--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/classfile/symbolTable.hpp Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,272 @@
+/*
+ * Copyright (c) 1997, 2017, 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.
+ *
+ */
+
+#ifndef SHARE_VM_CLASSFILE_SYMBOLTABLE_HPP
+#define SHARE_VM_CLASSFILE_SYMBOLTABLE_HPP
+
+#include "memory/allocation.inline.hpp"
+#include "oops/symbol.hpp"
+#include "utilities/hashtable.hpp"
+
+// The symbol table holds all Symbol*s and corresponding interned strings.
+// Symbol*s and literal strings should be canonicalized.
+//
+// The interned strings are created lazily.
+//
+// It is implemented as an open hash table with a fixed number of buckets.
+//
+// %note:
+// - symbolTableEntrys are allocated in blocks to reduce the space overhead.
+
+class BoolObjectClosure;
+class outputStream;
+class SerializeClosure;
+
+// TempNewSymbol acts as a handle class in a handle/body idiom and is
+// responsible for proper resource management of the body (which is a Symbol*).
+// The body is resource managed by a reference counting scheme.
+// TempNewSymbol can therefore be used to properly hold a newly created or referenced
+// Symbol* temporarily in scope.
+//
+// Routines in SymbolTable will initialize the reference count of a Symbol* before
+// it becomes "managed" by TempNewSymbol instances. As a handle class, TempNewSymbol
+// needs to maintain proper reference counting in context of copy semantics.
+//
+// In SymbolTable, new_symbol() and lookup() will create a Symbol* if not already in the
+// symbol table and add to the symbol's reference count.
+// probe() and lookup_only() will increment the refcount if symbol is found.
+class TempNewSymbol : public StackObj {
+ Symbol* _temp;
+
+ public:
+ TempNewSymbol() : _temp(NULL) {}
+
+ // Conversion from a Symbol* to a TempNewSymbol.
+ // Does not increment the current reference count.
+ TempNewSymbol(Symbol *s) : _temp(s) {}
+
+ // Copy constructor increments reference count.
+ TempNewSymbol(const TempNewSymbol& rhs) : _temp(rhs._temp) {
+ if (_temp != NULL) {
+ _temp->increment_refcount();
+ }
+ }
+
+ // Assignment operator uses a c++ trick called copy and swap idiom.
+ // rhs is passed by value so within the scope of this method it is a copy.
+ // At method exit it contains the former value of _temp, triggering the correct refcount
+ // decrement upon destruction.
+ void operator=(TempNewSymbol rhs) {
+ Symbol* tmp = rhs._temp;
+ rhs._temp = _temp;
+ _temp = tmp;
+ }
+
+ // Decrement reference counter so it can go away if it's unused
+ ~TempNewSymbol() {
+ if (_temp != NULL) {
+ _temp->decrement_refcount();
+ }
+ }
+
+ // Symbol* conversion operators
+ Symbol* operator -> () const { return _temp; }
+ bool operator == (Symbol* o) const { return _temp == o; }
+ operator Symbol*() { return _temp; }
+};
+
+template <class T, class N> class CompactHashtable;
+
+class SymbolTable : public RehashableHashtable<Symbol*, mtSymbol> {
+ friend class VMStructs;
+ friend class ClassFileParser;
+
+private:
+ // The symbol table
+ static SymbolTable* _the_table;
+
+ // Set if one bucket is out of balance due to hash algorithm deficiency
+ static bool _needs_rehashing;
+ static bool _lookup_shared_first;
+
+ // For statistics
+ static int _symbols_removed;
+ static int _symbols_counted;
+
+ // shared symbol table.
+ static CompactHashtable<Symbol*, char> _shared_table;
+
+ Symbol* allocate_symbol(const u1* name, int len, bool c_heap, TRAPS); // Assumes no characters larger than 0x7F
+
+ // Adding elements
+ Symbol* basic_add(int index, u1* name, int len, unsigned int hashValue,
+ bool c_heap, TRAPS);
+ bool basic_add(ClassLoaderData* loader_data,
+ const constantPoolHandle& cp, int names_count,
+ const char** names, int* lengths, int* cp_indices,
+ unsigned int* hashValues, TRAPS);
+
+ static void new_symbols(ClassLoaderData* loader_data,
+ const constantPoolHandle& cp, int names_count,
+ const char** name, int* lengths,
+ int* cp_indices, unsigned int* hashValues,
+ TRAPS) {
+ add(loader_data, cp, names_count, name, lengths, cp_indices, hashValues, THREAD);
+ }
+
+ static Symbol* lookup_shared(const char* name, int len, unsigned int hash);
+ Symbol* lookup_dynamic(int index, const char* name, int len, unsigned int hash);
+ Symbol* lookup(int index, const char* name, int len, unsigned int hash);
+
+ SymbolTable()
+ : RehashableHashtable<Symbol*, mtSymbol>(SymbolTableSize, sizeof (HashtableEntry<Symbol*, mtSymbol>)) {}
+
+ SymbolTable(HashtableBucket<mtSymbol>* t, int number_of_entries)
+ : RehashableHashtable<Symbol*, mtSymbol>(SymbolTableSize, sizeof (HashtableEntry<Symbol*, mtSymbol>), t,
+ number_of_entries) {}
+
+ // Arena for permanent symbols (null class loader) that are never unloaded
+ static Arena* _arena;
+ static Arena* arena() { return _arena; } // called for statistics
+
+ static void initialize_symbols(int arena_alloc_size = 0);
+
+ static volatile int _parallel_claimed_idx;
+
+ typedef SymbolTable::BucketUnlinkContext BucketUnlinkContext;
+ // Release any dead symbols. Unlinked bucket entries are collected in the given
+ // context to be freed later.
