1 /*
  2  * Copyright (c) 1997, 2023, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 20  * or visit www.oracle.com if you need additional information or have any
 21  * questions.
 22  *
 23  */
 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. Used during a retransform/class redefinition as well.
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_qdescriptor_at_put(int cp_index, int name_index, int resolved_klass_index) {
282       release_tag_at_put(cp_index, JVM_CONSTANT_UnresolvedClass | (jbyte) JVM_CONSTANT_QDescBit);
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 unresolved_klass_at_put(int cp_index, int name_index, int resolved_klass_index) {
291     release_tag_at_put(cp_index, JVM_CONSTANT_UnresolvedClass);
292 
293     assert((name_index & 0xffff0000) == 0, "must be");
294     assert((resolved_klass_index & 0xffff0000) == 0, "must be");
295     *int_at_addr(cp_index) =
296       build_int_from_shorts((jushort)resolved_klass_index, (jushort)name_index);
297   }
298 
299   void method_handle_index_at_put(int cp_index, int ref_kind, int ref_index) {
300     tag_at_put(cp_index, JVM_CONSTANT_MethodHandle);
301     *int_at_addr(cp_index) = ((jint) ref_index<<16) | ref_kind;
302   }
303 
304   void method_type_index_at_put(int cp_index, int ref_index) {
305     tag_at_put(cp_index, JVM_CONSTANT_MethodType);
306     *int_at_addr(cp_index) = ref_index;
307   }
308 
309   void dynamic_constant_at_put(int cp_index, int bsms_attribute_index, int name_and_type_index) {
310     tag_at_put(cp_index, JVM_CONSTANT_Dynamic);
311     *int_at_addr(cp_index) = ((jint) name_and_type_index<<16) | bsms_attribute_index;
312   }
313 
314   void invoke_dynamic_at_put(int cp_index, int bsms_attribute_index, int name_and_type_index) {
315     tag_at_put(cp_index, JVM_CONSTANT_InvokeDynamic);
316     *int_at_addr(cp_index) = ((jint) name_and_type_index<<16) | bsms_attribute_index;
317   }
318 
319   void unresolved_string_at_put(int cp_index, Symbol* s) {
320     assert(s->refcount() != 0, "should have nonzero refcount");
321     // Note that release_tag_at_put is not needed here because this is called only
322     // when constructing a ConstantPool in a single thread, with no possibility
323     // of concurrent access.
324     tag_at_put(cp_index, JVM_CONSTANT_String);
325     *symbol_at_addr(cp_index) = s;
326   }
327 
328   void int_at_put(int cp_index, jint i) {
329     tag_at_put(cp_index, JVM_CONSTANT_Integer);
330     *int_at_addr(cp_index) = i;
331   }
332 
333   void long_at_put(int cp_index, jlong l) {
334     tag_at_put(cp_index, JVM_CONSTANT_Long);
335     // *long_at_addr(which) = l;
336     Bytes::put_native_u8((address)long_at_addr(cp_index), *((u8*) &l));
337   }
338 
339   void float_at_put(int cp_index, jfloat f) {
340     tag_at_put(cp_index, JVM_CONSTANT_Float);
341     *float_at_addr(cp_index) = f;
342   }
343 
344   void double_at_put(int cp_index, jdouble d) {
345     tag_at_put(cp_index, JVM_CONSTANT_Double);
346     // *double_at_addr(which) = d;
347     // u8 temp = *(u8*) &d;
348     Bytes::put_native_u8((address) double_at_addr(cp_index), *((u8*) &d));
349   }
350 
351   Symbol** symbol_at_addr(int cp_index) const {
352     assert(is_within_bounds(cp_index), "index out of bounds");
353     return (Symbol**) &base()[cp_index];
354   }
355 
356   void symbol_at_put(int cp_index, Symbol* s) {
357     assert(s->refcount() != 0, "should have nonzero refcount");
358     tag_at_put(cp_index, JVM_CONSTANT_Utf8);
359     *symbol_at_addr(cp_index) = s;
360   }
361 
362   void string_at_put(int obj_index, oop str);
363 
364   // For temporary use while constructing constant pool
365   void string_index_at_put(int cp_index, int string_index) {
366     tag_at_put(cp_index, JVM_CONSTANT_StringIndex);
367     *int_at_addr(cp_index) = string_index;
368   }
369 
