| Austin Schuh | dace2a6 | 2020-08-18 10:56:48 -0700 | [diff] [blame] | 1 | /* mpz_mul_2exp -- Multiply a bignum by 2**CNT |
| 2 | |
| 3 | Copyright 1991, 1993, 1994, 1996, 2001, 2002, 2012 Free Software Foundation, |
| 4 | Inc. |
| 5 | |
| 6 | This file is part of the GNU MP Library. |
| 7 | |
| 8 | The GNU MP Library is free software; you can redistribute it and/or modify |
| 9 | it under the terms of either: |
| 10 | |
| 11 | * the GNU Lesser General Public License as published by the Free |
| 12 | Software Foundation; either version 3 of the License, or (at your |
| 13 | option) any later version. |
| 14 | |
| 15 | or |
| 16 | |
| 17 | * the GNU General Public License as published by the Free Software |
| 18 | Foundation; either version 2 of the License, or (at your option) any |
| 19 | later version. |
| 20 | |
| 21 | or both in parallel, as here. |
| 22 | |
| 23 | The GNU MP Library is distributed in the hope that it will be useful, but |
| 24 | WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY |
| 25 | or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| 26 | for more details. |
| 27 | |
| 28 | You should have received copies of the GNU General Public License and the |
| 29 | GNU Lesser General Public License along with the GNU MP Library. If not, |
| 30 | see https://www.gnu.org/licenses/. */ |
| 31 | |
| 32 | #include "gmp-impl.h" |
| 33 | |
| 34 | void |
| 35 | mpz_mul_2exp (mpz_ptr r, mpz_srcptr u, mp_bitcnt_t cnt) |
| 36 | { |
| 37 | mp_size_t un, rn; |
| 38 | mp_size_t limb_cnt; |
| 39 | mp_ptr rp; |
| 40 | mp_srcptr up; |
| 41 | mp_limb_t rlimb; |
| 42 | |
| 43 | un = ABSIZ (u); |
| 44 | limb_cnt = cnt / GMP_NUMB_BITS; |
| 45 | rn = un + limb_cnt; |
| 46 | |
| 47 | if (un == 0) |
| 48 | rn = 0; |
| 49 | else |
| 50 | { |
| 51 | rp = MPZ_REALLOC (r, rn + 1); |
| 52 | up = PTR(u); |
| 53 | |
| 54 | cnt %= GMP_NUMB_BITS; |
| 55 | if (cnt != 0) |
| 56 | { |
| 57 | rlimb = mpn_lshift (rp + limb_cnt, up, un, cnt); |
| 58 | rp[rn] = rlimb; |
| 59 | rn += (rlimb != 0); |
| 60 | } |
| 61 | else |
| 62 | { |
| 63 | MPN_COPY_DECR (rp + limb_cnt, up, un); |
| 64 | } |
| 65 | |
| 66 | /* Zero all whole limbs at low end. Do it here and not before calling |
| 67 | mpn_lshift, not to lose for U == R. */ |
| 68 | MPN_ZERO (rp, limb_cnt); |
| 69 | } |
| 70 | |
| 71 | SIZ(r) = SIZ(u) >= 0 ? rn : -rn; |
| 72 | } |