| /* mpz/gcd.c: Calculate the greatest common divisor of two integers. |
| |
| Copyright 1991, 1993, 1994, 1996, 2000-2002, 2005, 2010, 2015, 2016 |
| 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 either: |
| |
| * the GNU Lesser General Public License as published by the Free |
| Software Foundation; either version 3 of the License, or (at your |
| option) any later version. |
| |
| or |
| |
| * the GNU General Public License as published by the Free Software |
| Foundation; either version 2 of the License, or (at your option) any |
| later version. |
| |
| or both in parallel, as here. |
| |
| 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 General Public License |
| for more details. |
| |
| You should have received copies of the GNU General Public License and the |
| GNU Lesser General Public License along with the GNU MP Library. If not, |
| see https://www.gnu.org/licenses/. */ |
| |
| #include "gmp-impl.h" |
| #include "longlong.h" |
| |
| |
| void |
| mpz_gcd (mpz_ptr g, mpz_srcptr u, mpz_srcptr v) |
| { |
| 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; |
| mp_size_t usize; |
| mp_ptr vp; |
| mp_size_t vsize; |
| mp_size_t gsize; |
| TMP_DECL; |
| |
| up = PTR(u); |
| usize = ABSIZ (u); |
| vp = PTR(v); |
| vsize = ABSIZ (v); |
| /* GCD(0, V) == V. */ |
| if (usize == 0) |
| { |
| SIZ (g) = vsize; |
| if (g == v) |
| return; |
| tp = MPZ_NEWALLOC (g, vsize); |
| MPN_COPY (tp, vp, vsize); |
| return; |
| } |
| |
| /* GCD(U, 0) == U. */ |
| if (vsize == 0) |
| { |
| SIZ (g) = usize; |
| if (g == u) |
| return; |
| tp = MPZ_NEWALLOC (g, usize); |
| MPN_COPY (tp, up, usize); |
| return; |
| } |
| |
| if (usize == 1) |
| { |
| SIZ (g) = 1; |
| MPZ_NEWALLOC (g, 1)[0] = mpn_gcd_1 (vp, vsize, up[0]); |
| return; |
| } |
| |
| if (vsize == 1) |
| { |
| SIZ(g) = 1; |
| MPZ_NEWALLOC (g, 1)[0] = mpn_gcd_1 (up, usize, vp[0]); |
| return; |
| } |
| |
| TMP_MARK; |
| |
| /* Eliminate low zero bits from U and V and move to temporary storage. */ |
| tp = up; |
| while (*tp == 0) |
| tp++; |
| u_zero_limbs = tp - up; |
| usize -= u_zero_limbs; |
| count_trailing_zeros (u_zero_bits, *tp); |
| up = TMP_ALLOC_LIMBS (usize); |
| if (u_zero_bits != 0) |
| { |
| mpn_rshift (up, tp, usize, u_zero_bits); |
| usize -= up[usize - 1] == 0; |
| } |
| else |
| MPN_COPY (up, tp, usize); |
| |
| tp = vp; |
| while (*tp == 0) |
| tp++; |
| v_zero_limbs = tp - vp; |
| vsize -= v_zero_limbs; |
| count_trailing_zeros (v_zero_bits, *tp); |
| vp = TMP_ALLOC_LIMBS (vsize); |
| 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 |
| { |
| g_zero_limbs = u_zero_limbs; |
| if (u_zero_limbs < v_zero_limbs) |
| g_zero_bits = u_zero_bits; |
| else /* Equal. */ |
| g_zero_bits = MIN (u_zero_bits, v_zero_bits); |
| } |
| |
| /* Call mpn_gcd. The 2nd argument must not have more bits than the 1st. */ |
| vsize = (usize < vsize || (usize == vsize && up[usize-1] < vp[vsize-1])) |
| ? mpn_gcd (vp, vp, vsize, up, usize) |
| : mpn_gcd (vp, up, usize, vp, vsize); |
| |
| /* Here G <-- V << (g_zero_limbs*GMP_LIMB_BITS + g_zero_bits). */ |
| gsize = vsize + g_zero_limbs; |
| if (g_zero_bits != 0) |
| { |
| mp_limb_t cy_limb; |
| gsize += (vp[vsize - 1] >> (GMP_NUMB_BITS - g_zero_bits)) != 0; |
| tp = MPZ_NEWALLOC (g, gsize); |
| MPN_ZERO (tp, g_zero_limbs); |
| |
| tp = tp + g_zero_limbs; |
| cy_limb = mpn_lshift (tp, vp, vsize, g_zero_bits); |
| if (cy_limb != 0) |
| tp[vsize] = cy_limb; |
| } |
| else |
| { |
| tp = MPZ_NEWALLOC (g, gsize); |
| MPN_ZERO (tp, g_zero_limbs); |
| MPN_COPY (tp + g_zero_limbs, vp, vsize); |
| } |
| |
| SIZ (g) = gsize; |
| TMP_FREE; |
| } |