1 /*
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  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.
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  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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 20  * or visit www.oracle.com if you need additional information or have any
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 24 
 25 #ifndef SHARE_OOPS_CONSTANTPOOL_HPP
 26 #define SHARE_OOPS_CONSTANTPOOL_HPP
 27 
 28 #include "memory/allocation.hpp"
 29 #include "oops/arrayOop.hpp"
 30 #include "oops/cpCache.hpp"
 31 #include "oops/objArrayOop.hpp"
 32 #include "oops/oopHandle.hpp"
 33 #include "oops/symbol.hpp"
 34 #include "oops/typeArrayOop.hpp"
 35 #include "runtime/handles.hpp"
 36 #include "runtime/javaThread.hpp"
 37 #include "utilities/align.hpp"
 38 #include "utilities/bytes.hpp"
 39 #include "utilities/constantTag.hpp"
 40 #include "utilities/resourceHash.hpp"
 41 
 42 // A ConstantPool is an array containing class constants as described in the
 43 // class file.
 44 //
 45 // Most of the constant pool entries are written during class parsing, which
 46 // is safe.  For klass types, the constant pool entry is
 47 // modified when the entry is resolved.  If a klass constant pool
 48 // entry is read without a lock, only the resolved state guarantees that
 49 // the entry in the constant pool is a klass object and not a Symbol*.
 50 
 51 // This represents a JVM_CONSTANT_Class, JVM_CONSTANT_UnresolvedClass, or
 52 // JVM_CONSTANT_UnresolvedClassInError slot in the constant pool.
 53 class CPKlassSlot {
 54   // cp->symbol_at(_name_index) gives the name of the class.
 55   int _name_index;
 56 
 57   // cp->_resolved_klasses->at(_resolved_klass_index) gives the Klass* for the class.
 58   int _resolved_klass_index;
 59 public:
 60   enum {
 61     // This is used during constant pool merging where the resolved klass index is
 62     // not yet known, and will be computed at a later stage (during a call to
 63     // initialize_unresolved_klasses()).
 64     _temp_resolved_klass_index = 0xffff
 65   };
 66   CPKlassSlot(int n, int rk) {
 67     _name_index = n;
 68     _resolved_klass_index = rk;
 69   }
 70   int name_index() const {
 71     return _name_index;
 72   }
 73   int resolved_klass_index() const {
 74     assert(_resolved_klass_index != _temp_resolved_klass_index, "constant pool merging was incomplete");
 75     return _resolved_klass_index;
 76   }
 77 };
 78 
 79 class ConstantPool : public Metadata {
 80   friend class VMStructs;
 81   friend class JVMCIVMStructs;
 82   friend class BytecodeInterpreter;  // Directly extracts a klass in the pool for fast instanceof/checkcast
 83   friend class Universe;             // For null constructor
 84   friend class ClassPrelinker;       // CDS
 85  private:
 86   // If you add a new field that points to any metaspace object, you
 87   // must add this field to ConstantPool::metaspace_pointers_do().
 88   Array<u1>*           _tags;        // the tag array describing the constant pool's contents
 89   ConstantPoolCache*   _cache;       // the cache holding interpreter runtime information
 90   InstanceKlass*       _pool_holder; // the corresponding class
 91   Array<u2>*           _operands;    // for variable-sized (InvokeDynamic) nodes, usually empty
 92 
 93   // Consider using an array of compressed klass pointers to
 94   // save space on 64-bit platforms.
 95   Array<Klass*>*       _resolved_klasses;
 96 
 97   u2              _major_version;        // major version number of class file
 98   u2              _minor_version;        // minor version number of class file
 99 
100   // Constant pool index to the utf8 entry of the Generic signature,
101   // or 0 if none.
102   u2              _generic_signature_index;
103   // Constant pool index to the utf8 entry for the name of source file
104   // containing this klass, 0 if not specified.
