--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/runtime/handles.hpp Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,301 @@
+/*
+ * Copyright (c) 1997, 2017, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#ifndef SHARE_VM_RUNTIME_HANDLES_HPP
+#define SHARE_VM_RUNTIME_HANDLES_HPP
+
+#include "memory/arena.hpp"
+#include "oops/oop.hpp"
+#include "oops/oopsHierarchy.hpp"
+
+class InstanceKlass;
+class Klass;
+
+//------------------------------------------------------------------------------------------------------------------------
+// In order to preserve oops during garbage collection, they should be
+// allocated and passed around via Handles within the VM. A handle is
+// simply an extra indirection allocated in a thread local handle area.
+//
+// A handle is a ValueObj, so it can be passed around as a value, can
+// be used as a parameter w/o using &-passing, and can be returned as a
+// return value.
+//
+// oop parameters and return types should be Handles whenever feasible.
+//
+// Handles are declared in a straight-forward manner, e.g.
+//
+// oop obj = ...;
+// Handle h2(thread, obj); // allocate a new handle in thread
+// Handle h3; // declare handle only, no allocation occurs
+// ...
+// h3 = h1; // make h3 refer to same indirection as h1
+// oop obj2 = h2(); // get handle value
+// h1->print(); // invoking operation on oop
+//
+// Handles are specialized for different oop types to provide extra type
+// information and avoid unnecessary casting. For each oop type xxxOop
+// there is a corresponding handle called xxxHandle.
+
+//------------------------------------------------------------------------------------------------------------------------
+// Base class for all handles. Provides overloading of frequently
+// used operators for ease of use.
+
+class Handle VALUE_OBJ_CLASS_SPEC {
+ private:
+ oop* _handle;
+
+ protected:
+ oop obj() const { return _handle == NULL ? (oop)NULL : *_handle; }
+ oop non_null_obj() const { assert(_handle != NULL, "resolving NULL handle"); return *_handle; }
+
+ public:
+ // Constructors
+ Handle() { _handle = NULL; }
+ Handle(Thread* thread, oop obj);
+
+ // General access
+ oop operator () () const { return obj(); }
+ oop operator -> () const { return non_null_obj(); }
+ bool operator == (oop o) const { return obj() == o; }
+ bool operator == (const Handle& h) const { return obj() == h.obj(); }
+
+ // Null checks
+ bool is_null() const { return _handle == NULL; }
+ bool not_null() const { return _handle != NULL; }
+
+ // Debugging
+ void print() { obj()->print(); }
+
+ // Direct interface, use very sparingly.
+ // Used by JavaCalls to quickly convert handles and to create handles static data structures.
+ // Constructor takes a dummy argument to prevent unintentional type conversion in C++.
+ Handle(oop *handle, bool dummy) { _handle = handle; }
+
+ // Raw handle access. Allows easy duplication of Handles. This can be very unsafe
+ // since duplicates is only valid as long as original handle is alive.
+ oop* raw_value() { return _handle; }
+ static oop raw_resolve(oop *handle) { return handle == NULL ? (oop)NULL : *handle; }
+};
+
+// Specific Handles for different oop types
+#define DEF_HANDLE(type, is_a) \
+ class type##Handle: public Handle { \
+ protected: \
+ type##Oop obj() const { return (type##Oop)Handle::obj(); } \
+ type##Oop non_null_obj() const { return (type##Oop)Handle::non_null_obj(); } \
+ \
+ public: \
+ /* Constructors */ \
+ type##Handle () : Handle() {} \
+ type##Handle (Thread* thread, type##Oop obj) : Handle(thread, (oop)obj) { \
+ assert(is_null() || ((oop)obj)->is_a(), "illegal type"); \
+ } \
+ \
+ /* Operators for ease of use */ \
+ type##Oop operator () () const { return obj(); } \
+ type##Oop operator -> () const { return non_null_obj(); } \
+ };
+
+
+DEF_HANDLE(instance , is_instance_noinline )
+DEF_HANDLE(array , is_array_noinline )
+DEF_HANDLE(objArray , is_objArray_noinline )
+DEF_HANDLE(typeArray , is_typeArray_noinline )
+
+//------------------------------------------------------------------------------------------------------------------------
+
+// Metadata Handles. Unlike oop Handles these are needed to prevent metadata
+// from being reclaimed by RedefineClasses.
+// Metadata Handles should be passed around as const references to avoid copy construction
+// and destruction for parameters.
