klassOop instanceKlass instanceKlassHandle 62// 63 64//------------------------------------------------------------------------------------------------------------------------ 65// Base class for all handles. Provides overloading of frequently 66// used operators for ease of use. 67 68class Handle VALUE_OBJ_CLASS_SPEC { 69 private: 70 oop* _handle; 71 72 protected: 73 oop obj() const { return _handle == NULL ? (oop)NULL : *_handle; } 74 oop non_null_obj() const { assert(_handle != NULL, "resolving NULL handle"); return *_handle; } 75 76 public: 77 // Constructors 78 Handle() { _handle = NULL; } 79 Handle(oop obj); 80#ifndef ASSERT 81 Handle(Thread* thread, oop obj); 82#else 83 // Don't inline body with assert for current thread 84 Handle(Thread* thread, oop obj); 85#endif // ASSERT 86 87 // General access 88 oop operator () () const { return obj(); } 89 oop operator -> () const { return non_null_obj(); } 90 bool operator == (oop o) const { return obj() == o; } 91 bool operator == (const Handle& h) const { return obj() == h.obj(); } 92 93 // Null checks 94 bool is_null() const { return _handle == NULL; } 95 bool not_null() const { return _handle != NULL; } 96 97 // Debugging 98 void print() { obj()->print(); } 99 100 // Direct interface, use very sparingly. 101 // Used by JavaCalls to quickly convert handles and to create handles static data structures. 102 // Constructor takes a dummy argument to prevent unintentional type conversion in C++. 103 Handle(oop *handle, bool dummy) { _handle = handle; } 104 105 // Raw handle access. Allows easy duplication of Handles. This can be very unsafe 106 // since duplicates is only valid as long as original handle is alive. 107 oop* raw_value() { return _handle; } 108 static oop raw_resolve(oop *handle) { return handle == NULL ? (oop)NULL : *handle; } 109}; 110 111 112//------------------------------------------------------------------------------------------------------------------------ 113// Base class for Handles containing klassOops. Provides overloading of frequently 114// used operators for ease of use and typed access to the Klass part. 115class KlassHandle: public Handle { 116 protected: 117 klassOop obj() const { return (klassOop)Handle::obj(); } 118 klassOop non_null_obj() const { return (klassOop)Handle::non_null_obj(); } 119 Klass* as_klass() const { return non_null_obj()->klass_part(); } 120 121 public: 122 // Constructors 123 KlassHandle () : Handle() {} 124 KlassHandle (oop obj) : Handle(obj) { 125 assert(SharedSkipVerify || is_null() || obj->is_klass(), "not a klassOop"); 126 } 127 KlassHandle (Klass* kl) : Handle(kl ? kl->as_klassOop() : (klassOop)NULL) { 128 assert(SharedSkipVerify || is_null() || obj()->is_klass(), "not a klassOop"); 129 } 130 131 // Faster versions passing Thread 132 KlassHandle (Thread* thread, oop obj) : Handle(thread, obj) { 133 assert(SharedSkipVerify || is_null() || obj->is_klass(), "not a klassOop"); 134 } 135 KlassHandle (Thread *thread, Klass* kl) 136 : Handle(thread, kl ? kl->as_klassOop() : (klassOop)NULL) { 137 assert(is_null() || obj()->is_klass(), "not a klassOop"); 138 } 139 140 // General access 141 klassOop operator () () const { return obj(); } 142 Klass* operator -> () const { return as_klass(); } 143}; 144 145 146//------------------------------------------------------------------------------------------------------------------------ 147// Specific Handles for different oop types 148#define DEF_HANDLE(type, is_a) \ 149 