/* mpz/gcd.c: Calculate the greatest common divisor of two integers. Copyright (C) 1991, 1993, 1994, 1996 Free Software Foundation, Inc. This file is part of the GNU MP Library. The GNU MP Library is free software; you can redistribute it and/or modify it under the terms of the GNU Library General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. The GNU MP Library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public License for more details. You should have received a copy of the GNU Library General Public License along with the GNU MP Library; see the file COPYING.LIB. If not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ #include "gmp.h" #include "gmp-impl.h" #include "longlong.h" void *_mpz_realloc (); #ifndef BERKELEY_MP void #if __STDC__ mpz_gcd (mpz_ptr g, mpz_srcptr u, mpz_srcptr v) #else mpz_gcd (g, u, v) mpz_ptr g; mpz_srcptr u; mpz_srcptr v; #endif #else /* BERKELEY_MP */ void #if __STDC__ gcd (mpz_srcptr u, mpz_srcptr v, mpz_ptr g) #else gcd (u, v, g) mpz_ptr g; mpz_srcptr u; mpz_srcptr v; #endif #endif /* BERKELEY_MP */ { unsigned long int g_zero_bits, u_zero_bits, v_zero_bits; mp_size_t g_zero_limbs, u_zero_limbs, v_zero_limbs; mp_ptr tp; mp_ptr up = u->_mp_d; mp_size_t usize = ABS (u->_mp_size); mp_ptr vp = v->_mp_d; mp_size_t vsize = ABS (v->_mp_size); mp_size_t gsize; TMP_DECL (marker); /* GCD(0, V) == V. */ if (usize == 0) { g->_mp_size = vsize; if (g == v) return; if (g->_mp_alloc < vsize) _mpz_realloc (g, vsize); MPN_COPY (g->_mp_d, vp, vsize); return; } /* GCD(U, 0) == U. */ if (vsize == 0) { g->_mp_size = usize; if (g == u) return; if (g->_mp_alloc < usize) _mpz_realloc (g, usize); MPN_COPY (g->_mp_d, up, usize); return; } if (usize == 1) { g->_mp_size = 1; g->_mp_d[0] = mpn_gcd_1 (vp, vsize, up[0]); return; } if (vsize == 1) { g->_mp_size = 1; g->_mp_d[0] = mpn_gcd_1 (up, usize, vp[0]); return; } TMP_MARK (marker); /* Eliminate low zero bits from U and V and move to temporary storage. */ while (*up == 0) up++; u_zero_limbs = up - u->_mp_d; usize -= u_zero_limbs; count_trailing_zeros (u_zero_bits, *up); tp = up; up = (mp_ptr) TMP_ALLOC (usize * BYTES_PER_MP_LIMB); if (u_zero_bits != 0) { mpn_rshift (up, tp, usize, u_zero_bits); usize -= up[usize - 1] == 0; } else MPN_COPY (up, tp, usize); while (*vp == 0) vp++; v_zero_limbs = vp - v->_mp_d; vsize -= v_zero_limbs; count_trailing_zeros (v_zero_bits, *vp); tp = vp; vp = (mp_ptr) TMP_ALLOC (vsize * BYTES_PER_MP_LIMB); if (v_zero_bits != 0) { mpn_rshift (vp, tp, vsize, v_zero_bits); vsize -= vp[vsize - 1] == 0; } else MPN_COPY (vp, tp, vsize); if (u_zero_limbs > v_zero_limbs) { g_zero_limbs = v_zero_limbs; g_zero_bits = v_zero_bits; } else if (u_zero_limbs < v_zero_limbs) { g_zero_limbs = u_zero_limbs; g_zero_bits = u_zero_bits; } else /* Equal. */ { g_zero_limbs = u_zero_limbs; g_zero_bits = MIN (u_zero_bits, v_zero_bits); } /* Call mpn_gcd. The 1st argument must not have more bits than the 2nd. */ vsize = (usize < vsize || (usize == vsize && up[usize-1] < vp[vsize-1])) ? mpn_gcd (vp, up, usize, vp, vsize) : mpn_gcd (vp, vp, vsize, up, usize); /* Here G <-- V << (g_zero_limbs*BITS_PER_MP_LIMB + g_zero_bits). */ gsize = vsize + g_zero_limbs; if (g_zero_bits != 0) { mp_limb_t cy_limb; gsize += (vp[vsize - 1] >> (BITS_PER_MP_LIMB - g_zero_bits)) != 0; if (g->_mp_alloc < gsize) _mpz_realloc (g, gsize); MPN_ZERO (g->_mp_d, g_zero_limbs); tp = g->_mp_d + g_zero_limbs; cy_limb = mpn_lshift (tp, vp, vsize, g_zero_bits); if (cy_limb != 0) tp[vsize] = cy_limb; } else { if (g->_mp_alloc < gsize) _mpz_realloc (g, gsize); MPN_ZERO (g->_mp_d, g_zero_limbs); MPN_COPY (g->_mp_d + g_zero_limbs, vp, vsize); } g->_mp_size = gsize; TMP_FREE (marker); }