| /* |
| * Copyright (c) 2015, 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_UTILITIES_FAKERTTISUPPORT_HPP |
| #define SHARE_VM_UTILITIES_FAKERTTISUPPORT_HPP |
| |
| #include "utilities/globalDefinitions.hpp" |
| #include "utilities/debug.hpp" |
| |
| // Provides support for checked downcasts in a hierarchy of classes. |
| // The base class provides a member of this type, specialized on that |
| // base class and an associated tag type. Tags are small non-negative |
| // integer values uniquely associated with distinct classes in the |
| // hierarchy. A tag type is often an enum type. |
| // |
| // The concrete class specifies the concrete tag. |
| // |
| // The tag set specifies the set of classes in the derivation |
| // sequence. Classes in the derivation sequence add their associated |
| // tag during construction. Given the tag associated with a class, an |
| // object is an instance of that class if the tag is included in the |
| // object's set of recorded tags. |
| // |
| // A tag T is present in a tag set if the T'th bit of the tag set is |
| // one. |
| // |
| // Note: The representation of a tag set being uintx sets an upper |
| // bound on the size of a class hierarchy this utility can be used |
| // with. |
| template<typename T, typename TagType> |
| class FakeRttiSupport VALUE_OBJ_CLASS_SPEC { |
| friend class VMStructs; |
| public: |
| // Construct with the indicated concrete tag, and include the |
| // concrete tag in the associated tag set. |
| explicit FakeRttiSupport(TagType concrete_tag) : |
| _tag_set(tag_bit(concrete_tag)), _concrete_tag(concrete_tag) { } |
| |
| // Construct with the indicated concrete tag and tag set. |
| // Note: This constructor is public only to allow clients to set up |
| // "unusual" (or perhaps buggy) fake RTTI configurations. |
| FakeRttiSupport(TagType concrete_tag, uintx tag_set) : |
| _tag_set(tag_set), _concrete_tag(validate_tag(concrete_tag)) { } |
| |
| // Get the concrete tag. |
| TagType concrete_tag() const { return _concrete_tag; } |
| |
| // Test whether tag is in the tag set. |
| bool has_tag(TagType tag) const { |
| return (_tag_set & tag_bit(tag)) != 0; |
| } |
| |
| // Return a new support object which is the same as this, except tag |
| // has been added to the tag set. The tag must not already be |
| // present in the tag set. |
| FakeRttiSupport add_tag(TagType tag) const { |
| uintx tbit = tag_bit(tag); |
| assert((_tag_set & tbit) == 0, |
| "Tag " UINTX_FORMAT " is already present in tag set: " UINTX_FORMAT, |
| (uintx)tag, _tag_set); |
| return FakeRttiSupport(_concrete_tag, _tag_set | tbit); |
| } |
| |
| private: |
| uintx _tag_set; |
| TagType _concrete_tag; |
| |
| static uintx tag_bit(TagType tag) { |
| return ((uintx)1) << validate_tag(tag); |
| } |
| |
| static TagType validate_tag(TagType tag) { |
| assert(0 <= tag, "Tag " INTX_FORMAT " is negative", (intx)tag); |
| assert(tag < BitsPerWord, |
| "Tag " UINTX_FORMAT " is too large", (uintx)tag); |
| return tag; |
| } |
| }; |
| |
| #endif // include guard |