1 /* mpf_add -- Add two floats.
2
3 Copyright 1993, 1994, 1996, 2000, 2001, 2005 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.h"
32 #include "gmp-impl.h"
33
34 void
mpf_add(mpf_ptr r,mpf_srcptr u,mpf_srcptr v)35 mpf_add (mpf_ptr r, mpf_srcptr u, mpf_srcptr v)
36 {
37 mp_srcptr up, vp;
38 mp_ptr rp, tp;
39 mp_size_t usize, vsize, rsize;
40 mp_size_t prec;
41 mp_exp_t uexp;
42 mp_size_t ediff;
43 mp_limb_t cy;
44 int negate;
45 TMP_DECL;
46
47 usize = u->_mp_size;
48 vsize = v->_mp_size;
49
50 /* Handle special cases that don't work in generic code below. */
51 if (usize == 0)
52 {
53 set_r_v_maybe:
54 if (r != v)
55 mpf_set (r, v);
56 return;
57 }
58 if (vsize == 0)
59 {
60 v = u;
61 goto set_r_v_maybe;
62 }
63
64 /* If signs of U and V are different, perform subtraction. */
65 if ((usize ^ vsize) < 0)
66 {
67 __mpf_struct v_negated;
68 v_negated._mp_size = -vsize;
69 v_negated._mp_exp = v->_mp_exp;
70 v_negated._mp_d = v->_mp_d;
71 mpf_sub (r, u, &v_negated);
72 return;
73 }
74
75 TMP_MARK;
76
77 /* Signs are now known to be the same. */
78 negate = usize < 0;
79
80 /* Make U be the operand with the largest exponent. */
81 if (u->_mp_exp < v->_mp_exp)
82 {
83 mpf_srcptr t;
84 t = u; u = v; v = t;
85 usize = u->_mp_size;
86 vsize = v->_mp_size;
87 }
88
89 usize = ABS (usize);
90 vsize = ABS (vsize);
91 up = u->_mp_d;
92 vp = v->_mp_d;
93 rp = r->_mp_d;
94 prec = r->_mp_prec;
95 uexp = u->_mp_exp;
96 ediff = u->_mp_exp - v->_mp_exp;
97
98 /* If U extends beyond PREC, ignore the part that does. */
99 if (usize > prec)
100 {
101 up += usize - prec;
102 usize = prec;
103 }
104
105 /* If V extends beyond PREC, ignore the part that does.
106 Note that this may make vsize negative. */
107 if (vsize + ediff > prec)
108 {
109 vp += vsize + ediff - prec;
110 vsize = prec - ediff;
111 }
112
113 #if 0
114 /* Locate the least significant non-zero limb in (the needed parts
115 of) U and V, to simplify the code below. */
116 while (up[0] == 0)
117 up++, usize--;
118 while (vp[0] == 0)
119 vp++, vsize--;
120 #endif
121
122 /* Allocate temp space for the result. Allocate
123 just vsize + ediff later??? */
124 tp = TMP_ALLOC_LIMBS (prec);
125
126 if (ediff >= prec)
127 {
128 /* V completely cancelled. */
129 if (rp != up)
130 MPN_COPY_INCR (rp, up, usize);
131 rsize = usize;
132 }
133 else
134 {
135 /* uuuu | uuuu | uuuu | uuuu | uuuu */
136 /* vvvvvvv | vv | vvvvv | v | vv */
137
138 if (usize > ediff)
139 {
140 /* U and V partially overlaps. */
141 if (vsize + ediff <= usize)
142 {
143 /* uuuu */
144 /* v */
145 mp_size_t size;
146 size = usize - ediff - vsize;
147 MPN_COPY (tp, up, size);
148 cy = mpn_add (tp + size, up + size, usize - size, vp, vsize);
149 rsize = usize;
150 }
151 else
152 {
153 /* uuuu */
154 /* vvvvv */
155 mp_size_t size;
156 size = vsize + ediff - usize;
157 MPN_COPY (tp, vp, size);
158 cy = mpn_add (tp + size, up, usize, vp + size, usize - ediff);
159 rsize = vsize + ediff;
160 }
161 }
162 else
163 {
164 /* uuuu */
165 /* vv */
166 mp_size_t size;
167 size = vsize + ediff - usize;
168 MPN_COPY (tp, vp, vsize);
169 MPN_ZERO (tp + vsize, ediff - usize);
170 MPN_COPY (tp + size, up, usize);
171 cy = 0;
172 rsize = size + usize;
173 }
174
175 MPN_COPY (rp, tp, rsize);
176 rp[rsize] = cy;
177 rsize += cy;
178 uexp += cy;
179 }
180
181 r->_mp_size = negate ? -rsize : rsize;
182 r->_mp_exp = uexp;
183 TMP_FREE;
184 }
185