src/hotspot/share/oops/constantPool.hpp - master - githubmirror/panama-vector

src/hotspot/share/oops/constantPool.hpp
847 строк34 KB
Coleen Phillimore
8341120: NPE message can be wrong for null restricted fields
11 авг 2026, 21:27
11 авг 2026, 21:271abe579
/*
 * Copyright (c) 1997, 2026, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 *
 */

#ifndef SHARE_OOPS_CONSTANTPOOL_HPP
#define SHARE_OOPS_CONSTANTPOOL_HPP

#include "memory/allocation.hpp"
#include "oops/arrayOop.hpp"
#include "oops/bsmAttribute.hpp"
#include "oops/cpCache.hpp"
#include "oops/objArrayOop.hpp"
#include "oops/oopHandle.hpp"
#include "oops/symbol.hpp"
#include "oops/typeArrayOop.hpp"
#include "runtime/handles.hpp"
#include "runtime/javaThread.hpp"
#include "utilities/align.hpp"
#include "utilities/bytes.hpp"
#include "utilities/constantTag.hpp"
#include "utilities/hashTable.hpp"
#include "utilities/macros.hpp"

// A ConstantPool is an array containing class constants as described in the
// class file.
//
// Most of the constant pool entries are written during class parsing, which
// is safe.  For klass types, the constant pool entry is
// modified when the entry is resolved.  If a klass constant pool
// entry is read without a lock, only the resolved state guarantees that
// the entry in the constant pool is a klass object and not a Symbol*.

// This represents a JVM_CONSTANT_Class, JVM_CONSTANT_UnresolvedClass, or
// JVM_CONSTANT_UnresolvedClassInError slot in the constant pool.
class CPKlassSlot {
  // cp->symbol_at(_name_index) gives the name of the class.
  int _name_index;

  // cp->_resolved_klasses->at(_resolved_klass_index) gives the Klass* for the class.
  int _resolved_klass_index;
public:
  enum {
    // This is used during constant pool merging where the resolved klass index is
    // not yet known, and will be computed at a later stage (during a call to
    // initialize_unresolved_klasses()).
    _temp_resolved_klass_index = 0xffff
  };
  CPKlassSlot(int n, int rk) {
    _name_index = n;
    _resolved_klass_index = rk;
  }
  int name_index() const {
    return _name_index;
  }
  int resolved_klass_index() const {
    assert(_resolved_klass_index != _temp_resolved_klass_index, "constant pool merging was incomplete");
    return _resolved_klass_index;
  }
};

class ConstantPool : public Metadata {
  friend class VMStructs;
  friend class BytecodeInterpreter;  // Directly extracts a klass in the pool for fast instanceof/checkcast
  friend class Universe;             // For null constructor
  friend class AOTConstantPoolResolver;
 private:
  // If you add a new field that points to any metaspace object, you
  // must add this field to ConstantPool::metaspace_pointers_do().
  Array<u1>*           _tags;        // the tag array describing the constant pool's contents
  ConstantPoolCache*   _cache;       // the cache holding interpreter runtime information
  InstanceKlass*       _pool_holder; // the corresponding class

  BSMAttributeEntries _bsm_entries;

  // Consider using an array of compressed klass pointers to
  // save space on 64-bit platforms.
  Array<Klass*>*       _resolved_klasses;

  u2              _major_version;        // major version number of class file
  u2              _minor_version;        // minor version number of class file

  // Constant pool index to the utf8 entry of the Generic signature,
  // or 0 if none.
  u2              _generic_signature_index;
  // Constant pool index to the utf8 entry for the name of source file
  // containing this klass, 0 if not specified.
  u2              _source_file_name_index;

  enum {
    _has_preresolution    = 1,       // Flags
    _on_stack             = 2,
    _in_aot_cache         = 4,
    _has_dynamic_constant = 8,
    _is_for_method_handle_intrinsic = 16
  };

  u2              _flags;  // old fashioned bit twiddling

  int             _length; // number of elements in the array

  union {
    // set for CDS to restore resolved references
    int                _resolved_reference_length;
    // keeps version number for redefined classes (used in backtrace)
    int                _version;
  } _saved;

  void set_tags(Array<u1>* tags)                 { _tags = tags; }
  void tag_at_put(int cp_index, jbyte t)         { tags()->at_put(cp_index, t); }
  void release_tag_at_put(int cp_index, jbyte t) { tags()->release_at_put(cp_index, t); }

  u1* tag_addr_at(int cp_index) const            { return tags()->adr_at(cp_index); }

  u2 flags() const                             { return _flags; }
  void set_flags(u2 f)                         { _flags = f; }

