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comparison libtommath/bn_mp_radix_size.c @ 284:eed26cff980b

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propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583) to branch 'au.asn.ucc.matt.dropbear' (head fff0894a0399405a9410ea1c6d118f342cf2aa64)
author Matt Johnston <matt@ucc.asn.au>
date Wed, 08 Mar 2006 13:23:49 +0000
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children 5ff8218bcee9
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283:bd240aa12ba7 284:eed26cff980b
1 #include <tommath.h>
2 #ifdef BN_MP_RADIX_SIZE_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, [email protected], http://math.libtomcrypt.org
16 */
17
18 /* returns size of ASCII reprensentation */
19 int mp_radix_size (mp_int * a, int radix, int *size)
20 {
21 int res, digs;
22 mp_int t;
23 mp_digit d;
24
25 *size = 0;
26
27 /* special case for binary */
28 if (radix == 2) {
29 *size = mp_count_bits (a) + (a->sign == MP_NEG ? 1 : 0) + 1;
30 return MP_OKAY;
31 }
32
33 /* make sure the radix is in range */
34 if (radix < 2 || radix > 64) {
35 return MP_VAL;
36 }
37
38 if (mp_iszero(a) == MP_YES) {
39 *size = 2;
40 return MP_OKAY;
41 }
42
43 /* digs is the digit count */
44 digs = 0;
45
46 /* if it's negative add one for the sign */
47 if (a->sign == MP_NEG) {
48 ++digs;
49 }
50
51 /* init a copy of the input */
52 if ((res = mp_init_copy (&t, a)) != MP_OKAY) {
53 return res;
54 }
55
56 /* force temp to positive */
57 t.sign = MP_ZPOS;
58
59 /* fetch out all of the digits */
60 while (mp_iszero (&t) == MP_NO) {
61 if ((res = mp_div_d (&t, (mp_digit) radix, &t, &d)) != MP_OKAY) {
62 mp_clear (&t);
63 return res;
64 }
65 ++digs;
66 }
67 mp_clear (&t);
68
69 /* return digs + 1, the 1 is for the NULL byte that would be required. */
70 *size = digs + 1;
71 return MP_OKAY;
72 }
73
74 #endif