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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>
104 lines
3.1 KiB
C
104 lines
3.1 KiB
C
/* mpz_combit -- complement a specified bit.
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Copyright 2002, 2003, 2012, 2015 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_combit (mpz_ptr d, mp_bitcnt_t bit_index)
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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_index = bit_index / GMP_NUMB_BITS;
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mp_limb_t bit = (CNST_LIMB (1) << (bit_index % GMP_NUMB_BITS));
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/* Check for the most common case: Positive input, no realloc or
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normalization needed. */
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if (limb_index + 1 < dsize)
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dp[limb_index] ^= bit;
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/* Check for the hairy case. d < 0, and we have all zero bits to the
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right of the bit to toggle. */
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else if (limb_index < -dsize
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&& (limb_index == 0 || mpn_zero_p (dp, limb_index))
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&& (dp[limb_index] & (bit - 1)) == 0)
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{
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ASSERT (dsize < 0);
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dsize = -dsize;
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if (dp[limb_index] & bit)
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{
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/* We toggle the least significant one bit. Corresponds to
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an add, with potential carry propagation, on the absolute
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value. */
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dp = MPZ_REALLOC (d, 1 + dsize);
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dp[dsize] = 0;
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MPN_INCR_U (dp + limb_index, 1 + dsize - limb_index, bit);
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SIZ(d) = - dsize - dp[dsize];
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}
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else
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{
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/* We toggle a zero bit, subtract from the absolute value. */
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MPN_DECR_U (dp + limb_index, dsize - limb_index, bit);
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/* The absolute value shrinked by at most one bit. */
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dsize -= dp[dsize - 1] == 0;
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ASSERT (dsize > 0 && dp[dsize - 1] != 0);
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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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/* Simple case: Toggle the bit in the absolute value. */
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dsize = ABS(dsize);
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if (limb_index < dsize)
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{
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mp_limb_t dlimb;
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dlimb = dp[limb_index] ^ bit;
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dp[limb_index] = dlimb;
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/* Can happen only when limb_index = dsize - 1. Avoid SIZ(d)
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bookkeeping in the common case. */
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if (UNLIKELY ((dlimb == 0) + limb_index == dsize)) /* dsize == limb_index + 1 */
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{
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/* high limb became zero, must normalize */
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MPN_NORMALIZE (dp, limb_index);
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SIZ (d) = SIZ (d) >= 0 ? limb_index : -limb_index;
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}
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}
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else
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{
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dp = MPZ_REALLOC (d, limb_index + 1);
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MPN_ZERO(dp + dsize, limb_index - dsize);
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dp[limb_index++] = bit;
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SIZ(d) = SIZ(d) >= 0 ? limb_index : -limb_index;
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}
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}
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}
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