libtommath/bn_mp_from_sbin.c
2019-10-06 16:15:53 +02:00

26 lines
635 B
C

#include "tommath_private.h"
#ifdef BN_MP_FROM_SBIN_C
/* LibTomMath, multiple-precision integer library -- Tom St Denis */
/* SPDX-License-Identifier: Unlicense */
/* read signed bin, big endian, first byte is 0==positive or 1==negative */
mp_err mp_from_sbin(mp_int *a, const unsigned char *buf, size_t size)
{
mp_err err;
/* read magnitude */
if ((err = mp_from_ubin(a, buf + 1, size - 1u)) != MP_OKAY) {
return err;
}
/* first byte is 0 for positive, non-zero for negative */
if (buf[0] == (unsigned char)0) {
a->sign = MP_ZPOS;
} else {
a->sign = MP_NEG;
}
return MP_OKAY;
}
#endif