281 lines
8.4 KiB
C++
281 lines
8.4 KiB
C++
/*
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* Copyright 2003-2005 Sun Microsystems, Inc. All Rights Reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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* CA 95054 USA or visit www.sun.com if you need additional information or
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* have any questions.
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*
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*/
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// This is a generic hashtable, designed to be used for the symbol
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// and string tables.
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//
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// It is implemented as an open hash table with a fixed number of buckets.
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//
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// %note:
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// - TableEntrys are allocated in blocks to reduce the space overhead.
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class BasicHashtableEntry : public CHeapObj {
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friend class VMStructs;
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private:
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unsigned int _hash; // 32-bit hash for item
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// Link to next element in the linked list for this bucket. EXCEPT
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// bit 0 set indicates that this entry is shared and must not be
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// unlinked from the table. Bit 0 is set during the dumping of the
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// archive. Since shared entries are immutable, _next fields in the
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// shared entries will not change. New entries will always be
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// unshared and since pointers are align, bit 0 will always remain 0
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// with no extra effort.
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BasicHashtableEntry* _next;
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// Windows IA64 compiler requires subclasses to be able to access these
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protected:
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// Entry objects should not be created, they should be taken from the
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// free list with BasicHashtable.new_entry().
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BasicHashtableEntry() { ShouldNotReachHere(); }
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// Entry objects should not be destroyed. They should be placed on
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// the free list instead with BasicHashtable.free_entry().
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~BasicHashtableEntry() { ShouldNotReachHere(); }
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public:
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unsigned int hash() const { return _hash; }
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void set_hash(unsigned int hash) { _hash = hash; }
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unsigned int* hash_addr() { return &_hash; }
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static BasicHashtableEntry* make_ptr(BasicHashtableEntry* p) {
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return (BasicHashtableEntry*)((intptr_t)p & -2);
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}
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BasicHashtableEntry* next() const {
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return make_ptr(_next);
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}
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void set_next(BasicHashtableEntry* next) {
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_next = next;
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}
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BasicHashtableEntry** next_addr() {
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return &_next;
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}
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bool is_shared() const {
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return ((intptr_t)_next & 1) != 0;
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}
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void set_shared() {
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_next = (BasicHashtableEntry*)((intptr_t)_next | 1);
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}
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};
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class HashtableEntry : public BasicHashtableEntry {
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friend class VMStructs;
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private:
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oop _literal; // ref to item in table.
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public:
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// Literal
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oop literal() const { return _literal; }
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oop* literal_addr() { return &_literal; }
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void set_literal(oop s) { _literal = s; }
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HashtableEntry* next() const {
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return (HashtableEntry*)BasicHashtableEntry::next();
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}
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HashtableEntry** next_addr() {
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return (HashtableEntry**)BasicHashtableEntry::next_addr();
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}
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};
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class HashtableBucket : public CHeapObj {
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friend class VMStructs;
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private:
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// Instance variable
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BasicHashtableEntry* _entry;
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public:
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// Accessing
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void clear() { _entry = NULL; }
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// The following methods use order access methods to avoid race
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// conditions in multiprocessor systems.
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BasicHashtableEntry* get_entry() const;
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void set_entry(BasicHashtableEntry* l);
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// The following method is not MT-safe and must be done under lock.
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BasicHashtableEntry** entry_addr() { return &_entry; }
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};
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class BasicHashtable : public CHeapObj {
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friend class VMStructs;
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public:
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BasicHashtable(int table_size, int entry_size);
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BasicHashtable(int table_size, int entry_size,
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HashtableBucket* buckets, int number_of_entries);
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// Sharing support.
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void copy_buckets(char** top, char* end);
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void copy_table(char** top, char* end);
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// Bucket handling
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int hash_to_index(unsigned int full_hash) {
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int h = full_hash % _table_size;
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assert(h >= 0 && h < _table_size, "Illegal hash value");
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return h;
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}
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// Reverse the order of elements in each of the buckets.
