--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/src/share/vm/classfile/symbolTable.cpp Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,484 @@
+/*
+ * Copyright 1997-2006 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.
+ *
+ */
+
+# include "incls/_precompiled.incl"
+# include "incls/_symbolTable.cpp.incl"
+
+// --------------------------------------------------------------------------
+
+SymbolTable* SymbolTable::_the_table = NULL;
+
+// Lookup a symbol in a bucket.
+
+symbolOop SymbolTable::lookup(int index, const char* name,
+ int len, unsigned int hash) {
+ for (HashtableEntry* e = bucket(index); e != NULL; e = e->next()) {
+ if (e->hash() == hash) {
+ symbolOop sym = symbolOop(e->literal());
+ if (sym->equals(name, len)) {
+ return sym;
+ }
+ }
+ }
+ return NULL;
+}
+
+
+// We take care not to be blocking while holding the
+// SymbolTable_lock. Otherwise, the system might deadlock, since the
+// symboltable is used during compilation (VM_thread) The lock free
+// synchronization is simplified by the fact that we do not delete
+// entries in the symbol table during normal execution (only during
+// safepoints).
+
+symbolOop SymbolTable::lookup(const char* name, int len, TRAPS) {
+ unsigned int hashValue = hash_symbol(name, len);
+ int index = the_table()->hash_to_index(hashValue);
+
+ symbolOop s = the_table()->lookup(index, name, len, hashValue);
+
+ // Found
+ if (s != NULL) return s;
+
+ // Otherwise, add to symbol to table
+ return the_table()->basic_add(index, (u1*)name, len, hashValue, CHECK_NULL);
+}
+
+symbolOop SymbolTable::lookup(symbolHandle sym, int begin, int end, TRAPS) {
+ char* buffer;
+ int index, len;
+ unsigned int hashValue;
+ char* name;
+ {
+ debug_only(No_Safepoint_Verifier nsv;)
+
+ name = (char*)sym->base() + begin;
+ len = end - begin;
+ hashValue = hash_symbol(name, len);
+ index = the_table()->hash_to_index(hashValue);
+ symbolOop s = the_table()->lookup(index, name, len, hashValue);
+
+ // Found
+ if (s != NULL) return s;
+ }
+
+ // Otherwise, add to symbol to table. Copy to a C string first.
+ char stack_buf[128];
+ ResourceMark rm(THREAD);
+ if (len <= 128) {
+ buffer = stack_buf;
+ } else {
+ buffer = NEW_RESOURCE_ARRAY_IN_THREAD(THREAD, char, len);
+ }
+ for (int i=0; i<len; i++) {
+ buffer[i] = name[i];
+ }
+ // Make sure there is no safepoint in the code above since name can't move.
+ // We can't include the code in No_Safepoint_Verifier because of the
+ // ResourceMark.
+
+ return the_table()->basic_add(index, (u1*)buffer, len, hashValue, CHECK_NULL);
+}
+
+symbolOop SymbolTable::lookup_only(const char* name, int len,
+ unsigned int& hash) {
+ hash = hash_symbol(name, len);
+ int index = the_table()->hash_to_index(hash);
+
+ return the_table()->lookup(index, name, len, hash);
+}
+
+void SymbolTable::add(constantPoolHandle cp, int names_count,
+ const char** names, int* lengths, int* cp_indices,
+ unsigned int* hashValues, TRAPS) {
+ SymbolTable* table = the_table();
+ bool added = table->basic_add(cp, names_count, names, lengths,
+ cp_indices, hashValues, CHECK);
+ if (!added) {
+ // do it the hard way
+ for (int i=0; i<names_count; i++) {
+ int index = table->hash_to_index(hashValues[i]);
+ symbolOop sym = table->basic_add(index, (u1*)names[i], lengths[i],
+ hashValues[i], CHECK);
+ cp->symbol_at_put(cp_indices[i], sym);
+ }
+ }
+}
+
+// Needed for preloading classes in signatures when compiling.