105   u2              _source_file_name_index;
106 
107   enum {
108     _has_preresolution    = 1,       // Flags
109     _on_stack             = 2,
110     _is_shared            = 4,
111     _has_dynamic_constant = 8
112   };
113 
114   u2              _flags;  // old fashioned bit twiddling
115 
116   int             _length; // number of elements in the array
117 
118   union {
119     // set for CDS to restore resolved references
120     int                _resolved_reference_length;
121     // keeps version number for redefined classes (used in backtrace)
122     int                _version;
123   } _saved;
124 
125   void set_tags(Array<u1>* tags)                 { _tags = tags; }
126   void tag_at_put(int cp_index, jbyte t)         { tags()->at_put(cp_index, t); }
127   void release_tag_at_put(int cp_index, jbyte t) { tags()->release_at_put(cp_index, t); }
128 
129   u1* tag_addr_at(int cp_index) const            { return tags()->adr_at(cp_index); }
130 
131   void set_operands(Array<u2>* operands)       { _operands = operands; }
132 
133   u2 flags() const                             { return _flags; }
134   void set_flags(u2 f)                         { _flags = f; }
135 
136  private:
137   intptr_t* base() const { return (intptr_t*) (((char*) this) + sizeof(ConstantPool)); }
138 
139   intptr_t* obj_at_addr(int cp_index) const {
140     assert(is_within_bounds(cp_index), "index out of bounds");
141     return (intptr_t*) &base()[cp_index];
142   }
143 
144   jint* int_at_addr(int cp_index) const {
145     assert(is_within_bounds(cp_index), "index out of bounds");
146     return (jint*) &base()[cp_index];
147   }
148 
149   jlong* long_at_addr(int cp_index) const {
150     assert(is_within_bounds(cp_index), "index out of bounds");
151     return (jlong*) &base()[cp_index];
152   }
153 
154   jfloat* float_at_addr(int cp_index) const {
155     assert(is_within_bounds(cp_index), "index out of bounds");
156     return (jfloat*) &base()[cp_index];
157   }
158 
159   jdouble* double_at_addr(int cp_index) const {
160     assert(is_within_bounds(cp_index), "index out of bounds");
161     return (jdouble*) &base()[cp_index];
162   }
163 
164   ConstantPool(Array<u1>* tags);
165   ConstantPool();
166  public:
167   static ConstantPool* allocate(ClassLoaderData* loader_data, int length, TRAPS);
168 
169   virtual bool is_constantPool() const      { return true; }
170 
171   Array<u1>* tags() const                   { return _tags; }
172   Array<u2>* operands() const               { return _operands; }
173 
174   bool has_preresolution() const            { return (_flags & _has_preresolution) != 0; }
175   void set_has_preresolution() {
176     assert(!is_shared(), "should never be called on shared ConstantPools");
177     _flags |= _has_preresolution;
178   }
179 
180   // minor and major version numbers of class file
181   u2 major_version() const                 { return _major_version; }
182   void set_major_version(u2 major_version) { _major_version = major_version; }
183   u2 minor_version() const                 { return _minor_version; }
184   void set_minor_version(u2 minor_version) { _minor_version = minor_version; }
185 
186   // generics support
187   Symbol* generic_signature() const {
188     return (_generic_signature_index == 0) ?
189       nullptr : symbol_at(_generic_signature_index);
190   }
191   u2 generic_signature_index() const                   { return _generic_signature_index; }
192   void set_generic_signature_index(u2 sig_index)       { _generic_signature_index = sig_index; }
193 
194   // source file name
195   Symbol* source_file_name() const {
196     return (_source_file_name_index == 0) ?
197       nullptr : symbol_at(_source_file_name_index);
198   }
199   u2 source_file_name_index() const                    { return _source_file_name_index; }
200   void set_source_file_name_index(u2 sourcefile_index) { _source_file_name_index = sourcefile_index; }
201 
202   void copy_fields(const ConstantPool* orig);
203 
204   // Redefine classes support.  If a method referring to this constant pool
205   // is on the executing stack, or as a handle in vm code, this constant pool
206   // can't be removed from the set of previous versions saved in the instance
207   // class.
208   bool on_stack() const;
209   bool is_maybe_on_stack() const;
210   void set_on_stack(const bool value);
211 
212   // Faster than MetaspaceObj::is_shared() - used by set_on_stack()
213   bool is_shared() const                     { return (_flags & _is_shared) != 0; }
214 
215   bool has_dynamic_constant() const       { return (_flags & _has_dynamic_constant) != 0; }
216   void set_has_dynamic_constant()         { _flags |= _has_dynamic_constant; }
217 
218   // Klass holding pool
219   InstanceKlass* pool_holder() const      { return _pool_holder; }
220   void set_pool_holder(InstanceKlass* k)  { _pool_holder = k; }
221   InstanceKlass** pool_holder_addr()      { return &_pool_holder; }
222 
223   // Interpreter runtime support
224   ConstantPoolCache* cache() const        { return _cache; }
225   void set_cache(ConstantPoolCache* cache){ _cache = cache; }
226 
227   virtual void metaspace_pointers_do(MetaspaceClosure* iter);
228   virtual MetaspaceObj::Type type() const { return ConstantPoolType; }
229 
230   // Create object cache in the constant pool
231   void initialize_resolved_references(ClassLoaderData* loader_data,
232                                       const intStack& reference_map,
233                                       int constant_pool_map_length,
234                                       TRAPS);
235 
236   // resolved strings, methodHandles and callsite objects from the constant pool
237   objArrayOop resolved_references()  const;
238   objArrayOop resolved_references_or_null()  const;
239   oop resolved_reference_at(int obj_index) const;
240   oop set_resolved_reference_at(int index, oop new_value);
241 
242   // mapping resolved object array indexes to cp indexes and back.
243   int object_to_cp_index(int index)         { return reference_map()->at(index); }
244   int cp_to_object_index(int index);
245 
246   void set_resolved_klasses(Array<Klass*>* rk)  { _resolved_klasses = rk; }
247   Array<Klass*>* resolved_klasses() const       { return _resolved_klasses; }
248   void allocate_resolved_klasses(ClassLoaderData* loader_data, int num_klasses, TRAPS);
249   void initialize_unresolved_klasses(ClassLoaderData* loader_data, TRAPS);
250 
251   // Invokedynamic indexes.
252   // They must look completely different from normal indexes.
253   // The main reason is that byte swapping is sometimes done on normal indexes.
254   // Finally, it is helpful for debugging to tell the two apart.
255   static bool is_invokedynamic_index(int i) { return (i < 0); }
256   static int  decode_invokedynamic_index(int i) { assert(is_invokedynamic_index(i),  ""); return ~i; }
257   static int  encode_invokedynamic_index(int i) { assert(!is_invokedynamic_index(i), ""); return ~i; }
258 
259   // Given the per-instruction index of an indy instruction, report the
260   // main constant pool entry for its bootstrap specifier.
