projects / mirror_edk2.git / blame
| Commit | Line | Data |
|---|---|---|
| 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 | |
| 17 | IN INT32 Bit,\r | |
| 18 | IN VOID *Address\r | |
| 19 | )\r | |
| 20 | {\r | |
| 21 | UINT16 Word, Read;\r | |
| 22 | UINT16 Mask;\r | |
| 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 | |
| 9b8e4148 | 30 | Address = (VOID*)((UINT8*) Address + ((Bit >> 4) * sizeof(UINT16)));\r |
| e482753b AB |
31 | Mask = 1U << (Bit & 15);\r |
| 32 | \r | |
| 33 | for (Word = *(UINT16 *) Address; Word & Mask; Word = Read) {\r | |
| 34 | Read = InterlockedCompareExchange16 (Address, Word, Word & ~Mask);\r | |
| 35 | if (Read == Word) {\r | |
| 36 | return 1;\r | |
| 37 | }\r | |
| 38 | }\r | |
| 39 | return 0;\r | |
| 40 | }\r |