+
+symbolOop SymbolTable::probe(const char* name, int len) {
+ unsigned int hashValue = hash_symbol(name, len);
+ int index = the_table()->hash_to_index(hashValue);
+ return the_table()->lookup(index, name, len, hashValue);
+}
+
+
+symbolOop SymbolTable::basic_add(int index, u1 *name, int len,
+ unsigned int hashValue, TRAPS) {
+ assert(!Universe::heap()->is_in_reserved(name) || GC_locker::is_active(),
+ "proposed name of symbol must be stable");
+
+ // We assume that lookup() has been called already, that it failed,
+ // and symbol was not found. We create the symbol here.
+ symbolKlass* sk = (symbolKlass*) Universe::symbolKlassObj()->klass_part();
+ symbolOop s_oop = sk->allocate_symbol(name, len, CHECK_NULL);
+ symbolHandle sym (THREAD, s_oop);
+
+ // Allocation must be done before grapping the SymbolTable_lock lock
+ MutexLocker ml(SymbolTable_lock, THREAD);
+
+ assert(sym->equals((char*)name, len), "symbol must be properly initialized");
+
+ // Since look-up was done lock-free, we need to check if another
+ // thread beat us in the race to insert the symbol.
+
+ symbolOop test = lookup(index, (char*)name, len, hashValue);
+ if (test != NULL) {
+ // A race occured and another thread introduced the symbol, this one
+ // will be dropped and collected.
+ return test;
+ }
+
+ HashtableEntry* entry = new_entry(hashValue, sym());
+ add_entry(index, entry);
+ return sym();
+}
+
+bool SymbolTable::basic_add(constantPoolHandle cp, int names_count,
+ const char** names, int* lengths,
+ int* cp_indices, unsigned int* hashValues,
+ TRAPS) {
+ symbolKlass* sk = (symbolKlass*) Universe::symbolKlassObj()->klass_part();
+ symbolOop sym_oops[symbol_alloc_batch_size];
+ bool allocated = sk->allocate_symbols(names_count, names, lengths,
+ sym_oops, CHECK_false);
+ if (!allocated) {
+ return false;
+ }
+ symbolHandle syms[symbol_alloc_batch_size];
+ int i;
+ for (i=0; i<names_count; i++) {
+ syms[i] = symbolHandle(THREAD, sym_oops[i]);
+ }
+
+ // Allocation must be done before grabbing the SymbolTable_lock lock
+ MutexLocker ml(SymbolTable_lock, THREAD);
+
+ for (i=0; i<names_count; i++) {
+ assert(syms[i]->equals(names[i], lengths[i]), "symbol must be properly initialized");
+ // Since look-up was done lock-free, we need to check if another
+ // thread beat us in the race to insert the symbol.
+ int index = hash_to_index(hashValues[i]);
+ symbolOop test = lookup(index, names[i], lengths[i], hashValues[i]);
+ if (test != NULL) {
+ // A race occured and another thread introduced the symbol, this one
+ // will be dropped and collected. Use test instead.
+ cp->symbol_at_put(cp_indices[i], test);
+ } else {
+ symbolOop sym = syms[i]();
+ HashtableEntry* entry = new_entry(hashValues[i], sym);
+ add_entry(index, entry);
+ cp->symbol_at_put(cp_indices[i], sym);
+ }
+ }
+
+ return true;
+}
+
+
+void SymbolTable::verify() {
+ for (int i = 0; i < the_table()->table_size(); ++i) {
+ HashtableEntry* p = the_table()->bucket(i);
+ for ( ; p != NULL; p = p->next()) {
+ symbolOop s = symbolOop(p->literal());
+ guarantee(s != NULL, "symbol is NULL");
+ s->verify();
+ guarantee(s->is_perm(), "symbol not in permspace");
+ unsigned int h = hash_symbol((char*)s->bytes(), s->utf8_length());
+ guarantee(p->hash() == h, "broken hash in symbol table entry");
+ guarantee(the_table()->hash_to_index(h) == i,
+ "wrong index in symbol table");
+ }
+ }
+}