261   // From there, uncached_name/signature_ref_at will get the name/type.
262   inline u2 invokedynamic_bootstrap_ref_index_at(int indy_index) const;
263 
264   // Assembly code support
265   static ByteSize tags_offset()         { return byte_offset_of(ConstantPool, _tags); }
266   static ByteSize cache_offset()        { return byte_offset_of(ConstantPool, _cache); }
267   static ByteSize pool_holder_offset()  { return byte_offset_of(ConstantPool, _pool_holder); }
268   static ByteSize resolved_klasses_offset()    { return byte_offset_of(ConstantPool, _resolved_klasses); }
269 
270   // Storing constants
271 
272   // For temporary use while constructing constant pool
273   void klass_index_at_put(int cp_index, int name_index) {
274     tag_at_put(cp_index, JVM_CONSTANT_ClassIndex);
275     *int_at_addr(cp_index) = name_index;
276   }
277 
278   // Hidden class support:
279   void klass_at_put(int class_index, Klass* k);
280 
281   void unresolved_klass_at_put(int cp_index, int name_index, int resolved_klass_index) {
282     release_tag_at_put(cp_index, JVM_CONSTANT_UnresolvedClass);
283 
284     assert((name_index & 0xffff0000) == 0, "must be");
285     assert((resolved_klass_index & 0xffff0000) == 0, "must be");
286     *int_at_addr(cp_index) =
287       build_int_from_shorts((jushort)resolved_klass_index, (jushort)name_index);
288   }
289 
290   void method_handle_index_at_put(int cp_index, int ref_kind, int ref_index) {
291     tag_at_put(cp_index, JVM_CONSTANT_MethodHandle);
292     *int_at_addr(cp_index) = ((jint) ref_index<<16) | ref_kind;
293   }
294 
295   void method_type_index_at_put(int cp_index, int ref_index) {
296     tag_at_put(cp_index, JVM_CONSTANT_MethodType);
297     *int_at_addr(cp_index) = ref_index;
298   }
299 
300   void dynamic_constant_at_put(int cp_index, int bsms_attribute_index, int name_and_type_index) {
301     tag_at_put(cp_index, JVM_CONSTANT_Dynamic);
302     *int_at_addr(cp_index) = ((jint) name_and_type_index<<16) | bsms_attribute_index;
303   }
304 
305   void invoke_dynamic_at_put(int cp_index, int bsms_attribute_index, int name_and_type_index) {
306     tag_at_put(cp_index, JVM_CONSTANT_InvokeDynamic);
307     *int_at_addr(cp_index) = ((jint) name_and_type_index<<16) | bsms_attribute_index;
308   }
309 
310   void unresolved_string_at_put(int cp_index, Symbol* s) {
311     assert(s->refcount() != 0, "should have nonzero refcount");
312     // Note that release_tag_at_put is not needed here because this is called only
313     // when constructing a ConstantPool in a single thread, with no possibility
314     // of concurrent access.
315     tag_at_put(cp_index, JVM_CONSTANT_String);
316     *symbol_at_addr(cp_index) = s;
317   }
318 
319   void int_at_put(int cp_index, jint i) {
320     tag_at_put(cp_index, JVM_CONSTANT_Integer);
321     *int_at_addr(cp_index) = i;
322   }
323 
324   void long_at_put(int cp_index, jlong l) {
325     tag_at_put(cp_index, JVM_CONSTANT_Long);
326     // *long_at_addr(which) = l;
327     Bytes::put_native_u8((address)long_at_addr(cp_index), *((u8*) &l));
328   }
329 
330   void float_at_put(int cp_index, jfloat f) {
331     tag_at_put(cp_index, JVM_CONSTANT_Float);
332     *float_at_addr(cp_index) = f;
333   }
334 
335   void double_at_put(int cp_index, jdouble d) {
336     tag_at_put(cp_index, JVM_CONSTANT_Double);
337     // *double_at_addr(which) = d;
338     // u8 temp = *(u8*) &d;
339     Bytes::put_native_u8((address) double_at_addr(cp_index), *((u8*) &d));
340   }
341 
342   Symbol** symbol_at_addr(int cp_index) const {
343     assert(is_within_bounds(cp_index), "index out of bounds");
344     return (Symbol**) &base()[cp_index];
345   }
346 
347   void symbol_at_put(int cp_index, Symbol* s) {
348     assert(s->refcount() != 0, "should have nonzero refcount");
349     tag_at_put(cp_index, JVM_CONSTANT_Utf8);
350     *symbol_at_addr(cp_index) = s;
351   }
352 
353   void string_at_put(int obj_index, oop str);
354 
355   // For temporary use while constructing constant pool
356   void string_index_at_put(int cp_index, int string_index) {
357     tag_at_put(cp_index, JVM_CONSTANT_StringIndex);
358     *int_at_addr(cp_index) = string_index;
359   }
360 
361   void field_at_put(int cp_index, int class_index, int name_and_type_index) {
362     tag_at_put(cp_index, JVM_CONSTANT_Fieldref);
363     *int_at_addr(cp_index) = ((jint) name_and_type_index<<16) | class_index;
364   }
365 
366   void method_at_put(int cp_index, int class_index, int name_and_type_index) {
367     tag_at_put(cp_index, JVM_CONSTANT_Methodref);
368     *int_at_addr(cp_index) = ((jint) name_and_type_index<<16) | class_index;
369   }
370 
371   void interface_method_at_put(int cp_index, int class_index, int name_and_type_index) {
372     tag_at_put(cp_index, JVM_CONSTANT_InterfaceMethodref);
373     *int_at_addr(cp_index) = ((jint) name_and_type_index<<16) | class_index;  // Not so nice
374   }
375 
376   void name_and_type_at_put(int cp_index, int name_index, int signature_index) {
377     tag_at_put(cp_index, JVM_CONSTANT_NameAndType);
378     *int_at_addr(cp_index) = ((jint) signature_index<<16) | name_index;  // Not so nice
379   }
380 
381   // Tag query
382 
383   constantTag tag_at(int cp_index) const { return (constantTag)tags()->at_acquire(cp_index); }
384 
385   // Fetching constants
386 
387   Klass* klass_at(int cp_index, TRAPS) {
388     constantPoolHandle h_this(THREAD, this);
389     return klass_at_impl(h_this, cp_index, THREAD);
390   }
391 
392   CPKlassSlot klass_slot_at(int cp_index) const {
393     assert(tag_at(cp_index).is_unresolved_klass() || tag_at(cp_index).is_klass(),
394            "Corrupted constant pool");
395     int value = *int_at_addr(cp_index);
396     int name_index = extract_high_short_from_int(value);
397     int resolved_klass_index = extract_low_short_from_int(value);
398     return CPKlassSlot(name_index, resolved_klass_index);
