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4c74403188
Change-Id: Iae65e95cfa0d92091b8b0a424ae36d88efa76aa9 Reviewed-on: https://review.haiku-os.org/c/buildtools/+/3020 Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>
116 lines
2.9 KiB
C
116 lines
2.9 KiB
C
/* mpz_clrbit -- clear a specified bit.
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Copyright 1991, 1993-1995, 2001, 2002, 2012 Free Software Foundation, Inc.
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This file is part of the GNU MP Library.
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The GNU MP Library is free software; you can redistribute it and/or modify
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it under the terms of either:
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* the GNU Lesser General Public License as published by the Free
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Software Foundation; either version 3 of the License, or (at your
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option) any later version.
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or
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* the GNU General Public License as published by the Free Software
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Foundation; either version 2 of the License, or (at your option) any
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later version.
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or both in parallel, as here.
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The GNU MP Library is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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for more details.
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You should have received copies of the GNU General Public License and the
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GNU Lesser General Public License along with the GNU MP Library. If not,
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see https://www.gnu.org/licenses/. */
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#include "gmp-impl.h"
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void
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mpz_clrbit (mpz_ptr d, mp_bitcnt_t bit_idx)
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{
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mp_size_t dsize = SIZ (d);
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mp_ptr dp = PTR (d);
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mp_size_t limb_idx;
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mp_limb_t mask;
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limb_idx = bit_idx / GMP_NUMB_BITS;
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mask = CNST_LIMB(1) << (bit_idx % GMP_NUMB_BITS);
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if (dsize >= 0)
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{
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if (limb_idx < dsize)
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{
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mp_limb_t dlimb;
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dlimb = dp[limb_idx] & ~mask;
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dp[limb_idx] = dlimb;
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if (UNLIKELY ((dlimb == 0) + limb_idx == dsize)) /* dsize == limb_idx + 1 */
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{
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/* high limb became zero, must normalize */
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MPN_NORMALIZE (dp, limb_idx);
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SIZ (d) = limb_idx;
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}
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}
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else
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;
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}
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else
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{
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/* Simulate two's complement arithmetic, i.e. simulate
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1. Set OP = ~(OP - 1) [with infinitely many leading ones].
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2. clear the bit.
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3. Set OP = ~OP + 1. */
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dsize = -dsize;
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if (limb_idx < dsize)
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{
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mp_size_t zero_bound;
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/* No index upper bound on this loop, we're sure there's a non-zero limb
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sooner or later. */
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zero_bound = 0;
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while (dp[zero_bound] == 0)
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zero_bound++;
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if (limb_idx > zero_bound)
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{
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dp[limb_idx] |= mask;
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}
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else if (limb_idx == zero_bound)
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{
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mp_limb_t dlimb;
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dlimb = (((dp[limb_idx] - 1) | mask) + 1) & GMP_NUMB_MASK;
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dp[limb_idx] = dlimb;
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if (dlimb == 0)
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{
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/* Increment at limb_idx + 1. Extend the number with a zero limb
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for simplicity. */
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dp = MPZ_REALLOC (d, dsize + 1);
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dp[dsize] = 0;
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MPN_INCR_U (dp + limb_idx + 1, dsize - limb_idx, 1);
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dsize += dp[dsize];
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SIZ (d) = -dsize;
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}
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}
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else
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;
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}
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else
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{
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/* Ugh. The bit should be cleared outside of the end of the
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number. We have to increase the size of the number. */
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dp = MPZ_REALLOC (d, limb_idx + 1);
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SIZ (d) = -(limb_idx + 1);
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MPN_ZERO (dp + dsize, limb_idx - dsize);
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dp[limb_idx] = mask;
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}
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}
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}
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