mp_fread.c

   1 #include "tommath_private.h"
   2 #ifdef MP_FREAD_C
   3 /* LibTomMath, multiple-precision integer library -- Tom St Denis */
   4 /* SPDX-License-Identifier: Unlicense */
   5
   6 #ifndef MP_NO_FILE
   7 /* read a bigint from a file stream in ASCII */
   8 mp_err mp_fread(mp_int *a, int radix, FILE *stream)
   9 {
  10    mp_err err;
  11    mp_sign sign = MP_ZPOS;
  12    int ch;
  13
  14    /* make sure the radix is ok */
  15    if ((radix < 2) || (radix > 64)) {
  16       return MP_VAL;
  17    }
  18
  19    /* if first digit is - then set negative */
  20    ch = fgetc(stream);
  21    if (ch == (int)'-') {
  22       sign = MP_NEG;
  23       ch = fgetc(stream);
  24    }
  25
  26    /* no digits, return error */
  27    if (ch == EOF) {
  28       return MP_ERR;
  29    }
  30
  31    /* clear a */
  32    mp_zero(a);
  33
  34    do {
  35       uint8_t y;
  36       unsigned pos;
  37       ch = (radix <= 36) ? MP_TOUPPER(ch) : ch;
  38       pos = (unsigned)(ch - (int)'+');
  39       if (MP_RADIX_MAP_REVERSE_SIZE <= pos) {
  40          break;
  41       }
  42
  43       y = s_mp_radix_map_reverse[pos];
  44
  45       if (y >= radix) {
  46          break;
  47       }
  48
  49       /* shift up and add */
  50       if ((err = mp_mul_d(a, (mp_digit)radix, a)) != MP_OKAY) {
  51          return err;
  52       }
  53       if ((err = mp_add_d(a, y, a)) != MP_OKAY) {
  54          return err;
  55       }
  56    } while ((ch = fgetc(stream)) != EOF);
  57
  58    if (!mp_iszero(a)) {
  59       a->sign = sign;
  60    }
  61
  62    return MP_OKAY;
  63 }
  64 #endif
  65
  66 #endif