370   void field_at_put(int cp_index, int class_index, int name_and_type_index) {
371     tag_at_put(cp_index, JVM_CONSTANT_Fieldref);
372     *int_at_addr(cp_index) = ((jint) name_and_type_index<<16) | class_index;
373   }
374 
375   void method_at_put(int cp_index, int class_index, int name_and_type_index) {
376     tag_at_put(cp_index, JVM_CONSTANT_Methodref);
377     *int_at_addr(cp_index) = ((jint) name_and_type_index<<16) | class_index;
378   }
379 
380   void interface_method_at_put(int cp_index, int class_index, int name_and_type_index) {
381     tag_at_put(cp_index, JVM_CONSTANT_InterfaceMethodref);
382     *int_at_addr(cp_index) = ((jint) name_and_type_index<<16) | class_index;  // Not so nice
383   }
384 
385   void name_and_type_at_put(int cp_index, int name_index, int signature_index) {
386     tag_at_put(cp_index, JVM_CONSTANT_NameAndType);
387     *int_at_addr(cp_index) = ((jint) signature_index<<16) | name_index;  // Not so nice
388   }
389 
390   // Tag query
391 
392   constantTag tag_at(int cp_index) const { return (constantTag)tags()->at_acquire(cp_index); }
393 
394   // Fetching constants
395 
396   Klass* klass_at(int cp_index, TRAPS) {
397     constantPoolHandle h_this(THREAD, this);
398     return klass_at_impl(h_this, cp_index, THREAD);
399   }
400 
401   CPKlassSlot klass_slot_at(int cp_index) const {
402     assert(tag_at(cp_index).is_unresolved_klass() || tag_at(cp_index).is_klass(),
403            "Corrupted constant pool");
404     int value = *int_at_addr(cp_index);
405     int name_index = extract_high_short_from_int(value);
406     int resolved_klass_index = extract_low_short_from_int(value);
407     return CPKlassSlot(name_index, resolved_klass_index);
408   }
409 
410   Symbol* klass_name_at(int cp_index) const;  // Returns the name, w/o resolving.
411   int klass_name_index_at(int cp_index) const {
412     return klass_slot_at(cp_index).name_index();
413   }
414 
415   Klass* resolved_klass_at(int cp_index) const;  // Used by Compiler
416 
417   // RedefineClasses() API support:
418   Symbol* klass_at_noresolve(int cp_index) { return klass_name_at(cp_index); }
419   void temp_unresolved_klass_at_put(int cp_index, int name_index) {
420     // Used only during constant pool merging for class redefinition. The resolved klass index
421     // will be initialized later by a call to initialize_unresolved_klasses().
422     unresolved_klass_at_put(cp_index, name_index, CPKlassSlot::_temp_resolved_klass_index);
423   }
424 
425   jint int_at(int cp_index) {
426     assert(tag_at(cp_index).is_int(), "Corrupted constant pool");
427     return *int_at_addr(cp_index);
428   }
429 
430   jlong long_at(int cp_index) {
431     assert(tag_at(cp_index).is_long(), "Corrupted constant pool");
432     // return *long_at_addr(cp_index);
433     u8 tmp = Bytes::get_native_u8((address)&base()[cp_index]);
434     return *((jlong*)&tmp);
435   }
436 
437   jfloat float_at(int cp_index) {
438     assert(tag_at(cp_index).is_float(), "Corrupted constant pool");
439     return *float_at_addr(cp_index);
440   }
441 
442   jdouble double_at(int cp_index) {
443     assert(tag_at(cp_index).is_double(), "Corrupted constant pool");
444     u8 tmp = Bytes::get_native_u8((address)&base()[cp_index]);
445     return *((jdouble*)&tmp);
446   }
447 
448   Symbol* symbol_at(int cp_index) const {
449     assert(tag_at(cp_index).is_utf8(), "Corrupted constant pool");
450     return *symbol_at_addr(cp_index);
451   }
452 
453   oop string_at(int cp_index, int obj_index, TRAPS) {
454     constantPoolHandle h_this(THREAD, this);
455     return string_at_impl(h_this, cp_index, obj_index, THREAD);
456   }
457   oop string_at(int cp_index, TRAPS) {
458     int obj_index = cp_to_object_index(cp_index);
459     return string_at(cp_index, obj_index, THREAD);
460   }
461 
462   // Version that can be used before string oop array is created.
