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|
// file kernel/n/c/shift.c: shift of natural integers
/*-----------------------------------------------------------------------+
| Copyright 2005-2006, Michel Quercia (michel.quercia@prepas.org) |
| |
| This file is part of Numerix. Numerix is free software; you can |
| redistribute it and/or modify it under the terms of the GNU Lesser |
| General Public License as published by the Free Software Foundation; |
| either version 2.1 of the License, or (at your option) any later |
| version. |
| |
| The Numerix Library is distributed in the hope that it will be |
| useful, but WITHOUT ANY WARRANTY; without even the implied warranty |
| of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| Lesser General Public License for more details. |
| |
| You should have received a copy of the GNU Lesser General Public |
| License along with the GNU MP Library; see the file COPYING. If not, |
| write to the Free Software Foundation, Inc., 59 Temple Place - |
| Suite 330, Boston, MA 02111-1307, USA. |
+-----------------------------------------------------------------------+
| |
| Dcalages |
| |
+-----------------------------------------------------------------------*/
/* ---------------------------------------- Dcalage par adresses dcroissantes
entre :
a = naturel de longueur la > 0
b = naturel de longueur la
k = entier tel que 0 <= k < HW
sortie :
b <- a >> k
retourne a mod 2^k
remarque :
b peut recouvrir le haut de a
*/
#ifndef assembly_sn_shift_down
chiffre xn(shift_down)(chiffre *a, long la, chiffre *b, int k) {
if (k) {
long i;
#ifdef ndouble
ndouble r;
for (i=la-1, r=0; i>=0; i--) {r += (ndouble)a[i]; b[i] = r >> k; r <<= HW;}
return((r >> HW) & (((chiffre)1<<k)-1));
#else
chiffre r,s;
for (i=la-1, r=0; i>=0; i--) {
s = a[i];
b[i] = (r << (HW-k)) + (s >> k);
r = s;
}
return(r & (((chiffre)1<<k)-1));
#endif /* ndouble */
} else {
xn(move)(a,la,b);
return(0);
}
}
#endif /* assembly_sn_shift_down */
/* ---------------------------------------- Dcalage par adresses croissantes
entre :
a = naturel de longueur la > 0
b = naturel de longueur la
k = entier tel que 0 <= k < HW
sortie :
b <- a << k
retourne les k bits de poids fort de a
remarque :
b peut recouvrir le bas de a
*/
#ifndef assembly_sn_shift_up
chiffre xn(shift_up)(chiffre *a, long la, chiffre *b, int k) {
if (k) {
long i;
#ifdef ndouble
ndouble r;
for (i=0, r=0; i<la; i++) {r += (ndouble)a[i] << k; b[i] = r; r >>= HW;}
return(r);
#else
chiffre r,s;
for (i=0, r=0; i<la; i++) {
s = a[i];
b[i] = (s << k) + r;
r = s >> (HW-k);
}
return(r);
#endif
} else {
xn(move)(a,la,b);
return(0);
}
}
#endif /* assembly_sn_shift_up */
|