 private:
  intptr_t* base() const { return (intptr_t*) (((char*) this) + sizeof(ConstantPool)); }

  intptr_t* obj_at_addr(int cp_index) const {
    assert(is_within_bounds(cp_index), "index out of bounds");
    return (intptr_t*) &base()[cp_index];
  }

  jint* int_at_addr(int cp_index) const {
    assert(is_within_bounds(cp_index), "index out of bounds");
    return (jint*) &base()[cp_index];
  }

  jlong* long_at_addr(int cp_index) const {
    assert(is_within_bounds(cp_index), "index out of bounds");
    return (jlong*) &base()[cp_index];
  }

  jfloat* float_at_addr(int cp_index) const {
    assert(is_within_bounds(cp_index), "index out of bounds");
    return (jfloat*) &base()[cp_index];
  }

  jdouble* double_at_addr(int cp_index) const {
    assert(is_within_bounds(cp_index), "index out of bounds");
    return (jdouble*) &base()[cp_index];
  }

  ConstantPool(Array<u1>* tags);
  ConstantPool();
 public:
  static ConstantPool* allocate(ClassLoaderData* loader_data, int length, TRAPS);

  virtual bool is_constantPool() const      { return true; }

  Array<u1>* tags() const                   { return _tags; }

  BSMAttributeEntries& bsm_entries() {
    return _bsm_entries;
  }
  const BSMAttributeEntries& bsm_entries() const {
    return _bsm_entries;
  }

  bool has_preresolution() const            { return (_flags & _has_preresolution) != 0; }
  void set_has_preresolution() {
    assert(!in_aot_cache(), "should never be called on ConstantPools in AOT cache");
    _flags |= _has_preresolution;
  }

  // minor and major version numbers of class file
  u2 major_version() const                 { return _major_version; }
  void set_major_version(u2 major_version) { _major_version = major_version; }
  u2 minor_version() const                 { return _minor_version; }
  void set_minor_version(u2 minor_version) { _minor_version = minor_version; }

  // generics support
  Symbol* generic_signature() const {
    return (_generic_signature_index == 0) ?
      nullptr : symbol_at(_generic_signature_index);
  }
  u2 generic_signature_index() const                   { return _generic_signature_index; }
  void set_generic_signature_index(u2 sig_index)       { _generic_signature_index = sig_index; }

  // source file name
  Symbol* source_file_name() const {
    return (_source_file_name_index == 0) ?
      nullptr : symbol_at(_source_file_name_index);
  }
  u2 source_file_name_index() const                    { return _source_file_name_index; }
  void set_source_file_name_index(u2 sourcefile_index) { _source_file_name_index = sourcefile_index; }

  void copy_fields(const ConstantPool* orig);

  // Redefine classes support.  If a method referring to this constant pool
  // is on the executing stack, or as a handle in vm code, this constant pool
  // can't be removed from the set of previous versions saved in the instance
  // class.
  bool on_stack() const;
  bool is_maybe_on_stack() const;
  void set_on_stack(const bool value);

  // Shadows MetaspaceObj::in_aot_cache(). It's faster and is used by set_on_stack()
  bool in_aot_cache() const               { return (_flags & _in_aot_cache) != 0; }

  bool has_dynamic_constant() const       { return (_flags & _has_dynamic_constant) != 0; }
  void set_has_dynamic_constant()         { _flags |= _has_dynamic_constant; }

  bool is_for_method_handle_intrinsic() const  { return (_flags & _is_for_method_handle_intrinsic) != 0; }
  void set_is_for_method_handle_intrinsic()    { _flags |= _is_for_method_handle_intrinsic; }

  // Klass holding pool
  InstanceKlass* pool_holder() const      { return _pool_holder; }
  void set_pool_holder(InstanceKlass* k)  { _pool_holder = k; }
  InstanceKlass** pool_holder_addr()      { return &_pool_holder; }

  // Interpreter runtime support
  ConstantPoolCache* cache() const        { return _cache; }
  void set_cache(ConstantPoolCache* cache){ _cache = cache; }

  virtual void metaspace_pointers_do(MetaspaceClosure* iter);
  virtual MetaspaceObj::Type type() const { return ConstantPoolType; }

  // Create object cache in the constant pool
  void initialize_resolved_references(ClassLoaderData* loader_data,
                                      const intStack& reference_map,
                                      int constant_pool_map_length,
                                      TRAPS);

  // resolved strings, methodHandles and callsite objects from the constant pool
  refArrayOop resolved_references()  const;
  refArrayOop resolved_references_or_null()  const;
  oop resolved_reference_at(int obj_index) const;
  oop set_resolved_reference_at(int index, oop new_value);