+
+
+//---------------------------------------------------------------------------
+// Non-product code
+
+#ifndef PRODUCT
+
+void SymbolTable::print_histogram() {
+ MutexLocker ml(SymbolTable_lock);
+ const int results_length = 100;
+ int results[results_length];
+ int i,j;
+
+ // initialize results to zero
+ for (j = 0; j < results_length; j++) {
+ results[j] = 0;
+ }
+
+ int total = 0;
+ int max_symbols = 0;
+ int out_of_range = 0;
+ for (i = 0; i < the_table()->table_size(); i++) {
+ HashtableEntry* p = the_table()->bucket(i);
+ for ( ; p != NULL; p = p->next()) {
+ int counter = symbolOop(p->literal())->utf8_length();
+ total += counter;
+ if (counter < results_length) {
+ results[counter]++;
+ } else {
+ out_of_range++;
+ }
+ max_symbols = MAX2(max_symbols, counter);
+ }
+ }
+ tty->print_cr("Symbol Table:");
+ tty->print_cr("%8s %5d", "Total ", total);
+ tty->print_cr("%8s %5d", "Maximum", max_symbols);
+ tty->print_cr("%8s %3.2f", "Average",
+ ((float) total / (float) the_table()->table_size()));
+ tty->print_cr("%s", "Histogram:");
+ tty->print_cr(" %s %29s", "Length", "Number chains that length");
+ for (i = 0; i < results_length; i++) {
+ if (results[i] > 0) {
+ tty->print_cr("%6d %10d", i, results[i]);
+ }
+ }
+ int line_length = 70;
+ tty->print_cr("%s %30s", " Length", "Number chains that length");
+ for (i = 0; i < results_length; i++) {
+ if (results[i] > 0) {
+ tty->print("%4d", i);
+ for (j = 0; (j < results[i]) && (j < line_length); j++) {
+ tty->print("%1s", "*");
+ }
+ if (j == line_length) {
+ tty->print("%1s", "+");
+ }
+ tty->cr();
+ }
+ }
+ tty->print_cr(" %s %d: %d\n", "Number chains longer than",
+ results_length, out_of_range);
+}
+
+#endif // PRODUCT
+
+// --------------------------------------------------------------------------
+
+#ifdef ASSERT
+class StableMemoryChecker : public StackObj {
+ enum { _bufsize = wordSize*4 };
+
+ address _region;
+ jint _size;
+ u1 _save_buf[_bufsize];
+
+ int sample(u1* save_buf) {
+ if (_size <= _bufsize) {
+ memcpy(save_buf, _region, _size);
+ return _size;
+ } else {
+ // copy head and tail
+ memcpy(&save_buf[0], _region, _bufsize/2);
+ memcpy(&save_buf[_bufsize/2], _region + _size - _bufsize/2, _bufsize/2);
+ return (_bufsize/2)*2;
+ }
+ }
+
+ public:
+ StableMemoryChecker(const void* region, jint size) {
+ _region = (address) region;
+ _size = size;
+ sample(_save_buf);
+ }
+
+ bool verify() {
+ u1 check_buf[sizeof(_save_buf)];
+ int check_size = sample(check_buf);
+ return (0 == memcmp(_save_buf, check_buf, check_size));
+ }
+
+ void set_region(const void* region) { _region = (address) region; }
+};
+#endif
+
+
+// --------------------------------------------------------------------------
+
+
+// Compute the hash value for a java.lang.String object which would
+// contain the characters passed in. This hash value is used for at
+// least two purposes.
+//
+// (a) As the hash value used by the StringTable for bucket selection
+// and comparison (stored in the HashtableEntry structures). This
+// is used in the String.intern() method.
+//
+// (b) As the hash value used by the String object itself, in
+// String.hashCode(). This value is normally calculate in Java code
+// in the String.hashCode method(), but is precomputed for String
+// objects in the shared archive file.
+//
+// For this reason, THIS ALGORITHM MUST MATCH String.hashCode().
