Zephyr API Documentation  2.7.0-rc2
A Scalable Open Source RTOS
ffs.h
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1/*
2 * Copyright (c) 2015, Wind River Systems, Inc.
3 * Copyright (c) 2017, Oticon A/S
4 *
5 * SPDX-License-Identifier: Apache-2.0
6 */
7
8#ifndef ZEPHYR_INCLUDE_ARCH_COMMON_FFS_H_
9#define ZEPHYR_INCLUDE_ARCH_COMMON_FFS_H_
10
11#ifndef _ASMLANGUAGE
12
13#include <zephyr/types.h>
14
15#ifdef __cplusplus
16extern "C" {
17#endif
18
31static ALWAYS_INLINE unsigned int find_msb_set(uint32_t op)
32{
33 if (op == 0) {
34 return 0;
35 }
36
37 return 32 - __builtin_clz(op);
38}
39
40
53static ALWAYS_INLINE unsigned int find_lsb_set(uint32_t op)
54{
55#ifdef CONFIG_TOOLCHAIN_HAS_BUILTIN_FFS
56 return __builtin_ffs(op);
57
58#else
59 /*
60 * Toolchain does not have __builtin_ffs().
61 * Need to do this manually.
62 */
63 int bit;
64
65 if (op == 0) {
66 return 0;
67 }
68
69 for (bit = 0; bit < 32; bit++) {
70 if ((op & (1 << bit)) != 0) {
71 return (bit + 1);
72 }
73 }
74
75 /*
76 * This should never happen but we need to keep
77 * compiler happy.
78 */
79 return 0;
80#endif /* CONFIG_TOOLCHAIN_HAS_BUILTIN_FFS */
81}
82
83#ifdef __cplusplus
84}
85#endif
86
87#endif /* _ASMLANGUAGE */
88
89#endif /* ZEPHYR_INCLUDE_ARCH_COMMON_FFS_H_ */
#define ALWAYS_INLINE
Definition: common.h:116
static ALWAYS_INLINE unsigned int find_msb_set(uint32_t op)
find most significant bit set in a 32-bit word
Definition: ffs.h:31
static ALWAYS_INLINE unsigned int find_lsb_set(uint32_t op)
find least significant bit set in a 32-bit word
Definition: ffs.h:53
__UINT32_TYPE__ uint32_t
Definition: stdint.h:60