  // mapping resolved object array indexes to cp indexes and back.
  int object_to_cp_index(int index)         { return reference_map()->at(index); }
  int cp_to_object_index(int index);

  void set_resolved_klasses(Array<Klass*>* rk)  { _resolved_klasses = rk; }
  Array<Klass*>* resolved_klasses() const       { return _resolved_klasses; }
  void allocate_resolved_klasses(ClassLoaderData* loader_data, int num_klasses, TRAPS);
  void initialize_unresolved_klasses(ClassLoaderData* loader_data, TRAPS);

  // Given the per-instruction index of an indy instruction, report the
  // main constant pool entry for its bootstrap specifier.
  // From there, uncached_name/signature_ref_at will get the name/type.
  inline u2 invokedynamic_bootstrap_ref_index_at(int indy_index) const;

  // Assembly code support
  static ByteSize tags_offset()         { return byte_offset_of(ConstantPool, _tags); }
  static ByteSize cache_offset()        { return byte_offset_of(ConstantPool, _cache); }
  static ByteSize pool_holder_offset()  { return byte_offset_of(ConstantPool, _pool_holder); }
  static ByteSize resolved_klasses_offset()    { return byte_offset_of(ConstantPool, _resolved_klasses); }

  // Storing constants

  // For temporary use while constructing constant pool
  void klass_index_at_put(int cp_index, int name_index) {
    tag_at_put(cp_index, JVM_CONSTANT_ClassIndex);
    *int_at_addr(cp_index) = name_index;
  }

  // Hidden class support:
  void klass_at_put(int class_index, Klass* k);

  void unresolved_klass_at_put(int cp_index, int name_index, int resolved_klass_index) {
    release_tag_at_put(cp_index, JVM_CONSTANT_UnresolvedClass);

    assert((name_index & 0xffff0000) == 0, "must be");
    assert((resolved_klass_index & 0xffff0000) == 0, "must be");
    *int_at_addr(cp_index) =
      build_int_from_shorts((jushort)resolved_klass_index, (jushort)name_index);
  }

  void method_handle_index_at_put(int cp_index, int ref_kind, int ref_index) {
    tag_at_put(cp_index, JVM_CONSTANT_MethodHandle);
    *int_at_addr(cp_index) = ((jint) ref_index<<16) | ref_kind;
  }

  void method_type_index_at_put(int cp_index, int ref_index) {
    tag_at_put(cp_index, JVM_CONSTANT_MethodType);
    *int_at_addr(cp_index) = ref_index;
  }

  void dynamic_constant_at_put(int cp_index, int bsms_attribute_index, int name_and_type_index) {
    tag_at_put(cp_index, JVM_CONSTANT_Dynamic);
    *int_at_addr(cp_index) = ((jint) name_and_type_index<<16) | bsms_attribute_index;
  }

  void invoke_dynamic_at_put(int cp_index, int bsms_attribute_index, int name_and_type_index) {
    tag_at_put(cp_index, JVM_CONSTANT_InvokeDynamic);
    *int_at_addr(cp_index) = ((jint) name_and_type_index<<16) | bsms_attribute_index;
  }

  void unresolved_string_at_put(int cp_index, Symbol* s) {
    assert(s->refcount() != 0, "should have nonzero refcount");
    // Note that release_tag_at_put is not needed here because this is called only
    // when constructing a ConstantPool in a single thread, with no possibility
    // of concurrent access.
    tag_at_put(cp_index, JVM_CONSTANT_String);
    *symbol_at_addr(cp_index) = s;
  }

  void int_at_put(int cp_index, jint i) {
    tag_at_put(cp_index, JVM_CONSTANT_Integer);
    *int_at_addr(cp_index) = i;
  }

  void long_at_put(int cp_index, jlong l) {
    tag_at_put(cp_index, JVM_CONSTANT_Long);
    // *long_at_addr(which) = l;
    Bytes::put_native_u8((address)long_at_addr(cp_index), *((u8*) &l));
  }

  void float_at_put(int cp_index, jfloat f) {
    tag_at_put(cp_index, JVM_CONSTANT_Float);
    *float_at_addr(cp_index) = f;
  }

  void double_at_put(int cp_index, jdouble d) {
    tag_at_put(cp_index, JVM_CONSTANT_Double);
    // *double_at_addr(which) = d;
    // u8 temp = *(u8*) &d;
    Bytes::put_native_u8((address) double_at_addr(cp_index), *((u8*) &d));
  }

