62 lines
1.4 KiB
C
62 lines
1.4 KiB
C
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/* LibTomMath, multiple-precision integer library -- Tom St Denis
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*
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* LibTomMath is library that provides for multiple-precision
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* integer arithmetic as well as number theoretic functionality.
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*
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* The library is designed directly after the MPI library by
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* Michael Fromberger but has been written from scratch with
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* additional optimizations in place.
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*
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* The library is free for all purposes without any express
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* guarantee it works.
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*
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* Tom St Denis, tomstdenis@iahu.ca, http://math.libtomcrypt.org
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*/
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#include <tommath.h>
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/* read a bigint from a file stream in ASCII */
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int mp_fread(mp_int *a, int radix, FILE *stream)
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{
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int err, ch, neg, y;
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/* clear a */
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mp_zero(a);
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/* if first digit is - then set negative */
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ch = fgetc(stream);
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if (ch == '-') {
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neg = MP_NEG;
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ch = fgetc(stream);
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} else {
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neg = MP_ZPOS;
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}
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for (;;) {
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/* find y in the radix map */
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for (y = 0; y < radix; y++) {
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if (mp_s_rmap[y] == ch) {
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break;
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}
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}
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if (y == radix) {
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break;
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}
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/* shift up and add */
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if ((err = mp_mul_d(a, radix, a)) != MP_OKAY) {
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return err;
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}
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if ((err = mp_add_d(a, y, a)) != MP_OKAY) {
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return err;
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}
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ch = fgetc(stream);
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}
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if (mp_cmp_d(a, 0) != MP_EQ) {
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a->sign = neg;
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}
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return MP_OKAY;
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}
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