81 lines
3.0 KiB
C++
81 lines
3.0 KiB
C++
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/*
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* Copyright (c) 2017, 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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#ifndef SHARE_GC_Z_ZBITFIELD_HPP
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#define SHARE_GC_Z_ZBITFIELD_HPP
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#include "memory/allocation.hpp"
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#include "utilities/debug.hpp"
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//
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// Example
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// -------
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//
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// typedef ZBitField<uint64_t, uint8_t, 0, 2, 3> field_word_aligned_size;
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// typedef ZBitField<uint64_t, uint32_t, 2, 30> field_length;
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//
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//
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// 6 3 3
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// 3 2 1 2 10
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// +-----------------------------------+---------------------------------+--+
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// |11111111 11111111 11111111 11111111|11111111 11111111 11111111 111111|11|
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// +-----------------------------------+---------------------------------+--+
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// | | |
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// | 31-2 field_length (30-bits) * |
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// | |
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// | 1-0 field_word_aligned_size (2-bits) *
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// |
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// * 63-32 Unused (32-bits)
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//
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//
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// field_word_aligned_size::encode(16) = 2
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// field_length::encode(2342) = 9368
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//
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// field_word_aligned_size::decode(9368 | 2) = 16
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// field_length::decode(9368 | 2) = 2342
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//
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template <typename ContainerType, typename ValueType, int FieldShift, int FieldBits, int ValueShift = 0>
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class ZBitField : public AllStatic {
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private:
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static const int ContainerBits = sizeof(ContainerType) * BitsPerByte;
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STATIC_ASSERT(FieldBits < ContainerBits);
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STATIC_ASSERT(FieldShift + FieldBits <= ContainerBits);
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STATIC_ASSERT(ValueShift + FieldBits <= ContainerBits);
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static const ContainerType FieldMask = (((ContainerType)1 << FieldBits) - 1);
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public:
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static ValueType decode(ContainerType container) {
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return (ValueType)(((container >> FieldShift) & FieldMask) << ValueShift);
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}
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static ContainerType encode(ValueType value) {
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assert(((ContainerType)value & (FieldMask << ValueShift)) == (ContainerType)value, "Invalid value");
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return ((ContainerType)value >> ValueShift) << FieldShift;
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}
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};
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#endif // SHARE_GC_Z_ZBITFIELD_HPP
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