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comparison bn_mp_radix_size.c @ 1:22d5cf7d4b1a libtommath

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Renaming branch
author Matt Johnston <matt@ucc.asn.au>
date Mon, 31 May 2004 18:23:46 +0000
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-1:000000000000 1:22d5cf7d4b1a
1 /* LibTomMath, multiple-precision integer library -- Tom St Denis
2 *
3 * LibTomMath is a library that provides multiple-precision
4 * integer arithmetic as well as number theoretic functionality.
5 *
6 * The library was designed directly after the MPI library by
7 * Michael Fromberger but has been written from scratch with
8 * additional optimizations in place.
9 *
10 * The library is free for all purposes without any express
11 * guarantee it works.
12 *
13 * Tom St Denis, [email protected], http://math.libtomcrypt.org
14 */
15 #include <tommath.h>
16
17 /* returns size of ASCII reprensentation */
18 int mp_radix_size (mp_int * a, int radix, int *size)
19 {
20 int res, digs;
21 mp_int t;
22 mp_digit d;
23
24 *size = 0;
25
26 /* special case for binary */
27 if (radix == 2) {
28 *size = mp_count_bits (a) + (a->sign == MP_NEG ? 1 : 0) + 1;
29 return MP_OKAY;
30 }
31
32 /* make sure the radix is in range */
33 if (radix < 2 || radix > 64) {
34 return MP_VAL;
35 }
36
37 /* init a copy of the input */
38 if ((res = mp_init_copy (&t, a)) != MP_OKAY) {
39 return res;
40 }
41
42 /* digs is the digit count */
43 digs = 0;
44
45 /* if it's negative add one for the sign */
46 if (t.sign == MP_NEG) {
47 ++digs;
48 t.sign = MP_ZPOS;
49 }
50
51 /* fetch out all of the digits */
52 while (mp_iszero (&t) == 0) {
53 if ((res = mp_div_d (&t, (mp_digit) radix, &t, &d)) != MP_OKAY) {
54 mp_clear (&t);
55 return res;
56 }
57 ++digs;
58 }
59 mp_clear (&t);
60
61 /* return digs + 1, the 1 is for the NULL byte that would be required. */
62 *size = digs + 1;
63 return MP_OKAY;
64 }
65