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e482753b AB |
1 | /** @file\r |
2 | Implementation of TestAndClearBit using compare-exchange primitive\r | |
3 | \r | |
4 | Copyright (C) 2015, Linaro Ltd.\r | |
9b8e4148 | 5 | Copyright (c) 2015, Intel Corporation. All rights reserved.<BR>\r |
e482753b | 6 | \r |
b26f0cf9 | 7 | SPDX-License-Identifier: BSD-2-Clause-Patent\r |
e482753b AB |
8 | \r |
9 | **/\r | |
10 | \r | |
11 | #include <Base.h>\r | |
12 | #include <Library/SynchronizationLib.h>\r | |
13 | \r | |
14 | INT32\r | |
15 | EFIAPI\r | |
16 | TestAndClearBit (\r | |
ac0a286f MK |
17 | IN INT32 Bit,\r |
18 | IN VOID *Address\r | |
e482753b AB |
19 | )\r |
20 | {\r | |
ac0a286f MK |
21 | UINT16 Word, Read;\r |
22 | UINT16 Mask;\r | |
e482753b AB |
23 | \r |
24 | //\r | |
25 | // Calculate the effective address relative to 'Address' based on the\r | |
26 | // higher order bits of 'Bit'. Use signed shift instead of division to\r | |
27 | // ensure we round towards -Inf, and end up with a positive shift in\r | |
28 | // 'Bit', even if 'Bit' itself is negative.\r | |
29 | //\r | |
ac0a286f MK |
30 | Address = (VOID *)((UINT8 *)Address + ((Bit >> 4) * sizeof (UINT16)));\r |
31 | Mask = 1U << (Bit & 15);\r | |
e482753b | 32 | \r |
ac0a286f | 33 | for (Word = *(UINT16 *)Address; Word &Mask; Word = Read) {\r |
e482753b AB |
34 | Read = InterlockedCompareExchange16 (Address, Word, Word & ~Mask);\r |
35 | if (Read == Word) {\r | |
36 | return 1;\r | |
37 | }\r | |
38 | }\r | |
ac0a286f | 39 | \r |
e482753b AB |
40 | return 0;\r |
41 | }\r |