463   oop uncached_string_at(int cp_index, TRAPS);
464 
465   // only called when we are sure a string entry is already resolved (via an
466   // earlier string_at call.
467   oop resolved_string_at(int cp_index) {
468     assert(tag_at(cp_index).is_string(), "Corrupted constant pool");
469     // Must do an acquire here in case another thread resolved the klass
470     // behind our back, lest we later load stale values thru the oop.
471     // we might want a volatile_obj_at in ObjArrayKlass.
472     int obj_index = cp_to_object_index(cp_index);
473     return resolved_reference_at(obj_index);
474   }
475 
476   Symbol* unresolved_string_at(int cp_index) {
477     assert(tag_at(cp_index).is_string(), "Corrupted constant pool");
478     return *symbol_at_addr(cp_index);
479   }
480 
481   // Returns an UTF8 for a CONSTANT_String entry at a given index.
482   // UTF8 char* representation was chosen to avoid conversion of
483   // java_lang_Strings at resolved entries into Symbol*s
484   // or vice versa.
485   char* string_at_noresolve(int cp_index);
486 
487   jint name_and_type_at(int cp_index) {
488     assert(tag_at(cp_index).is_name_and_type(), "Corrupted constant pool");
489     return *int_at_addr(cp_index);
490   }
491 
492   int method_handle_ref_kind_at(int cp_index) {
493     assert(tag_at(cp_index).is_method_handle() ||
494            tag_at(cp_index).is_method_handle_in_error(), "Corrupted constant pool");
495     return extract_low_short_from_int(*int_at_addr(cp_index));  // mask out unwanted ref_index bits
496   }
497   int method_handle_index_at(int cp_index) {
498     assert(tag_at(cp_index).is_method_handle() ||
499            tag_at(cp_index).is_method_handle_in_error(), "Corrupted constant pool");
500     return extract_high_short_from_int(*int_at_addr(cp_index));  // shift out unwanted ref_kind bits
501   }
502   int method_type_index_at(int cp_index) {
503     assert(tag_at(cp_index).is_method_type() ||
504            tag_at(cp_index).is_method_type_in_error(), "Corrupted constant pool");
505     return *int_at_addr(cp_index);
506   }
507 
508   // Derived queries:
509   Symbol* method_handle_name_ref_at(int cp_index) {
510     int member = method_handle_index_at(cp_index);
511     return uncached_name_ref_at(member);
512   }
513   Symbol* method_handle_signature_ref_at(int cp_index) {
514     int member = method_handle_index_at(cp_index);
515     return uncached_signature_ref_at(member);
516   }
517   u2 method_handle_klass_index_at(int cp_index) {
518     int member = method_handle_index_at(cp_index);
519     return uncached_klass_ref_index_at(member);
520   }
521   Symbol* method_type_signature_at(int cp_index) {
522     int sym = method_type_index_at(cp_index);
523     return symbol_at(sym);
524   }
525 
526   u2 bootstrap_name_and_type_ref_index_at(int cp_index) {
527     assert(tag_at(cp_index).has_bootstrap(), "Corrupted constant pool");
528     return extract_high_short_from_int(*int_at_addr(cp_index));
529   }
530   u2 bootstrap_methods_attribute_index(int cp_index) {
531     assert(tag_at(cp_index).has_bootstrap(), "Corrupted constant pool");
532     return extract_low_short_from_int(*int_at_addr(cp_index));
533   }
534   int bootstrap_operand_base(int cp_index) {
535     int bsms_attribute_index = bootstrap_methods_attribute_index(cp_index);
536     return operand_offset_at(operands(), bsms_attribute_index);
537   }
538   // The first part of the operands array consists of an index into the second part.
