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tsch-asn.h
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32 
33 /**
34  * \file
35  * TSCH 5-Byte Absolute Slot Number (ASN) management
36  * \author
37  * Simon Duquennoy <simonduq@sics.se>
38  *
39  */
40 
41 #ifndef __TSCH_ASN_H__
42 #define __TSCH_ASN_H__
43 
44 /************ Types ***********/
45 
46 /* The ASN is an absolute slot number over 5 bytes. */
47 struct asn_t {
48  uint32_t ls4b; /* least significant 4 bytes */
49  uint8_t ms1b; /* most significant 1 byte */
50 };
51 
52 /* For quick modulo operation on ASN */
53 struct asn_divisor_t {
54  uint16_t val; /* Divisor value */
55  uint16_t asn_ms1b_remainder; /* Remainder of the operation 0x100000000 / val */
56 };
57 
58 /************ Macros **********/
59 
60 /* Initialize ASN */
61 #define ASN_INIT(asn, ms1b_, ls4b_) do { \
62  (asn).ms1b = (ms1b_); \
63  (asn).ls4b = (ls4b_); \
64 } while(0);
65 
66 /* Increment an ASN by inc (32 bits) */
67 #define ASN_INC(asn, inc) do { \
68  uint32_t new_ls4b = (asn).ls4b + (inc); \
69  if(new_ls4b < (asn).ls4b) { (asn).ms1b++; } \
70  (asn).ls4b = new_ls4b; \
71 } while(0);
72 
73 /* Decrement an ASN by inc (32 bits) */
74 #define ASN_DEC(asn, dec) do { \
75  uint32_t new_ls4b = (asn).ls4b - (dec); \
76  if(new_ls4b > (asn).ls4b) { (asn).ms1b--; } \
77  (asn).ls4b = new_ls4b; \
78 } while(0);
79 
80 /* Returns the 32-bit diff between asn1 and asn2 */
81 #define ASN_DIFF(asn1, asn2) \
82  ((asn1).ls4b - (asn2).ls4b)
83 
84 /* Initialize a struct asn_divisor_t */
85 #define ASN_DIVISOR_INIT(div, val_) do { \
86  (div).val = (val_); \
87  (div).asn_ms1b_remainder = ((0xffffffff % (val_)) + 1) % (val_); \
88 } while(0);
89 
90 /* Returns the result (16 bits) of a modulo operation on ASN,
91  * with divisor being a struct asn_divisor_t */
92 #define ASN_MOD(asn, div) \
93  ((uint16_t)((asn).ls4b % (div).val) \
94  + (uint16_t)((asn).ms1b * (div).asn_ms1b_remainder % (div).val)) \
95  % (div).val
96 
97 #endif /* __TSCH_ASN_H__ */
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