| 1 | /* mpz_ui_sub -- Subtract an unsigned one-word integer and an mpz_t. |
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| 2 | |
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| 3 | Copyright 2002 Free Software Foundation, Inc. |
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| 4 | |
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| 5 | This file is part of the GNU MP Library. |
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| 6 | |
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| 7 | The GNU MP Library is free software; you can redistribute it and/or modify |
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| 8 | it under the terms of the GNU Lesser General Public License as published by |
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| 9 | the Free Software Foundation; either version 2.1 of the License, or (at your |
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| 10 | option) any later version. |
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| 11 | |
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| 12 | The GNU MP Library is distributed in the hope that it will be useful, but |
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| 13 | WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY |
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| 14 | or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public |
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| 15 | License for more details. |
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| 16 | |
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| 17 | You should have received a copy of the GNU Lesser General Public License |
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| 18 | along with the GNU MP Library; see the file COPYING.LIB. If not, write to |
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| 19 | the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
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| 20 | MA 02111-1307, USA. */ |
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| 21 | |
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| 22 | #include "gmp.h" |
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| 23 | #include "gmp-impl.h" |
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| 24 | |
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| 25 | void |
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| 26 | mpz_ui_sub (mpz_ptr w, unsigned long int uval, mpz_srcptr v) |
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| 27 | { |
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| 28 | mp_ptr vp, wp; |
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| 29 | mp_size_t vn, wn; |
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| 30 | mp_limb_t cy; |
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| 31 | |
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| 32 | #if GMP_NAIL_BITS != 0 |
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| 33 | if (uval > GMP_NUMB_MAX) |
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| 34 | { |
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| 35 | mpz_t u; |
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| 36 | mp_limb_t ul[2]; |
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| 37 | PTR(u) = ul; |
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| 38 | ul[0] = uval & GMP_NUMB_MASK; |
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| 39 | ul[1] = uval >> GMP_NUMB_BITS; |
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| 40 | SIZ(u) = 2; |
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| 41 | mpz_sub (w, u, v); |
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| 42 | return; |
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| 43 | } |
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| 44 | #endif |
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| 45 | |
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| 46 | vp = PTR(v); |
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| 47 | vn = SIZ(v); |
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| 48 | |
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| 49 | wp = PTR(w); |
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| 50 | |
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| 51 | if (vn > 1) |
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| 52 | { |
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| 53 | wp = MPZ_REALLOC (w, vn); |
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| 54 | vp = PTR(v); |
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| 55 | mpn_sub_1 (wp, vp, vn, (mp_limb_t) uval); |
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| 56 | wn = -(vn - (wp[vn - 1] == 0)); |
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| 57 | } |
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| 58 | else if (vn == 1) |
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| 59 | { |
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| 60 | if (uval >= vp[0]) |
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| 61 | { |
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| 62 | wp[0] = uval - vp[0]; |
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| 63 | wn = wp[0] != 0; |
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| 64 | } |
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| 65 | else |
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| 66 | { |
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| 67 | wp[0] = vp[0] - uval; |
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| 68 | wn = -1; |
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| 69 | } |
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| 70 | } |
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| 71 | else if (vn == 0) |
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| 72 | { |
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| 73 | wp[0] = uval; |
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| 74 | wn = uval != 0; |
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| 75 | } |
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| 76 | else /* (vn < 0) */ |
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| 77 | { |
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| 78 | vn = -vn; |
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| 79 | wp = MPZ_REALLOC (w, vn + 1); |
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| 80 | vp = PTR(v); |
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| 81 | cy = mpn_add_1 (wp, vp, vn, (mp_limb_t) uval); |
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| 82 | wp[vn] = cy; |
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| 83 | wn = vn + (cy != 0); |
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| 84 | } |
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| 85 | |
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| 86 | SIZ(w) = wn; |
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| 87 | } |
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