  Symbol** symbol_at_addr(int cp_index) const {
    assert(is_within_bounds(cp_index), "index out of bounds");
    return (Symbol**) &base()[cp_index];
  }

  void symbol_at_put(int cp_index, Symbol* s) {
    assert(s->refcount() != 0, "should have nonzero refcount");
    tag_at_put(cp_index, JVM_CONSTANT_Utf8);
    *symbol_at_addr(cp_index) = s;
  }

  void string_at_put(int obj_index, oop str);

  // For temporary use while constructing constant pool
  void string_index_at_put(int cp_index, int string_index) {
    tag_at_put(cp_index, JVM_CONSTANT_StringIndex);
    *int_at_addr(cp_index) = string_index;
  }

  void field_at_put(int cp_index, int class_index, int name_and_type_index) {
    tag_at_put(cp_index, JVM_CONSTANT_Fieldref);
    *int_at_addr(cp_index) = ((jint) name_and_type_index<<16) | class_index;
  }

  void method_at_put(int cp_index, int class_index, int name_and_type_index) {
    tag_at_put(cp_index, JVM_CONSTANT_Methodref);
    *int_at_addr(cp_index) = ((jint) name_and_type_index<<16) | class_index;
  }

  void interface_method_at_put(int cp_index, int class_index, int name_and_type_index) {
    tag_at_put(cp_index, JVM_CONSTANT_InterfaceMethodref);
    *int_at_addr(cp_index) = ((jint) name_and_type_index<<16) | class_index;  // Not so nice
  }

  void name_and_type_at_put(int cp_index, int name_index, int signature_index) {
    tag_at_put(cp_index, JVM_CONSTANT_NameAndType);
    *int_at_addr(cp_index) = ((jint) signature_index<<16) | name_index;  // Not so nice
  }

  // Tag query

  constantTag tag_at(int cp_index) const { return (constantTag)tags()->at_acquire(cp_index); }

  // Fetching constants

  Klass* klass_at(int cp_index, TRAPS) {
    constantPoolHandle h_this(THREAD, this);
    return klass_at_impl(h_this, cp_index, THREAD);
  }

  CPKlassSlot klass_slot_at(int cp_index) const {
    assert(tag_at(cp_index).is_unresolved_klass() || tag_at(cp_index).is_klass(),
           "Corrupted constant pool");
    int value = *int_at_addr(cp_index);
    int name_index = extract_high_short_from_int(value);
    int resolved_klass_index = extract_low_short_from_int(value);
    return CPKlassSlot(name_index, resolved_klass_index);
  }

  Symbol* klass_name_at(int cp_index) const;  // Returns the name, w/o resolving.
  int klass_name_index_at(int cp_index) const {
    return klass_slot_at(cp_index).name_index();
  }

  Klass* resolved_klass_at(int cp_index) const;  // Used by Compiler

  // RedefineClasses() API support:
  Symbol* klass_at_noresolve(int cp_index) { return klass_name_at(cp_index); }
  void temp_unresolved_klass_at_put(int cp_index, int name_index) {
    // Used only during constant pool merging for class redefinition. The resolved klass index
    // will be initialized later by a call to initialize_unresolved_klasses().
    unresolved_klass_at_put(cp_index, name_index, CPKlassSlot::_temp_resolved_klass_index);
  }

  jint int_at(int cp_index) const {
    assert(tag_at(cp_index).is_int(), "Corrupted constant pool");
    return *int_at_addr(cp_index);
  }

  jlong long_at(int cp_index) {
    assert(tag_at(cp_index).is_long(), "Corrupted constant pool");
    // return *long_at_addr(cp_index);
    u8 tmp = Bytes::get_native_u8((address)&base()[cp_index]);
    return *((jlong*)&tmp);
  }

  jfloat float_at(int cp_index) {
    assert(tag_at(cp_index).is_float(), "Corrupted constant pool");
    return *float_at_addr(cp_index);
  }

  jdouble double_at(int cp_index) {
    assert(tag_at(cp_index).is_double(), "Corrupted constant pool");
    u8 tmp = Bytes::get_native_u8((address)&base()[cp_index]);
    return *((jdouble*)&tmp);
  }

  Symbol* symbol_at(int cp_index) const {
    assert(tag_at(cp_index).is_utf8(), "Corrupted constant pool");
    return *symbol_at_addr(cp_index);
  }

  oop string_at(int cp_index, int obj_index, TRAPS) {
    constantPoolHandle h_this(THREAD, this);
    return string_at_impl(h_this, cp_index, obj_index, THREAD);
  }
  oop string_at(int cp_index, TRAPS) {
    int obj_index = cp_to_object_index(cp_index);
    return string_at(cp_index, obj_index, THREAD);
  }

