1 /*

     2  * Copyright (c) 1997, 2013, 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_VM_CLASSFILE_STRINGTABLE_HPP

    26 #define SHARE_VM_CLASSFILE_STRINGTABLE_HPP

    27 

    28 #include "memory/allocation.inline.hpp"

    29 #include "utilities/hashtable.hpp"

    30 

    31 class StringTable : public Hashtable<oop, mtSymbol> {

    32   friend class VMStructs;

    33   friend class Symbol;

    34 

    35 private:

    36   // The string table

    37   static StringTable* _the_table;

    38 

    39   // Set if one bucket is out of balance due to hash algorithm deficiency

    40   static bool _needs_rehashing;

    41 

    42   // Claimed high water mark for parallel chunked scanning

    43   static volatile int _parallel_claimed_idx;

    44 

    45   static oop intern(Handle string_or_null, jchar* chars, int length, TRAPS);

    46   oop basic_add(int index, Handle string_or_null, jchar* name, int len,

    47                 unsigned int hashValue, TRAPS);

    48 

    49   oop lookup(int index, jchar* chars, int length, unsigned int hashValue);

    50 

    51   // Apply the give oop closure to the entries to the buckets

    52   // in the range [start_idx, end_idx).

    53   static void buckets_oops_do(OopClosure* f, int start_idx, int end_idx);

    54   // Unlink or apply the give oop closure to the entries to the buckets

    55   // in the range [start_idx, end_idx).

    56   static void buckets_unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f, int start_idx, int end_idx, int* processed, int* removed);

    57 

    58   StringTable() : Hashtable<oop, mtSymbol>((int)StringTableSize,

    59                               sizeof (HashtableEntry<oop, mtSymbol>)) {}

    60 

    61   StringTable(HashtableBucket<mtSymbol>* t, int number_of_entries)

    62     : Hashtable<oop, mtSymbol>((int)StringTableSize, sizeof (HashtableEntry<oop, mtSymbol>), t,

    63                      number_of_entries) {}

    64 public:

    65   // The string table

    66   static StringTable* the_table() { return _the_table; }

    67 

    68   // Size of one bucket in the string table.  Used when checking for rollover.

    69   static uint bucket_size() { return sizeof(HashtableBucket<mtSymbol>); }

    70 

    71   static void create_table() {

    72     assert(_the_table == NULL, "One string table allowed.");

    73     _the_table = new StringTable();

    74   }

    75 

    76   // GC support

    77   //   Delete pointers to otherwise-unreachable objects.

    78   static void unlink_or_oops_do(BoolObjectClosure* cl, OopClosure* f) {

    79     int processed = 0;

    80     int removed = 0;

    81     unlink_or_oops_do(cl, f, &processed, &removed);

    82   }

    83   static void unlink(BoolObjectClosure* cl) {

    84     int processed = 0;

    85     int removed = 0;

    86     unlink_or_oops_do(cl, NULL, &processed, &removed);

    87   }

    88   static void unlink_or_oops_do(BoolObjectClosure* cl, OopClosure* f, int* processed, int* removed);

    89   static void unlink(BoolObjectClosure* cl, int* processed, int* removed) {

    90     unlink_or_oops_do(cl, NULL, processed, removed);

    91   }

    92   // Serially invoke "f->do_oop" on the locations of all oops in the table.

    93   static void oops_do(OopClosure* f);

    94 

    95   // Possibly parallel versions of the above

    96   static void possibly_parallel_unlink_or_oops_do(BoolObjectClosure* cl, OopClosure* f, int* processed, int* removed);

    97   static void possibly_parallel_unlink(BoolObjectClosure* cl, int* processed, int* removed) {

    98     possibly_parallel_unlink_or_oops_do(cl, NULL, processed, removed);

    99   }

   100   static void possibly_parallel_oops_do(OopClosure* f);

   101 

   102   // Hashing algorithm, used as the hash value used by the

   103   //     StringTable for bucket selection and comparison (stored in the

   104   //     HashtableEntry structures).  This is used in the String.intern() method.

   105   static unsigned int hash_string(const jchar* s, int len);

   106 

   107   // Internal test.

   108   static void test_alt_hash() PRODUCT_RETURN;

   109 

   110   // Probing

   111   static oop lookup(Symbol* symbol);

   112   static oop lookup(jchar* chars, int length);

   113 

   114   // Interning

   115   static oop intern(Symbol* symbol, TRAPS);

   116   static oop intern(oop string, TRAPS);

   117   static oop intern(const char *utf8_string, TRAPS);

   118 

   119   // Debugging

   120   static void verify();

   121   static void dump(outputStream* st);

   122 

   123   enum VerifyMesgModes {

   124     _verify_quietly    = 0,

   125     _verify_with_mesgs = 1

   126   };

   127 

   128   enum VerifyRetTypes {

   129     _verify_pass          = 0,

   130     _verify_fail_continue = 1,

   131     _verify_fail_done     = 2

   132   };

   133 

   134   static VerifyRetTypes compare_entries(int bkt1, int e_cnt1,

   135                                         HashtableEntry<oop, mtSymbol>* e_ptr1,

   136                                         int bkt2, int e_cnt2,

   137                                         HashtableEntry<oop, mtSymbol>* e_ptr2);

   138   static VerifyRetTypes verify_entry(int bkt, int e_cnt,

   139                                      HashtableEntry<oop, mtSymbol>* e_ptr,

   140                                      VerifyMesgModes mesg_mode);

   141   static int verify_and_compare_entries();

   142 

   143   // Sharing

   144   static void copy_buckets(char** top, char*end) {

   145     the_table()->Hashtable<oop, mtSymbol>::copy_buckets(top, end);

   146   }

   147   static void copy_table(char** top, char*end) {

   148     the_table()->Hashtable<oop, mtSymbol>::copy_table(top, end);

   149   }

   150   static void reverse() {

   151     the_table()->Hashtable<oop, mtSymbol>::reverse();

   152   }

   153 

   154   // Rehash the symbol table if it gets out of balance

   155   static void rehash_table();

   156   static bool needs_rehashing() { return _needs_rehashing; }

   157 

   158   // Parallel chunked scanning

   159   static void clear_parallel_claimed_index() { _parallel_claimed_idx = 0; }

   160   static int parallel_claimed_index() { return _parallel_claimed_idx; }

   161 };

   162 #endif // SHARE_VM_CLASSFILE_STRINGTABLE_HPP