tsch-asn.h

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/**
 * \addtogroup tsch
 * @{
 * \file
 *         TSCH 5-Byte Absolute Slot Number (ASN) management
 * \author
 *         Simon Duquennoy <simonduq@sics.se>
*/

#ifndef __TSCH_ASN_H__
#define __TSCH_ASN_H__

/************ Types ***********/

/** \brief The ASN is an absolute slot number over 5 bytes. */
struct tsch_asn_t {
  uint32_t ls4b; /* least significant 4 bytes */
  uint8_t  ms1b; /* most significant 1 byte */
};

/** \brief For quick modulo operation on ASN */
struct tsch_asn_divisor_t {
  uint16_t val; /* Divisor value */
  uint16_t asn_ms1b_remainder; /* Remainder of the operation 0x100000000 / val */
};

/************ Macros **********/

/** \brief Initialize ASN */
#define TSCH_ASN_INIT(asn, ms1b_, ls4b_) do { \
    (asn).ms1b = (ms1b_); \
    (asn).ls4b = (ls4b_); \
} while(0);

/** \brief Increment an ASN by inc (32 bits) */
#define TSCH_ASN_INC(asn, inc) do { \
    uint32_t new_ls4b = (asn).ls4b + (inc); \
    if(new_ls4b < (asn).ls4b) { (asn).ms1b++; } \
    (asn).ls4b = new_ls4b; \
} while(0);

/** \brief Decrement an ASN by inc (32 bits) */
#define TSCH_ASN_DEC(asn, dec) do { \
    uint32_t new_ls4b = (asn).ls4b - (dec); \
    if(new_ls4b > (asn).ls4b) { (asn).ms1b--; } \
    (asn).ls4b = new_ls4b; \
} while(0);

/** \brief Returns the 32-bit diff between asn1 and asn2 */
#define TSCH_ASN_DIFF(asn1, asn2) \
  ((asn1).ls4b - (asn2).ls4b)

/** \brief Initialize a struct asn_divisor_t */
#define TSCH_ASN_DIVISOR_INIT(div, val_) do { \
    (div).val = (val_); \
    (div).asn_ms1b_remainder = ((0xffffffff % (val_)) + 1) % (val_); \
} while(0);

/** \brief Returns the result (16 bits) of a modulo operation on ASN,
 * with divisor being a struct asn_divisor_t */
#define TSCH_ASN_MOD(asn, div) \
  ((uint16_t)((asn).ls4b % (div).val) \
   + (uint16_t)((asn).ms1b * (div).asn_ms1b_remainder % (div).val)) \
  % (div).val

#endif /* __TSCH_ASN_H__ */
/** @} */