1 /* mpz_sub_ui -- Subtract an unsigned one-word integer from an MP_INT.
3 Copyright (C) 1991 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 General Public License as published by
9 the Free Software Foundation; either version 2, or (at your option)
12 The GNU MP Library is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with the GNU MP Library; see the file COPYING. If not, write to
19 the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */
26 mpz_sub_ui (MP_INT *dif, const MP_INT *min, mp_limb sub)
28 mpz_sub_ui (dif, min, sub)
36 mp_size minsize, difsize;
40 abs_minsize = ABS (minsize);
42 /* If not space for SUM (and possible carry), increase space. */
43 difsize = abs_minsize + 1;
44 if (dif->alloc < difsize)
45 _mpz_realloc (dif, difsize);
47 /* These must be after realloc (ADD1 may be the same as SUM). */
53 MPN_COPY (difp, minp, abs_minsize);
66 difsize = mpn_add (difp, minp, abs_minsize, &sub, 1);
68 difp[abs_minsize] = 1;
69 difsize = -(difsize + abs_minsize);
73 /* The signs are different. Need exact comparision to determine
74 which operand to subtract from which. */
75 if (abs_minsize == 1 && minp[0] < sub)
76 difsize = -(abs_minsize
77 + mpn_sub (difp, &sub, 1, minp, 1));
79 difsize = (abs_minsize
80 + mpn_sub (difp, minp, abs_minsize, &sub, 1));