65 lines
2.0 KiB
C
65 lines
2.0 KiB
C
/* __mpn_submul_1 -- multiply the S1_SIZE long limb vector pointed to by S1_PTR
|
|
by S2_LIMB, subtract the S1_SIZE least significant limbs of the product
|
|
from the limb vector pointed to by RES_PTR. Return the most significant
|
|
limb of the product, adjusted for carry-out from the subtraction.
|
|
|
|
Copyright (C) 1992, 1993, 1994 Free Software Foundation, Inc.
|
|
|
|
This file is part of the GNU MP Library.
|
|
|
|
The GNU MP Library is free software; you can redistribute it and/or modify
|
|
it under the terms of the GNU Library General Public License as published by
|
|
the Free Software Foundation; either version 2 of the License, or (at your
|
|
option) any later version.
|
|
|
|
The GNU MP 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 Library General Public
|
|
License for more details.
|
|
|
|
You should have received a copy of the GNU Library General Public License
|
|
along with the GNU MP Library; see the file COPYING.LIB. If not, write to
|
|
the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
|
|
|
|
#include "gmp.h"
|
|
#include "gmp-impl.h"
|
|
#include "longlong.h"
|
|
|
|
mp_limb
|
|
__mpn_submul_1 (res_ptr, s1_ptr, s1_size, s2_limb)
|
|
register mp_ptr res_ptr;
|
|
register mp_srcptr s1_ptr;
|
|
mp_size_t s1_size;
|
|
register mp_limb s2_limb;
|
|
{
|
|
register mp_limb cy_limb;
|
|
register mp_size_t j;
|
|
register mp_limb prod_high, prod_low;
|
|
register mp_limb x;
|
|
|
|
/* The loop counter and index J goes from -SIZE to -1. This way
|
|
the loop becomes faster. */
|
|
j = -s1_size;
|
|
|
|
/* Offset the base pointers to compensate for the negative indices. */
|
|
res_ptr -= j;
|
|
s1_ptr -= j;
|
|
|
|
cy_limb = 0;
|
|
do
|
|
{
|
|
umul_ppmm (prod_high, prod_low, s1_ptr[j], s2_limb);
|
|
|
|
prod_low += cy_limb;
|
|
cy_limb = (prod_low < cy_limb) + prod_high;
|
|
|
|
x = res_ptr[j];
|
|
prod_low = x - prod_low;
|
|
cy_limb += (prod_low > x);
|
|
res_ptr[j] = prod_low;
|
|
}
|
|
while (++j != 0);
|
|
|
|
return cy_limb;
|
|
}
|