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 /*

  * Copyright (c) 1997, 2010, 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

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  */

 // 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 and string types, the constant pool entry is

 // modified when the entry is resolved.  If a klass or string constant pool

 // entry is read without a lock, only the resolved state guarantees that

 // the entry in the constant pool is a klass or String object and

 // not a symbolOop.

 class SymbolHashMap;

 class constantPoolOopDesc : public oopDesc {

   friend class VMStructs;

   friend class BytecodeInterpreter;  // Directly extracts an oop in the pool for fast instanceof/checkcast

  private:

   typeArrayOop         _tags; // the tag array describing the constant pool's contents

   constantPoolCacheOop _cache;         // the cache holding interpreter runtime information

   klassOop             _pool_holder;   // the corresponding class

   int                  _flags;         // a few header bits to describe contents for GC

   int                  _length; // number of elements in the array

   volatile bool        _is_conc_safe; // if true, safe for concurrent

                                       // GC processing

   // only set to non-zero if constant pool is merged by RedefineClasses

   int                  _orig_length;

   void set_tags(typeArrayOop tags)             { oop_store_without_check((oop*)&_tags, tags); }

   void tag_at_put(int which, jbyte t)          { tags()->byte_at_put(which, t); }

   void release_tag_at_put(int which, jbyte t)  { tags()->release_byte_at_put(which, t); }

   enum FlagBit {

     FB_has_invokedynamic = 1,

     FB_has_pseudo_string = 2

   };

   int flags() const                         { return _flags; }

   void set_flags(int f)                     { _flags = f; }

   bool flag_at(FlagBit fb) const            { return (_flags & (1 << (int)fb)) != 0; }

   void set_flag_at(FlagBit fb);

   // no clear_flag_at function; they only increase

  private:

   intptr_t* base() const { return (intptr_t*) (((char*) this) + sizeof(constantPoolOopDesc)); }

   oop* tags_addr()       { return (oop*)&_tags; }

   oop* cache_addr()      { return (oop*)&_cache; }

   oop* obj_at_addr(int which) const {

     assert(is_within_bounds(which), "index out of bounds");

     return (oop*) &base()[which];

   }

   jint* int_at_addr(int which) const {

     assert(is_within_bounds(which), "index out of bounds");

     return (jint*) &base()[which];

   }

   jlong* long_at_addr(int which) const {

     assert(is_within_bounds(which), "index out of bounds");

     return (jlong*) &base()[which];

   }

   jfloat* float_at_addr(int which) const {

     assert(is_within_bounds(which), "index out of bounds");

     return (jfloat*) &base()[which];

   }

   jdouble* double_at_addr(int which) const {

     assert(is_within_bounds(which), "index out of bounds");

     return (jdouble*) &base()[which];

   }

  public:

   typeArrayOop tags() const                 { return _tags; }

   bool has_pseudo_string() const            { return flag_at(FB_has_pseudo_string); }

   bool has_invokedynamic() const            { return flag_at(FB_has_invokedynamic); }

   void set_pseudo_string()                  {    set_flag_at(FB_has_pseudo_string); }

   void set_invokedynamic()                  {    set_flag_at(FB_has_invokedynamic); }

   // Klass holding pool

   klassOop pool_holder() const              { return _pool_holder; }

   void set_pool_holder(klassOop k)          { oop_store_without_check((oop*)&_pool_holder, (oop) k); }

   oop* pool_holder_addr()                   { return (oop*)&_pool_holder; }

   // Interpreter runtime support

   constantPoolCacheOop cache() const        { return _cache; }

   void set_cache(constantPoolCacheOop cache){ oop_store((oop*)&_cache, cache); }

   // Assembly code support

   static int tags_offset_in_bytes()         { return offset_of(constantPoolOopDesc, _tags); }

   static int cache_offset_in_bytes()        { return offset_of(constantPoolOopDesc, _cache); }

   static int pool_holder_offset_in_bytes()  { return offset_of(constantPoolOopDesc, _pool_holder); }

   // Storing constants

   void klass_at_put(int which, klassOop k) {

     oop_store_without_check((volatile oop *)obj_at_addr(which), oop(k));

