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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 /* read a bigint from a file stream in ASCII */ |
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18 int mp_fread(mp_int *a, int radix, FILE *stream) |
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19 { |
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20 int err, ch, neg, y; |
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21 |
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22 /* clear a */ |
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23 mp_zero(a); |
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24 |
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25 /* if first digit is - then set negative */ |
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26 ch = fgetc(stream); |
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27 if (ch == '-') { |
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28 neg = MP_NEG; |
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29 ch = fgetc(stream); |
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30 } else { |
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31 neg = MP_ZPOS; |
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32 } |
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33 |
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34 for (;;) { |
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35 /* find y in the radix map */ |
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36 for (y = 0; y < radix; y++) { |
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37 if (mp_s_rmap[y] == ch) { |
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38 break; |
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39 } |
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40 } |
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41 if (y == radix) { |
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42 break; |
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43 } |
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44 |
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45 /* shift up and add */ |
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46 if ((err = mp_mul_d(a, radix, a)) != MP_OKAY) { |
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47 return err; |
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48 } |
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49 if ((err = mp_add_d(a, y, a)) != MP_OKAY) { |
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50 return err; |
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51 } |
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52 |
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53 ch = fgetc(stream); |
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54 } |
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55 if (mp_cmp_d(a, 0) != MP_EQ) { |
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56 a->sign = neg; |
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57 } |
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58 |
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59 return MP_OKAY; |
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60 } |
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61 |
