diff options
Diffstat (limited to 'third_party/heimdal/lib/hcrypto/libtommath/bn_mp_mul_2.c')
-rw-r--r-- | third_party/heimdal/lib/hcrypto/libtommath/bn_mp_mul_2.c | 64 |
1 files changed, 64 insertions, 0 deletions
diff --git a/third_party/heimdal/lib/hcrypto/libtommath/bn_mp_mul_2.c b/third_party/heimdal/lib/hcrypto/libtommath/bn_mp_mul_2.c new file mode 100644 index 0000000..bc0691a --- /dev/null +++ b/third_party/heimdal/lib/hcrypto/libtommath/bn_mp_mul_2.c @@ -0,0 +1,64 @@ +#include "tommath_private.h" +#ifdef BN_MP_MUL_2_C +/* LibTomMath, multiple-precision integer library -- Tom St Denis */ +/* SPDX-License-Identifier: Unlicense */ + +/* b = a*2 */ +mp_err mp_mul_2(const mp_int *a, mp_int *b) +{ + int x, oldused; + mp_err err; + + /* grow to accomodate result */ + if (b->alloc < (a->used + 1)) { + if ((err = mp_grow(b, a->used + 1)) != MP_OKAY) { + return err; + } + } + + oldused = b->used; + b->used = a->used; + + { + mp_digit r, rr, *tmpa, *tmpb; + + /* alias for source */ + tmpa = a->dp; + + /* alias for dest */ + tmpb = b->dp; + + /* carry */ + r = 0; + for (x = 0; x < a->used; x++) { + + /* get what will be the *next* carry bit from the + * MSB of the current digit + */ + rr = *tmpa >> (mp_digit)(MP_DIGIT_BIT - 1); + + /* now shift up this digit, add in the carry [from the previous] */ + *tmpb++ = ((*tmpa++ << 1uL) | r) & MP_MASK; + + /* copy the carry that would be from the source + * digit into the next iteration + */ + r = rr; + } + + /* new leading digit? */ + if (r != 0u) { + /* add a MSB which is always 1 at this point */ + *tmpb = 1; + ++(b->used); + } + + /* now zero any excess digits on the destination + * that we didn't write to + */ + MP_ZERO_DIGITS(b->dp + b->used, oldused - b->used); + } + b->sign = a->sign; + return MP_OKAY; +} +#endif |