diff options
Diffstat (limited to '')
-rw-r--r-- | third_party/heimdal/lib/hcrypto/libtommath/bn_mp_mul_2d.c | 69 |
1 files changed, 69 insertions, 0 deletions
diff --git a/third_party/heimdal/lib/hcrypto/libtommath/bn_mp_mul_2d.c b/third_party/heimdal/lib/hcrypto/libtommath/bn_mp_mul_2d.c new file mode 100644 index 0000000..87354de --- /dev/null +++ b/third_party/heimdal/lib/hcrypto/libtommath/bn_mp_mul_2d.c @@ -0,0 +1,69 @@ +#include "tommath_private.h" +#ifdef BN_MP_MUL_2D_C +/* LibTomMath, multiple-precision integer library -- Tom St Denis */ +/* SPDX-License-Identifier: Unlicense */ + +/* shift left by a certain bit count */ +mp_err mp_mul_2d(const mp_int *a, int b, mp_int *c) +{ + mp_digit d; + mp_err err; + + /* copy */ + if (a != c) { + if ((err = mp_copy(a, c)) != MP_OKAY) { + return err; + } + } + + if (c->alloc < (c->used + (b / MP_DIGIT_BIT) + 1)) { + if ((err = mp_grow(c, c->used + (b / MP_DIGIT_BIT) + 1)) != MP_OKAY) { + return err; + } + } + + /* shift by as many digits in the bit count */ + if (b >= MP_DIGIT_BIT) { + if ((err = mp_lshd(c, b / MP_DIGIT_BIT)) != MP_OKAY) { + return err; + } + } + + /* shift any bit count < MP_DIGIT_BIT */ + d = (mp_digit)(b % MP_DIGIT_BIT); + if (d != 0u) { + mp_digit *tmpc, shift, mask, r, rr; + int x; + + /* bitmask for carries */ + mask = ((mp_digit)1 << d) - (mp_digit)1; + + /* shift for msbs */ + shift = (mp_digit)MP_DIGIT_BIT - d; + + /* alias */ + tmpc = c->dp; + + /* carry */ + r = 0; + for (x = 0; x < c->used; x++) { + /* get the higher bits of the current word */ + rr = (*tmpc >> shift) & mask; + + /* shift the current word and OR in the carry */ + *tmpc = ((*tmpc << d) | r) & MP_MASK; + ++tmpc; + + /* set the carry to the carry bits of the current word */ + r = rr; + } + + /* set final carry */ + if (r != 0u) { + c->dp[(c->used)++] = r; + } + } + mp_clamp(c); + return MP_OKAY; +} +#endif |