539   // Extract a 32-bit index value from the first part.
540   static int operand_offset_at(Array<u2>* operands, int bsms_attribute_index) {
541     int n = (bsms_attribute_index * 2);
542     assert(n >= 0 && n+2 <= operands->length(), "oob");
543     // The first 32-bit index points to the beginning of the second part
544     // of the operands array.  Make sure this index is in the first part.
545     DEBUG_ONLY(int second_part = build_int_from_shorts(operands->at(0),
546                                                        operands->at(1)));
547     assert(second_part == 0 || n+2 <= second_part, "oob (2)");
548     int offset = build_int_from_shorts(operands->at(n+0),
549                                        operands->at(n+1));
550     // The offset itself must point into the second part of the array.
551     assert(offset == 0 || offset >= second_part && offset <= operands->length(), "oob (3)");
552     return offset;
553   }
554   static void operand_offset_at_put(Array<u2>* operands, int bsms_attribute_index, int offset) {
555     int n = bsms_attribute_index * 2;
556     assert(n >= 0 && n+2 <= operands->length(), "oob");
557     operands->at_put(n+0, extract_low_short_from_int(offset));
558     operands->at_put(n+1, extract_high_short_from_int(offset));
559   }
560   static int operand_array_length(Array<u2>* operands) {
561     if (operands == nullptr || operands->length() == 0)  return 0;
562     int second_part = operand_offset_at(operands, 0);
563     return (second_part / 2);
564   }
565 
566 #ifdef ASSERT
567   // operand tuples fit together exactly, end to end
568   static int operand_limit_at(Array<u2>* operands, int bsms_attribute_index) {
569     int nextidx = bsms_attribute_index + 1;
570     if (nextidx == operand_array_length(operands))
571       return operands->length();
572     else
573       return operand_offset_at(operands, nextidx);
574   }
575   int bootstrap_operand_limit(int cp_index) {
576     int bsms_attribute_index = bootstrap_methods_attribute_index(cp_index);
577     return operand_limit_at(operands(), bsms_attribute_index);
578   }
579 #endif //ASSERT
580 
581   // Layout of InvokeDynamic and Dynamic bootstrap method specifier
582   // data in second part of operands array.  This encodes one record in
583   // the BootstrapMethods attribute.  The whole specifier also includes
584   // the name and type information from the main constant pool entry.