399   }
400 
401   Symbol* klass_name_at(int cp_index) const;  // Returns the name, w/o resolving.
402   int klass_name_index_at(int cp_index) const {
403     return klass_slot_at(cp_index).name_index();
404   }
405 
406   Klass* resolved_klass_at(int cp_index) const;  // Used by Compiler
407 
408   // RedefineClasses() API support:
409   Symbol* klass_at_noresolve(int cp_index) { return klass_name_at(cp_index); }
410   void temp_unresolved_klass_at_put(int cp_index, int name_index) {
411     // Used only during constant pool merging for class redefinition. The resolved klass index
412     // will be initialized later by a call to initialize_unresolved_klasses().
413     unresolved_klass_at_put(cp_index, name_index, CPKlassSlot::_temp_resolved_klass_index);
414   }
415 
416   jint int_at(int cp_index) {
417     assert(tag_at(cp_index).is_int(), "Corrupted constant pool");
418     return *int_at_addr(cp_index);
419   }
420 
421   jlong long_at(int cp_index) {
422     assert(tag_at(cp_index).is_long(), "Corrupted constant pool");
423     // return *long_at_addr(cp_index);
424     u8 tmp = Bytes::get_native_u8((address)&base()[cp_index]);
425     return *((jlong*)&tmp);
426   }
427 
428   jfloat float_at(int cp_index) {
429     assert(tag_at(cp_index).is_float(), "Corrupted constant pool");
430     return *float_at_addr(cp_index);
431   }
432 
433   jdouble double_at(int cp_index) {
434     assert(tag_at(cp_index).is_double(), "Corrupted constant pool");
435     u8 tmp = Bytes::get_native_u8((address)&base()[cp_index]);
436     return *((jdouble*)&tmp);
437   }
438 
439   Symbol* symbol_at(int cp_index) const {
440     assert(tag_at(cp_index).is_utf8(), "Corrupted constant pool");
441     return *symbol_at_addr(cp_index);
442   }
443 
444   oop string_at(int cp_index, int obj_index, TRAPS) {
445     constantPoolHandle h_this(THREAD, this);
446     return string_at_impl(h_this, cp_index, obj_index, THREAD);
447   }
448   oop string_at(int cp_index, TRAPS) {
449     int obj_index = cp_to_object_index(cp_index);
450     return string_at(cp_index, obj_index, THREAD);
451   }
452 
453   // Version that can be used before string oop array is created.
454   oop uncached_string_at(int cp_index, TRAPS);
455 
456   // only called when we are sure a string entry is already resolved (via an
457   // earlier string_at call.
458   oop resolved_string_at(int cp_index) {
459     assert(tag_at(cp_index).is_string(), "Corrupted constant pool");
460     // Must do an acquire here in case another thread resolved the klass
461     // behind our back, lest we later load stale values thru the oop.
462     // we might want a volatile_obj_at in ObjArrayKlass.
463     int obj_index = cp_to_object_index(cp_index);
464     return resolved_reference_at(obj_index);
465   }
466 
467   Symbol* unresolved_string_at(int cp_index) {
468     assert(tag_at(cp_index).is_string(), "Corrupted constant pool");
469     return *symbol_at_addr(cp_index);
470   }
471 
472   // Returns an UTF8 for a CONSTANT_String entry at a given index.
473   // UTF8 char* representation was chosen to avoid conversion of
474   // java_lang_Strings at resolved entries into Symbol*s
475   // or vice versa.
