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85 lines
1.9 KiB
C
85 lines
1.9 KiB
C
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/*
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* Copyright (C) 2015 Kaspar Schleiser <kaspar@schleiser.de>
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*
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* This file is subject to the terms and conditions of the GNU Lesser
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* General Public License v2.1. See the file LICENSE in the top level
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* directory for more details.
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*/
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/**
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* @brief Provides integer division functions
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*
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* This header provides some integer division functions that can be used
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* to prevent linking in compiler-generated ones, which are often larger.
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*
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* @file
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* @ingroup sys_util
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* @author Kaspar Schleiser <kaspar@schleiser.de>
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* @{
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*/
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#ifndef DIV_H
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#define DIV_H
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#include <assert.h>
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#include <stdint.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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/**
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* @brief Integer divide val by 15625
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*
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* @pre val <= 16383999997
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*
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* @param[in] val dividend
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* @return (val / 15625)
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*/
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static inline uint64_t div_u64_by_15625(uint64_t val)
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{
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/* a higher value would overflow 2^64 in the multiplication that follows */
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assert(val <= 16383999997LLU);
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return (val * 0x431bde83UL) >> (12 + 32);
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}
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/**
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* @brief Integer divide val by 1000000
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*
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* @pre val <= 1048575999808
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*
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* @param[in] val dividend
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* @return (val / 1000000)
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*/
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static inline uint64_t div_u64_by_1000000(uint64_t val)
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{
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/* a higher value would overflow 2^64 in the multiplication that follows */
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assert(val <= 1048575999808LLU);
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return div_u64_by_15625(val>>6);
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}
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/**
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* @brief Divide val by (15625/512)
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*
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* This is used to quantize a 1MHz value to the closest 32768Hz value,
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* e.g., for timers.
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*
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* The algorithm actually multiplies by 512 first, then divides by 15625,
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* keeping the result closer to a floored floating point division.
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*
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* @param[in] val dividend
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* @return (val / (15625/512))
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*/
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static inline uint32_t div_u32_by_15625div512(uint32_t val)
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{
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return ((uint64_t)(val) * 0x431bde83ul) >> (12 + 32 - 9);
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}
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#ifdef __cplusplus
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}
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#endif
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/** @} */
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#endif /* DIV_H */
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