Mercurial > dropbear

annotate libtommath/bn_mp_radix_size.c @ 1060:4c733310c21d nocircbuffer

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reword comment for clarity
author Matt Johnston <matt@ucc.asn.au>
date Sun, 01 Mar 2015 23:26:42 +0800
parents 5ff8218bcee9
children 60fc6476e044
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1 #include <tommath.h>
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2 #ifdef BN_MP_RADIX_SIZE_C
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3 /* LibTomMath, multiple-precision integer library -- Tom St Denis
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4 *
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5 * LibTomMath is a library that provides multiple-precision
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6 * integer arithmetic as well as number theoretic functionality.
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7 *
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8 * The library was designed directly after the MPI library by
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9 * Michael Fromberger but has been written from scratch with
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10 * additional optimizations in place.
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11 *
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12 * The library is free for all purposes without any express
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13 * guarantee it works.
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14 *
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15 * Tom St Denis, [email protected], http://math.libtomcrypt.com
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16 */
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17
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18 /* returns size of ASCII reprensentation */
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19 int mp_radix_size (mp_int * a, int radix, int *size)
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20 {
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21 int res, digs;
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22 mp_int t;
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23 mp_digit d;
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24
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25 *size = 0;
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26
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27 /* special case for binary */
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28 if (radix == 2) {
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29 *size = mp_count_bits (a) + (a->sign == MP_NEG ? 1 : 0) + 1;
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30 return MP_OKAY;
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31 }
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32
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33 /* make sure the radix is in range */
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34 if (radix < 2 || radix > 64) {
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35 return MP_VAL;
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36 }
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37
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38 if (mp_iszero(a) == MP_YES) {
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39 *size = 2;
284
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40 return MP_OKAY;
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41 }
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42
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43 /* digs is the digit count */
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44 digs = 0;
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45
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46 /* if it's negative add one for the sign */
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47 if (a->sign == MP_NEG) {
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48 ++digs;
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49 }
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50
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51 /* init a copy of the input */
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52 if ((res = mp_init_copy (&t, a)) != MP_OKAY) {
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53 return res;
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54 }
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55
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56 /* force temp to positive */
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57 t.sign = MP_ZPOS;
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58
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59 /* fetch out all of the digits */
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60 while (mp_iszero (&t) == MP_NO) {
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61 if ((res = mp_div_d (&t, (mp_digit) radix, &t, &d)) != MP_OKAY) {
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62 mp_clear (&t);
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63 return res;
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64 }
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65 ++digs;
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66 }
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67 mp_clear (&t);
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68
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69 /* return digs + 1, the 1 is for the NULL byte that would be required. */
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70 *size = digs + 1;
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71 return MP_OKAY;
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72 }
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73
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74 #endif
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75
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76 /* $Source: /cvs/libtom/libtommath/bn_mp_radix_size.c,v $ */
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77 /* $Revision: 1.4 $ */
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78 /* $Date: 2006/03/31 14:18:44 $ */