476   char* string_at_noresolve(int cp_index);
477 
478   jint name_and_type_at(int cp_index) {
479     assert(tag_at(cp_index).is_name_and_type(), "Corrupted constant pool");
480     return *int_at_addr(cp_index);
481   }
482 
483   int method_handle_ref_kind_at(int cp_index) {
484     assert(tag_at(cp_index).is_method_handle() ||
485            tag_at(cp_index).is_method_handle_in_error(), "Corrupted constant pool");
486     return extract_low_short_from_int(*int_at_addr(cp_index));  // mask out unwanted ref_index bits
487   }
488   int method_handle_index_at(int cp_index) {
489     assert(tag_at(cp_index).is_method_handle() ||
490            tag_at(cp_index).is_method_handle_in_error(), "Corrupted constant pool");
491     return extract_high_short_from_int(*int_at_addr(cp_index));  // shift out unwanted ref_kind bits
492   }
493   int method_type_index_at(int cp_index) {
494     assert(tag_at(cp_index).is_method_type() ||
495            tag_at(cp_index).is_method_type_in_error(), "Corrupted constant pool");
496     return *int_at_addr(cp_index);
497   }
498 
499   // Derived queries:
500   Symbol* method_handle_name_ref_at(int cp_index) {
501     int member = method_handle_index_at(cp_index);
502     return uncached_name_ref_at(member);
503   }
504   Symbol* method_handle_signature_ref_at(int cp_index) {
505     int member = method_handle_index_at(cp_index);
506     return uncached_signature_ref_at(member);
507   }
508   u2 method_handle_klass_index_at(int cp_index) {
509     int member = method_handle_index_at(cp_index);
510     return uncached_klass_ref_index_at(member);
511   }
512   Symbol* method_type_signature_at(int cp_index) {
513     int sym = method_type_index_at(cp_index);
514     return symbol_at(sym);
515   }
516 
517   u2 bootstrap_name_and_type_ref_index_at(int cp_index) {
518     assert(tag_at(cp_index).has_bootstrap(), "Corrupted constant pool");
519     return extract_high_short_from_int(*int_at_addr(cp_index));
520   }
521   u2 bootstrap_methods_attribute_index(int cp_index) {
522     assert(tag_at(cp_index).has_bootstrap(), "Corrupted constant pool");
523     return extract_low_short_from_int(*int_at_addr(cp_index));
524   }
525   int bootstrap_operand_base(int cp_index) {
526     int bsms_attribute_index = bootstrap_methods_attribute_index(cp_index);
527     return operand_offset_at(operands(), bsms_attribute_index);
528   }
529   // The first part of the operands array consists of an index into the second part.
530   // Extract a 32-bit index value from the first part.
531   static int operand_offset_at(Array<u2>* operands, int bsms_attribute_index) {
532     int n = (bsms_attribute_index * 2);
533     assert(n >= 0 && n+2 <= operands->length(), "oob");
534     // The first 32-bit index points to the beginning of the second part
535     // of the operands array.  Make sure this index is in the first part.
536     DEBUG_ONLY(int second_part = build_int_from_shorts(operands->at(0),
537                                                        operands->at(1)));
538     assert(second_part == 0 || n+2 <= second_part, "oob (2)");
539     int offset = build_int_from_shorts(operands->at(n+0),
540                                        operands->at(n+1));
541     // The offset itself must point into the second part of the array.
542     assert(offset == 0 || offset >= second_part && offset <= operands->length(), "oob (3)");
543     return offset;
544   }
545   static void operand_offset_at_put(Array<u2>* operands, int bsms_attribute_index, int offset) {
546     int n = bsms_attribute_index * 2;
547     assert(n >= 0 && n+2 <= operands->length(), "oob");
548     operands->at_put(n+0, extract_low_short_from_int(offset));
549     operands->at_put(n+1, extract_high_short_from_int(offset));
550   }
551   static int operand_array_length(Array<u2>* operands) {
552     if (operands == nullptr || operands->length() == 0)  return 0;
553     int second_part = operand_offset_at(operands, 0);
554     return (second_part / 2);
555   }
556 
557 #ifdef ASSERT
558   // operand tuples fit together exactly, end to end
559   static int operand_limit_at(Array<u2>* operands, int bsms_attribute_index) {
560     int nextidx = bsms_attribute_index + 1;
561     if (nextidx == operand_array_length(operands))
562       return operands->length();
563     else
564       return operand_offset_at(operands, nextidx);
565   }
566   int bootstrap_operand_limit(int cp_index) {
567     int bsms_attribute_index = bootstrap_methods_attribute_index(cp_index);
568     return operand_limit_at(operands(), bsms_attribute_index);
569   }
570 #endif //ASSERT
571 
572   // Layout of InvokeDynamic and Dynamic bootstrap method specifier
573   // data in second part of operands array.  This encodes one record in
574   // the BootstrapMethods attribute.  The whole specifier also includes
575   // the name and type information from the main constant pool entry.
