/*
* Copyright 2003-2005 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
* CA 95054 USA or visit www.sun.com if you need additional information or
* have any questions.
*
*/
// 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:
// - TableEntrys are allocated in blocks to reduce the space overhead.
class BasicHashtableEntry : public CHeapObj {
friend class VMStructs;
private:
unsigned int _hash; // 32-bit hash for item
// Link to next element in the linked list for this bucket. EXCEPT
// bit 0 set indicates that this entry is shared and must not be
// unlinked from the table. Bit 0 is set during the dumping of the
// archive. Since shared entries are immutable, _next fields in the
// shared entries will not change. New entries will always be
// unshared and since pointers are align, bit 0 will always remain 0
// with no extra effort.
BasicHashtableEntry* _next;
// Windows IA64 compiler requires subclasses to be able to access these
protected:
// Entry objects should not be created, they should be taken from the
// free list with BasicHashtable.new_entry().
BasicHashtableEntry() { ShouldNotReachHere(); }
// Entry objects should not be destroyed. They should be placed on
// the free list instead with BasicHashtable.free_entry().
~BasicHashtableEntry() { ShouldNotReachHere(); }
public:
unsigned int hash() const { return _hash; }
void set_hash(unsigned int hash) { _hash = hash; }
unsigned int* hash_addr() { return &_hash; }
static BasicHashtableEntry* make_ptr(BasicHashtableEntry* p) {
return (BasicHashtableEntry*)((intptr_t)p & -2);
}
BasicHashtableEntry* next() const {
return make_ptr(_next);
}
void set_next(BasicHashtableEntry* next) {
_next = next;
}
BasicHashtableEntry** next_addr() {
return &_next;
}
bool is_shared() const {
return ((intptr_t)_next & 1) != 0;
}
void set_shared() {
_next = (BasicHashtableEntry*)((intptr_t)_next | 1);
}
};
class HashtableEntry : public BasicHashtableEntry {
friend class VMStructs;
private:
oop _literal; // ref to item in table.
public:
// Literal
oop literal() const { return _literal; }
oop* literal_addr() { return &_literal; }
void set_literal(oop s) { _literal = s; }
HashtableEntry* next() const {
return (HashtableEntry*)BasicHashtableEntry::next();
}
HashtableEntry** next_addr() {
return (HashtableEntry**)BasicHashtableEntry::next_addr();
}
};
class HashtableBucket : public CHeapObj {
friend class VMStructs;
private:
// Instance variable
BasicHashtableEntry* _entry;
public:
// Accessing
void clear() { _entry = NULL; }
// The following methods use order access methods to avoid race
// conditions in multiprocessor systems.
BasicHashtableEntry* get_entry() const;
void set_entry(BasicHashtableEntry* l);
// The following method is not MT-safe and must be done under lock.
BasicHashtableEntry** entry_addr() { return &_entry; }
};
class BasicHashtable : public CHeapObj {
friend class VMStructs;
public:
BasicHashtable(int table_size, int entry_size);
BasicHashtable(int table_size, int entry_size,
HashtableBucket* buckets, int number_of_entries);
// Sharing support.
void copy_buckets(char** top, char* end);
void copy_table(char** top, char* end);
// Bucket handling
int hash_to_index(unsigned int full_hash) {
int h = full_hash % _table_size;
assert(h >= 0 && h < _table_size, "Illegal hash value");
return h;
}
// Reverse the order of elements in each of the buckets.
void reverse();
private:
// Instance variables
int _table_size;
HashtableBucket* _buckets;
BasicHashtableEntry* _free_list;
char* _first_free_entry;
char* _end_block;
int _entry_size;
int _number_of_entries;
protected:
#ifdef ASSERT
int _lookup_count;
int _lookup_length;
void verify_lookup_length(double load);
#endif
void initialize(int table_size, int entry_size, int number_of_entries);
// Accessor
int entry_size() const { return _entry_size; }
int table_size() { return _table_size; }
// The following method is MT-safe and may be used with caution.
BasicHashtableEntry* bucket(int i);
// The following method is not MT-safe and must be done under lock.
BasicHashtableEntry** bucket_addr(int i) { return _buckets[i].entry_addr(); }
// Table entry management
BasicHashtableEntry* new_entry(unsigned int hashValue);
public:
void set_entry(int index, BasicHashtableEntry* entry);
void add_entry(int index, BasicHashtableEntry* entry);
void free_entry(BasicHashtableEntry* entry);
int number_of_entries() { return _number_of_entries; }
void verify() PRODUCT_RETURN;
};
class Hashtable : public BasicHashtable {
friend class VMStructs;
public:
Hashtable(int table_size, int entry_size)
: BasicHashtable(table_size, entry_size) { }
Hashtable(int table_size, int entry_size,
HashtableBucket* buckets, int number_of_entries)
: BasicHashtable(table_size, entry_size, buckets, number_of_entries) { }
// Invoke "f->do_oop" on the locations of all oops in the table.
void oops_do(OopClosure* f);
// Debugging
void print() PRODUCT_RETURN;
// GC support
// Delete pointers to otherwise-unreachable objects.
void unlink(BoolObjectClosure* cl);
// Reverse the order of elements in each of the buckets. Hashtable
// entries which refer to objects at a lower address than 'boundary'
// are separated from those which refer to objects at higher
// addresses, and appear first in the list.
void reverse(void* boundary = NULL);
protected:
static unsigned int hash_symbol(const char* s, int len);
unsigned int compute_hash(symbolHandle name) {
return (unsigned int) name->identity_hash();
}
int index_for(symbolHandle name) {
return hash_to_index(compute_hash(name));
}
// Table entry management
HashtableEntry* new_entry(unsigned int hashValue, oop obj);
// The following method is MT-safe and may be used with caution.
HashtableEntry* bucket(int i) {
return (HashtableEntry*)BasicHashtable::bucket(i);
}
// The following method is not MT-safe and must be done under lock.
HashtableEntry** bucket_addr(int i) {
return (HashtableEntry**)BasicHashtable::bucket_addr(i);
}
};
// Verions of hashtable where two handles are used to compute the index.
class TwoOopHashtable : public Hashtable {
friend class VMStructs;
protected:
TwoOopHashtable(int table_size, int entry_size)
: Hashtable(table_size, entry_size) {}
TwoOopHashtable(int table_size, int entry_size, HashtableBucket* t,
int number_of_entries)
: Hashtable(table_size, entry_size, t, number_of_entries) {}
public:
unsigned int compute_hash(symbolHandle name, Handle loader) {
// Be careful with identity_hash(), it can safepoint and if this
// were one expression, the compiler could choose to unhandle each
// oop before calling identity_hash() for either of them. If the first
// causes a GC, the next would fail.
unsigned int name_hash = name->identity_hash();
unsigned int loader_hash = loader.is_null() ? 0 : loader->identity_hash();
return name_hash ^ loader_hash;
}
int index_for(symbolHandle name, Handle loader) {
return hash_to_index(compute_hash(name, loader));
}
};