585   enum {
586          _indy_bsm_offset  = 0,  // CONSTANT_MethodHandle bsm
587          _indy_argc_offset = 1,  // u2 argc
588          _indy_argv_offset = 2   // u2 argv[argc]
589   };
590 
591   // These functions are used in RedefineClasses for CP merge
592 
593   int operand_offset_at(int bsms_attribute_index) {
594     assert(0 <= bsms_attribute_index &&
595            bsms_attribute_index < operand_array_length(operands()),
596            "Corrupted CP operands");
597     return operand_offset_at(operands(), bsms_attribute_index);
598   }
599   u2 operand_bootstrap_method_ref_index_at(int bsms_attribute_index) {
600     int offset = operand_offset_at(bsms_attribute_index);
601     return operands()->at(offset + _indy_bsm_offset);
602   }
603   u2 operand_argument_count_at(int bsms_attribute_index) {
604     int offset = operand_offset_at(bsms_attribute_index);
605     u2 argc = operands()->at(offset + _indy_argc_offset);
606     return argc;
607   }
608   u2 operand_argument_index_at(int bsms_attribute_index, int j) {
609     int offset = operand_offset_at(bsms_attribute_index);
610     return operands()->at(offset + _indy_argv_offset + j);
611   }
612   int operand_next_offset_at(int bsms_attribute_index) {
613     int offset = operand_offset_at(bsms_attribute_index) + _indy_argv_offset
614                    + operand_argument_count_at(bsms_attribute_index);
615     return offset;
616   }
617   // Compare a bootstrap specifier data in the operands arrays
618   bool compare_operand_to(int bsms_attribute_index1, const constantPoolHandle& cp2,
619                           int bsms_attribute_index2);
620   // Find a bootstrap specifier data in the operands array
621   int find_matching_operand(int bsms_attribute_index, const constantPoolHandle& search_cp,
622                             int operands_cur_len);
623   // Resize the operands array with delta_len and delta_size
624   void resize_operands(int delta_len, int delta_size, TRAPS);
625   // Extend the operands array with the length and size of the ext_cp operands
626   void extend_operands(const constantPoolHandle& ext_cp, TRAPS);
627   // Shrink the operands array to a smaller array with new_len length
628   void shrink_operands(int new_len, TRAPS);
629 
630   u2 bootstrap_method_ref_index_at(int cp_index) {
631     assert(tag_at(cp_index).has_bootstrap(), "Corrupted constant pool");
632     int op_base = bootstrap_operand_base(cp_index);
633     return operands()->at(op_base + _indy_bsm_offset);
634   }
635   u2 bootstrap_argument_count_at(int cp_index) {
636     assert(tag_at(cp_index).has_bootstrap(), "Corrupted constant pool");
637     int op_base = bootstrap_operand_base(cp_index);
638     u2 argc = operands()->at(op_base + _indy_argc_offset);
639     DEBUG_ONLY(int end_offset = op_base + _indy_argv_offset + argc;
640                int next_offset = bootstrap_operand_limit(cp_index));
641     assert(end_offset == next_offset, "matched ending");
642     return argc;
643   }
644   u2 bootstrap_argument_index_at(int cp_index, int j) {
645     int op_base = bootstrap_operand_base(cp_index);
646     DEBUG_ONLY(int argc = operands()->at(op_base + _indy_argc_offset));
647     assert((uint)j < (uint)argc, "oob");
648     return operands()->at(op_base + _indy_argv_offset + j);
649   }
650 
651   // The following methods (name/signature/klass_ref_at, klass_ref_at_noresolve,
652   // name_and_type_ref_index_at) all expect to be passed indices obtained
653   // directly from the bytecode.
654   // If the indices are meant to refer to fields or methods, they are
655   // actually rewritten indices that point to entries in their respective structures
656   // i.e. ResolvedMethodEntries or ResolvedFieldEntries.
657   // The routine to_cp_index manages the adjustment
658   // of these values back to constant pool indices.
659 
660   // There are also "uncached" versions which do not adjust the operand index; see below.