class type##Handle; \ 150 class type##Handle: public Handle { \ 151 protected: \ 152 type##Oop obj() const { return (type##Oop)Handle::obj(); } \ 153 type##Oop non_null_obj() const { return (type##Oop)Handle::non_null_obj(); } \ 154 \ 155 public: \ 156 /* Constructors */ \ 157 type##Handle () : Handle() {} \ 158 type##Handle (type##Oop obj) : Handle((oop)obj) { \ 159 assert(SharedSkipVerify || is_null() || ((oop)obj)->is_a(), \ 160 "illegal type"); \ 161 } \ 162 type##Handle (Thread* thread, type##Oop obj) : Handle(thread, (oop)obj) { \ 163 assert(SharedSkipVerify || is_null() || ((oop)obj)->is_a(), "illegal type"); \ 164 } \ 165 \ 166 /* Special constructor, use sparingly */ \ 167 type##Handle (type##Oop *handle, bool dummy) : Handle((oop*)handle, dummy) {} \ 168 \ 169 /* Operators for ease of use */ \ 170 type##Oop operator () () const { return obj(); } \ 171 type##Oop operator -> () const { return non_null_obj(); } \ 172 }; 173 174 175DEF_HANDLE(instance , is_instance ) 176DEF_HANDLE(method , is_method ) 177DEF_HANDLE(constMethod , is_constMethod ) 178DEF_HANDLE(methodData , is_methodData ) 179DEF_HANDLE(array , is_array ) 180DEF_HANDLE(constantPool , is_constantPool ) 181DEF_HANDLE(constantPoolCache, is_constantPoolCache) 182DEF_HANDLE(objArray , is_objArray ) 183DEF_HANDLE(typeArray , is_typeArray ) 184DEF_HANDLE(symbol , is_symbol ) 185 186//------------------------------------------------------------------------------------------------------------------------ 187// Specific KlassHandles for different Klass types 188 189#define DEF_KLASS_HANDLE(type, is_a) \ 190 class type##Handle : public KlassHandle { \ 191 public: \ 192 /* Constructors */ \ 193 type##Handle () : KlassHandle() {} \ 194 type##Handle (klassOop obj) : KlassHandle(obj) { \ 195 assert(SharedSkipVerify || is_null() || obj->klass_part()->is_a(), \ 196 "illegal type"); \ 197 } \ 198 type##Handle (Thread* thread, klassOop obj) : KlassHandle(thread, obj) { \ 199 assert(SharedSkipVerify || is_null() || obj->klass_part()->is_a(), \ 200 "illegal type"); \ 201 } \ 202 \ 203 /* Access to klass part */ \ 204 type* operator -> () const { return (type*)obj()->klass_part(); } \ 205 \ 206 static type##Handle cast(KlassHandle h) { return type##Handle(h()); } \ 207 \ 208 }; 209 210 211DEF_KLASS_HANDLE(instanceKlass , oop_is_instance_slow ) 212DEF_KLASS_HANDLE(methodKlass , oop_is_method ) 213DEF_KLASS_HANDLE(constMethodKlass , oop_is_constMethod ) 214DEF_KLASS_HANDLE(klassKlass , oop_is_klass ) 215DEF_KLASS_HANDLE(arrayKlassKlass , oop_is_arrayKlass ) 216DEF_KLASS_HANDLE(objArrayKlassKlass , oop_is_objArrayKlass ) 217DEF_KLASS_HANDLE(typeArrayKlassKlass , oop_is_typeArrayKlass) 218DEF_KLASS_HANDLE(arrayKlass , oop_is_array ) 219DEF_KLASS_HANDLE(typeArrayKlass , oop_is_typeArray_slow) 220DEF_KLASS_HANDLE(objArrayKlass , oop_is_objArray_slow ) 221DEF_KLASS_HANDLE(symbolKlass , oop_is_symbol ) 222DEF_KLASS_HANDLE(constantPoolKlass , oop_is_constantPool ) 223DEF_KLASS_HANDLE(constantPoolCacheKlass, oop_is_constantPool ) 224 225 226//------------------------------------------------------------------------------------------------------------------------ 227// Thread local handle area 228 229class HandleArea: public Arena { 230 friend class HandleMark; 231 friend class NoHandleMark; 232 friend class ResetNoHandleMark; 233#ifdef ASSERT 234 int _handle_mark_nesting; 235 int _no_handle_mark_nesting; 236#endif 237 HandleArea* _prev; // link to outer (older) area 238 public: 