1 /* mpn_sub_n -- Subtract two limb vectors of equal, non-zero length.
3 Copyright (C) 1992, 1993, 1994, 1996 Free Software Foundation, Inc.
5 This file is part of the GNU MP Library.
7 The GNU MP Library is free software; you can redistribute it and/or modify
8 it under the terms of the GNU Library General Public License as published by
9 the Free Software Foundation; either version 2 of the License, or (at your
10 option) any later version.
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 Library General Public
15 License for more details.
17 You should have received a copy of the GNU Library General Public License
18 along with the GNU MP Library; see the file COPYING.LIB. If not, write to
19 the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
26 mpn_sub_n (mp_ptr res_ptr
, mp_srcptr s1_ptr
, mp_srcptr s2_ptr
, mp_size_t size
)
28 mpn_sub_n (res_ptr
, s1_ptr
, s2_ptr
, size
)
29 register mp_ptr res_ptr
;
30 register mp_srcptr s1_ptr
;
31 register mp_srcptr s2_ptr
;
35 register mp_limb x
, y
, cy
;
38 /* The loop counter and index J goes from -SIZE to -1. This way
39 the loop becomes faster. */
42 /* Offset the base pointers to compensate for the negative indices. */
52 y
+= cy
; /* add previous carry to subtrahend */
53 cy
= (y
< cy
); /* get out carry from that addition */
54 y
= x
- y
; /* main subtract */
55 cy
= (y
> x
) + cy
; /* get out carry from the subtract, combine */