+ // This allows multiple threads to work on the table at once.
+ static void buckets_unlink(int start_idx, int end_idx, BucketUnlinkContext* context);
+public:
+ enum {
+ symbol_alloc_batch_size = 8,
+ // Pick initial size based on java -version size measurements
+ symbol_alloc_arena_size = 360*K
+ };
+
+ // The symbol table
+ static SymbolTable* the_table() { return _the_table; }
+
+ // Size of one bucket in the string table. Used when checking for rollover.
+ static uint bucket_size() { return sizeof(HashtableBucket<mtSymbol>); }
+
+ static void create_table() {
+ assert(_the_table == NULL, "One symbol table allowed.");
+ _the_table = new SymbolTable();
+ initialize_symbols(symbol_alloc_arena_size);
+ }
+
+ static unsigned int hash_symbol(const char* s, int len);
+ static unsigned int hash_shared_symbol(const char* s, int len);
+
+ static Symbol* lookup(const char* name, int len, TRAPS);
+ // lookup only, won't add. Also calculate hash.
+ static Symbol* lookup_only(const char* name, int len, unsigned int& hash);
+ // Only copy to C string to be added if lookup failed.
+ static Symbol* lookup(const Symbol* sym, int begin, int end, TRAPS);
+
+ static void release(Symbol* sym);
+
+ // Look up the address of the literal in the SymbolTable for this Symbol*
+ static Symbol** lookup_symbol_addr(Symbol* sym);
+
+ // jchar (UTF16) version of lookups
+ static Symbol* lookup_unicode(const jchar* name, int len, TRAPS);
+ static Symbol* lookup_only_unicode(const jchar* name, int len, unsigned int& hash);
+
+ static void add(ClassLoaderData* loader_data,
+ const constantPoolHandle& cp, int names_count,
+ const char** names, int* lengths, int* cp_indices,
+ unsigned int* hashValues, TRAPS);
+
+ // Release any dead symbols
+ static void unlink() {
+ int processed = 0;
+ int removed = 0;
+ unlink(&processed, &removed);
+ }
+ static void unlink(int* processed, int* removed);
+ // Release any dead symbols, possibly parallel version
+ static void possibly_parallel_unlink(int* processed, int* removed);
+
+ // iterate over symbols
+ static void symbols_do(SymbolClosure *cl);
+ static void metaspace_pointers_do(MetaspaceClosure* it);
+
+ // Symbol creation
+ static Symbol* new_symbol(const char* utf8_buffer, int length, TRAPS) {
+ assert(utf8_buffer != NULL, "just checking");
+ return lookup(utf8_buffer, length, THREAD);
+ }
+ static Symbol* new_symbol(const char* name, TRAPS) {
+ return new_symbol(name, (int)strlen(name), THREAD);
+ }
+ static Symbol* new_symbol(const Symbol* sym, int begin, int end, TRAPS) {
+ assert(begin <= end && end <= sym->utf8_length(), "just checking");
+ return lookup(sym, begin, end, THREAD);
+ }
+
+ // Create a symbol in the arena for symbols that are not deleted
+ static Symbol* new_permanent_symbol(const char* name, TRAPS);
+
+ // Symbol lookup
+ static Symbol* lookup(int index, const char* name, int len, TRAPS);
+
+ // Needed for preloading classes in signatures when compiling.
+ // Returns the symbol is already present in symbol table, otherwise
+ // NULL. NO ALLOCATION IS GUARANTEED!
+ static Symbol* probe(const char* name, int len) {
+ unsigned int ignore_hash;
+ return lookup_only(name, len, ignore_hash);
+ }
+ static Symbol* probe_unicode(const jchar* name, int len) {
+ unsigned int ignore_hash;
+ return lookup_only_unicode(name, len, ignore_hash);
+ }
+
+ // Histogram
+ static void print_histogram() PRODUCT_RETURN;
+ static void print() PRODUCT_RETURN;
+
+ // Debugging
+ static void verify();
+ static void dump(outputStream* st, bool verbose=false);
+ static void read(const char* filename, TRAPS);
+
+ // Sharing
+ static void write_to_archive();
+ static void serialize(SerializeClosure* soc);
+ static u4 encode_shared(Symbol* sym);
+ static Symbol* decode_shared(u4 offset);
+
+ // Rehash the symbol table if it gets out of balance
+ static void rehash_table();
+ static bool needs_rehashing() { return _needs_rehashing; }
+ // Parallel chunked scanning
+ static void clear_parallel_claimed_index() { _parallel_claimed_idx = 0; }
+ static int parallel_claimed_index() { return _parallel_claimed_idx; }
+};
+
+#endif // SHARE_VM_CLASSFILE_SYMBOLTABLE_HPP