576   enum {
577          _indy_bsm_offset  = 0,  // CONSTANT_MethodHandle bsm
578          _indy_argc_offset = 1,  // u2 argc
579          _indy_argv_offset = 2   // u2 argv[argc]
580   };
581 
582   // These functions are used in RedefineClasses for CP merge
583 
584   int operand_offset_at(int bsms_attribute_index) {
585     assert(0 <= bsms_attribute_index &&
586            bsms_attribute_index < operand_array_length(operands()),
587            "Corrupted CP operands");
588     return operand_offset_at(operands(), bsms_attribute_index);
589   }
590   u2 operand_bootstrap_method_ref_index_at(int bsms_attribute_index) {
591     int offset = operand_offset_at(bsms_attribute_index);
592     return operands()->at(offset + _indy_bsm_offset);
593   }
594   u2 operand_argument_count_at(int bsms_attribute_index) {
595     int offset = operand_offset_at(bsms_attribute_index);
596     u2 argc = operands()->at(offset + _indy_argc_offset);
597     return argc;
598   }
599   u2 operand_argument_index_at(int bsms_attribute_index, int j) {
600     int offset = operand_offset_at(bsms_attribute_index);
601     return operands()->at(offset + _indy_argv_offset + j);
602   }
603   int operand_next_offset_at(int bsms_attribute_index) {
604     int offset = operand_offset_at(bsms_attribute_index) + _indy_argv_offset
605                    + operand_argument_count_at(bsms_attribute_index);
606     return offset;
607   }
608   // Compare a bootstrap specifier data in the operands arrays
609   bool compare_operand_to(int bsms_attribute_index1, const constantPoolHandle& cp2,
610                           int bsms_attribute_index2);
611   // Find a bootstrap specifier data in the operands array
612   int find_matching_operand(int bsms_attribute_index, const constantPoolHandle& search_cp,
613                             int operands_cur_len);
614   // Resize the operands array with delta_len and delta_size
615   void resize_operands(int delta_len, int delta_size, TRAPS);
616   // Extend the operands array with the length and size of the ext_cp operands
617   void extend_operands(const constantPoolHandle& ext_cp, TRAPS);
618   // Shrink the operands array to a smaller array with new_len length
619   void shrink_operands(int new_len, TRAPS);
620 
621   u2 bootstrap_method_ref_index_at(int cp_index) {
622     assert(tag_at(cp_index).has_bootstrap(), "Corrupted constant pool");
623     int op_base = bootstrap_operand_base(cp_index);
624     return operands()->at(op_base + _indy_bsm_offset);
625   }
626   u2 bootstrap_argument_count_at(int cp_index) {
627     assert(tag_at(cp_index).has_bootstrap(), "Corrupted constant pool");
628     int op_base = bootstrap_operand_base(cp_index);
629     u2 argc = operands()->at(op_base + _indy_argc_offset);
630     DEBUG_ONLY(int end_offset = op_base + _indy_argv_offset + argc;
631                int next_offset = bootstrap_operand_limit(cp_index));
632     assert(end_offset == next_offset, "matched ending");
633     return argc;
634   }
635   u2 bootstrap_argument_index_at(int cp_index, int j) {
636     int op_base = bootstrap_operand_base(cp_index);
637     DEBUG_ONLY(int argc = operands()->at(op_base + _indy_argc_offset));
638     assert((uint)j < (uint)argc, "oob");
639     return operands()->at(op_base + _indy_argv_offset + j);
640   }
641 
642   // The following methods (name/signature/klass_ref_at, klass_ref_at_noresolve,
643   // name_and_type_ref_index_at) all expect to be passed indices obtained
644   // directly from the bytecode.
645   // If the indices are meant to refer to fields or methods, they are
646   // actually rewritten indices that point to entries in their respective structures
647   // i.e. ResolvedMethodEntries or ResolvedFieldEntries.
648   // The routine to_cp_index manages the adjustment
649   // of these values back to constant pool indices.
650 
651   // There are also "uncached" versions which do not adjust the operand index; see below.
652 
653   // Lookup for entries consisting of (klass_index, name_and_type index)
654   Klass* klass_ref_at(int which, Bytecodes::Code code, TRAPS);
655   Symbol* klass_ref_at_noresolve(int which, Bytecodes::Code code);
656   Symbol* name_ref_at(int which, Bytecodes::Code code) {
657     int name_index = name_ref_index_at(name_and_type_ref_index_at(which, code));
658     return symbol_at(name_index);
659   }
660   Symbol* signature_ref_at(int which, Bytecodes::Code code) {
661     int signature_index = signature_ref_index_at(name_and_type_ref_index_at(which, code));
662     return symbol_at(signature_index);
663   }
664 
665   u2 klass_ref_index_at(int which, Bytecodes::Code code);
666   u2 name_and_type_ref_index_at(int which, Bytecodes::Code code);
667 
668   constantTag tag_ref_at(int cp_cache_index, Bytecodes::Code code);
669 
670   int to_cp_index(int which, Bytecodes::Code code);
671 
672   // Lookup for entries consisting of (name_index, signature_index)
673   u2 name_ref_index_at(int cp_index);            // ==  low-order jshort of name_and_type_at(cp_index)
674   u2 signature_ref_index_at(int cp_index);       // == high-order jshort of name_and_type_at(cp_index)
675 
676   BasicType basic_type_for_signature_at(int cp_index) const;
677 
678   // Resolve string constants (to prevent allocation during compilation)
679   void resolve_string_constants(TRAPS) {
680     constantPoolHandle h_this(THREAD, this);
681     resolve_string_constants_impl(h_this, CHECK);
682   }
683 
684 #if INCLUDE_CDS
685   // CDS support
686   objArrayOop prepare_resolved_references_for_archiving() NOT_CDS_JAVA_HEAP_RETURN_(nullptr);
687   void add_dumped_interned_strings() NOT_CDS_JAVA_HEAP_RETURN;
688   bool maybe_archive_resolved_klass_at(int cp_index);
689   void remove_unshareable_info();
690   void restore_unshareable_info(TRAPS);
691 #endif
692 
693  private:
694   enum { _no_index_sentinel = -1, _possible_index_sentinel = -2 };
695  public:
696 
697   // Get the tag for a constant, which may involve a constant dynamic
698   constantTag constant_tag_at(int cp_index);
699   // Get the basic type for a constant, which may involve a constant dynamic
700   BasicType basic_type_for_constant_at(int cp_index);
701 
702   // Resolve late bound constants.
