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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>
73 lines
1.9 KiB
C
73 lines
1.9 KiB
C
/* mpz_invert (inv, x, n). Find multiplicative inverse of X in Z(N).
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If X has an inverse, return non-zero and store inverse in INVERSE,
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otherwise, return 0 and put garbage in INVERSE.
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Copyright 1996-2001, 2005, 2012, 2014 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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int
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mpz_invert (mpz_ptr inverse, mpz_srcptr x, mpz_srcptr n)
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{
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mpz_t gcd, tmp;
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mp_size_t xsize, nsize, size;
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TMP_DECL;
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xsize = ABSIZ (x);
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nsize = ABSIZ (n);
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size = MAX (xsize, nsize) + 1;
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TMP_MARK;
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MPZ_TMP_INIT (gcd, size);
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MPZ_TMP_INIT (tmp, size);
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mpz_gcdext (gcd, tmp, (mpz_ptr) 0, x, n);
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/* If no inverse existed, return with an indication of that. */
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if (!MPZ_EQUAL_1_P (gcd))
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{
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TMP_FREE;
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return 0;
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}
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/* Make sure we return a positive inverse. */
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if (SIZ (tmp) < 0)
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{
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if (SIZ (n) < 0)
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mpz_sub (inverse, tmp, n);
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else
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mpz_add (inverse, tmp, n);
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}
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else
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mpz_set (inverse, tmp);
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TMP_FREE;
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return 1;
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}
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