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comparison 3rdparty/libtommath/bn_mp_get_int.c @ 0:2cf249471370

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author Takahiro SHIMIZU <anatofuz@cr.ie.u-ryukyu.ac.jp>
date Tue, 08 May 2018 16:09:12 +0900
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1 #include <tommath_private.h>
2 #ifdef BN_MP_GET_INT_C
3 /* LibTomMath, multiple-precision integer library -- Tom St Denis
4 *
5 * LibTomMath is a library that provides multiple-precision
6 * integer arithmetic as well as number theoretic functionality.
7 *
8 * The library was designed directly after the MPI library by
9 * Michael Fromberger but has been written from scratch with
10 * additional optimizations in place.
11 *
12 * The library is free for all purposes without any express
13 * guarantee it works.
14 *
15 * Tom St Denis, tstdenis82@gmail.com, http://libtom.org
16 */
17
18 /* get the lower 32-bits of an mp_int */
19 unsigned long mp_get_int(mp_int * a)
20 {
21 int i;
22 mp_min_u32 res;
23
24 if (a->used == 0) {
25 return 0;
26 }
27
28 /* get number of digits of the lsb we have to read */
29 i = MIN(a->used,(int)(((sizeof(unsigned long) * CHAR_BIT) + DIGIT_BIT - 1) / DIGIT_BIT)) - 1;
30
31 /* get most significant digit of result */
32 res = DIGIT(a,i);
33
34 while (--i >= 0) {
35 res = (res << DIGIT_BIT) | DIGIT(a,i);
36 }
37
38 /* force result to 32-bits always so it is consistent on non 32-bit platforms */
39 return res & 0xFFFFFFFFUL;
40 }
41 #endif
42
43 /* $Source$ */
44 /* $Revision$ */
45 /* $Date$ */