661 
662   // Lookup for entries consisting of (klass_index, name_and_type index)
663   Klass* klass_ref_at(int which, Bytecodes::Code code, TRAPS);
664   Symbol* klass_ref_at_noresolve(int which, Bytecodes::Code code);
665   Symbol* name_ref_at(int which, Bytecodes::Code code) {
666     int name_index = name_ref_index_at(name_and_type_ref_index_at(which, code));
667     return symbol_at(name_index);
668   }
669   Symbol* signature_ref_at(int which, Bytecodes::Code code) {
670     int signature_index = signature_ref_index_at(name_and_type_ref_index_at(which, code));
671     return symbol_at(signature_index);
672   }
673 
674   u2 klass_ref_index_at(int which, Bytecodes::Code code);
675   u2 name_and_type_ref_index_at(int which, Bytecodes::Code code);
676 
677   constantTag tag_ref_at(int cp_cache_index, Bytecodes::Code code);
678 
679   int to_cp_index(int which, Bytecodes::Code code);
680 
681   // Lookup for entries consisting of (name_index, signature_index)
682   u2 name_ref_index_at(int cp_index);            // ==  low-order jshort of name_and_type_at(cp_index)
683   u2 signature_ref_index_at(int cp_index);       // == high-order jshort of name_and_type_at(cp_index)
684 
685   BasicType basic_type_for_signature_at(int cp_index) const;
686 
687   // Resolve string constants (to prevent allocation during compilation)
688   void resolve_string_constants(TRAPS) {
689     constantPoolHandle h_this(THREAD, this);
690     resolve_string_constants_impl(h_this, CHECK);
691   }
692 
693 #if INCLUDE_CDS
694   // CDS support
695   objArrayOop prepare_resolved_references_for_archiving() NOT_CDS_JAVA_HEAP_RETURN_(nullptr);
696   void add_dumped_interned_strings() NOT_CDS_JAVA_HEAP_RETURN;
697   bool maybe_archive_resolved_klass_at(int cp_index);
698   void remove_unshareable_info();
699   void restore_unshareable_info(TRAPS);
700 #endif
701 
702  private:
703   enum { _no_index_sentinel = -1, _possible_index_sentinel = -2 };
704  public:
705 
706   // Get the tag for a constant, which may involve a constant dynamic
707   constantTag constant_tag_at(int cp_index);
708   // Get the basic type for a constant, which may involve a constant dynamic
709   BasicType basic_type_for_constant_at(int cp_index);
710 
711   // Resolve late bound constants.
712   oop resolve_constant_at(int cp_index, TRAPS) {
713     constantPoolHandle h_this(THREAD, this);
714     return resolve_constant_at_impl(h_this, cp_index, _no_index_sentinel, nullptr, THREAD);
715   }
716 
717   oop resolve_cached_constant_at(int cache_index, TRAPS) {
718     constantPoolHandle h_this(THREAD, this);
719     return resolve_constant_at_impl(h_this, _no_index_sentinel, cache_index, nullptr, THREAD);
720   }
721 
722   oop resolve_possibly_cached_constant_at(int cp_index, TRAPS) {
723     constantPoolHandle h_this(THREAD, this);
724     return resolve_constant_at_impl(h_this, cp_index, _possible_index_sentinel, nullptr, THREAD);
725   }
726 
727   oop find_cached_constant_at(int cp_index, bool& found_it, TRAPS) {
728     constantPoolHandle h_this(THREAD, this);
729     return resolve_constant_at_impl(h_this, cp_index, _possible_index_sentinel, &found_it, THREAD);
730   }
731 
732   void copy_bootstrap_arguments_at(int cp_index,
733                                    int start_arg, int end_arg,
734                                    objArrayHandle info, int pos,
735                                    bool must_resolve, Handle if_not_available, TRAPS) {
736     constantPoolHandle h_this(THREAD, this);
737     copy_bootstrap_arguments_at_impl(h_this, cp_index, start_arg, end_arg,
738                                      info, pos, must_resolve, if_not_available, THREAD);
739   }
740 
741   // Klass name matches name at offset
742   bool klass_name_at_matches(const InstanceKlass* k, int cp_index);
743 
744   // Sizing
745   int length() const                   { return _length; }
746   void set_length(int length)          { _length = length; }
747 
748   // Tells whether index is within bounds.
749   bool is_within_bounds(int index) const {
750     return 0 <= index && index < length();
751   }
752 
753   // Sizing (in words)
754   static int header_size()             {
755     return align_up((int)sizeof(ConstantPool), wordSize) / wordSize;
756   }
757   static int size(int length)          { return align_metadata_size(header_size() + length); }
758   int size() const                     { return size(length()); }
759 
760   // ConstantPools should be stored in the read-only region of CDS archive.
761   static bool is_read_only_by_default() { return true; }
762 
763   friend class ClassFileParser;
764   friend class SystemDictionary;
765 
766   // Used by CDS. These classes need to access the private ConstantPool() constructor.
767   template <class T> friend class CppVtableTesterA;
768   template <class T> friend class CppVtableTesterB;
769   template <class T> friend class CppVtableCloner;
770 
771   // Used by compiler to prevent classloading.