     // The interpreter assumes when the tag is stored, the klass is resolved

     // and the klassOop is a klass rather than a symbolOop, so we need

     // hardware store ordering here.

     release_tag_at_put(which, JVM_CONSTANT_Class);

     if (UseConcMarkSweepGC) {

       // In case the earlier card-mark was consumed by a concurrent

       // marking thread before the tag was updated, redirty the card.

       oop_store_without_check((volatile oop *)obj_at_addr(which), oop(k));

     }

   }

   // For temporary use while constructing constant pool

   void klass_index_at_put(int which, int name_index) {

     tag_at_put(which, JVM_CONSTANT_ClassIndex);

     *int_at_addr(which) = name_index;

   }

   // Temporary until actual use

   void unresolved_klass_at_put(int which, symbolOop s) {

     // Overwrite the old index with a GC friendly value so

     // that if GC looks during the transition it won't try

     // to treat a small integer as oop.

     *obj_at_addr(which) = NULL;

     release_tag_at_put(which, JVM_CONSTANT_UnresolvedClass);

     oop_store_without_check(obj_at_addr(which), oop(s));

   }

   void method_handle_index_at_put(int which, int ref_kind, int ref_index) {

     tag_at_put(which, JVM_CONSTANT_MethodHandle);

     *int_at_addr(which) = ((jint) ref_index<<16) | ref_kind;

   }

   void method_type_index_at_put(int which, int ref_index) {

     tag_at_put(which, JVM_CONSTANT_MethodType);

     *int_at_addr(which) = ref_index;

   }

   void invoke_dynamic_at_put(int which, int bootstrap_method_index, int name_and_type_index) {

     tag_at_put(which, JVM_CONSTANT_InvokeDynamic);

     *int_at_addr(which) = ((jint) name_and_type_index<<16) | bootstrap_method_index;

   }

   // Temporary until actual use

   void unresolved_string_at_put(int which, symbolOop s) {

     *obj_at_addr(which) = NULL;

     release_tag_at_put(which, JVM_CONSTANT_UnresolvedString);

     oop_store_without_check(obj_at_addr(which), oop(s));

   }

   void int_at_put(int which, jint i) {

     tag_at_put(which, JVM_CONSTANT_Integer);

     *int_at_addr(which) = i;

   }

   void long_at_put(int which, jlong l) {

     tag_at_put(which, JVM_CONSTANT_Long);

     // *long_at_addr(which) = l;

     Bytes::put_native_u8((address)long_at_addr(which), *((u8*) &l));

   }

   void float_at_put(int which, jfloat f) {

     tag_at_put(which, JVM_CONSTANT_Float);

     *float_at_addr(which) = f;

   }

   void double_at_put(int which, jdouble d) {

     tag_at_put(which, JVM_CONSTANT_Double);

     // *double_at_addr(which) = d;

     // u8 temp = *(u8*) &d;

     Bytes::put_native_u8((address) double_at_addr(which), *((u8*) &d));

   }

   void symbol_at_put(int which, symbolOop s) {

     tag_at_put(which, JVM_CONSTANT_Utf8);

     oop_store_without_check(obj_at_addr(which), oop(s));

   }

   void string_at_put(int which, oop str) {

     oop_store((volatile oop*)obj_at_addr(which), str);

     release_tag_at_put(which, JVM_CONSTANT_String);

     if (UseConcMarkSweepGC) {

       // In case the earlier card-mark was consumed by a concurrent

       // marking thread before the tag was updated, redirty the card.

       oop_store_without_check((volatile oop *)obj_at_addr(which), str);

     }

   }

   void object_at_put(int which, oop str) {

     oop_store((volatile oop*) obj_at_addr(which), str);

     release_tag_at_put(which, JVM_CONSTANT_Object);

     if (UseConcMarkSweepGC) {

       // In case the earlier card-mark was consumed by a concurrent

       // marking thread before the tag was updated, redirty the card.

       oop_store_without_check((volatile oop*) obj_at_addr(which), str);

     }

   }

   // For temporary use while constructing constant pool

   void string_index_at_put(int which, int string_index) {

     tag_at_put(which, JVM_CONSTANT_StringIndex);

     *int_at_addr(which) = string_index;

