1 /*
2 * Copyright (c) 2017, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 */
23
24 #ifndef SHARE_GC_Z_ZBITFIELD_HPP
25 #define SHARE_GC_Z_ZBITFIELD_HPP
26
27 #include "memory/allocation.hpp"
28 #include "utilities/debug.hpp"
29
30 //
31 // Example
32 // -------
33 //
34 // typedef ZBitField<uint64_t, uint8_t, 0, 2, 3> field_word_aligned_size;
35 // typedef ZBitField<uint64_t, uint32_t, 2, 30> field_length;
36 //
37 //
38 // 6 3 3
39 // 3 2 1 2 10
40 // +-----------------------------------+---------------------------------+--+
41 // |11111111 11111111 11111111 11111111|11111111 11111111 11111111 111111|11|
42 // +-----------------------------------+---------------------------------+--+
43 // | | |
44 // | 31-2 field_length (30-bits) * |
45 // | |
46 // | 1-0 field_word_aligned_size (2-bits) *
47 // |
48 // * 63-32 Unused (32-bits)
49 //
50 //
51 // field_word_aligned_size::encode(16) = 2
52 // field_length::encode(2342) = 9368
53 //
54 // field_word_aligned_size::decode(9368 | 2) = 16
55 // field_length::decode(9368 | 2) = 2342
56 //
57
58 template <typename ContainerType, typename ValueType, int FieldShift, int FieldBits, int ValueShift = 0>
59 class ZBitField : public AllStatic {
60 private:
61 static const int ContainerBits = sizeof(ContainerType) * BitsPerByte;
62
63 STATIC_ASSERT(FieldBits < ContainerBits);
64 STATIC_ASSERT(FieldShift + FieldBits <= ContainerBits);
65 STATIC_ASSERT(ValueShift + FieldBits <= ContainerBits);
66
67 static const ContainerType FieldMask = (((ContainerType)1 << FieldBits) - 1);
68
69 public:
70 static ValueType decode(ContainerType container) {
71 return (ValueType)(((container >> FieldShift) & FieldMask) << ValueShift);
72 }
73
74 static ContainerType encode(ValueType value) {
75 assert(((ContainerType)value & (FieldMask << ValueShift)) == (ContainerType)value, "Invalid value");
76 return ((ContainerType)value >> ValueShift) << FieldShift;
77 }
78 };
79
80 #endif // SHARE_GC_Z_ZBITFIELD_HPP