  // Version that can be used before string oop array is created.
  oop uncached_string_at(int cp_index, TRAPS);

  // only called when we are sure a string entry is already resolved (via an
  // earlier string_at call.
  oop resolved_string_at(int cp_index) {
    assert(tag_at(cp_index).is_string(), "Corrupted constant pool");
    // Must do an acquire here in case another thread resolved the klass
    // behind our back, lest we later load stale values thru the oop.
    // we might want a volatile_obj_at in ObjArrayKlass.
    int obj_index = cp_to_object_index(cp_index);
    return resolved_reference_at(obj_index);
  }

  Symbol* unresolved_string_at(int cp_index) {
    assert(tag_at(cp_index).is_string(), "Corrupted constant pool");
    return *symbol_at_addr(cp_index);
  }

  // Returns an UTF8 for a CONSTANT_String entry at a given index.
  // UTF8 char* representation was chosen to avoid conversion of
  // java_lang_Strings at resolved entries into Symbol*s
  // or vice versa.
  char* string_at_noresolve(int cp_index);

  jint name_and_type_at(int cp_index) {
    assert(tag_at(cp_index).is_name_and_type(), "Corrupted constant pool");
    return *int_at_addr(cp_index);
  }

  int method_handle_ref_kind_at(int cp_index) {
    assert(tag_at(cp_index).is_method_handle() ||
           tag_at(cp_index).is_method_handle_in_error(), "Corrupted constant pool");
    return extract_low_short_from_int(*int_at_addr(cp_index));  // mask out unwanted ref_index bits
  }
  int method_handle_index_at(int cp_index) {
    assert(tag_at(cp_index).is_method_handle() ||
           tag_at(cp_index).is_method_handle_in_error(), "Corrupted constant pool");
    return extract_high_short_from_int(*int_at_addr(cp_index));  // shift out unwanted ref_kind bits
  }
  int method_type_index_at(int cp_index) {
    assert(tag_at(cp_index).is_method_type() ||
           tag_at(cp_index).is_method_type_in_error(), "Corrupted constant pool");
    return *int_at_addr(cp_index);
  }

  // Derived queries:
  Symbol* method_handle_name_ref_at(int cp_index) {
    int member = method_handle_index_at(cp_index);
    return uncached_name_ref_at(member);
  }
  Symbol* method_handle_signature_ref_at(int cp_index) {
    int member = method_handle_index_at(cp_index);
    return uncached_signature_ref_at(member);
  }
  u2 method_handle_klass_index_at(int cp_index) {
    int member = method_handle_index_at(cp_index);
    return uncached_klass_ref_index_at(member);
  }
  Symbol* method_type_signature_at(int cp_index) {
    int sym = method_type_index_at(cp_index);
    return symbol_at(sym);
  }

  u2 bootstrap_name_and_type_ref_index_at(int cp_index) {
    assert(tag_at(cp_index).has_bootstrap(), "Corrupted constant pool");
    return extract_high_short_from_int(*int_at_addr(cp_index));
  }
  u2 bootstrap_methods_attribute_index(int cp_index) {
    assert(tag_at(cp_index).has_bootstrap(), "Corrupted constant pool");
    return extract_low_short_from_int(*int_at_addr(cp_index));
  }

  BSMAttributeEntry* bsm_attribute_entry(int bsms_attribute_index) {
    return _bsm_entries.entry(bsms_attribute_index);
  }

  bool compare_bootstrap_entry_to(int bsms_attribute_index1, const constantPoolHandle& cp2,
                                  int bsms_attribute_index2);
  // Find a BSM entry in search_cp that matches the BSM at bsm_attribute_index.
  // Return -1 if not found.
  int find_matching_bsm_entry(int bsms_attribute_index, const constantPoolHandle& search_cp,
                              int offset_limit);
  // Extend the BSM attribute storage to fit both the current data and the BSM data in ext_cp.
  // Use the returned InsertionIterator to fill out the newly allocated space.
  BSMAttributeEntries::InsertionIterator start_extension(const constantPoolHandle& ext_cp, TRAPS);
  void end_extension(BSMAttributeEntries::InsertionIterator iter, TRAPS);

  u2 bootstrap_method_ref_index_at(int cp_index) {
    assert(tag_at(cp_index).has_bootstrap(), "Corrupted constant pool");
    int bsmai = bootstrap_methods_attribute_index(cp_index);
    return bsm_attribute_entry(bsmai)->bootstrap_method_index();
  }
  u2 bootstrap_argument_count_at(int cp_index) {
    assert(tag_at(cp_index).has_bootstrap(), "Corrupted constant pool");
    int bsmai = bootstrap_methods_attribute_index(cp_index);
    return bsm_attribute_entry(bsmai)->argument_count();
  }
  u2 bootstrap_argument_index_at(int cp_index, int j) {
    int bsmai = bootstrap_methods_attribute_index(cp_index);
    BSMAttributeEntry* bsme = bsm_attribute_entry(bsmai);
    assert(j < bsme->argument_count(), "oob");
    return bsm_attribute_entry(bsmai)->argument(checked_cast<u2>(j));
  }

