1170808Sdelphij/* mpn_lshift -- Shift left low level. 2170808Sdelphij 3170808SdelphijCopyright (C) 1991, 1993, 1994, 1996 Free Software Foundation, Inc. 4170808Sdelphij 5170808SdelphijThis file is part of the GNU MP Library. 6170808Sdelphij 7171087SdelphijThe GNU MP Library is free software; you can redistribute it and/or modify 8170808Sdelphijit under the terms of the GNU Lesser General Public License as published by 9170808Sdelphijthe Free Software Foundation; either version 2.1 of the License, or (at your 10option) any later version. 11 12The GNU MP Library is distributed in the hope that it will be useful, but 13WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 14or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public 15License for more details. 16 17You should have received a copy of the GNU Lesser General Public License 18along with the GNU MP Library; see the file COPYING.LIB. If not, write to 19the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, 20MA 02111-1307, USA. */ 21 22#include <config.h> 23#include "gmp-impl.h" 24 25/* Shift U (pointed to by UP and USIZE digits long) CNT bits to the left 26 and store the USIZE least significant digits of the result at WP. 27 Return the bits shifted out from the most significant digit. 28 29 Argument constraints: 30 1. 0 < CNT < BITS_PER_MP_LIMB 31 2. If the result is to be written over the input, WP must be >= UP. 32*/ 33 34mp_limb_t 35#if __STDC__ 36mpn_lshift (register mp_ptr wp, 37 register mp_srcptr up, mp_size_t usize, 38 register unsigned int cnt) 39#else 40mpn_lshift (wp, up, usize, cnt) 41 register mp_ptr wp; 42 register mp_srcptr up; 43 mp_size_t usize; 44 register unsigned int cnt; 45#endif 46{ 47 register mp_limb_t high_limb, low_limb; 48 register unsigned sh_1, sh_2; 49 register mp_size_t i; 50 mp_limb_t retval; 51 52#ifdef DEBUG 53 if (usize == 0 || cnt == 0) 54 abort (); 55#endif 56 57 sh_1 = cnt; 58#if 0 59 if (sh_1 == 0) 60 { 61 if (wp != up) 62 { 63 /* Copy from high end to low end, to allow specified input/output 64 overlapping. */ 65 for (i = usize - 1; i >= 0; i--) 66 wp[i] = up[i]; 67 } 68 return 0; 69 } 70#endif 71 72 wp += 1; 73 sh_2 = BITS_PER_MP_LIMB - sh_1; 74 i = usize - 1; 75 low_limb = up[i]; 76 retval = low_limb >> sh_2; 77 high_limb = low_limb; 78 while (--i >= 0) 79 { 80 low_limb = up[i]; 81 wp[i] = (high_limb << sh_1) | (low_limb >> sh_2); 82 high_limb = low_limb; 83 } 84 wp[i] = high_limb << sh_1; 85 86 return retval; 87} 88