--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/share/vm/runtime/jniHandles.hpp	Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,212 @@
+/*
+ * Copyright 1998-2007 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.
+ *
+ */
+
+class JNIHandleBlock;
+
+
+// Interface for creating and resolving local/global JNI handles
+
+class JNIHandles : AllStatic {
+  friend class VMStructs;
+ private:
+  static JNIHandleBlock* _global_handles;             // First global handle block
+  static JNIHandleBlock* _weak_global_handles;        // First weak global handle block
+  static oop _deleted_handle;                         // Sentinel marking deleted handles
+
+ public:
+  // Resolve handle into oop
+  inline static oop resolve(jobject handle);
+  // Resolve externally provided handle into oop with some guards
+  inline static oop resolve_external_guard(jobject handle);
+  // Resolve handle into oop, result guaranteed not to be null
+  inline static oop resolve_non_null(jobject handle);
+
+  // Local handles
+  static jobject make_local(oop obj);
+  static jobject make_local(JNIEnv* env, oop obj);    // Fast version when env is known
+  static jobject make_local(Thread* thread, oop obj); // Even faster version when current thread is known
+  inline static void destroy_local(jobject handle);
+
+  // Global handles
+  static jobject make_global(Handle  obj);
+  static void destroy_global(jobject handle);
+
+  // Weak global handles
+  static jobject make_weak_global(Handle obj);
+  static void destroy_weak_global(jobject handle);
+
+  // jmethodID handling (as Weak global handles).
+  // Because the useful life-span of a jmethodID cannot be determined, once created they are
+  // never reclaimed.  The methods to which they refer, however, can be GC'ed away if the class
+  // is unloaded or if the method is made obsolete or deleted -- in these cases, the jmethodID
+  // refers to NULL (as is the case for any weak reference).
+  static jmethodID make_jmethod_id(methodHandle mh);
+  static void destroy_jmethod_id(jmethodID mid);
+  inline static methodOop resolve_jmethod_id(jmethodID mid);
+  inline static methodOop checked_resolve_jmethod_id(jmethodID mid); // NULL on invalid jmethodID
+  static void change_method_associated_with_jmethod_id(jmethodID jmid, methodHandle mh);
+
+  // Sentinel marking deleted handles in block. Note that we cannot store NULL as
+  // the sentinel, since clearing weak global JNI refs are done by storing NULL in
+  // the handle. The handle may not be reused before destroy_weak_global is called.
+  static oop deleted_handle()   { return _deleted_handle; }
+
+  // Initialization
+  static void initialize();
+
+  // Debugging
+  static void print_on(outputStream* st);
+  static void print()           { print_on(tty); }
+  static void verify();
+  static bool is_local_handle(Thread* thread, jobject handle);
+  static bool is_frame_handle(JavaThread* thr, jobject obj);
+  static bool is_global_handle(jobject handle);
+  static bool is_weak_global_handle(jobject handle);
+  static long global_handle_memory_usage();
+  static long weak_global_handle_memory_usage();
+
+  // Garbage collection support(global handles only, local handles are traversed from thread)
+  // Traversal of regular global handles
+  static void oops_do(OopClosure* f);
+  // Traversal of weak global handles. Unreachable oops are cleared.
+  static void weak_oops_do(BoolObjectClosure* is_alive, OopClosure* f);
+};
+
+
+
+// JNI handle blocks holding local/global JNI handles
+
+class JNIHandleBlock : public CHeapObj {
+  friend class VMStructs;
+ private:
+  enum SomeConstants {
+    block_size_in_oops  = 32                    // Number of handles per handle block
+  };
+
+  oop             _handles[block_size_in_oops]; // The handles
+  int             _top;                         // Index of next unused handle
+  JNIHandleBlock* _next;                        // Link to next block
+
+  // The following instance variables are only used by the first block in a chain.
+  // Having two types of blocks complicates the code and the space overhead in negligble.