772   static Method*          method_at_if_loaded      (const constantPoolHandle& this_cp, int which);
773   static bool       has_appendix_at_if_loaded      (const constantPoolHandle& this_cp, int which);
774   static oop            appendix_at_if_loaded      (const constantPoolHandle& this_cp, int which);
775   static bool has_local_signature_at_if_loaded     (const constantPoolHandle& this_cp, int which);
776   static Klass*            klass_at_if_loaded      (const constantPoolHandle& this_cp, int which);
777 
778   // Routines currently used for annotations (only called by jvm.cpp) but which might be used in the
779   // future by other Java code. These take constant pool indices rather than
780   // constant pool cache indices as do the peer methods above.
781   Symbol* uncached_klass_ref_at_noresolve(int cp_index);
782   Symbol* uncached_name_ref_at(int cp_index) {
783     int name_index = name_ref_index_at(uncached_name_and_type_ref_index_at(cp_index));
784     return symbol_at(name_index);
785   }
786   Symbol* uncached_signature_ref_at(int cp_index) {
787     int signature_index = signature_ref_index_at(uncached_name_and_type_ref_index_at(cp_index));
788     return symbol_at(signature_index);
789   }
790   u2 uncached_klass_ref_index_at(int cp_index);
791   u2 uncached_name_and_type_ref_index_at(int cp_index);
792 
793   // Sharing
794   int pre_resolve_shared_klasses(TRAPS);
795 
796   // Debugging
797   const char* printable_name_at(int cp_index) PRODUCT_RETURN0;
798 
799  private:
800 
801   void set_resolved_references(OopHandle s) { _cache->set_resolved_references(s); }
802   Array<u2>* reference_map() const        {  return (_cache == nullptr) ? nullptr :  _cache->reference_map(); }
803   void set_reference_map(Array<u2>* o)    { _cache->set_reference_map(o); }
804 
805   // Used while constructing constant pool (only by ClassFileParser)
806   jint klass_index_at(int cp_index) {
807     assert(tag_at(cp_index).is_klass_index(), "Corrupted constant pool");
808     return *int_at_addr(cp_index);
809   }
810 
811   jint string_index_at(int cp_index) {
812     assert(tag_at(cp_index).is_string_index(), "Corrupted constant pool");
813     return *int_at_addr(cp_index);
814   }
815 
816   // Performs the LinkResolver checks
817   static void verify_constant_pool_resolve(const constantPoolHandle& this_cp, Klass* klass, TRAPS);
818 
819   // Implementation of methods that needs an exposed 'this' pointer, in order to
820   // handle GC while executing the method
821   static Klass* klass_at_impl(const constantPoolHandle& this_cp, int cp_index, TRAPS);
822   static oop string_at_impl(const constantPoolHandle& this_cp, int cp_index, int obj_index, TRAPS);
823 
824   static void trace_class_resolution(const constantPoolHandle& this_cp, Klass* k);
825 
826   // Resolve string constants (to prevent allocation during compilation)
827   static void resolve_string_constants_impl(const constantPoolHandle& this_cp, TRAPS);
828 
829   static oop resolve_constant_at_impl(const constantPoolHandle& this_cp, int cp_index, int cache_index,
830                                       bool* status_return, TRAPS);
831   static void copy_bootstrap_arguments_at_impl(const constantPoolHandle& this_cp, int cp_index,
832                                                int start_arg, int end_arg,
833                                                objArrayHandle info, int pos,
834                                                bool must_resolve, Handle if_not_available, TRAPS);
835 
836   // Exception handling
837   static void save_and_throw_exception(const constantPoolHandle& this_cp, int cp_index, constantTag tag, TRAPS);
838 
839  public:
840   // Exception handling
841   static void throw_resolution_error(const constantPoolHandle& this_cp, int which, TRAPS);
842 
