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 /*

  * Copyright (c) 2003, 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

  * questions.

  *

  */

 #include "precompiled.hpp"

 #include "memory/allocation.inline.hpp"

 #include "memory/resourceArea.hpp"

 #include "oops/oop.inline.hpp"

 #include "runtime/safepoint.hpp"

 #include "utilities/dtrace.hpp"

 #include "utilities/hashtable.hpp"

 #include "utilities/hashtable.inline.hpp"

 HS_DTRACE_PROBE_DECL4(hs_private, hashtable__new_entry,

   void*, unsigned int, oop, void*);

 // This is a generic hashtable, designed to be used for the symbol

 // and string tables.

 //

 // It is implemented as an open hash table with a fixed number of buckets.

 //

 // %note:

 //  - HashtableEntrys are allocated in blocks to reduce the space overhead.

 BasicHashtableEntry* BasicHashtable::new_entry(unsigned int hashValue) {

   BasicHashtableEntry* entry;

   if (_free_list) {

     entry = _free_list;

     _free_list = _free_list->next();

   } else {

     if (_first_free_entry + _entry_size >= _end_block) {

       int block_size = MIN2(512, MAX2((int)_table_size / 2, (int)_number_of_entries));

       int len = _entry_size * block_size;

       len = 1 << log2_intptr(len); // round down to power of 2

       assert(len >= _entry_size, "");

       _first_free_entry = NEW_C_HEAP_ARRAY(char, len);

       _end_block = _first_free_entry + len;

     }

     entry = (BasicHashtableEntry*)_first_free_entry;

     _first_free_entry += _entry_size;

   }

   assert(_entry_size % HeapWordSize == 0, "");

   entry->set_hash(hashValue);

   return entry;

 }

 HashtableEntry* Hashtable::new_entry(unsigned int hashValue, oop obj) {

   HashtableEntry* entry;

   entry = (HashtableEntry*)BasicHashtable::new_entry(hashValue);

   entry->set_literal(obj);   // clears literal string field

   HS_DTRACE_PROBE4(hs_private, hashtable__new_entry,

     this, hashValue, obj, entry);

   return entry;

 }

 // GC support

 void Hashtable::unlink(BoolObjectClosure* is_alive) {

   // Readers of the table are unlocked, so we should only be removing

   // entries at a safepoint.

   assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");

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

     for (HashtableEntry** p = bucket_addr(i); *p != NULL; ) {

       HashtableEntry* entry = *p;

       if (entry->is_shared()) {

         break;

       }

       assert(entry->literal() != NULL, "just checking");

       if (is_alive->do_object_b(entry->literal())) {

         p = entry->next_addr();

       } else {

         *p = entry->next();

         free_entry(entry);

       }

     }

   }

 }

 void Hashtable::oops_do(OopClosure* f) {

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

     HashtableEntry** p = bucket_addr(i);

     HashtableEntry* entry = bucket(i);

     while (entry != NULL) {

       f->do_oop(entry->literal_addr());

       // Did the closure remove the literal from the table?

       if (entry->literal() == NULL) {

         assert(!entry->is_shared(), "immutable hashtable entry?");

         *p = entry->next();

         free_entry(entry);

       } else {

         p = entry->next_addr();

       }

       entry = (HashtableEntry*)HashtableEntry::make_ptr(*p);

     }

   }

 }

 // Reverse the order of elements in the hash buckets.

 void BasicHashtable::reverse() {

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

     BasicHashtableEntry* new_list = NULL;

     BasicHashtableEntry* p = bucket(i);

     while (p != NULL) {

       BasicHashtableEntry* next = p->next();

       p->set_next(new_list);

       new_list = p;

       p = next;

     }

     *bucket_addr(i) = new_list;

   }

 }

 // Copy the table to the shared space.

 void BasicHashtable::copy_table(char** top, char* end) {

   // Dump the hash table entries.

   intptr_t *plen = (intptr_t*)(*top);

   *top += sizeof(*plen);

   int i;

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

     for (BasicHashtableEntry** p = _buckets[i].entry_addr();

                               *p != NULL;

                                p = (*p)->next_addr()) {

       if (*top + entry_size() > end) {

         warning("\nThe shared miscellaneous data space is not large "

                 "enough to \npreload requested classes.  Use "

                 "-XX:SharedMiscDataSize= to increase \nthe initial "

                 "size of the miscellaneous data space.\n");

         exit(2);

       }

       *p = (BasicHashtableEntry*)memcpy(*top, *p, entry_size());

       *top += entry_size();

     }

   }

   *plen = (char*)(*top) - (char*)plen - sizeof(*plen);

   // Set the shared bit.

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

     for (BasicHashtableEntry* p = bucket(i); p != NULL; p = p->next()) {

       p->set_shared();

     }

   }

 }

 // Reverse the order of elements in the hash buckets.

 void Hashtable::reverse(void* boundary) {

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

     HashtableEntry* high_list = NULL;

     HashtableEntry* low_list = NULL;

     HashtableEntry* last_low_entry = NULL;

     HashtableEntry* p = bucket(i);

     while (p != NULL) {

       HashtableEntry* next = p->next();

       if ((void*)p->literal() >= boundary) {

         p->set_next(high_list);

         high_list = p;

       } else {

         p->set_next(low_list);

         low_list = p;

         if (last_low_entry == NULL) {

           last_low_entry = p;

         }

       }

       p = next;

     }

     if (low_list != NULL) {

       *bucket_addr(i) = low_list;

       last_low_entry->set_next(high_list);

     } else {

       *bucket_addr(i) = high_list;

     }

   }

 }

 // Dump the hash table buckets.

 void BasicHashtable::copy_buckets(char** top, char* end) {

   intptr_t len = _table_size * sizeof(HashtableBucket);

   *(intptr_t*)(*top) = len;

   *top += sizeof(intptr_t);

   *(intptr_t*)(*top) = _number_of_entries;

   *top += sizeof(intptr_t);

   if (*top + len > end) {

     warning("\nThe shared miscellaneous data space is not large "

             "enough to \npreload requested classes.  Use "

             "-XX:SharedMiscDataSize= to increase \nthe initial "

             "size of the miscellaneous data space.\n");

     exit(2);

   }

   _buckets = (HashtableBucket*)memcpy(*top, _buckets, len);

   *top += len;

 }

 #ifndef PRODUCT

 void Hashtable::print() {

   ResourceMark rm;

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

     HashtableEntry* entry = bucket(i);

     while(entry != NULL) {

       tty->print("%d : ", i);

       entry->literal()->print();

       tty->cr();

       entry = entry->next();

     }

   }

 }

 void BasicHashtable::verify() {

   int count = 0;

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

     for (BasicHashtableEntry* p = bucket(i); p != NULL; p = p->next()) {

       ++count;

     }

   }

   assert(count == number_of_entries(), "number of hashtable entries incorrect");

 }

 #endif // PRODUCT

 #ifdef ASSERT

 void BasicHashtable::verify_lookup_length(double load) {

   if ((double)_lookup_length / (double)_lookup_count > load * 2.0) {

     warning("Performance bug: SystemDictionary lookup_count=%d "

             "lookup_length=%d average=%lf load=%f",

             _lookup_count, _lookup_length,

             (double) _lookup_length / _lookup_count, load);

   }

 }

 #endif