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