hashtable.hpp revision 2112:3adec115d40d
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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_VM_UTILITIES_HASHTABLE_HPP 26#define SHARE_VM_UTILITIES_HASHTABLE_HPP 27 28#include "memory/allocation.hpp" 29#include "oops/oop.hpp" 30#include "oops/symbol.hpp" 31#include "runtime/handles.hpp" 32 33// This is a generic hashtable, designed to be used for the symbol 34// and string tables. 35// 36// It is implemented as an open hash table with a fixed number of buckets. 37// 38// %note: 39// - TableEntrys are allocated in blocks to reduce the space overhead. 40 41 42 43class BasicHashtableEntry : public CHeapObj { 44 friend class VMStructs; 45private: 46 unsigned int _hash; // 32-bit hash for item 47 48 // Link to next element in the linked list for this bucket. EXCEPT 49 // bit 0 set indicates that this entry is shared and must not be 50 // unlinked from the table. Bit 0 is set during the dumping of the 51 // archive. Since shared entries are immutable, _next fields in the 52 // shared entries will not change. New entries will always be 53 // unshared and since pointers are align, bit 0 will always remain 0 54 // with no extra effort. 55 BasicHashtableEntry* _next; 56 57 // Windows IA64 compiler requires subclasses to be able to access these 58protected: 59 // Entry objects should not be created, they should be taken from the 60 // free list with BasicHashtable.new_entry(). 61 BasicHashtableEntry() { ShouldNotReachHere(); } 62 // Entry objects should not be destroyed. They should be placed on 63 // the free list instead with BasicHashtable.free_entry(). 64 ~BasicHashtableEntry() { ShouldNotReachHere(); } 65 66public: 67 68 unsigned int hash() const { return _hash; } 69 void set_hash(unsigned int hash) { _hash = hash; } 70 unsigned int* hash_addr() { return &_hash; } 71 72 static BasicHashtableEntry* make_ptr(BasicHashtableEntry* p) { 73 return (BasicHashtableEntry*)((intptr_t)p & -2); 74 } 75 76 BasicHashtableEntry* next() const { 77 return make_ptr(_next); 78 } 79 80 void set_next(BasicHashtableEntry* next) { 81 _next = next; 82 } 83 84 BasicHashtableEntry** next_addr() { 85 return &_next; 86 } 87 88 bool is_shared() const { 89 return ((intptr_t)_next & 1) != 0; 90 } 91 92 void set_shared() { 93 _next = (BasicHashtableEntry*)((intptr_t)_next | 1); 94 } 95}; 96 97 98 99template <class T> class HashtableEntry : public BasicHashtableEntry { 100 friend class VMStructs; 101private: 102 T _literal; // ref to item in table. 103 104public: 105 // Literal 106 T literal() const { return _literal; } 107 T* literal_addr() { return &_literal; } 108 void set_literal(T s) { _literal = s; } 109 110 HashtableEntry* next() const { 111 return (HashtableEntry*)BasicHashtableEntry::next(); 112 } 113 HashtableEntry** next_addr() { 114 return (HashtableEntry**)BasicHashtableEntry::next_addr(); 115 } 116}; 117 118 119 120class HashtableBucket : public CHeapObj { 121 friend class VMStructs; 122private: 123 // Instance variable 124 BasicHashtableEntry* _entry; 125 126public: 127 // Accessing 128 void clear() { _entry = NULL; } 129 130 // The following methods use order access methods to avoid race 131 // conditions in multiprocessor systems. 132 BasicHashtableEntry* get_entry() const; 133 void set_entry(BasicHashtableEntry* l); 134 135 // The following method is not MT-safe and must be done under lock. 136 BasicHashtableEntry** entry_addr() { return &_entry; } 137}; 138 139 140class BasicHashtable : public CHeapObj { 141 friend class VMStructs; 142 143public: 144 BasicHashtable(int table_size, int entry_size); 145 BasicHashtable(int table_size, int entry_size, 146 HashtableBucket* buckets, int number_of_entries); 147 148 // Sharing support. 149 void copy_buckets(char** top, char* end); 150 void copy_table(char** top, char* end); 151 152 // Bucket handling 153 int hash_to_index(unsigned int full_hash) { 154 int h = full_hash % _table_size; 155 assert(h >= 0 && h < _table_size, "Illegal hash value"); 156 return h; 157 } 158 159 // Reverse the order of elements in each of the buckets. 