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Annotation of OpenXM/src/kan96xx/gmp-2.0.2-ssh-2/mpz/gcd.c, Revision 1.1.1.1

1.1       takayama    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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