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comparison bn_mp_read_radix.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 /* read a string [ASCII] in a given radix */
18 int mp_read_radix (mp_int * a, char *str, int radix)
19 {
20 int y, res, neg;
21 char ch;
22
23 /* make sure the radix is ok */
24 if (radix < 2 || radix > 64) {
25 return MP_VAL;
26 }
27
28 /* if the leading digit is a
29 * minus set the sign to negative.
30 */
31 if (*str == '-') {
32 ++str;
33 neg = MP_NEG;
34 } else {
35 neg = MP_ZPOS;
36 }
37
38 /* set the integer to the default of zero */
39 mp_zero (a);
40
41 /* process each digit of the string */
42 while (*str) {
43 /* if the radix < 36 the conversion is case insensitive
44 * this allows numbers like 1AB and 1ab to represent the same value
45 * [e.g. in hex]
46 */
47 ch = (char) ((radix < 36) ? toupper (*str) : *str);
48 for (y = 0; y < 64; y++) {
49 if (ch == mp_s_rmap[y]) {
50 break;
51 }
52 }
53
54 /* if the char was found in the map
55 * and is less than the given radix add it
56 * to the number, otherwise exit the loop.
57 */
58 if (y < radix) {
59 if ((res = mp_mul_d (a, (mp_digit) radix, a)) != MP_OKAY) {
60 return res;
61 }
62 if ((res = mp_add_d (a, (mp_digit) y, a)) != MP_OKAY) {
63 return res;
64 }
65 } else {
66 break;
67 }
68 ++str;
69 }
70
71 /* set the sign only if a != 0 */
72 if (mp_iszero(a) != 1) {
73 a->sign = neg;
74 }
75 return MP_OKAY;
76 }