Zephyr API Documentation
4.0.0-rc2
A Scalable Open Source RTOS
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ilog2.h
Go to the documentation of this file.
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/*
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* Copyright (c) 2021 Intel Corporation
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#ifndef ZEPHYR_INCLUDE_MATH_ILOG2_H_
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#define ZEPHYR_INCLUDE_MATH_ILOG2_H_
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#include <
stdint.h
>
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#include <
zephyr/toolchain.h
>
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#include <
zephyr/arch/common/ffs.h
>
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#include <
zephyr/sys/util.h
>
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#define ilog2_compile_time_const_u32(n) \
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( \
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((n) < 2) ? 0 : \
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(((n) & BIT(31)) == BIT(31)) ? 31 : \
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(((n) & BIT(30)) == BIT(30)) ? 30 : \
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(((n) & BIT(29)) == BIT(29)) ? 29 : \
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(((n) & BIT(28)) == BIT(28)) ? 28 : \
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(((n) & BIT(27)) == BIT(27)) ? 27 : \
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(((n) & BIT(26)) == BIT(26)) ? 26 : \
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(((n) & BIT(25)) == BIT(25)) ? 25 : \
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(((n) & BIT(24)) == BIT(24)) ? 24 : \
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(((n) & BIT(23)) == BIT(23)) ? 23 : \
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(((n) & BIT(22)) == BIT(22)) ? 22 : \
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(((n) & BIT(21)) == BIT(21)) ? 21 : \
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(((n) & BIT(20)) == BIT(20)) ? 20 : \
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(((n) & BIT(19)) == BIT(19)) ? 19 : \
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(((n) & BIT(18)) == BIT(18)) ? 18 : \
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(((n) & BIT(17)) == BIT(17)) ? 17 : \
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(((n) & BIT(16)) == BIT(16)) ? 16 : \
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(((n) & BIT(15)) == BIT(15)) ? 15 : \
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(((n) & BIT(14)) == BIT(14)) ? 14 : \
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(((n) & BIT(13)) == BIT(13)) ? 13 : \
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(((n) & BIT(12)) == BIT(12)) ? 12 : \
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(((n) & BIT(11)) == BIT(11)) ? 11 : \
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(((n) & BIT(10)) == BIT(10)) ? 10 : \
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(((n) & BIT(9)) == BIT(9)) ? 9 : \
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(((n) & BIT(8)) == BIT(8)) ? 8 : \
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(((n) & BIT(7)) == BIT(7)) ? 7 : \
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(((n) & BIT(6)) == BIT(6)) ? 6 : \
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(((n) & BIT(5)) == BIT(5)) ? 5 : \
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(((n) & BIT(4)) == BIT(4)) ? 4 : \
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(((n) & BIT(3)) == BIT(3)) ? 3 : \
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(((n) & BIT(2)) == BIT(2)) ? 2 : \
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1 \
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)
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/*
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* This is in #define form as this needs to also work on
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* compile time constants. Doing this as a static inline
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* function will result in compiler complaining with
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* "initializer element is not constant".
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*/
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#define ilog2(n) \
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( \
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__builtin_constant_p(n) ? \
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ilog2_compile_time_const_u32(n) : \
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find_msb_set(n) - 1 \
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)
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#endif
/* ZEPHYR_INCLUDE_MATH_ILOG2_H_ */
ffs.h
stdint.h
util.h
Misc utilities.
toolchain.h
Macros to abstract toolchain specific capabilities.
zephyr
math
ilog2.h
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