239 // Constructor 240 HandleArea(HandleArea* prev) { 241 debug_only(_handle_mark_nesting = 0); 242 debug_only(_no_handle_mark_nesting = 0); 243 _prev = prev; 244 } 245 246 // Handle allocation 247 private: 248 oop* real_allocate_handle(oop obj) { 249#ifdef ASSERT 250 oop* handle = (oop*) (UseMallocOnly ? internal_malloc_4(oopSize) : Amalloc_4(oopSize)); 251#else 252 oop* handle = (oop*) Amalloc_4(oopSize); 253#endif 254 *handle = obj; 255 return handle; 256 } 257 public: 258#ifdef ASSERT 259 oop* allocate_handle(oop obj); 260#else 261 oop* allocate_handle(oop obj) { return real_allocate_handle(obj); } 262#endif 263 264 // Garbage collection support 265 void oops_do(OopClosure* f); 266 267 // Number of handles in use 268 size_t used() const { return Arena::used() / oopSize; } 269 270 debug_only(bool no_handle_mark_active() { return _no_handle_mark_nesting > 0; }) 271}; 272 273 274//------------------------------------------------------------------------------------------------------------------------ 275// Handles are allocated in a (growable) thread local handle area. Deallocation 276// is managed using a HandleMark. It should normally not be necessary to use 277// HandleMarks manually. 278// 279// A HandleMark constructor will record the current handle area top, and the 280// desctructor will reset the top, destroying all handles allocated in between. 281// The following code will therefore NOT work: 282// 283// Handle h; 284// { 285// HandleMark hm; 286// h = Handle(obj); 287// } 288// h()->print(); // WRONG, h destroyed by HandleMark destructor. 289// 290// If h has to be preserved, it can be converted to an oop or a local JNI handle 291// across the HandleMark boundary. 292 293// The base class of HandleMark should have been StackObj but we also heap allocate 294// a HandleMark when a thread is created. 295 296class HandleMark { 297 private: 298 Thread *_thread; // thread that owns this mark 299 HandleArea *_area; // saved handle area 300 Chunk *_chunk; // saved arena chunk 301 char *_hwm, *_max; // saved arena info 302 NOT_PRODUCT(size_t _size_in_bytes;) // size of handle area 303 // Link to previous active HandleMark in thread 304 HandleMark* _previous_handle_mark; 305 306 void initialize(Thread* thread); // common code for constructors 307 void set_previous_handle_mark(HandleMark* mark) { _previous_handle_mark = mark; } 308 HandleMark* previous_handle_mark() const { return _previous_handle_mark; } 309 310 public: 311 HandleMark(); // see handles_inline.hpp 312 HandleMark(Thread* thread) { initialize(thread); } 313 ~HandleMark(); 314 315 // Functions used by HandleMarkCleaner 316 // called in the constructor of HandleMarkCleaner 317 void push(); 318 // called in the destructor of HandleMarkCleaner 319 void pop_and_restore(); 320}; 321 322//------------------------------------------------------------------------------------------------------------------------ 323// A NoHandleMark stack object will verify that no handles are allocated 324// in its scope. Enabled in debug mode only. 325 326class NoHandleMark: public StackObj { 327 public: 328#ifdef ASSERT 329 NoHandleMark(); 330 ~NoHandleMark(); 331#else 332 NoHandleMark() {} 333 ~NoHandleMark() {} 334#endif 335}; 336 337 338class ResetNoHandleMark: public StackObj { 339 int _no_handle_mark_nesting; 340 public: 341#ifdef ASSERT 342 ResetNoHandleMark(); 343 ~ResetNoHandleMark(); 344#else 345 ResetNoHandleMark() {} 346 ~ResetNoHandleMark() {} 347#endif 348}; 349