annotate bn_mp_fread.c @ 2:86e0b50a9b58 libtommath-orig ltm-0.30-orig

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author Matt Johnston <matt@ucc.asn.au>
date Mon, 31 May 2004 18:25:22 +0000
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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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