div.h
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1 /*
2  * Copyright (C) 2015 Kaspar Schleiser <kaspar@schleiser.de>
3  * Copyright (C) 2016 Eistec AB
4  *
5  * This file is subject to the terms and conditions of the GNU Lesser
6  * General Public License v2.1. See the file LICENSE in the top level
7  * directory for more details.
8  */
9 
23 #ifndef DIV_H
24 #define DIV_H
25 
26 #include <assert.h>
27 #include <stdint.h>
28 
29 #ifdef __cplusplus
30 extern "C" {
31 #endif
32 
36 #define DIV_H_INV_15625_32 0x431bde83ul
37 
41 #define DIV_H_INV_15625_64 0x431bde82d7b634dbull
42 
46 #define DIV_H_INV_15625_SHIFT 12
47 
61 uint64_t _div_mulhi64(const uint64_t a, const uint64_t b);
62 
69 static inline uint64_t div_u64_by_15625(uint64_t val)
70 {
71  if (val > 16383999997ull) {
72  return (_div_mulhi64(DIV_H_INV_15625_64, val) >> DIV_H_INV_15625_SHIFT);
73  }
74  return (val * DIV_H_INV_15625_32) >> (DIV_H_INV_15625_SHIFT + 32);
75 }
76 
90 static inline uint32_t div_u64_by_125(uint64_t val)
91 {
92  /* a higher value would overflow the result type */
93  assert(val <= 536870911999LLU);
94 
95  uint32_t hi = val >> 32;
96  uint32_t lo = val;
97  uint32_t r = (lo >> 16) + (hi << 16);
98  uint32_t res = r / 125;
99  r = ((r % 125) << 16) + (lo & 0xFFFF);
100  res = (res << 16) + r / 125;
101  return res;
102 }
103 
110 static inline uint64_t div_u64_by_1000000(uint64_t val)
111 {
112  return div_u64_by_15625(val) >> 6;
113 }
114 
129 static inline uint32_t div_u32_by_15625div512(uint32_t val)
130 {
131  return ((uint64_t)(val) * DIV_H_INV_15625_32) >> (DIV_H_INV_15625_SHIFT + 32 - 9);
132 }
133 
143 static inline uint64_t div_u64_by_15625div512(uint64_t val)
144 {
145  /*
146  * This saves around 1400 bytes of ROM on Cortex-M platforms (both ARMv6 and
147  * ARMv7) from avoiding linking against __aeabi_uldivmod and related helpers
148  */
149  if (val > 16383999997ull) {
150  /* this would overflow 2^64 in the multiplication that follows, need to
151  * use the long version */
152  return (_div_mulhi64(DIV_H_INV_15625_64, val) >> (DIV_H_INV_15625_SHIFT - 9));
153  }
154  return (val * DIV_H_INV_15625_32) >> (DIV_H_INV_15625_SHIFT + 32 - 9);
155 }
156 
163 static inline uint32_t div_u32_by_44488(uint32_t val)
164 {
165  return ((uint64_t)val * 0xBC8F1391UL) >> (15 + 32);
166 }
167 
174 static inline uint32_t div_u32_mod_44488(uint32_t val)
175 {
176  return val - (div_u32_by_44488(val)*44488);
177 }
178 
179 #ifdef __cplusplus
180 }
181 #endif
182 
183 #endif /* DIV_H */
static uint64_t div_u64_by_1000000(uint64_t val)
Integer divide val by 1000000.
Definition: div.h:110
#define DIV_H_INV_15625_64
Approximation of (2**l)/d for d=15625, l=12, 64 bits.
Definition: div.h:41
static uint64_t div_u64_by_15625div512(uint64_t val)
Divide val by (15625/512)
Definition: div.h:143
static uint32_t div_u32_by_44488(uint32_t val)
Integer divide val by 44488.
Definition: div.h:163
POSIX.1-2008 compliant version of the assert macro.
#define assert(cond)
abort the program if assertion is false
Definition: assert.h:104
static uint64_t div_u64_by_15625(uint64_t val)
Integer divide val by 15625, 64 bit version.
Definition: div.h:69
static uint32_t div_u64_by_125(uint64_t val)
Integer divide val by 125.
Definition: div.h:90
#define DIV_H_INV_15625_SHIFT
Required shifts for division by 15625, l above.
Definition: div.h:46
static uint32_t div_u32_mod_44488(uint32_t val)
Modulo 44488.
Definition: div.h:174
static uint32_t div_u32_by_15625div512(uint32_t val)
Divide val by (15625/512)
Definition: div.h:129
#define DIV_H_INV_15625_32
Approximation of (2**l)/d for d=15625, l=12, 32 bits.
Definition: div.h:36