   }

   void field_at_put(int which, int class_index, int name_and_type_index) {

     tag_at_put(which, JVM_CONSTANT_Fieldref);

     *int_at_addr(which) = ((jint) name_and_type_index<<16) | class_index;

   }

   void method_at_put(int which, int class_index, int name_and_type_index) {

     tag_at_put(which, JVM_CONSTANT_Methodref);

     *int_at_addr(which) = ((jint) name_and_type_index<<16) | class_index;

   }

   void interface_method_at_put(int which, int class_index, int name_and_type_index) {

     tag_at_put(which, JVM_CONSTANT_InterfaceMethodref);

     *int_at_addr(which) = ((jint) name_and_type_index<<16) | class_index;  // Not so nice

   }

   void name_and_type_at_put(int which, int name_index, int signature_index) {

     tag_at_put(which, JVM_CONSTANT_NameAndType);

     *int_at_addr(which) = ((jint) signature_index<<16) | name_index;  // Not so nice

   }

   // Tag query

   constantTag tag_at(int which) const { return (constantTag)tags()->byte_at_acquire(which); }

   // Whether the entry is a pointer that must be GC'd.

   bool is_pointer_entry(int which) {

     constantTag tag = tag_at(which);

     return tag.is_klass() ||

       tag.is_unresolved_klass() ||

       tag.is_symbol() ||

       tag.is_unresolved_string() ||

       tag.is_string() ||

       tag.is_object();

   }

   // Fetching constants

   klassOop klass_at(int which, TRAPS) {

     constantPoolHandle h_this(THREAD, this);

     return klass_at_impl(h_this, which, CHECK_NULL);

   }

   symbolOop klass_name_at(int which);  // Returns the name, w/o resolving.

   klassOop resolved_klass_at(int which) {  // Used by Compiler

     guarantee(tag_at(which).is_klass(), "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.

     return klassOop((oop)OrderAccess::load_ptr_acquire(obj_at_addr(which)));

   }

   // This method should only be used with a cpool lock or during parsing or gc

   symbolOop unresolved_klass_at(int which) {     // Temporary until actual use

     symbolOop s = symbolOop((oop)OrderAccess::load_ptr_acquire(obj_at_addr(which)));

     // check that the klass is still unresolved.

     assert(tag_at(which).is_unresolved_klass(), "Corrupted constant pool");

     return s;

   }

   // RedefineClasses() API support:

   symbolOop klass_at_noresolve(int which) { return klass_name_at(which); }

   jint int_at(int which) {

     assert(tag_at(which).is_int(), "Corrupted constant pool");

     return *int_at_addr(which);

   }

   jlong long_at(int which) {

     assert(tag_at(which).is_long(), "Corrupted constant pool");

     // return *long_at_addr(which);

     u8 tmp = Bytes::get_native_u8((address)&base()[which]);

     return *((jlong*)&tmp);

   }

   jfloat float_at(int which) {

     assert(tag_at(which).is_float(), "Corrupted constant pool");

     return *float_at_addr(which);

   }

   jdouble double_at(int which) {

     assert(tag_at(which).is_double(), "Corrupted constant pool");

     u8 tmp = Bytes::get_native_u8((address)&base()[which]);

     return *((jdouble*)&tmp);

   }

   symbolOop symbol_at(int which) {

     assert(tag_at(which).is_utf8(), "Corrupted constant pool");

     return symbolOop(*obj_at_addr(which));

   }

   oop string_at(int which, TRAPS) {

     constantPoolHandle h_this(THREAD, this);

     return string_at_impl(h_this, which, CHECK_NULL);

   }

   oop object_at(int which) {

     assert(tag_at(which).is_object(), "Corrupted constant pool");

     return *obj_at_addr(which);

   }

   // A "pseudo-string" is an non-string oop that has found is way into

   // a String entry.

   // Under AnonymousClasses this can happen if the user patches a live

   // object into a CONSTANT_String entry of an anonymous class.

