1 /* mpz_addmul, mpz_submul -- add or subtract multiple.
2
3 Copyright 2001, 2004, 2005, 2012 Free Software Foundation, Inc.
4
5 This file is part of the GNU MP Library.
6
7 The GNU MP Library is free software; you can redistribute it and/or modify
8 it under the terms of either:
9
10 * the GNU Lesser General Public License as published by the Free
11 Software Foundation; either version 3 of the License, or (at your
12 option) any later version.
13
14 or
15
16 * the GNU General Public License as published by the Free Software
17 Foundation; either version 2 of the License, or (at your option) any
18 later version.
19
20 or both in parallel, as here.
21
22 The GNU MP Library is distributed in the hope that it will be useful, but
23 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
24 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
25 for more details.
26
27 You should have received copies of the GNU General Public License and the
28 GNU Lesser General Public License along with the GNU MP Library. If not,
29 see https://www.gnu.org/licenses/. */
30
31 #include "gmp-impl.h"
32
33
34 /* expecting x and y both with non-zero high limbs */
35 #define mpn_cmp_twosizes_lt(xp,xsize, yp,ysize) \
36 ((xsize) < (ysize) \
37 || ((xsize) == (ysize) && mpn_cmp (xp, yp, xsize) < 0))
38
39
40 /* sub>=0 means an addmul w += x*y, sub<0 means a submul w -= x*y.
41
42 The signs of w, x and y are fully accounted for by each flipping "sub".
43
44 The sign of w is retained for the result, unless the absolute value
45 submul underflows, in which case it flips. */
46
47 static void __gmpz_aorsmul (REGPARM_3_1 (mpz_ptr w, mpz_srcptr x, mpz_srcptr y, mp_size_t sub)) REGPARM_ATTR (1);
48 #define mpz_aorsmul(w,x,y,sub) __gmpz_aorsmul (REGPARM_3_1 (w, x, y, sub))
49
50 REGPARM_ATTR (1) static void
mpz_aorsmul(mpz_ptr w,mpz_srcptr x,mpz_srcptr y,mp_size_t sub)51 mpz_aorsmul (mpz_ptr w, mpz_srcptr x, mpz_srcptr y, mp_size_t sub)
52 {
53 mp_size_t xsize, ysize, tsize, wsize, wsize_signed;
54 mp_ptr wp, tp;
55 mp_limb_t c, high;
56 TMP_DECL;
57
58 /* w unaffected if x==0 or y==0 */
59 xsize = SIZ(x);
60 ysize = SIZ(y);
61 if (xsize == 0 || ysize == 0)
62 return;
63
64 /* make x the bigger of the two */
65 if (ABS(ysize) > ABS(xsize))
66 {
67 MPZ_SRCPTR_SWAP (x, y);
68 MP_SIZE_T_SWAP (xsize, ysize);
69 }
70
71 sub ^= ysize;
72 ysize = ABS(ysize);
73
74 /* use mpn_addmul_1/mpn_submul_1 if possible */
75 if (ysize == 1)
76 {
77 mpz_aorsmul_1 (w, x, PTR(y)[0], sub);
78 return;
79 }
80
81 sub ^= xsize;
82 xsize = ABS(xsize);
83
84 wsize_signed = SIZ(w);
85 sub ^= wsize_signed;
86 wsize = ABS(wsize_signed);
87
88 tsize = xsize + ysize;
89 wp = MPZ_REALLOC (w, MAX (wsize, tsize) + 1);
90
91 if (wsize_signed == 0)
92 {
93 /* Nothing to add to, just set w=x*y. No w==x or w==y overlap here,
94 since we know x,y!=0 but w==0. */
95 high = mpn_mul (wp, PTR(x),xsize, PTR(y),ysize);
96 tsize -= (high == 0);
97 SIZ(w) = (sub >= 0 ? tsize : -tsize);
98 return;
99 }
100
101 TMP_MARK;
102 tp = TMP_ALLOC_LIMBS (tsize);
103
104 high = mpn_mul (tp, PTR(x),xsize, PTR(y),ysize);
105 tsize -= (high == 0);
106 ASSERT (tp[tsize-1] != 0);
107 if (sub >= 0)
108 {
109 mp_srcptr up = wp;
110 mp_size_t usize = wsize;
111
112 if (usize < tsize)
113 {
114 up = tp;
115 usize = tsize;
116 tp = wp;
117 tsize = wsize;
118
119 wsize = usize;
120 }
121
122 c = mpn_add (wp, up,usize, tp,tsize);
123 wp[wsize] = c;
124 wsize += (c != 0);
125 }
126 else
127 {
128 mp_srcptr up = wp;
129 mp_size_t usize = wsize;
130
131 if (mpn_cmp_twosizes_lt (up,usize, tp,tsize))
132 {
133 up = tp;
134 usize = tsize;
135 tp = wp;
136 tsize = wsize;
137
138 wsize = usize;
139 wsize_signed = -wsize_signed;
140 }
141
142 ASSERT_NOCARRY (mpn_sub (wp, up,usize, tp,tsize));
143 wsize = usize;
144 MPN_NORMALIZE (wp, wsize);
145 }
146
147 SIZ(w) = (wsize_signed >= 0 ? wsize : -wsize);
148
149 TMP_FREE;
150 }
151
152
153 void
mpz_addmul(mpz_ptr w,mpz_srcptr u,mpz_srcptr v)154 mpz_addmul (mpz_ptr w, mpz_srcptr u, mpz_srcptr v)
155 {
156 mpz_aorsmul (w, u, v, (mp_size_t) 0);
157 }
158
159 void
mpz_submul(mpz_ptr w,mpz_srcptr u,mpz_srcptr v)160 mpz_submul (mpz_ptr w, mpz_srcptr u, mpz_srcptr v)
161 {
162 mpz_aorsmul (w, u, v, (mp_size_t) -1);
163 }
164