1/* mpz_kronecker_ui -- mpz+ulong Kronecker/Jacobi symbol. 2 3Copyright 1999-2002 Free Software Foundation, Inc. 4 5This file is part of the GNU MP Library. 6 7The GNU MP Library is free software; you can redistribute it and/or modify 8it under the terms of either: 9 10 * the GNU Lesser General Public License as published by the Free 11 Software Foundation; either version 3 of the License, or (at your 12 option) any later version. 13 14or 15 16 * the GNU General Public License as published by the Free Software 17 Foundation; either version 2 of the License, or (at your option) any 18 later version. 19 20or both in parallel, as here. 21 22The GNU MP Library is distributed in the hope that it will be useful, but 23WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 24or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 25for more details. 26 27You should have received copies of the GNU General Public License and the 28GNU Lesser General Public License along with the GNU MP Library. If not, 29see https://www.gnu.org/licenses/. */ 30 31#include "gmp-impl.h" 32#include "longlong.h" 33 34 35int 36mpz_kronecker_ui (mpz_srcptr a, unsigned long b) 37{ 38 mp_srcptr a_ptr; 39 mp_size_t a_size; 40 mp_limb_t a_rem; 41 int result_bit1; 42 43 a_size = SIZ(a); 44 if (a_size == 0) 45 return JACOBI_0U (b); 46 47 if (b > GMP_NUMB_MAX) 48 { 49 mp_limb_t blimbs[2]; 50 mpz_t bz; 51 ALLOC(bz) = numberof (blimbs); 52 PTR(bz) = blimbs; 53 mpz_set_ui (bz, b); 54 return mpz_kronecker (a, bz); 55 } 56 57 a_ptr = PTR(a); 58 if ((b & 1) != 0) 59 { 60 result_bit1 = JACOBI_ASGN_SU_BIT1 (a_size, b); 61 } 62 else 63 { 64 mp_limb_t a_low = a_ptr[0]; 65 int twos; 66 67 if (b == 0) 68 return JACOBI_LS0 (a_low, a_size); /* (a/0) */ 69 70 if (! (a_low & 1)) 71 return 0; /* (even/even)=0 */ 72 73 /* (a/2)=(2/a) for a odd */ 74 count_trailing_zeros (twos, b); 75 b >>= twos; 76 result_bit1 = (JACOBI_TWOS_U_BIT1 (twos, a_low) 77 ^ JACOBI_ASGN_SU_BIT1 (a_size, b)); 78 } 79 80 if (b == 1) 81 return JACOBI_BIT1_TO_PN (result_bit1); /* (a/1)=1 for any a */ 82 83 a_size = ABS(a_size); 84 85 /* (a/b) = (a mod b / b) */ 86 JACOBI_MOD_OR_MODEXACT_1_ODD (result_bit1, a_rem, a_ptr, a_size, b); 87 return mpn_jacobi_base (a_rem, (mp_limb_t) b, result_bit1); 88} 89