+  JNIHandleBlock* _last;                        // Last block in use
+  JNIHandleBlock* _pop_frame_link;              // Block to restore on PopLocalFrame call
+  oop*            _free_list;                   // Handle free list
+  int             _allocate_before_rebuild;     // Number of blocks to allocate before rebuilding free list
+
+  #ifndef PRODUCT
+  JNIHandleBlock* _block_list_link;             // Link for list below
+  static JNIHandleBlock* _block_list;           // List of all allocated blocks (for debugging only)
+  #endif
+
+  static JNIHandleBlock* _block_free_list;      // Free list of currently unused blocks
+  static int      _blocks_allocated;            // For debugging/printing
+
+  // Fill block with bad_handle values
+  void zap();
+
+  // No more handles in the both the current and following blocks
+  void clear() { _top = 0; }
+
+  // Free list computation
+  void rebuild_free_list();
+
+ public:
+  // Handle allocation
+  jobject allocate_handle(oop obj);
+
+  // Block allocation and block free list management
+  static JNIHandleBlock* allocate_block(Thread* thread = NULL);
+  static void release_block(JNIHandleBlock* block, Thread* thread = NULL);
+
+  // JNI PushLocalFrame/PopLocalFrame support
+  JNIHandleBlock* pop_frame_link() const          { return _pop_frame_link; }
+  void set_pop_frame_link(JNIHandleBlock* block)  { _pop_frame_link = block; }
+
+  // Stub generator support
+  static int top_offset_in_bytes()                { return offset_of(JNIHandleBlock, _top); }
+
+  // Garbage collection support
+  // Traversal of regular handles
+  void oops_do(OopClosure* f);
+  // Traversal of weak handles. Unreachable oops are cleared.
+  void weak_oops_do(BoolObjectClosure* is_alive, OopClosure* f);
+
+  // Debugging
+  bool chain_contains(jobject handle) const;    // Does this block or following blocks contain handle
+  bool contains(jobject handle) const;          // Does this block contain handle
+  int length() const;                           // Length of chain starting with this block
+  long memory_usage() const;
+  #ifndef PRODUCT
+  static bool any_contains(jobject handle);     // Does any block currently in use contain handle
+  static void print_statistics();
+  #endif
+};
+
+
+inline oop JNIHandles::resolve(jobject handle) {
+  oop result = (handle == NULL ? (oop)NULL : *(oop*)handle);
+  assert(result != NULL || (handle == NULL || !CheckJNICalls || is_weak_global_handle(handle)), "Invalid value read from jni handle");
+  assert(result != badJNIHandle, "Pointing to zapped jni handle area");
+  return result;
+};
+
+
+inline oop JNIHandles::resolve_external_guard(jobject handle) {
+  if (handle == NULL) return NULL;
+  oop result = *(oop*)handle;
+  if (result == NULL || result == badJNIHandle) return NULL;
+  return result;
+};
+
+
+inline oop JNIHandles::resolve_non_null(jobject handle) {
+  assert(handle != NULL, "JNI handle should not be null");
+  oop result = *(oop*)handle;
+  assert(result != NULL, "Invalid value read from jni handle");
+  assert(result != badJNIHandle, "Pointing to zapped jni handle area");
+  // Don't let that private _deleted_handle object escape into the wild.
+  assert(result != deleted_handle(), "Used a deleted global handle.");
+  return result;
+};
+
+inline methodOop JNIHandles::resolve_jmethod_id(jmethodID mid) {
+  return (methodOop) resolve_non_null((jobject)mid);
+};
+
+inline methodOop JNIHandles::checked_resolve_jmethod_id(jmethodID mid) {
+  jobject handle = (jobject)mid;
+  if (is_weak_global_handle(handle)) {
+    return (methodOop) resolve_non_null(handle);
+  } else {
+    return (methodOop) NULL;
+  }
+};
+
+
+inline void JNIHandles::destroy_local(jobject handle) {
+  if (handle != NULL) {
+    *((oop*)handle) = deleted_handle(); // Mark the handle as deleted, allocate will reuse it
+  }
+}