   // Method oops internally created for method handles may also

   // use pseudo-strings to link themselves to related metaobjects.

   bool is_pseudo_string_at(int which);

   oop pseudo_string_at(int which) {

     assert(tag_at(which).is_string(), "Corrupted constant pool");

     return *obj_at_addr(which);

   }

   void pseudo_string_at_put(int which, oop x) {

     assert(AnonymousClasses, "");

     set_pseudo_string();        // mark header

     assert(tag_at(which).is_string() || tag_at(which).is_unresolved_string(), "Corrupted constant pool");

     string_at_put(which, x);    // this works just fine

   }

   // only called when we are sure a string entry is already resolved (via an

   // earlier string_at call.

   oop resolved_string_at(int which) {

     assert(tag_at(which).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.

     return (oop)OrderAccess::load_ptr_acquire(obj_at_addr(which));

   }

   // This method should only be used with a cpool lock or during parsing or gc

   symbolOop unresolved_string_at(int which) {    // Temporary until actual use

     symbolOop s = symbolOop((oop)OrderAccess::load_ptr_acquire(obj_at_addr(which)));

     // check that the string is still unresolved.

     assert(tag_at(which).is_unresolved_string(), "Corrupted constant pool");

     return s;

   }

   // 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 symbolOops

   // or vice versa.

   // Caller is responsible for checking for pseudo-strings.

   char* string_at_noresolve(int which);

   jint name_and_type_at(int which) {

     assert(tag_at(which).is_name_and_type(), "Corrupted constant pool");

     return *int_at_addr(which);

   }

   int method_handle_ref_kind_at(int which) {

     assert(tag_at(which).is_method_handle(), "Corrupted constant pool");

     return extract_low_short_from_int(*int_at_addr(which));  // mask out unwanted ref_index bits

   }

   int method_handle_index_at(int which) {

     assert(tag_at(which).is_method_handle(), "Corrupted constant pool");

     return extract_high_short_from_int(*int_at_addr(which));  // shift out unwanted ref_kind bits

   }

   int method_type_index_at(int which) {

     assert(tag_at(which).is_method_type(), "Corrupted constant pool");

     return *int_at_addr(which);

   }

   // Derived queries:

   symbolOop method_handle_name_ref_at(int which) {

     int member = method_handle_index_at(which);

     return impl_name_ref_at(member, true);

   }

   symbolOop method_handle_signature_ref_at(int which) {

     int member = method_handle_index_at(which);

     return impl_signature_ref_at(member, true);

   }

   int method_handle_klass_index_at(int which) {

     int member = method_handle_index_at(which);

     return impl_klass_ref_index_at(member, true);

   }

   symbolOop method_type_signature_at(int which) {

     int sym = method_type_index_at(which);

     return symbol_at(sym);

   }

   int invoke_dynamic_bootstrap_method_ref_index_at(int which) {

     assert(tag_at(which).is_invoke_dynamic(), "Corrupted constant pool");

     jint ref_index = *int_at_addr(which);

     return extract_low_short_from_int(ref_index);

   }

   int invoke_dynamic_name_and_type_ref_index_at(int which) {

     assert(tag_at(which).is_invoke_dynamic(), "Corrupted constant pool");

     jint ref_index = *int_at_addr(which);

     return extract_high_short_from_int(ref_index);

   }

   // 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 constant pool cache indices.

   // The routine remap_instruction_operand_from_cache 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.

   // FIXME: Consider renaming these with a prefix "cached_" to make the distinction clear.

   // In a few cases (the verifier) there are uses before a cpcache has been built,

   // which are handled by a dynamic check in remap_instruction_operand_from_cache.

   // FIXME: Remove the dynamic check, and adjust all callers to specify the correct mode.

   // Lookup for entries consisting of (klass_index, name_and_type index)

   klassOop klass_ref_at(int which, TRAPS);

   symbolOop klass_ref_at_noresolve(int which);

   symbolOop name_ref_at(int which)                { return impl_name_ref_at(which, false); }

   symbolOop signature_ref_at(int which)           { return impl_signature_ref_at(which, false); }

   int klass_ref_index_at(int which)               { return impl_klass_ref_index_at(which, false); }

   int name_and_type_ref_index_at(int which)       { return impl_name_and_type_ref_index_at(which, false); }

