mp_grow.c

   1 #include "tommath_private.h"
   2 #ifdef MP_GROW_C
   3 /* LibTomMath, multiple-precision integer library -- Tom St Denis */
   4 /* SPDX-License-Identifier: Unlicense */
   5
   6 /* grow as required */
   7 mp_err mp_grow(mp_int *a, int size)
   8 {
   9    if (size < 0) {
  10       return MP_VAL;
  11    }
  12
  13    /* if the alloc size is smaller alloc more ram */
  14    if (a->alloc < size) {
  15       mp_digit *dp;
  16
  17       if (size > MP_MAX_DIGIT_COUNT) {
  18          return MP_OVF;
  19       }
  20
  21       /* reallocate the array a->dp
  22        *
  23        * We store the return in a temporary variable
  24        * in case the operation failed we don't want
  25        * to overwrite the dp member of a.
  26        */
  27       dp = (mp_digit *) MP_REALLOC(a->dp,
  28                                    (size_t)a->alloc * sizeof(mp_digit),
  29                                    (size_t)size * sizeof(mp_digit));
  30       if (dp == NULL) {
  31          /* reallocation failed but "a" is still valid [can be freed] */
  32          return MP_MEM;
  33       }
  34
  35       /* reallocation succeeded so set a->dp */
  36       a->dp = dp;
  37
  38       /* zero excess digits */
  39       s_mp_zero_digs(a->dp + a->alloc, size - a->alloc);
  40       a->alloc = size;
  41    }
  42    return MP_OKAY;
  43 }
  44 #endif