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void reverse();
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private:
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// Instance variables
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int _table_size;
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HashtableBucket* _buckets;
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BasicHashtableEntry* _free_list;
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char* _first_free_entry;
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char* _end_block;
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int _entry_size;
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int _number_of_entries;
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protected:
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#ifdef ASSERT
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int _lookup_count;
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int _lookup_length;
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void verify_lookup_length(double load);
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#endif
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void initialize(int table_size, int entry_size, int number_of_entries);
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// Accessor
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int entry_size() const { return _entry_size; }
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int table_size() { return _table_size; }
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// The following method is MT-safe and may be used with caution.
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BasicHashtableEntry* bucket(int i);
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// The following method is not MT-safe and must be done under lock.
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BasicHashtableEntry** bucket_addr(int i) { return _buckets[i].entry_addr(); }
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// Table entry management
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BasicHashtableEntry* new_entry(unsigned int hashValue);
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public:
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void set_entry(int index, BasicHashtableEntry* entry);
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void add_entry(int index, BasicHashtableEntry* entry);
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void free_entry(BasicHashtableEntry* entry);
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int number_of_entries() { return _number_of_entries; }
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void verify() PRODUCT_RETURN;
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};
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class Hashtable : public BasicHashtable {
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friend class VMStructs;
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public:
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Hashtable(int table_size, int entry_size)
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: BasicHashtable(table_size, entry_size) { }
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Hashtable(int table_size, int entry_size,
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HashtableBucket* buckets, int number_of_entries)
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: BasicHashtable(table_size, entry_size, buckets, number_of_entries) { }
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// Invoke "f->do_oop" on the locations of all oops in the table.
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void oops_do(OopClosure* f);
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// Debugging
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void print() PRODUCT_RETURN;
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// GC support
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// Delete pointers to otherwise-unreachable objects.
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void unlink(BoolObjectClosure* cl);
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// Reverse the order of elements in each of the buckets. Hashtable
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// entries which refer to objects at a lower address than 'boundary'
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// are separated from those which refer to objects at higher
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// addresses, and appear first in the list.
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void reverse(void* boundary = NULL);
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protected:
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static unsigned int hash_symbol(const char* s, int len);
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unsigned int compute_hash(symbolHandle name) {
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return (unsigned int) name->identity_hash();
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}
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int index_for(symbolHandle name) {
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return hash_to_index(compute_hash(name));
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}
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// Table entry management
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HashtableEntry* new_entry(unsigned int hashValue, oop obj);
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// The following method is MT-safe and may be used with caution.
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HashtableEntry* bucket(int i) {
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return (HashtableEntry*)BasicHashtable::bucket(i);
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}
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// The following method is not MT-safe and must be done under lock.
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HashtableEntry** bucket_addr(int i) {
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return (HashtableEntry**)BasicHashtable::bucket_addr(i);
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}
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};
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// Verions of hashtable where two handles are used to compute the index.
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class TwoOopHashtable : public Hashtable {
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friend class VMStructs;
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protected:
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TwoOopHashtable(int table_size, int entry_size)
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: Hashtable(table_size, entry_size) {}
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TwoOopHashtable(int table_size, int entry_size, HashtableBucket* t,
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int number_of_entries)
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: Hashtable(table_size, entry_size, t, number_of_entries) {}
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public:
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unsigned int compute_hash(symbolHandle name, Handle loader) {
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// Be careful with identity_hash(), it can safepoint and if this
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// were one expression, the compiler could choose to unhandle each
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// oop before calling identity_hash() for either of them. If the first
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// causes a GC, the next would fail.
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unsigned int name_hash = name->identity_hash();
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unsigned int loader_hash = loader.is_null() ? 0 : loader->identity_hash();
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return name_hash ^ loader_hash;
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}
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int index_for(symbolHandle name, Handle loader) {
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return hash_to_index(compute_hash(name, loader));
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}
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};
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