kc3-lang/libtommath/bn_mp_lshd.c

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• Hash : c4fb2241
  Author :
  Date : 2019-04-09T11:08:26
  

  rename macros in tommath_private to use MP_* prefix

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• bn_mp_lshd.c

• #include "tommath_private.h"
  #ifdef BN_MP_LSHD_C
  /* LibTomMath, multiple-precision integer library -- Tom St Denis */
  /* SPDX-License-Identifier: Unlicense */
  
  /* shift left a certain amount of digits */
  int mp_lshd(mp_int *a, int b)
  {
     int     x, res;
  
     /* if its less than zero return */
     if (b <= 0) {
        return MP_OKAY;
     }
     /* no need to shift 0 around */
     if (MP_IS_ZERO(a)) {
        return MP_OKAY;
     }
  
     /* grow to fit the new digits */
     if (a->alloc < (a->used + b)) {
        if ((res = mp_grow(a, a->used + b)) != MP_OKAY) {
           return res;
        }
     }
  
     {
        mp_digit *top, *bottom;
  
        /* increment the used by the shift amount then copy upwards */
        a->used += b;
  
        /* top */
        top = a->dp + a->used - 1;
  
        /* base */
        bottom = (a->dp + a->used - 1) - b;
  
        /* much like mp_rshd this is implemented using a sliding window
         * except the window goes the otherway around.  Copying from
         * the bottom to the top.  see bn_mp_rshd.c for more info.
         */
        for (x = a->used - 1; x >= b; x--) {
           *top-- = *bottom--;
        }
  
        /* zero the lower digits */
        top = a->dp;
        for (x = 0; x < b; x++) {
           *top++ = 0;
        }
     }
     return MP_OKAY;
  }
  #endif
  

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