  // The following methods (name/signature/klass_ref_at, klass_ref_at_noresolve,
  // name_and_type_ref_index_at) all expect to be passed indices obtained
  // directly from the bytecode.
  // If the indices are meant to refer to fields or methods, they are
  // actually rewritten indices that point to entries in their respective structures
  // i.e. ResolvedMethodEntries or ResolvedFieldEntries.
  // The routine to_cp_index manages the adjustment
  // of these values back to constant pool indices.

  // There are also "uncached" versions which do not adjust the operand index; see below.

  // Lookup for entries consisting of (klass_index, name_and_type index)
  Klass* klass_ref_at(int which, Bytecodes::Code code, TRAPS);
  Symbol* klass_ref_at_noresolve(int which, Bytecodes::Code code);
  Symbol* name_ref_at(int which, Bytecodes::Code code) {
    int name_index = name_ref_index_at(name_and_type_ref_index_at(which, code));
    return symbol_at(name_index);
  }
  Symbol* signature_ref_at(int which, Bytecodes::Code code) {
    int signature_index = signature_ref_index_at(name_and_type_ref_index_at(which, code));
    return symbol_at(signature_index);
  }

  // Returns a resolved klass or nullptr if not resolved.  Does not try to resolve the class.
  Klass* resolved_klass_ref_at(int which, Bytecodes::Code code) {
    jint ref_index = klass_ref_index_at(which, code);
    return resolved_klass_at(ref_index);
  }

  u2 klass_ref_index_at(int which, Bytecodes::Code code);
  u2 name_and_type_ref_index_at(int which, Bytecodes::Code code);

  constantTag tag_ref_at(int cp_cache_index, Bytecodes::Code code);

  int to_cp_index(int which, Bytecodes::Code code);

  bool is_resolved(int which, Bytecodes::Code code);

  // Lookup for entries consisting of (name_index, signature_index)
  u2 name_ref_index_at(int cp_index);            // ==  low-order jshort of name_and_type_at(cp_index)
  u2 signature_ref_index_at(int cp_index);       // == high-order jshort of name_and_type_at(cp_index)

  BasicType basic_type_for_signature_at(int cp_index) const;

  // Resolve string constants (to prevent allocation during compilation)
  void resolve_string_constants(TRAPS) {
    constantPoolHandle h_this(THREAD, this);
    resolve_string_constants_impl(h_this, CHECK);
  }

#if INCLUDE_CDS
  // CDS support
  refArrayOop prepare_resolved_references_for_archiving() NOT_CDS_JAVA_HEAP_RETURN_(nullptr);
  void remove_unshareable_info();
  void restore_unshareable_info(TRAPS);
private:
  void remove_unshareable_entries();
  void remove_resolved_klass_if_non_deterministic(int cp_index);
  template <typename Function> void iterate_archivable_resolved_references(Function function);
#endif

 private:
  enum { _no_index_sentinel = -1, _possible_index_sentinel = -2 };
 public:

  // Get the tag for a constant, which may involve a constant dynamic
  constantTag constant_tag_at(int cp_index);
  // Get the basic type for a constant, which may involve a constant dynamic
  BasicType basic_type_for_constant_at(int cp_index);

  // Resolve late bound constants.
  oop resolve_constant_at(int cp_index, TRAPS) {
    constantPoolHandle h_this(THREAD, this);
    return resolve_constant_at_impl(h_this, cp_index, _no_index_sentinel, nullptr, THREAD);
  }

  oop resolve_cached_constant_at(int cache_index, TRAPS) {
    constantPoolHandle h_this(THREAD, this);
    return resolve_constant_at_impl(h_this, _no_index_sentinel, cache_index, nullptr, THREAD);
  }

  oop resolve_possibly_cached_constant_at(int cp_index, TRAPS) {
    constantPoolHandle h_this(THREAD, this);
    return resolve_constant_at_impl(h_this, cp_index, _possible_index_sentinel, nullptr, THREAD);
  }