   // Lookup for entries consisting of (name_index, signature_index)

   int name_ref_index_at(int which_nt);            // ==  low-order jshort of name_and_type_at(which_nt)

   int signature_ref_index_at(int which_nt);       // == high-order jshort of name_and_type_at(which_nt)

   BasicType basic_type_for_signature_at(int which);

   // 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);

   }

   // Resolve late bound constants.

   oop resolve_constant_at(int index, TRAPS) {

     constantPoolHandle h_this(THREAD, this);

     return resolve_constant_at_impl(h_this, index, -1, THREAD);

   }

   oop resolve_cached_constant_at(int cache_index, TRAPS) {

     constantPoolHandle h_this(THREAD, this);

     return resolve_constant_at_impl(h_this, -1, cache_index, THREAD);

   }

   // Klass name matches name at offset

   bool klass_name_at_matches(instanceKlassHandle k, int which);

   // 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();

   }

   static int header_size()             { return sizeof(constantPoolOopDesc)/HeapWordSize; }

   static int object_size(int length)   { return align_object_size(header_size() + length); }

   int object_size()                    { return object_size(length()); }

   bool is_conc_safe()                  { return _is_conc_safe; }

   void set_is_conc_safe(bool v)        { _is_conc_safe = v; }

   friend class constantPoolKlass;

   friend class ClassFileParser;

   friend class SystemDictionary;

   // Used by compiler to prevent classloading.

   static klassOop klass_at_if_loaded          (constantPoolHandle this_oop, int which);

   static klassOop klass_ref_at_if_loaded      (constantPoolHandle this_oop, int which);

   // Same as above - but does LinkResolving.

   static klassOop klass_ref_at_if_loaded_check(constantPoolHandle this_oop, int which, TRAPS);

   // 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.

   symbolOop uncached_klass_ref_at_noresolve(int which);

   symbolOop uncached_name_ref_at(int which)                 { return impl_name_ref_at(which, true); }

   symbolOop uncached_signature_ref_at(int which)            { return impl_signature_ref_at(which, true); }

   int       uncached_klass_ref_index_at(int which)          { return impl_klass_ref_index_at(which, true); }

   int       uncached_name_and_type_ref_index_at(int which)  { return impl_name_and_type_ref_index_at(which, true); }

   // Sharing

   int pre_resolve_shared_klasses(TRAPS);

   void shared_symbols_iterate(OopClosure* closure0);

   void shared_tags_iterate(OopClosure* closure0);

   void shared_strings_iterate(OopClosure* closure0);

   // Debugging

   const char* printable_name_at(int which) PRODUCT_RETURN0;

 #ifdef ASSERT

   enum { CPCACHE_INDEX_TAG = 0x10000 };  // helps keep CP cache indices distinct from CP indices

 #else

   enum { CPCACHE_INDEX_TAG = 0 };        // in product mode, this zero value is a no-op

 #endif //ASSERT

  private:

   symbolOop impl_name_ref_at(int which, bool uncached);

   symbolOop impl_signature_ref_at(int which, bool uncached);

   int       impl_klass_ref_index_at(int which, bool uncached);

   int       impl_name_and_type_ref_index_at(int which, bool uncached);

   int remap_instruction_operand_from_cache(int operand);  // operand must be biased by CPCACHE_INDEX_TAG

   // Used while constructing constant pool (only by ClassFileParser)

   jint klass_index_at(int which) {

     assert(tag_at(which).is_klass_index(), "Corrupted constant pool");

     return *int_at_addr(which);

   }

   jint string_index_at(int which) {

     assert(tag_at(which).is_string_index(), "Corrupted constant pool");

     return *int_at_addr(which);

   }

   // Performs the LinkResolver checks

   static void verify_constant_pool_resolve(constantPoolHandle this_oop, KlassHandle klass, TRAPS);

   // Implementation of methods that needs an exposed 'this' pointer, in order to

   // handle GC while executing the method

   static klassOop klass_at_impl(constantPoolHandle this_oop, int which, TRAPS);

   static oop string_at_impl(constantPoolHandle this_oop, int which, TRAPS);

   // Resolve string constants (to prevent allocation during compilation)

   static void resolve_string_constants_impl(constantPoolHandle this_oop, TRAPS);

   static oop resolve_constant_at_impl(constantPoolHandle this_oop, int index, int cache_index, TRAPS);

  public:

