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Annotation of OpenXM_contrib/gmp/mpz/kronzs.c, Revision 1.1.1.1

1.1       maekawa     1: /* mpz_kronecker_si -- Kronecker/Jacobi symbol. */
                      2:
                      3: /*
                      4: Copyright (C) 1999, 2000 Free Software Foundation, Inc.
                      5:
                      6: This file is part of the GNU MP Library.
                      7:
                      8: The GNU MP Library is free software; you can redistribute it and/or modify
                      9: it under the terms of the GNU Lesser General Public License as published by
                     10: the Free Software Foundation; either version 2.1 of the License, or (at your
                     11: option) any later version.
                     12:
                     13: The GNU MP Library is distributed in the hope that it will be useful, but
                     14: WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
                     15: or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
                     16: License for more details.
                     17:
                     18: You should have received a copy of the GNU Lesser General Public License
                     19: along with the GNU MP Library; see the file COPYING.LIB.  If not, write to
                     20: the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
                     21: MA 02111-1307, USA.
                     22: */
                     23:
                     24: #include "gmp.h"
                     25: #include "gmp-impl.h"
                     26: #include "longlong.h"
                     27:
                     28:
                     29: /* This function is expected to be often used with b odd, so there's a test
                     30:    for this before invoking count_trailing_zeros().
                     31:
                     32:    After the absolute value of b is established it's treated as an unsigned
                     33:    long, because 0x80..00 doesn't fit in a signed long. */
                     34:
                     35: int
                     36: #if __STDC__
                     37: mpz_kronecker_si (mpz_srcptr a, long b)
                     38: #else
                     39: mpz_kronecker_si (a, b)
                     40:      mpz_srcptr a;
                     41:      long       b;
                     42: #endif
                     43: {
                     44:   int  result_bit1;
                     45:   int  twos;
                     46:
                     47:   if (b == 0)
                     48:     return JACOBI_Z0 (a);
                     49:
                     50:   result_bit1 = JACOBI_BSGN_ZS_BIT1(a, b);
                     51:   b = ABS (b);
                     52:
                     53:   if (b == 1)
                     54:     return JACOBI_BIT1_TO_PN (result_bit1);  /* (a/1) = 1 for any a */
                     55:
                     56:   if (b & 1)
                     57:     return mpn_jacobi_base (mpz_fdiv_ui (a, b), b, result_bit1);
                     58:
                     59:   /* result 0 if both a,b even */
                     60:   if (mpz_even_p (a))
                     61:     return 0;
                     62:
                     63:   /* (a/2)=(2/a) when a odd */
                     64:   count_trailing_zeros (twos, b);
                     65:   result_bit1 ^= JACOBI_TWOS_U_BIT1 (twos, PTR(a)[0]);
                     66:
                     67:   b = ((unsigned long) b) >> twos;
                     68:   if (b == 1)
                     69:     return JACOBI_BIT1_TO_PN (result_bit1);
                     70:   else
                     71:     return mpn_jacobi_base (mpz_fdiv_ui (a, b), b, result_bit1);
                     72: }
                     73:
                     74: