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1 | /** @file\r | |
2 | Implementation of TestAndClearBit using compare-exchange primitive\r | |
3 | \r | |
4 | Copyright (C) 2015, Linaro Ltd.\r | |
5 | Copyright (c) 2015, Intel Corporation. All rights reserved.<BR>\r | |
6 | \r | |
7 | This program and the accompanying materials\r | |
8 | are licensed and made available under the terms and conditions of the BSD License\r | |
9 | which accompanies this distribution. The full text of the license may be found at\r | |
10 | http://opensource.org/licenses/bsd-license.php\r | |
11 | \r | |
12 | THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,\r | |
13 | WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.\r | |
14 | \r | |
15 | **/\r | |
16 | \r | |
17 | #include <Base.h>\r | |
18 | #include <Library/SynchronizationLib.h>\r | |
19 | \r | |
20 | INT32\r | |
21 | EFIAPI\r | |
22 | TestAndClearBit (\r | |
23 | IN INT32 Bit,\r | |
24 | IN VOID *Address\r | |
25 | )\r | |
26 | {\r | |
27 | UINT16 Word, Read;\r | |
28 | UINT16 Mask;\r | |
29 | \r | |
30 | //\r | |
31 | // Calculate the effective address relative to 'Address' based on the\r | |
32 | // higher order bits of 'Bit'. Use signed shift instead of division to\r | |
33 | // ensure we round towards -Inf, and end up with a positive shift in\r | |
34 | // 'Bit', even if 'Bit' itself is negative.\r | |
35 | //\r | |
36 | Address = (VOID*)((UINT8*) Address + ((Bit >> 4) * sizeof(UINT16)));\r | |
37 | Mask = 1U << (Bit & 15);\r | |
38 | \r | |
39 | for (Word = *(UINT16 *) Address; Word & Mask; Word = Read) {\r | |
40 | Read = InterlockedCompareExchange16 (Address, Word, Word & ~Mask);\r | |
41 | if (Read == Word) {\r | |
42 | return 1;\r | |
43 | }\r | |
44 | }\r | |
45 | return 0;\r | |
46 | }\r |