  oop find_cached_constant_at(int cp_index, bool& found_it, TRAPS) {
    constantPoolHandle h_this(THREAD, this);
    return resolve_constant_at_impl(h_this, cp_index, _possible_index_sentinel, &found_it, THREAD);
  }

  void copy_bootstrap_arguments_at(int cp_index,
                                   int start_arg, int end_arg,
                                   refArrayHandle info, int pos,
                                   bool must_resolve, Handle if_not_available, TRAPS) {
    constantPoolHandle h_this(THREAD, this);
    copy_bootstrap_arguments_at_impl(h_this, cp_index, start_arg, end_arg,
                                     info, pos, must_resolve, if_not_available, THREAD);
  }

  // Klass name matches name at offset
  bool klass_name_at_matches(const InstanceKlass* k, int cp_index);

  // Sizing
  int length() const                   { return _length; }
  void set_length(int length)          { _length = length; }

  // Tells whether index is within bounds.
  bool is_within_bounds(int index) const {
    return 0 <= index && index < length();
  }

  // Sizing (in words)
  static int header_size()             {
    return align_up((int)sizeof(ConstantPool), wordSize) / wordSize;
  }
  static int size(int length)          { return align_metadata_size(header_size() + length); }
  int size() const                     { return size(length()); }

  // ConstantPools should be stored in the read-only region of CDS archive.
  static bool is_read_only_by_default() { return true; }

  friend class ClassFileParser;
  friend class SystemDictionary;

  // Used by CDS. These classes need to access the private ConstantPool() constructor.
  template <class T> friend class CppVtableTesterA;
  template <class T> friend class CppVtableTesterB;
  template <class T> friend class CppVtableCloner;

  // Used by compiler to prevent classloading.
  static Method*          method_at_if_loaded      (const constantPoolHandle& this_cp, int which);
  static bool       has_appendix_at_if_loaded      (const constantPoolHandle& this_cp, int which, Bytecodes::Code code);
  static oop            appendix_at_if_loaded      (const constantPoolHandle& this_cp, int which, Bytecodes::Code code);
  static bool has_local_signature_at_if_loaded     (const constantPoolHandle& this_cp, int which, Bytecodes::Code code);
  static Klass*            klass_at_if_loaded      (const constantPoolHandle& this_cp, int which);

  // Routines currently used for annotations (only called by jvm.cpp) but which might be used in the
  // future by other Java code. These take constant pool indices rather than
  // constant pool cache indices as do the peer methods above.
  Symbol* uncached_klass_ref_at_noresolve(int cp_index);
  Symbol* uncached_name_ref_at(int cp_index) {
    int name_index = name_ref_index_at(uncached_name_and_type_ref_index_at(cp_index));
    return symbol_at(name_index);
  }
  Symbol* uncached_signature_ref_at(int cp_index) {
    int signature_index = signature_ref_index_at(uncached_name_and_type_ref_index_at(cp_index));
    return symbol_at(signature_index);
  }
  u2 uncached_klass_ref_index_at(int cp_index);
  u2 uncached_name_and_type_ref_index_at(int cp_index);

  // Sharing
  int pre_resolve_shared_klasses(TRAPS);

  // Debugging
  const char* printable_name_at(int cp_index) PRODUCT_RETURN_NULL;

 private:

  void set_resolved_references(OopHandle s) { _cache->set_resolved_references(s); }
  Array<u2>* reference_map() const        {  return (_cache == nullptr) ? nullptr :  _cache->reference_map(); }
  void set_reference_map(Array<u2>* o)    { _cache->set_reference_map(o); }

  // Used while constructing constant pool (only by ClassFileParser)
  jint klass_index_at(int cp_index) {
    assert(tag_at(cp_index).is_klass_index(), "Corrupted constant pool");
    return *int_at_addr(cp_index);
  }

  jint string_index_at(int cp_index) {
    assert(tag_at(cp_index).is_string_index(), "Corrupted constant pool");
    return *int_at_addr(cp_index);
  }

  // Performs the LinkResolver checks
  static void verify_constant_pool_resolve(const constantPoolHandle& this_cp, Klass* klass, TRAPS);

  // Implementation of methods that needs an exposed 'this' pointer, in order to
  // handle GC while executing the method
  static Klass* klass_at_impl(const constantPoolHandle& this_cp, int cp_index, TRAPS);
  static oop string_at_impl(const constantPoolHandle& this_cp, int cp_index, int obj_index, TRAPS);

  static void trace_class_resolution(const constantPoolHandle& this_cp, Klass* k);

