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64 lines
2.9 KiB
C++
64 lines
2.9 KiB
C++
/*
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* Copyright (c) 2000, 2023, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*
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*/
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#ifndef SHARE_UTILITIES_SIZES_HPP
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#define SHARE_UTILITIES_SIZES_HPP
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#include "utilities/globalDefinitions.hpp"
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// The following two classes are used to represent 'sizes' and 'offsets' in the VM;
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// they serve as 'unit' types. ByteSize is used for sizes measured in bytes, while
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// WordSize is used for sizes measured in machine words (i.e., 32bit or 64bit words
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// depending on platform).
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//
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// These classes should help doing a transition from (currently) word-size based offsets
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// to byte-size based offsets in the VM (this will be important if we desire to pack
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// objects more densely in the VM for 64bit machines). Such a transition should proceed
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// in two steps to minimize the risk of introducing hard-to-find bugs:
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//
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// a) first transition the whole VM into a form where all sizes are strongly typed
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// b) change all WordSize's to ByteSize's where desired and fix the compilation errors
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enum class WordSize : int {};
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constexpr WordSize in_WordSize(int size) { return static_cast<WordSize>(size); }
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constexpr int in_words(WordSize x) { return static_cast<int>(x); }
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enum class ByteSize : int {};
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constexpr ByteSize in_ByteSize(int size) { return static_cast<ByteSize>(size); }
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constexpr int in_bytes(ByteSize x) { return static_cast<int>(x); }
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constexpr ByteSize operator + (ByteSize x, ByteSize y) { return in_ByteSize(in_bytes(x) + in_bytes(y)); }
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constexpr ByteSize operator - (ByteSize x, ByteSize y) { return in_ByteSize(in_bytes(x) - in_bytes(y)); }
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constexpr ByteSize operator * (ByteSize x, int y) { return in_ByteSize(in_bytes(x) * y ); }
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constexpr bool operator == (ByteSize x, int y) { return in_bytes(x) == y; }
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constexpr bool operator != (ByteSize x, int y) { return in_bytes(x) != y; }
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// Use the following #define to get C++ field member offsets
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#define byte_offset_of(klass,field) in_ByteSize((int)offset_of(klass, field))
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#endif // SHARE_UTILITIES_SIZES_HPP
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