| 1 | /* mpn_lshift -- Shift left low level. |
|---|
| 2 | |
|---|
| 3 | Copyright (C) 1991-2022 Free Software Foundation, Inc. |
|---|
| 4 | |
|---|
| 5 | This file is part of the GNU MP Library. |
|---|
| 6 | |
|---|
| 7 | The GNU MP Library is free software; you can redistribute it and/or modify |
|---|
| 8 | it under the terms of the GNU Lesser General Public License as published by |
|---|
| 9 | the Free Software Foundation; either version 2.1 of the License, or (at your |
|---|
| 10 | option) any later version. |
|---|
| 11 | |
|---|
| 12 | The GNU MP Library is distributed in the hope that it will be useful, but |
|---|
| 13 | WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY |
|---|
| 14 | or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public |
|---|
| 15 | License for more details. |
|---|
| 16 | |
|---|
| 17 | You should have received a copy of the GNU Lesser General Public License |
|---|
| 18 | along with the GNU MP Library; see the file COPYING.LIB. If not, see |
|---|
| 19 | <https://www.gnu.org/licenses/>. */ |
|---|
| 20 | |
|---|
| 21 | #include <gmp.h> |
|---|
| 22 | #include "gmp-impl.h" |
|---|
| 23 | |
|---|
| 24 | /* Shift U (pointed to by UP and USIZE digits long) CNT bits to the left |
|---|
| 25 | and store the USIZE least significant digits of the result at WP. |
|---|
| 26 | Return the bits shifted out from the most significant digit. |
|---|
| 27 | |
|---|
| 28 | Argument constraints: |
|---|
| 29 | 1. 0 < CNT < BITS_PER_MP_LIMB |
|---|
| 30 | 2. If the result is to be written over the input, WP must be >= UP. |
|---|
| 31 | */ |
|---|
| 32 | |
|---|
| 33 | mp_limb_t |
|---|
| 34 | mpn_lshift (register mp_ptr wp, |
|---|
| 35 | register mp_srcptr up, mp_size_t usize, |
|---|
| 36 | register unsigned int cnt) |
|---|
| 37 | { |
|---|
| 38 | register mp_limb_t high_limb, low_limb; |
|---|
| 39 | register unsigned sh_1, sh_2; |
|---|
| 40 | register mp_size_t i; |
|---|
| 41 | mp_limb_t retval; |
|---|
| 42 | |
|---|
| 43 | #ifdef DEBUG |
|---|
| 44 | if (usize == 0 || cnt == 0) |
|---|
| 45 | abort (); |
|---|
| 46 | #endif |
|---|
| 47 | |
|---|
| 48 | sh_1 = cnt; |
|---|
| 49 | #if 0 |
|---|
| 50 | if (sh_1 == 0) |
|---|
| 51 | { |
|---|
| 52 | if (wp != up) |
|---|
| 53 | { |
|---|
| 54 | /* Copy from high end to low end, to allow specified input/output |
|---|
| 55 | overlapping. */ |
|---|
| 56 | for (i = usize - 1; i >= 0; i--) |
|---|
| 57 | wp[i] = up[i]; |
|---|
| 58 | } |
|---|
| 59 | return 0; |
|---|
| 60 | } |
|---|
| 61 | #endif |
|---|
| 62 | |
|---|
| 63 | wp += 1; |
|---|
| 64 | sh_2 = BITS_PER_MP_LIMB - sh_1; |
|---|
| 65 | i = usize - 1; |
|---|
| 66 | low_limb = up[i]; |
|---|
| 67 | retval = low_limb >> sh_2; |
|---|
| 68 | high_limb = low_limb; |
|---|
| 69 | while (--i >= 0) |
|---|
| 70 | { |
|---|
| 71 | low_limb = up[i]; |
|---|
| 72 | wp[i] = (high_limb << sh_1) | (low_limb >> sh_2); |
|---|
| 73 | high_limb = low_limb; |
|---|
| 74 | } |
|---|
| 75 | wp[i] = high_limb << sh_1; |
|---|
| 76 | |
|---|
| 77 | return retval; |
|---|
| 78 | } |
|---|
| 79 | |
|---|