  // Resolve string constants (to prevent allocation during compilation)
  static void resolve_string_constants_impl(const constantPoolHandle& this_cp, TRAPS);

  static oop resolve_constant_at_impl(const constantPoolHandle& this_cp, int cp_index, int cache_index,
                                      bool* status_return, TRAPS);
  static void copy_bootstrap_arguments_at_impl(const constantPoolHandle& this_cp, int cp_index,
                                               int start_arg, int end_arg,
                                               refArrayHandle info, int pos,
                                               bool must_resolve, Handle if_not_available, TRAPS);

  // Exception handling
  static void save_and_throw_exception(const constantPoolHandle& this_cp, int cp_index, constantTag tag, TRAPS);

 public:
  // Exception handling
  static void throw_resolution_error(const constantPoolHandle& this_cp, int which, TRAPS);

  // Merging ConstantPool* support:
  bool compare_entry_to(int index1, const constantPoolHandle& cp2, int index2);
  void copy_cp_to(int start_cpi, int end_cpi, const constantPoolHandle& to_cp, int to_cpi, TRAPS) {
    constantPoolHandle h_this(THREAD, this);
    copy_cp_to_impl(h_this, start_cpi, end_cpi, to_cp, to_cpi, THREAD);
  }
  static void copy_cp_to_impl(const constantPoolHandle& from_cp, int start_cpi, int end_cpi, const constantPoolHandle& to_cp, int to_cpi, TRAPS);
  static void copy_entry_to(const constantPoolHandle& from_cp, int from_cpi, const constantPoolHandle& to_cp, int to_cpi);
  static void copy_bsm_entries(const constantPoolHandle& from_cp, const constantPoolHandle& to_cp, TRAPS);
  int  find_matching_entry(int pattern_i, const constantPoolHandle& search_cp);
  int  version() const                    { return _saved._version; }
  void set_version(int version)           { _saved._version = version; }
  void increment_and_save_version(int version) {
    _saved._version = version >= 0 ? (version + 1) : version;  // keep overflow
  }

  void set_resolved_reference_length(int length) { _saved._resolved_reference_length = length; }
  int  resolved_reference_length() const  { return _saved._resolved_reference_length; }

  // Decrease ref counts of symbols that are in the constant pool
  // when the holder class is unloaded
  void unreference_symbols();

  // Deallocate constant pool for RedefineClasses
  void deallocate_contents(ClassLoaderData* loader_data);
  void release_C_heap_structures();

  // JVMTI access - GetConstantPool, RetransformClasses, ...
  friend class JvmtiConstantPoolReconstituter;

 private:
  class SymbolHash: public CHeapObj<mtSymbol> {
    HashTable<const Symbol*, u2, 256, AnyObj::C_HEAP, mtSymbol, Symbol::compute_hash> _table;

   public:
    void add_if_absent(const Symbol* sym, u2 value) {
      bool created;
      _table.put_if_absent(sym, value, &created);
    }

    u2 symbol_to_value(const Symbol* sym) {
      u2* value = _table.get(sym);
      return (value == nullptr) ? 0 : *value;
    }
  }; // End SymbolHash class

  jint cpool_entry_size(jint idx);
  jint hash_entries_to(SymbolHash *symmap, SymbolHash *classmap);

  // Copy cpool bytes into byte array.
  // Returns:
  //  int > 0, count of the raw cpool bytes that have been copied
  //        0, OutOfMemory error
  //       -1, Internal error
  int  copy_cpool_bytes(int cpool_size,
                        SymbolHash* tbl,
                        unsigned char *bytes);

 public:
  // Verify
  void verify_on(outputStream* st);

  // Printing
  void print_on(outputStream* st) const;
  void print_value_on(outputStream* st) const;
  void print_entry_on(int index, outputStream* st);

  const char* internal_name() const { return "{constant pool}"; }

  // ResolvedFieldEntry getters
  inline ResolvedFieldEntry* resolved_field_entry_at(int field_index);
  inline int resolved_field_entries_length() const;

  // ResolvedMethodEntry getters
  inline ResolvedMethodEntry* resolved_method_entry_at(int method_index);
  inline int resolved_method_entries_length() const;
  inline oop appendix_if_resolved(int method_index) const;

  // ResolvedIndyEntry getters
  inline ResolvedIndyEntry* resolved_indy_entry_at(int index);
  inline int resolved_indy_entries_length() const;
  inline oop resolved_reference_from_indy(int index) const;
  inline oop resolved_reference_from_method(int index) const;
};

#endif // SHARE_OOPS_CONSTANTPOOL_HPP