Annotation of OpenXM_contrib/gmp/mpf/add.c, Revision 1.1.1.1
1.1 maekawa 1: /* mpf_add -- Add two floats.
2:
3: Copyright (C) 1993, 1994, 1996 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 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.
11:
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.
16:
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., 59 Temple Place - Suite 330, Boston,
20: MA 02111-1307, USA. */
21:
22: #include "gmp.h"
23: #include "gmp-impl.h"
24:
25: void
26: #if __STDC__
27: mpf_add (mpf_ptr r, mpf_srcptr u, mpf_srcptr v)
28: #else
29: mpf_add (r, u, v)
30: mpf_ptr r;
31: mpf_srcptr u;
32: mpf_srcptr v;
33: #endif
34: {
35: mp_srcptr up, vp;
36: mp_ptr rp, tp;
37: mp_size_t usize, vsize, rsize;
38: mp_size_t prec;
39: mp_exp_t uexp;
40: mp_size_t ediff;
41: mp_limb_t cy;
42: int negate;
43: TMP_DECL (marker);
44:
45: usize = u->_mp_size;
46: vsize = v->_mp_size;
47:
48: /* Handle special cases that don't work in generic code below. */
49: if (usize == 0)
50: {
51: mpf_set (r, v);
52: return;
53: }
54: if (vsize == 0)
55: {
56: mpf_set (r, u);
57: return;
58: }
59:
60: /* If signs of U and V are different, perform subtraction. */
61: if ((usize ^ vsize) < 0)
62: {
63: __mpf_struct v_negated;
64: v_negated._mp_size = -vsize;
65: v_negated._mp_exp = v->_mp_exp;
66: v_negated._mp_d = v->_mp_d;
67: mpf_sub (r, u, &v_negated);
68: return;
69: }
70:
71: TMP_MARK (marker);
72:
73: /* Signs are now known to be the same. */
74: negate = usize < 0;
75:
76: /* Make U be the operand with the largest exponent. */
77: if (u->_mp_exp < v->_mp_exp)
78: {
79: mpf_srcptr t;
80: t = u; u = v; v = t;
81: usize = u->_mp_size;
82: vsize = v->_mp_size;
83: }
84:
85: usize = ABS (usize);
86: vsize = ABS (vsize);
87: up = u->_mp_d;
88: vp = v->_mp_d;
89: rp = r->_mp_d;
90: prec = r->_mp_prec;
91: uexp = u->_mp_exp;
92: ediff = u->_mp_exp - v->_mp_exp;
93:
94: /* If U extends beyond PREC, ignore the part that does. */
95: if (usize > prec)
96: {
97: up += usize - prec;
98: usize = prec;
99: }
100:
101: /* If V extends beyond PREC, ignore the part that does.
102: Note that this may make vsize negative. */
103: if (vsize + ediff > prec)
104: {
105: vp += vsize + ediff - prec;
106: vsize = prec - ediff;
107: }
108:
109: #if 0
110: /* Locate the least significant non-zero limb in (the needed parts
111: of) U and V, to simplify the code below. */
112: while (up[0] == 0)
113: up++, usize--;
114: while (vp[0] == 0)
115: vp++, vsize--;
116: #endif
117:
118: /* Allocate temp space for the result. Allocate
119: just vsize + ediff later??? */
120: tp = (mp_ptr) TMP_ALLOC (prec * BYTES_PER_MP_LIMB);
121:
122: if (ediff >= prec)
123: {
124: /* V completely cancelled. */
125: if (tp != up)
126: MPN_COPY (rp, up, usize);
127: rsize = usize;
128: }
129: else
130: {
131: /* uuuu | uuuu | uuuu | uuuu | uuuu */
132: /* vvvvvvv | vv | vvvvv | v | vv */
133:
134: if (usize > ediff)
135: {
136: /* U and V partially overlaps. */
137: if (vsize + ediff <= usize)
138: {
139: /* uuuu */
140: /* v */
141: mp_size_t size;
142: size = usize - ediff - vsize;
143: MPN_COPY (tp, up, size);
144: cy = mpn_add (tp + size, up + size, usize - size, vp, vsize);
145: rsize = usize;
146: }
147: else
148: {
149: /* uuuu */
150: /* vvvvv */
151: mp_size_t size;
152: size = vsize + ediff - usize;
153: MPN_COPY (tp, vp, size);
154: cy = mpn_add (tp + size, up, usize, vp + size, usize - ediff);
155: rsize = vsize + ediff;
156: }
157: }
158: else
159: {
160: /* uuuu */
161: /* vv */
162: mp_size_t size;
163: size = vsize + ediff - usize;
164: MPN_COPY (tp, vp, vsize);
165: MPN_ZERO (tp + vsize, ediff - usize);
166: MPN_COPY (tp + size, up, usize);
167: cy = 0;
168: rsize = size + usize;
169: }
170:
171: MPN_COPY (rp, tp, rsize);
172: rp[rsize] = cy;
173: rsize += cy;
174: uexp += cy;
175: }
176:
177: r->_mp_size = negate ? -rsize : rsize;
178: r->_mp_exp = uexp;
179: TMP_FREE (marker);
180: }
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