libtommath/bn_mp_to_sbin.c

#include "tommath_private.h"
#ifdef BN_MP_TO_SBIN_C
/* LibTomMath, multiple-precision integer library -- Tom St Denis */
/* SPDX-License-Identifier: Unlicense */

/* store in signed [big endian] format */
mp_err mp_to_sbin(const mp_int *a, unsigned char *b, size_t maxlen, size_t *written)
{
   mp_err err;
   if (maxlen == 0u) {
      return MP_VAL;
   }

   if ((err = mp_to_ubin(a, b + 1, maxlen - 1u, written)) != MP_OKAY) {
      return err;
   }
   if (written != NULL) {
      (*written)++;
   }
   b[0] = (a->sign == MP_ZPOS) ? (unsigned char)0 : (unsigned char)1;
   return MP_OKAY;
}
#endif