| /* |
| * 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 |
| } |
| } |