Annotation of OpenXM_contrib/gmp/mpz/gcd.c, Revision 1.1.1.2
1.1 maekawa 1: /* mpz/gcd.c: Calculate the greatest common divisor of two integers.
2:
1.1.1.2 ! maekawa 3: Copyright (C) 1991, 1993, 1994, 1996, 2000 Free Software Foundation, Inc.
1.1 maekawa 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
1.1.1.2 ! maekawa 8: it under the terms of the GNU Lesser General Public License as published by
! 9: the Free Software Foundation; either version 2.1 of the License, or (at your
1.1 maekawa 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
1.1.1.2 ! maekawa 14: or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
1.1 maekawa 15: License for more details.
16:
1.1.1.2 ! maekawa 17: You should have received a copy of the GNU Lesser General Public License
1.1 maekawa 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: #include "longlong.h"
1.1.1.2 ! maekawa 25: #ifdef BERKELEY_MP
! 26: #include "mp.h"
! 27: #endif
1.1 maekawa 28:
29:
30: #ifndef BERKELEY_MP
31: void
32: #if __STDC__
33: mpz_gcd (mpz_ptr g, mpz_srcptr u, mpz_srcptr v)
34: #else
35: mpz_gcd (g, u, v)
36: mpz_ptr g;
37: mpz_srcptr u;
38: mpz_srcptr v;
39: #endif
40: #else /* BERKELEY_MP */
41: void
42: #if __STDC__
43: gcd (mpz_srcptr u, mpz_srcptr v, mpz_ptr g)
44: #else
45: gcd (u, v, g)
46: mpz_ptr g;
47: mpz_srcptr u;
48: mpz_srcptr v;
49: #endif
50: #endif /* BERKELEY_MP */
51:
52: {
53: unsigned long int g_zero_bits, u_zero_bits, v_zero_bits;
54: mp_size_t g_zero_limbs, u_zero_limbs, v_zero_limbs;
55: mp_ptr tp;
56: mp_ptr up = u->_mp_d;
57: mp_size_t usize = ABS (u->_mp_size);
58: mp_ptr vp = v->_mp_d;
59: mp_size_t vsize = ABS (v->_mp_size);
60: mp_size_t gsize;
61: TMP_DECL (marker);
62:
63: /* GCD(0, V) == V. */
64: if (usize == 0)
65: {
66: g->_mp_size = vsize;
67: if (g == v)
68: return;
69: if (g->_mp_alloc < vsize)
70: _mpz_realloc (g, vsize);
71: MPN_COPY (g->_mp_d, vp, vsize);
72: return;
73: }
74:
75: /* GCD(U, 0) == U. */
76: if (vsize == 0)
77: {
78: g->_mp_size = usize;
79: if (g == u)
80: return;
81: if (g->_mp_alloc < usize)
82: _mpz_realloc (g, usize);
83: MPN_COPY (g->_mp_d, up, usize);
84: return;
85: }
86:
87: if (usize == 1)
88: {
89: g->_mp_size = 1;
90: g->_mp_d[0] = mpn_gcd_1 (vp, vsize, up[0]);
91: return;
92: }
93:
94: if (vsize == 1)
95: {
96: g->_mp_size = 1;
97: g->_mp_d[0] = mpn_gcd_1 (up, usize, vp[0]);
98: return;
99: }
100:
101: TMP_MARK (marker);
102:
103: /* Eliminate low zero bits from U and V and move to temporary storage. */
104: while (*up == 0)
105: up++;
106: u_zero_limbs = up - u->_mp_d;
107: usize -= u_zero_limbs;
108: count_trailing_zeros (u_zero_bits, *up);
109: tp = up;
110: up = (mp_ptr) TMP_ALLOC (usize * BYTES_PER_MP_LIMB);
111: if (u_zero_bits != 0)
112: {
113: mpn_rshift (up, tp, usize, u_zero_bits);
114: usize -= up[usize - 1] == 0;
115: }
116: else
117: MPN_COPY (up, tp, usize);
118:
119: while (*vp == 0)
120: vp++;
121: v_zero_limbs = vp - v->_mp_d;
122: vsize -= v_zero_limbs;
123: count_trailing_zeros (v_zero_bits, *vp);
124: tp = vp;
125: vp = (mp_ptr) TMP_ALLOC (vsize * BYTES_PER_MP_LIMB);
126: if (v_zero_bits != 0)
127: {
128: mpn_rshift (vp, tp, vsize, v_zero_bits);
129: vsize -= vp[vsize - 1] == 0;
130: }
131: else
132: MPN_COPY (vp, tp, vsize);
133:
134: if (u_zero_limbs > v_zero_limbs)
135: {
136: g_zero_limbs = v_zero_limbs;
137: g_zero_bits = v_zero_bits;
138: }
139: else if (u_zero_limbs < v_zero_limbs)
140: {
141: g_zero_limbs = u_zero_limbs;
142: g_zero_bits = u_zero_bits;
143: }
144: else /* Equal. */
145: {
146: g_zero_limbs = u_zero_limbs;
147: g_zero_bits = MIN (u_zero_bits, v_zero_bits);
148: }
149:
1.1.1.2 ! maekawa 150: /* Call mpn_gcd. The 2nd argument must not have more bits than the 1st. */
1.1 maekawa 151: vsize = (usize < vsize || (usize == vsize && up[usize-1] < vp[vsize-1]))
1.1.1.2 ! maekawa 152: ? mpn_gcd (vp, vp, vsize, up, usize)
! 153: : mpn_gcd (vp, up, usize, vp, vsize);
1.1 maekawa 154:
155: /* Here G <-- V << (g_zero_limbs*BITS_PER_MP_LIMB + g_zero_bits). */
156: gsize = vsize + g_zero_limbs;
157: if (g_zero_bits != 0)
158: {
159: mp_limb_t cy_limb;
160: gsize += (vp[vsize - 1] >> (BITS_PER_MP_LIMB - g_zero_bits)) != 0;
161: if (g->_mp_alloc < gsize)
162: _mpz_realloc (g, gsize);
163: MPN_ZERO (g->_mp_d, g_zero_limbs);
164:
165: tp = g->_mp_d + g_zero_limbs;
166: cy_limb = mpn_lshift (tp, vp, vsize, g_zero_bits);
167: if (cy_limb != 0)
168: tp[vsize] = cy_limb;
169: }
170: else
171: {
172: if (g->_mp_alloc < gsize)
173: _mpz_realloc (g, gsize);
174: MPN_ZERO (g->_mp_d, g_zero_limbs);
175: MPN_COPY (g->_mp_d + g_zero_limbs, vp, vsize);
176: }
177:
178: g->_mp_size = gsize;
179: TMP_FREE (marker);
180: }
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