+
+int StringTable::hash_string(jchar* s, int len) {
+ unsigned h = 0;
+ while (len-- > 0) {
+ h = 31*h + (unsigned) *s;
+ s++;
+ }
+ return h;
+}
+
+
+StringTable* StringTable::_the_table = NULL;
+
+oop StringTable::lookup(int index, jchar* name,
+ int len, unsigned int hash) {
+ for (HashtableEntry* l = bucket(index); l != NULL; l = l->next()) {
+ if (l->hash() == hash) {
+ if (java_lang_String::equals(l->literal(), name, len)) {
+ return l->literal();
+ }
+ }
+ }
+ return NULL;
+}
+
+
+oop StringTable::basic_add(int index, Handle string_or_null, jchar* name,
+ int len, unsigned int hashValue, TRAPS) {
+ debug_only(StableMemoryChecker smc(name, len * sizeof(name[0])));
+ assert(!Universe::heap()->is_in_reserved(name) || GC_locker::is_active(),
+ "proposed name of symbol must be stable");
+
+ Handle string;
+ // try to reuse the string if possible
+ if (!string_or_null.is_null() && string_or_null()->is_perm()) {
+ string = string_or_null;
+ } else {
+ string = java_lang_String::create_tenured_from_unicode(name, len, CHECK_NULL);
+ }
+
+ // Allocation must be done before grapping the SymbolTable_lock lock
+ MutexLocker ml(StringTable_lock, THREAD);
+
+ assert(java_lang_String::equals(string(), name, len),
+ "string must be properly initialized");
+
+ // Since look-up was done lock-free, we need to check if another
+ // thread beat us in the race to insert the symbol.
+
+ oop test = lookup(index, name, len, hashValue); // calls lookup(u1*, int)
+ if (test != NULL) {
+ // Entry already added
+ return test;
+ }
+
+ HashtableEntry* entry = new_entry(hashValue, string());
+ add_entry(index, entry);
+ return string();
+}
+
+
+oop StringTable::lookup(symbolOop symbol) {
+ ResourceMark rm;
+ int length;
+ jchar* chars = symbol->as_unicode(length);
+ unsigned int hashValue = hash_string(chars, length);
+ int index = the_table()->hash_to_index(hashValue);
+ return the_table()->lookup(index, chars, length, hashValue);
+}
+
+
+oop StringTable::intern(Handle string_or_null, jchar* name,
+ int len, TRAPS) {
+ unsigned int hashValue = hash_string(name, len);
+ int index = the_table()->hash_to_index(hashValue);
+ oop string = the_table()->lookup(index, name, len, hashValue);
+
+ // Found
+ if (string != NULL) return string;
+
+ // Otherwise, add to symbol to table
+ return the_table()->basic_add(index, string_or_null, name, len,
+ hashValue, CHECK_NULL);
+}
+
+oop StringTable::intern(symbolOop symbol, TRAPS) {
+ if (symbol == NULL) return NULL;
+ ResourceMark rm(THREAD);
+ int length;
+ jchar* chars = symbol->as_unicode(length);
+ Handle string;
+ oop result = intern(string, chars, length, CHECK_NULL);
+ return result;
+}
+
+
+oop StringTable::intern(oop string, TRAPS)
+{
+ if (string == NULL) return NULL;
+ ResourceMark rm(THREAD);
+ int length;
+ Handle h_string (THREAD, string);
+ jchar* chars = java_lang_String::as_unicode_string(string, length);
+ oop result = intern(h_string, chars, length, CHECK_NULL);
+ return result;
+}
+
+
+oop StringTable::intern(const char* utf8_string, TRAPS) {
+ if (utf8_string == NULL) return NULL;
+ ResourceMark rm(THREAD);
+ int length = UTF8::unicode_length(utf8_string);
+ jchar* chars = NEW_RESOURCE_ARRAY(jchar, length);
+ UTF8::convert_to_unicode(utf8_string, chars, length);
+ Handle string;
+ oop result = intern(string, chars, length, CHECK_NULL);
+ return result;
+}
+
+void StringTable::verify() {
+ for (int i = 0; i < the_table()->table_size(); ++i) {
+ HashtableEntry* p = the_table()->bucket(i);
+ for ( ; p != NULL; p = p->next()) {
+ oop s = p->literal();
+ guarantee(s != NULL, "interned string is NULL");
+ guarantee(s->is_perm(), "interned string not in permspace");
+
+ int length;
+ jchar* chars = java_lang_String::as_unicode_string(s, length);
+ unsigned int h = hash_string(chars, length);
+ guarantee(p->hash() == h, "broken hash in string table entry");
+ guarantee(the_table()->hash_to_index(h) == i,
+ "wrong index in string table");
+ }
+ }
+}