+
+// Specific Handles for different oop types
+#define DEF_METADATA_HANDLE(name, type) \
+ class name##Handle; \
+ class name##Handle : public StackObj { \
+ type* _value; \
+ Thread* _thread; \
+ protected: \
+ type* obj() const { return _value; } \
+ type* non_null_obj() const { assert(_value != NULL, "resolving NULL _value"); return _value; } \
+ \
+ public: \
+ /* Constructors */ \
+ name##Handle () : _value(NULL), _thread(NULL) {} \
+ name##Handle (type* obj); \
+ name##Handle (Thread* thread, type* obj); \
+ \
+ name##Handle (const name##Handle &h); \
+ name##Handle& operator=(const name##Handle &s); \
+ \
+ /* Destructor */ \
+ ~name##Handle (); \
+ void remove(); \
+ \
+ /* Operators for ease of use */ \
+ type* operator () () const { return obj(); } \
+ type* operator -> () const { return non_null_obj(); } \
+ \
+ bool operator == (type* o) const { return obj() == o; } \
+ bool operator == (const name##Handle& h) const { return obj() == h.obj(); } \
+ \
+ /* Null checks */ \
+ bool is_null() const { return _value == NULL; } \
+ bool not_null() const { return _value != NULL; } \
+ };
+
+
+DEF_METADATA_HANDLE(method, Method)
+DEF_METADATA_HANDLE(constantPool, ConstantPool)
+
+//------------------------------------------------------------------------------------------------------------------------
+// Thread local handle area
+class HandleArea: public Arena {
+ friend class HandleMark;
+ friend class NoHandleMark;
+ friend class ResetNoHandleMark;
+#ifdef ASSERT
+ int _handle_mark_nesting;
+ int _no_handle_mark_nesting;
+#endif
+ HandleArea* _prev; // link to outer (older) area
+ public:
+ // Constructor
+ HandleArea(HandleArea* prev) : Arena(mtThread, Chunk::tiny_size) {
+ debug_only(_handle_mark_nesting = 0);
+ debug_only(_no_handle_mark_nesting = 0);
+ _prev = prev;
+ }
+
+ // Handle allocation
+ private:
+ oop* real_allocate_handle(oop obj) {
+#ifdef ASSERT
+ oop* handle = (oop*) (UseMallocOnly ? internal_malloc_4(oopSize) : Amalloc_4(oopSize));
+#else
+ oop* handle = (oop*) Amalloc_4(oopSize);
+#endif
+ *handle = obj;
+ return handle;
+ }
+ public:
+#ifdef ASSERT
+ oop* allocate_handle(oop obj);
+#else
+ oop* allocate_handle(oop obj) { return real_allocate_handle(obj); }
+#endif
+
+ // Garbage collection support
+ void oops_do(OopClosure* f);
+
+ // Number of handles in use
+ size_t used() const { return Arena::used() / oopSize; }
+
+ debug_only(bool no_handle_mark_active() { return _no_handle_mark_nesting > 0; })
+};
+
+
+//------------------------------------------------------------------------------------------------------------------------
+// Handles are allocated in a (growable) thread local handle area. Deallocation
+// is managed using a HandleMark. It should normally not be necessary to use
+// HandleMarks manually.
+//
+// A HandleMark constructor will record the current handle area top, and the
+// destructor will reset the top, destroying all handles allocated in between.
+// The following code will therefore NOT work:
+//
+// Handle h;
+// {
+// HandleMark hm;
+// h = Handle(THREAD, obj);
+// }
+// h()->print(); // WRONG, h destroyed by HandleMark destructor.
+//
+// If h has to be preserved, it can be converted to an oop or a local JNI handle
+// across the HandleMark boundary.
+
+// The base class of HandleMark should have been StackObj but we also heap allocate
+// a HandleMark when a thread is created. The operator new is for this special case.
+
+class HandleMark {
+ private:
+ Thread *_thread; // thread that owns this mark
+ HandleArea *_area; // saved handle area
+ Chunk *_chunk; // saved arena chunk
+ char *_hwm, *_max; // saved arena info
+ size_t _size_in_bytes; // size of handle area
+ // Link to previous active HandleMark in thread
+ HandleMark* _previous_handle_mark;
+
+ void initialize(Thread* thread); // common code for constructors
+ void set_previous_handle_mark(HandleMark* mark) { _previous_handle_mark = mark; }
+ HandleMark* previous_handle_mark() const { return _previous_handle_mark; }
+
+ size_t size_in_bytes() const { return _size_in_bytes; }
+ public:
+ HandleMark(); // see handles_inline.hpp
+ HandleMark(Thread* thread) { initialize(thread); }
+ ~HandleMark();
+
+ // Functions used by HandleMarkCleaner
+ // called in the constructor of HandleMarkCleaner
+ void push();
+ // called in the destructor of HandleMarkCleaner
+ void pop_and_restore();
+ // overloaded operators
+ void* operator new(size_t size) throw();
+ void* operator new [](size_t size) throw();
+ void operator delete(void* p);
+ void operator delete[](void* p);
+};
+
+//------------------------------------------------------------------------------------------------------------------------
+// A NoHandleMark stack object will verify that no handles are allocated
+// in its scope. Enabled in debug mode only.
+
+class NoHandleMark: public StackObj {
+ public:
+#ifdef ASSERT
+ NoHandleMark();
+ ~NoHandleMark();
+#else
+ NoHandleMark() {}
+ ~NoHandleMark() {}
+#endif
+};
+
+
+class ResetNoHandleMark: public StackObj {
+ int _no_handle_mark_nesting;
+ public:
+#ifdef ASSERT
+ ResetNoHandleMark();
+ ~ResetNoHandleMark();
+#else
+ ResetNoHandleMark() {}
+ ~ResetNoHandleMark() {}
+#endif
+};
+
+#endif // SHARE_VM_RUNTIME_HANDLES_HPP