703   oop resolve_constant_at(int cp_index, TRAPS) {
704     constantPoolHandle h_this(THREAD, this);
705     return resolve_constant_at_impl(h_this, cp_index, _no_index_sentinel, nullptr, THREAD);
706   }
707 
708   oop resolve_cached_constant_at(int cache_index, TRAPS) {
709     constantPoolHandle h_this(THREAD, this);
710     return resolve_constant_at_impl(h_this, _no_index_sentinel, cache_index, nullptr, THREAD);
711   }
712 
713   oop resolve_possibly_cached_constant_at(int cp_index, TRAPS) {
714     constantPoolHandle h_this(THREAD, this);
715     return resolve_constant_at_impl(h_this, cp_index, _possible_index_sentinel, nullptr, THREAD);
716   }
717 
718   oop find_cached_constant_at(int cp_index, bool& found_it, TRAPS) {
719     constantPoolHandle h_this(THREAD, this);
720     return resolve_constant_at_impl(h_this, cp_index, _possible_index_sentinel, &found_it, THREAD);
721   }
722 
723   void copy_bootstrap_arguments_at(int cp_index,
724                                    int start_arg, int end_arg,
725                                    objArrayHandle info, int pos,
726                                    bool must_resolve, Handle if_not_available, TRAPS) {
727     constantPoolHandle h_this(THREAD, this);
728     copy_bootstrap_arguments_at_impl(h_this, cp_index, start_arg, end_arg,
729                                      info, pos, must_resolve, if_not_available, THREAD);
730   }
731 
732   // Klass name matches name at offset
733   bool klass_name_at_matches(const InstanceKlass* k, int cp_index);
734 
735   // Sizing
736   int length() const                   { return _length; }
737   void set_length(int length)          { _length = length; }
738 
739   // Tells whether index is within bounds.
740   bool is_within_bounds(int index) const {
741     return 0 <= index && index < length();
742   }
743 
744   // Sizing (in words)
745   static int header_size()             {
746     return align_up((int)sizeof(ConstantPool), wordSize) / wordSize;
747   }
748   static int size(int length)          { return align_metadata_size(header_size() + length); }
749   int size() const                     { return size(length()); }
750 
751   // ConstantPools should be stored in the read-only region of CDS archive.
752   static bool is_read_only_by_default() { return true; }
753 
754   friend class ClassFileParser;
755   friend class SystemDictionary;
756 
757   // Used by CDS. These classes need to access the private ConstantPool() constructor.
758   template <class T> friend class CppVtableTesterA;
759   template <class T> friend class CppVtableTesterB;
760   template <class T> friend class CppVtableCloner;
761 
762   // Used by compiler to prevent classloading.
763   static Method*          method_at_if_loaded      (const constantPoolHandle& this_cp, int which);
764   static bool       has_appendix_at_if_loaded      (const constantPoolHandle& this_cp, int which);
765   static oop            appendix_at_if_loaded      (const constantPoolHandle& this_cp, int which);
766   static bool has_local_signature_at_if_loaded     (const constantPoolHandle& this_cp, int which);
767   static Klass*            klass_at_if_loaded      (const constantPoolHandle& this_cp, int which);
768 
769   // Routines currently used for annotations (only called by jvm.cpp) but which might be used in the
770   // future by other Java code. These take constant pool indices rather than
771   // constant pool cache indices as do the peer methods above.
772   Symbol* uncached_klass_ref_at_noresolve(int cp_index);
773   Symbol* uncached_name_ref_at(int cp_index) {
774     int name_index = name_ref_index_at(uncached_name_and_type_ref_index_at(cp_index));
775     return symbol_at(name_index);
776   }
777   Symbol* uncached_signature_ref_at(int cp_index) {
778     int signature_index = signature_ref_index_at(uncached_name_and_type_ref_index_at(cp_index));
779     return symbol_at(signature_index);
780   }
781   u2 uncached_klass_ref_index_at(int cp_index);
782   u2 uncached_name_and_type_ref_index_at(int cp_index);
783 
784   // Sharing
785   int pre_resolve_shared_klasses(TRAPS);
786 
787   // Debugging
788   const char* printable_name_at(int cp_index) PRODUCT_RETURN0;
789 
790  private:
791 
792   void set_resolved_references(OopHandle s) { _cache->set_resolved_references(s); }
793   Array<u2>* reference_map() const        {  return (_cache == nullptr) ? nullptr :  _cache->reference_map(); }
794   void set_reference_map(Array<u2>* o)    { _cache->set_reference_map(o); }
795 
796   // Used while constructing constant pool (only by ClassFileParser)
797   jint klass_index_at(int cp_index) {
798     assert(tag_at(cp_index).is_klass_index(), "Corrupted constant pool");
799     return *int_at_addr(cp_index);
800   }
801 
802   jint string_index_at(int cp_index) {
803     assert(tag_at(cp_index).is_string_index(), "Corrupted constant pool");
804     return *int_at_addr(cp_index);
805   }
806 
807   // Performs the LinkResolver checks
808   static void verify_constant_pool_resolve(const constantPoolHandle& this_cp, Klass* klass, TRAPS);
809 
810   // Implementation of methods that needs an exposed 'this' pointer, in order to
