| /* mpz_ui_sub -- Subtract an unsigned one-word integer and an mpz_t. |
| |
| Copyright 2002, 2004 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 Lesser General Public License as published by |
| the Free Software Foundation; either version 3 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 Lesser General Public |
| License for more details. |
| |
| You should have received a copy of the GNU Lesser General Public License |
| along with the GNU MP Library. If not, see http://www.gnu.org/licenses/. */ |
| |
| #include "gmp.h" |
| #include "gmp-impl.h" |
| |
| void |
| mpz_ui_sub (mpz_ptr w, unsigned long int uval, mpz_srcptr v) |
| { |
| mp_ptr vp, wp; |
| mp_size_t vn, wn; |
| mp_limb_t cy; |
| |
| #if BITS_PER_ULONG > GMP_NUMB_BITS /* avoid warnings about shift amount */ |
| if (uval > GMP_NUMB_MAX) |
| { |
| mpz_t u; |
| mp_limb_t ul[2]; |
| PTR(u) = ul; |
| ul[0] = uval & GMP_NUMB_MASK; |
| ul[1] = uval >> GMP_NUMB_BITS; |
| SIZ(u) = 2; |
| mpz_sub (w, u, v); |
| return; |
| } |
| #endif |
| |
| vp = PTR(v); |
| vn = SIZ(v); |
| |
| wp = PTR(w); |
| |
| if (vn > 1) |
| { |
| wp = MPZ_REALLOC (w, vn); |
| vp = PTR(v); |
| mpn_sub_1 (wp, vp, vn, (mp_limb_t) uval); |
| wn = -(vn - (wp[vn - 1] == 0)); |
| } |
| else if (vn == 1) |
| { |
| if (uval >= vp[0]) |
| { |
| wp[0] = uval - vp[0]; |
| wn = wp[0] != 0; |
| } |
| else |
| { |
| wp[0] = vp[0] - uval; |
| wn = -1; |
| } |
| } |
| else if (vn == 0) |
| { |
| wp[0] = uval; |
| wn = uval != 0; |
| } |
| else /* (vn < 0) */ |
| { |
| vn = -vn; |
| wp = MPZ_REALLOC (w, vn + 1); |
| vp = PTR(v); |
| cy = mpn_add_1 (wp, vp, vn, (mp_limb_t) uval); |
| wp[vn] = cy; |
| wn = vn + (cy != 0); |
| } |
| |
| SIZ(w) = wn; |
| } |