843   // Merging ConstantPool* support:
844   bool compare_entry_to(int index1, const constantPoolHandle& cp2, int index2);
845   void copy_cp_to(int start_cpi, int end_cpi, const constantPoolHandle& to_cp, int to_cpi, TRAPS) {
846     constantPoolHandle h_this(THREAD, this);
847     copy_cp_to_impl(h_this, start_cpi, end_cpi, to_cp, to_cpi, THREAD);
848   }
849   static void copy_cp_to_impl(const constantPoolHandle& from_cp, int start_cpi, int end_cpi, const constantPoolHandle& to_cp, int to_cpi, TRAPS);
850   static void copy_entry_to(const constantPoolHandle& from_cp, int from_cpi, const constantPoolHandle& to_cp, int to_cpi);
851   static void copy_operands(const constantPoolHandle& from_cp, const constantPoolHandle& to_cp, TRAPS);
852   int  find_matching_entry(int pattern_i, const constantPoolHandle& search_cp);
853   int  version() const                    { return _saved._version; }
854   void set_version(int version)           { _saved._version = version; }
855   void increment_and_save_version(int version) {
856     _saved._version = version >= 0 ? (version + 1) : version;  // keep overflow
857   }
858 
859   void set_resolved_reference_length(int length) { _saved._resolved_reference_length = length; }
860   int  resolved_reference_length() const  { return _saved._resolved_reference_length; }
861 
862   // Decrease ref counts of symbols that are in the constant pool
863   // when the holder class is unloaded
864   void unreference_symbols();
865 
866   // Deallocate constant pool for RedefineClasses
867   void deallocate_contents(ClassLoaderData* loader_data);
868   void release_C_heap_structures();
869 
870   // JVMTI access - GetConstantPool, RetransformClasses, ...
871   friend class JvmtiConstantPoolReconstituter;
872 
873  private:
874   class SymbolHash: public CHeapObj<mtSymbol> {
875     ResourceHashtable<const Symbol*, u2, 256, AnyObj::C_HEAP, mtSymbol, Symbol::compute_hash> _table;
876 
877    public:
878     void add_if_absent(const Symbol* sym, u2 value) {
879       bool created;
880       _table.put_if_absent(sym, value, &created);
881     }
882 
883     u2 symbol_to_value(const Symbol* sym) {
884       u2* value = _table.get(sym);
885       return (value == nullptr) ? 0 : *value;
886     }
887   }; // End SymbolHash class
888 
889   jint cpool_entry_size(jint idx);
890   jint hash_entries_to(SymbolHash *symmap, SymbolHash *classmap);
891 
892   // Copy cpool bytes into byte array.
893   // Returns:
894   //  int > 0, count of the raw cpool bytes that have been copied
895   //        0, OutOfMemory error
896   //       -1, Internal error
897   int  copy_cpool_bytes(int cpool_size,
898                         SymbolHash* tbl,
899                         unsigned char *bytes);
900 
901  public:
902   // Verify
903   void verify_on(outputStream* st);
904 
905   // Printing
906   void print_on(outputStream* st) const;
907   void print_value_on(outputStream* st) const;
908   void print_entry_on(int index, outputStream* st);
909 
910   const char* internal_name() const { return "{constant pool}"; }
911 
912   // ResolvedFieldEntry getters
913   inline ResolvedFieldEntry* resolved_field_entry_at(int field_index);
914   inline int resolved_field_entries_length() const;
915 
916   // ResolvedMethodEntry getters
917   inline ResolvedMethodEntry* resolved_method_entry_at(int method_index);
918   inline int resolved_method_entries_length() const;
919   inline oop appendix_if_resolved(int method_index) const;
920 
921   // ResolvedIndyEntry getters
922   inline ResolvedIndyEntry* resolved_indy_entry_at(int index);
923   inline int resolved_indy_entries_length() const;
924   inline oop resolved_reference_from_indy(int index) const;
925   inline oop resolved_reference_from_method(int index) const;
926 };
927 
928 #endif // SHARE_OOPS_CONSTANTPOOL_HPP