| /* mpz_setbit -- set a specified bit. |
| |
| Copyright 1991, 1993, 1994, 1995, 1997, 1999, 2001, 2002 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_setbit (mpz_ptr d, unsigned long int bit_index) |
| { |
| mp_size_t dsize = d->_mp_size; |
| mp_ptr dp = d->_mp_d; |
| mp_size_t limb_index; |
| |
| limb_index = bit_index / GMP_NUMB_BITS; |
| if (dsize >= 0) |
| { |
| if (limb_index < dsize) |
| { |
| dp[limb_index] |= (mp_limb_t) 1 << (bit_index % GMP_NUMB_BITS); |
| d->_mp_size = dsize; |
| } |
| else |
| { |
| /* Ugh. The bit should be set outside of the end of the |
| number. We have to increase the size of the number. */ |
| if (UNLIKELY (d->_mp_alloc < limb_index + 1)) |
| dp = _mpz_realloc (d, limb_index + 1); |
| MPN_ZERO (dp + dsize, limb_index - dsize); |
| dp[limb_index] = (mp_limb_t) 1 << (bit_index % GMP_NUMB_BITS); |
| d->_mp_size = limb_index + 1; |
| } |
| } |
| else |
| { |
| mp_size_t zero_bound; |
| |
| /* Simulate two's complement arithmetic, i.e. simulate |
| 1. Set OP = ~(OP - 1) [with infinitely many leading ones]. |
| 2. Set the bit. |
| 3. Set OP = ~OP + 1. */ |
| |
| dsize = -dsize; |
| |
| /* No upper bound on this loop, we're sure there's a non-zero limb |
| sooner ot later. */ |
| for (zero_bound = 0; ; zero_bound++) |
| if (dp[zero_bound] != 0) |
| break; |
| |
| if (limb_index > zero_bound) |
| { |
| if (limb_index < dsize) |
| { |
| mp_limb_t dlimb; |
| dlimb = dp[limb_index]; |
| dlimb &= ~((mp_limb_t) 1 << (bit_index % GMP_NUMB_BITS)); |
| dp[limb_index] = dlimb; |
| |
| if (UNLIKELY (dlimb == 0 && limb_index == dsize-1)) |
| { |
| /* high limb became zero, must normalize */ |
| do { |
| dsize--; |
| } while (dsize > 0 && dp[dsize-1] == 0); |
| d->_mp_size = -dsize; |
| } |
| } |
| } |
| else if (limb_index == zero_bound) |
| { |
| dp[limb_index] = ((dp[limb_index] - 1) |
| & ~((mp_limb_t) 1 << (bit_index % GMP_NUMB_BITS))) + 1; |
| if (dp[limb_index] == 0) |
| { |
| mp_size_t i; |
| for (i = limb_index + 1; i < dsize; i++) |
| { |
| dp[i] += 1; |
| if (dp[i] != 0) |
| goto fin; |
| } |
| /* We got carry all way out beyond the end of D. Increase |
| its size (and allocation if necessary). */ |
| dsize++; |
| if (UNLIKELY (d->_mp_alloc < dsize)) |
| dp = _mpz_realloc (d, dsize); |
| dp[i] = 1; |
| d->_mp_size = -dsize; |
| fin:; |
| } |
| } |
| else |
| { |
| mpn_decr_u (dp + limb_index, |
| (mp_limb_t) 1 << (bit_index % GMP_NUMB_BITS)); |
| dsize -= dp[dsize - 1] == 0; |
| d->_mp_size = -dsize; |
| } |
| } |
| } |