kc3-lang/libtommath/mp_lshd.c

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• Hash : c7686f24
  Author :
  Date : 2022-10-02T12:58:53
  

  slightly edit, update and run typos.sh Signed-off-by: Steffen Jaeckel <s@jaeckel.eu>

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• mp_lshd.c

• #include "tommath_private.h"
  #ifdef MP_LSHD_C
  /* LibTomMath, multiple-precision integer library -- Tom St Denis */
  /* SPDX-License-Identifier: Unlicense */
  
  /* shift left a certain amount of digits */
  mp_err mp_lshd(mp_int *a, int b)
  {
     mp_err err;
     int x;
  
     /* if its less than zero return */
     if (b <= 0) {
        return MP_OKAY;
     }
     /* no need to shift 0 around */
     if (mp_iszero(a)) {
        return MP_OKAY;
     }
  
     /* grow to fit the new digits */
     if ((err = mp_grow(a, a->used + b)) != MP_OKAY) {
        return err;
     }
  
     /* increment the used by the shift amount then copy upwards */
     a->used += b;
  
     /* much like mp_rshd this is implemented using a sliding window
      * except the window goes the other way around.  Copying from
      * the bottom to the top.  see mp_rshd.c for more info.
      */
     for (x = a->used; x --> b;) {
        a->dp[x] = a->dp[x - b];
     }
  
     /* zero the lower digits */
     s_mp_zero_digs(a->dp, b);
  
     return MP_OKAY;
  }
  #endif
  

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