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/*
* Copyright (C) 2015 Kaspar Schleiser <kaspar@schleiser.de>
*
* This file is subject to the terms and conditions of the GNU Lesser
* General Public License v2.1. See the file LICENSE in the top level
* directory for more details.
*/
/**
* @brief Provides integer division functions
*
* This header provides some integer division functions that can be used
* to prevent linking in compiler-generated ones, which are often larger.
*
* @file
* @ingroup sys_util
* @author Kaspar Schleiser <kaspar@schleiser.de>
* @{
*/
#ifndef DIV_H
#define DIV_H
#include <assert.h>
#include <stdint.h>
#ifdef __cplusplus
extern "C" {
#endif
/**
* @brief Integer divide val by 15625
*
* @pre val <= 16383999997
*
* @param[in] val dividend
* @return (val / 15625)
*/
static inline uint64_t div_u64_by_15625(uint64_t val)
{
/* a higher value would overflow 2^64 in the multiplication that follows */
assert(val <= 16383999997LLU);
return (val * 0x431bde83UL) >> (12 + 32);
}
/**
* @brief Integer divide val by 1000000
*
* @pre val <= 1048575999808
*
* @param[in] val dividend
* @return (val / 1000000)
*/
static inline uint64_t div_u64_by_1000000(uint64_t val)
{
/* a higher value would overflow 2^64 in the multiplication that follows */
assert(val <= 1048575999808LLU);
return div_u64_by_15625(val>>6);
}
/**
* @brief Divide val by (15625/512)
*
* This is used to quantize a 1MHz value to the closest 32768Hz value,
* e.g., for timers.
*
* The algorithm actually multiplies by 512 first, then divides by 15625,
* keeping the result closer to a floored floating point division.
*
* @param[in] val dividend
* @return (val / (15625/512))
*/
static inline uint32_t div_u32_by_15625div512(uint32_t val)
{
return ((uint64_t)(val) * 0x431bde83ul) >> (12 + 32 - 9);
}
/**
* @brief Integer divide val by 44488
*
* @param[in] val dividend
* @return (val / 44488)
*/
static inline uint32_t div_u32_by_44488(uint32_t val)
{
return ((uint64_t)val * 0xBC8F1391UL) >> (15 + 32);
}
/**
* @brief Modulo 44488
*
* @param[in] val dividend
* @return (val % 44488)
*/
static inline uint32_t div_u32_mod_44488(uint32_t val)
{
return val - (div_u32_by_44488(val)*44488);
}
#ifdef __cplusplus
}
#endif
/** @} */
#endif /* DIV_H */