811   // handle GC while executing the method
812   static Klass* klass_at_impl(const constantPoolHandle& this_cp, int cp_index, TRAPS);
813   static oop string_at_impl(const constantPoolHandle& this_cp, int cp_index, int obj_index, TRAPS);
814 
815   static void trace_class_resolution(const constantPoolHandle& this_cp, Klass* k);
816 
817   // Resolve string constants (to prevent allocation during compilation)
818   static void resolve_string_constants_impl(const constantPoolHandle& this_cp, TRAPS);
819 
820   static oop resolve_constant_at_impl(const constantPoolHandle& this_cp, int cp_index, int cache_index,
821                                       bool* status_return, TRAPS);
822   static void copy_bootstrap_arguments_at_impl(const constantPoolHandle& this_cp, int cp_index,
823                                                int start_arg, int end_arg,
824                                                objArrayHandle info, int pos,
825                                                bool must_resolve, Handle if_not_available, TRAPS);
826 
827   // Exception handling
828   static void save_and_throw_exception(const constantPoolHandle& this_cp, int cp_index, constantTag tag, TRAPS);
829 
830  public:
831   // Exception handling
832   static void throw_resolution_error(const constantPoolHandle& this_cp, int which, TRAPS);
833 
834   // Merging ConstantPool* support:
835   bool compare_entry_to(int index1, const constantPoolHandle& cp2, int index2);
836   void copy_cp_to(int start_cpi, int end_cpi, const constantPoolHandle& to_cp, int to_cpi, TRAPS) {
837     constantPoolHandle h_this(THREAD, this);
838     copy_cp_to_impl(h_this, start_cpi, end_cpi, to_cp, to_cpi, THREAD);
839   }
840   static void copy_cp_to_impl(const constantPoolHandle& from_cp, int start_cpi, int end_cpi, const constantPoolHandle& to_cp, int to_cpi, TRAPS);
841   static void copy_entry_to(const constantPoolHandle& from_cp, int from_cpi, const constantPoolHandle& to_cp, int to_cpi);
842   static void copy_operands(const constantPoolHandle& from_cp, const constantPoolHandle& to_cp, TRAPS);
843   int  find_matching_entry(int pattern_i, const constantPoolHandle& search_cp);
844   int  version() const                    { return _saved._version; }
845   void set_version(int version)           { _saved._version = version; }
846   void increment_and_save_version(int version) {
847     _saved._version = version >= 0 ? (version + 1) : version;  // keep overflow
848   }
849 
850   void set_resolved_reference_length(int length) { _saved._resolved_reference_length = length; }
851   int  resolved_reference_length() const  { return _saved._resolved_reference_length; }
852 
853   // Decrease ref counts of symbols that are in the constant pool
854   // when the holder class is unloaded
855   void unreference_symbols();
856 
857   // Deallocate constant pool for RedefineClasses
858   void deallocate_contents(ClassLoaderData* loader_data);
859   void release_C_heap_structures();
860 
861   // JVMTI access - GetConstantPool, RetransformClasses, ...
862   friend class JvmtiConstantPoolReconstituter;
863 
864  private:
865   class SymbolHash: public CHeapObj<mtSymbol> {
866     ResourceHashtable<const Symbol*, u2, 256, AnyObj::C_HEAP, mtSymbol, Symbol::compute_hash> _table;
867 
868    public:
869     void add_if_absent(const Symbol* sym, u2 value) {
870       bool created;
871       _table.put_if_absent(sym, value, &created);
872     }
873 
874     u2 symbol_to_value(const Symbol* sym) {
875       u2* value = _table.get(sym);
876       return (value == nullptr) ? 0 : *value;
877     }
878   }; // End SymbolHash class
879 
880   jint cpool_entry_size(jint idx);
881   jint hash_entries_to(SymbolHash *symmap, SymbolHash *classmap);
882 
883   // Copy cpool bytes into byte array.
884   // Returns:
885   //  int > 0, count of the raw cpool bytes that have been copied
886   //        0, OutOfMemory error
887   //       -1, Internal error
888   int  copy_cpool_bytes(int cpool_size,
889                         SymbolHash* tbl,
890                         unsigned char *bytes);
891 
892  public:
893   // Verify
894   void verify_on(outputStream* st);
895 
896   // Printing
897   void print_on(outputStream* st) const;
898   void print_value_on(outputStream* st) const;
899   void print_entry_on(int index, outputStream* st);
900 
901   const char* internal_name() const { return "{constant pool}"; }
902 
903   // ResolvedFieldEntry getters
904   inline ResolvedFieldEntry* resolved_field_entry_at(int field_index);
905   inline int resolved_field_entries_length() const;
906 
907   // ResolvedMethodEntry getters
908   inline ResolvedMethodEntry* resolved_method_entry_at(int method_index);
909   inline int resolved_method_entries_length() const;
910   inline oop appendix_if_resolved(int method_index) const;
911 
912   // ResolvedIndyEntry getters
913   inline ResolvedIndyEntry* resolved_indy_entry_at(int index);
914   inline int resolved_indy_entries_length() const;
915   inline oop resolved_reference_from_indy(int index) const;
916   inline oop resolved_reference_from_method(int index) const;
917 };
918 
919 #endif // SHARE_OOPS_CONSTANTPOOL_HPP