160 void reverse(); 161 162 static unsigned int hash_symbol(const char* s, int len); 163 164private: 165 // Instance variables 166 int _table_size; 167 HashtableBucket* _buckets; 168 BasicHashtableEntry* _free_list; 169 char* _first_free_entry; 170 char* _end_block; 171 int _entry_size; 172 int _number_of_entries; 173 174protected: 175 176#ifdef ASSERT 177 int _lookup_count; 178 int _lookup_length; 179 void verify_lookup_length(double load); 180#endif 181 182 void initialize(int table_size, int entry_size, int number_of_entries); 183 184 // Accessor 185 int entry_size() const { return _entry_size; } 186 int table_size() { return _table_size; } 187 188 // The following method is MT-safe and may be used with caution. 189 BasicHashtableEntry* bucket(int i); 190 191 // The following method is not MT-safe and must be done under lock. 192 BasicHashtableEntry** bucket_addr(int i) { return _buckets[i].entry_addr(); } 193 194 // Table entry management 195 BasicHashtableEntry* new_entry(unsigned int hashValue); 196 197public: 198 void set_entry(int index, BasicHashtableEntry* entry); 199 200 void add_entry(int index, BasicHashtableEntry* entry); 201 202 void free_entry(BasicHashtableEntry* entry); 203 204 int number_of_entries() { return _number_of_entries; } 205 206 void verify() PRODUCT_RETURN; 207}; 208 209 210template <class T> class Hashtable : public BasicHashtable { 211 friend class VMStructs; 212 213public: 214 Hashtable(int table_size, int entry_size) 215 : BasicHashtable(table_size, entry_size) { } 216 217 Hashtable(int table_size, int entry_size, 218 HashtableBucket* buckets, int number_of_entries) 219 : BasicHashtable(table_size, entry_size, buckets, number_of_entries) { } 220 221 // Debugging 222 void print() PRODUCT_RETURN; 223 224 // Reverse the order of elements in each of the buckets. Hashtable 225 // entries which refer to objects at a lower address than 'boundary' 226 // are separated from those which refer to objects at higher 227 // addresses, and appear first in the list. 228 void reverse(void* boundary = NULL); 229 230protected: 231 232 unsigned int compute_hash(Symbol* name) { 233 return (unsigned int) name->identity_hash(); 234 } 235 236 int index_for(Symbol* name) { 237 return hash_to_index(compute_hash(name)); 238 } 239 240 // Table entry management 241 HashtableEntry<T>* new_entry(unsigned int hashValue, T obj); 242 243 // The following method is MT-safe and may be used with caution. 244 HashtableEntry<T>* bucket(int i) { 245 return (HashtableEntry<T>*)BasicHashtable::bucket(i); 246 } 247 248 // The following method is not MT-safe and must be done under lock. 249 HashtableEntry<T>** bucket_addr(int i) { 250 return (HashtableEntry<T>**)BasicHashtable::bucket_addr(i); 251 } 252}; 253 254 255// Verions of hashtable where two handles are used to compute the index. 256 257template <class T> class TwoOopHashtable : public Hashtable<T> { 258 friend class VMStructs; 259protected: 260 TwoOopHashtable(int table_size, int entry_size) 261 : Hashtable<T>(table_size, entry_size) {} 262 263 TwoOopHashtable(int table_size, int entry_size, HashtableBucket* t, 264 int number_of_entries) 265 : Hashtable<T>(table_size, entry_size, t, number_of_entries) {} 266 267public: 268 unsigned int compute_hash(Symbol* name, Handle loader) { 269 // Be careful with identity_hash(), it can safepoint and if this 270 // were one expression, the compiler could choose to unhandle each 271 // oop before calling identity_hash() for either of them. If the first 272 // causes a GC, the next would fail. 273 unsigned int name_hash = name->identity_hash(); 274 unsigned int loader_hash = loader.is_null() ? 0 : loader->identity_hash(); 275 return name_hash ^ loader_hash; 276 } 277 278 int index_for(Symbol* name, Handle loader) { 279 return this->hash_to_index(compute_hash(name, loader)); 280 } 281}; 282 283#endif // SHARE_VM_UTILITIES_HASHTABLE_HPP 284