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