mirror of https://github.com/macssh/macssh.git
67 lines
1.7 KiB
C
67 lines
1.7 KiB
C
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/* mpz_kronecker_ui -- Kronecker/Jacobi symbol. */
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/*
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Copyright (C) 1999, 2000 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 the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or (at your
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option) any later version.
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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 Lesser General Public
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License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with the GNU MP Library; see the file COPYING.LIB. If not, write to
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the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
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MA 02111-1307, USA.
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*/
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#include "gmp.h"
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#include "gmp-impl.h"
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#include "longlong.h"
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/* This function is expected to be often used with b an odd prime, so the
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code for odd b is nice and short. */
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int
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#if __STDC__
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mpz_kronecker_ui (mpz_srcptr a, unsigned long b)
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#else
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mpz_kronecker_ui (a, b)
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mpz_srcptr a;
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unsigned long b;
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#endif
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{
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int twos;
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if (b & 1)
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{
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if (b != 1)
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return mpn_jacobi_base (mpz_fdiv_ui (a, b), b, 0);
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else
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return 1; /* (a/1)=1 for any a */
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}
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if (b == 0)
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return JACOBI_Z0 (a);
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/* (a/2)=0 if a even */
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if (mpz_even_p (a))
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return 0;
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/* (a/2)=(2/a) when a odd */
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count_trailing_zeros (twos, b);
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b >>= twos;
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if (b == 1)
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return JACOBI_TWOS_U (twos, PTR(a)[0]);
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return mpn_jacobi_base (mpz_fdiv_ui (a, b), b,
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JACOBI_TWOS_U_BIT1(twos, PTR(a)[0]));
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}
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