bn_mp_get_int.c 1.16 KB
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#include "tommath_private.h"
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#ifdef BN_MP_GET_INT_C
/* LibTomMath, multiple-precision integer library -- Tom St Denis
 *
 * LibTomMath is a library that provides multiple-precision
 * integer arithmetic as well as number theoretic functionality.
 *
 * The library was designed directly after the MPI library by
 * Michael Fromberger but has been written from scratch with
 * additional optimizations in place.
 *
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 * SPDX-License-Identifier: Unlicense
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 */

/* get the lower 32-bits of an mp_int */
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unsigned long mp_get_int(const mp_int *a)
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{
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   int i;
   mp_min_u32 res;
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   if (a->used == 0) {
      return 0;
   }
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   /* get number of digits of the lsb we have to read */
   i = MIN(a->used, ((((int)sizeof(unsigned long) * CHAR_BIT) + DIGIT_BIT - 1) / DIGIT_BIT)) - 1;
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   /* get most significant digit of result */
   res = DIGIT(a, i);
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   while (--i >= 0) {
      res = (res << DIGIT_BIT) | DIGIT(a, i);
   }
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   /* force result to 32-bits always so it is consistent on non 32-bit platforms */
   return res & 0xFFFFFFFFUL;
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}
#endif

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/* ref:         HEAD -> master, tag: v1.1.0 */
/* git commit:  08549ad6bc8b0cede0b357a9c341c5c6473a9c55 */
/* commit time: 2019-01-28 20:32:32 +0100 */