213 lines
8.4 KiB
C++
213 lines
8.4 KiB
C++
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/*
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* Copyright 1998-2007 Sun Microsystems, Inc. All Rights Reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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* CA 95054 USA or visit www.sun.com if you need additional information or
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* have any questions.
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*
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*/
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class JNIHandleBlock;
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// Interface for creating and resolving local/global JNI handles
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class JNIHandles : AllStatic {
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friend class VMStructs;
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private:
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static JNIHandleBlock* _global_handles; // First global handle block
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static JNIHandleBlock* _weak_global_handles; // First weak global handle block
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static oop _deleted_handle; // Sentinel marking deleted handles
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public:
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// Resolve handle into oop
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inline static oop resolve(jobject handle);
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// Resolve externally provided handle into oop with some guards
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inline static oop resolve_external_guard(jobject handle);
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// Resolve handle into oop, result guaranteed not to be null
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inline static oop resolve_non_null(jobject handle);
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// Local handles
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static jobject make_local(oop obj);
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static jobject make_local(JNIEnv* env, oop obj); // Fast version when env is known
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static jobject make_local(Thread* thread, oop obj); // Even faster version when current thread is known
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inline static void destroy_local(jobject handle);
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// Global handles
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static jobject make_global(Handle obj);
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static void destroy_global(jobject handle);
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// Weak global handles
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static jobject make_weak_global(Handle obj);
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static void destroy_weak_global(jobject handle);
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// jmethodID handling (as Weak global handles).
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// Because the useful life-span of a jmethodID cannot be determined, once created they are
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// never reclaimed. The methods to which they refer, however, can be GC'ed away if the class
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// is unloaded or if the method is made obsolete or deleted -- in these cases, the jmethodID
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// refers to NULL (as is the case for any weak reference).
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static jmethodID make_jmethod_id(methodHandle mh);
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static void destroy_jmethod_id(jmethodID mid);
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inline static methodOop resolve_jmethod_id(jmethodID mid);
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inline static methodOop checked_resolve_jmethod_id(jmethodID mid); // NULL on invalid jmethodID
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static void change_method_associated_with_jmethod_id(jmethodID jmid, methodHandle mh);
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// Sentinel marking deleted handles in block. Note that we cannot store NULL as
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// the sentinel, since clearing weak global JNI refs are done by storing NULL in
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// the handle. The handle may not be reused before destroy_weak_global is called.
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static oop deleted_handle() { return _deleted_handle; }
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// Initialization
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static void initialize();
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// Debugging
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static void print_on(outputStream* st);
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static void print() { print_on(tty); }
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static void verify();
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static bool is_local_handle(Thread* thread, jobject handle);
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static bool is_frame_handle(JavaThread* thr, jobject obj);
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static bool is_global_handle(jobject handle);
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static bool is_weak_global_handle(jobject handle);
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static long global_handle_memory_usage();
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static long weak_global_handle_memory_usage();
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// Garbage collection support(global handles only, local handles are traversed from thread)
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// Traversal of regular global handles
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static void oops_do(OopClosure* f);
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// Traversal of weak global handles. Unreachable oops are cleared.
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static void weak_oops_do(BoolObjectClosure* is_alive, OopClosure* f);
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};
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// JNI handle blocks holding local/global JNI handles
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class JNIHandleBlock : public CHeapObj {
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friend class VMStructs;
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private:
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enum SomeConstants {
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block_size_in_oops = 32 // Number of handles per handle block
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};
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oop _handles[block_size_in_oops]; // The handles
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int _top; // Index of next unused handle
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JNIHandleBlock* _next; // Link to next block
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// The following instance variables are only used by the first block in a chain.
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// Having two types of blocks complicates the code and the space overhead in negligble.
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JNIHandleBlock* _last; // Last block in use
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JNIHandleBlock* _pop_frame_link; // Block to restore on PopLocalFrame call
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oop* _free_list; // Handle free list
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int _allocate_before_rebuild; // Number of blocks to allocate before rebuilding free list
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#ifndef PRODUCT
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JNIHandleBlock* _block_list_link; // Link for list below
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static JNIHandleBlock* _block_list; // List of all allocated blocks (for debugging only)
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#endif
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static JNIHandleBlock* _block_free_list; // Free list of currently unused blocks
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static int _blocks_allocated; // For debugging/printing
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// Fill block with bad_handle values
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void zap();
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// No more handles in the both the current and following blocks
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void clear() { _top = 0; }
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// Free list computation
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void rebuild_free_list();
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public:
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// Handle allocation
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jobject allocate_handle(oop obj);
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// Block allocation and block free list management
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static JNIHandleBlock* allocate_block(Thread* thread = NULL);
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static void release_block(JNIHandleBlock* block, Thread* thread = NULL);
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// JNI PushLocalFrame/PopLocalFrame support
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JNIHandleBlock* pop_frame_link() const { return _pop_frame_link; }
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void set_pop_frame_link(JNIHandleBlock* block) { _pop_frame_link = block; }
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// Stub generator support
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static int top_offset_in_bytes() { return offset_of(JNIHandleBlock, _top); }
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// Garbage collection support
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// Traversal of regular handles
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void oops_do(OopClosure* f);
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// Traversal of weak handles. Unreachable oops are cleared.
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void weak_oops_do(BoolObjectClosure* is_alive, OopClosure* f);
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// Debugging
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bool chain_contains(jobject handle) const; // Does this block or following blocks contain handle
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bool contains(jobject handle) const; // Does this block contain handle
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int length() const; // Length of chain starting with this block
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long memory_usage() const;
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#ifndef PRODUCT
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static bool any_contains(jobject handle); // Does any block currently in use contain handle
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static void print_statistics();
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#endif
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};
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inline oop JNIHandles::resolve(jobject handle) {
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oop result = (handle == NULL ? (oop)NULL : *(oop*)handle);
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assert(result != NULL || (handle == NULL || !CheckJNICalls || is_weak_global_handle(handle)), "Invalid value read from jni handle");
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assert(result != badJNIHandle, "Pointing to zapped jni handle area");
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return result;
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};
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inline oop JNIHandles::resolve_external_guard(jobject handle) {
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if (handle == NULL) return NULL;
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oop result = *(oop*)handle;
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if (result == NULL || result == badJNIHandle) return NULL;
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return result;
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};
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inline oop JNIHandles::resolve_non_null(jobject handle) {
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assert(handle != NULL, "JNI handle should not be null");
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oop result = *(oop*)handle;
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assert(result != NULL, "Invalid value read from jni handle");
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assert(result != badJNIHandle, "Pointing to zapped jni handle area");
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// Don't let that private _deleted_handle object escape into the wild.
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assert(result != deleted_handle(), "Used a deleted global handle.");
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return result;
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};
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inline methodOop JNIHandles::resolve_jmethod_id(jmethodID mid) {
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return (methodOop) resolve_non_null((jobject)mid);
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};
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inline methodOop JNIHandles::checked_resolve_jmethod_id(jmethodID mid) {
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jobject handle = (jobject)mid;
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if (is_weak_global_handle(handle)) {
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return (methodOop) resolve_non_null(handle);
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} else {
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return (methodOop) NULL;
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}
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};
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inline void JNIHandles::destroy_local(jobject handle) {
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if (handle != NULL) {
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*((oop*)handle) = deleted_handle(); // Mark the handle as deleted, allocate will reuse it
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}
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}
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