   // Merging constantPoolOop support:

   bool compare_entry_to(int index1, constantPoolHandle cp2, int index2, TRAPS);

   void copy_cp_to(int start_i, int end_i, constantPoolHandle to_cp, int to_i,

     TRAPS);

   void copy_entry_to(int from_i, constantPoolHandle to_cp, int to_i, TRAPS);

   int  find_matching_entry(int pattern_i, constantPoolHandle search_cp, TRAPS);

   int  orig_length() const                { return _orig_length; }

   void set_orig_length(int orig_length)   { _orig_length = orig_length; }

   // JVMTI accesss - GetConstantPool, RetransformClasses, ...

   friend class JvmtiConstantPoolReconstituter;

  private:

   jint cpool_entry_size(jint idx);

   jint hash_entries_to(SymbolHashMap *symmap, SymbolHashMap *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,

                         SymbolHashMap* tbl,

                         unsigned char *bytes);

 };

 class SymbolHashMapEntry : public CHeapObj {

  private:

   unsigned int        _hash;   // 32-bit hash for item

   SymbolHashMapEntry* _next;   // Next element in the linked list for this bucket

   symbolOop           _symbol; // 1-st part of the mapping: symbol => value

   u2                  _value;  // 2-nd part of the mapping: symbol => value

  public:

   unsigned   int hash() const             { return _hash;   }

   void       set_hash(unsigned int hash)  { _hash = hash;   }

   SymbolHashMapEntry* next() const        { return _next;   }

   void set_next(SymbolHashMapEntry* next) { _next = next;   }

   symbolOop  symbol() const               { return _symbol; }

   void       set_symbol(symbolOop sym)    { _symbol = sym;  }

   u2         value() const                {  return _value; }

   void       set_value(u2 value)          { _value = value; }

   SymbolHashMapEntry(unsigned int hash, symbolOop symbol, u2 value)

     : _hash(hash), _symbol(symbol), _value(value), _next(NULL) {}

 }; // End SymbolHashMapEntry class

 class SymbolHashMapBucket : public CHeapObj {

 private:

   SymbolHashMapEntry*    _entry;

 public:

   SymbolHashMapEntry* entry() const         {  return _entry; }

   void set_entry(SymbolHashMapEntry* entry) { _entry = entry; }

   void clear()                              { _entry = NULL;  }

 }; // End SymbolHashMapBucket class

 class SymbolHashMap: public CHeapObj {

  private:

   // Default number of entries in the table

   enum SymbolHashMap_Constants {

     _Def_HashMap_Size = 256

   };

   int                   _table_size;

   SymbolHashMapBucket*  _buckets;

   void initialize_table(int table_size) {

     _table_size = table_size;

     _buckets = NEW_C_HEAP_ARRAY(SymbolHashMapBucket, table_size);

     for (int index = 0; index < table_size; index++) {

       _buckets[index].clear();

     }

   }

  public:

   int table_size() const        { return _table_size; }

   SymbolHashMap()               { initialize_table(_Def_HashMap_Size); }

   SymbolHashMap(int table_size) { initialize_table(table_size); }

   // hash P(31) from Kernighan & Ritchie

   static unsigned int compute_hash(const char* str, int len) {

     unsigned int hash = 0;

     while (len-- > 0) {

       hash = 31*hash + (unsigned) *str;

       str++;

     }

     return hash;

   }

   SymbolHashMapEntry* bucket(int i) {

     return _buckets[i].entry();

   }

   void add_entry(symbolOop sym, u2 value);

   SymbolHashMapEntry* find_entry(symbolOop sym);

   u2 symbol_to_value(symbolOop sym) {

     SymbolHashMapEntry *entry = find_entry(sym);

     return (entry == NULL) ? 0 : entry->value();

   }

   ~SymbolHashMap() {

     SymbolHashMapEntry* next;

     for (int i = 0; i < _table_size; i++) {

       for (SymbolHashMapEntry* cur = bucket(i); cur != NULL; cur = next) {

         next = cur->next();

         delete(cur);

       }

     }

     delete _buckets;

   }

 }; // End SymbolHashMap class