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hotspot/src/share/vm/utilities/hashtable.cpp

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+/*
+ * 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.
+ *
+ */
+
+# include "incls/_precompiled.incl"
+# include "incls/_hashtable.cpp.incl"
+
+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 {
+    const int block_size = 500;
+    if (_first_free_entry == _end_block) {
+      int len = _entry_size * block_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;
+  }
+
+  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