diff options
Diffstat (limited to 'gnu/lib/libgmp/mpz/fdiv_r_2exp.c')
-rw-r--r-- | gnu/lib/libgmp/mpz/fdiv_r_2exp.c | 88 |
1 files changed, 88 insertions, 0 deletions
diff --git a/gnu/lib/libgmp/mpz/fdiv_r_2exp.c b/gnu/lib/libgmp/mpz/fdiv_r_2exp.c new file mode 100644 index 00000000000..04190b1b0aa --- /dev/null +++ b/gnu/lib/libgmp/mpz/fdiv_r_2exp.c @@ -0,0 +1,88 @@ +/* mpz_fdiv_r_2exp -- Divide a integer by 2**CNT and produce a remainder. + +Copyright (C) 1991, 1993, 1994, 1995 Free Software Foundation, Inc. + +This file is part of the GNU MP Library. + +The GNU MP Library is free software; you can redistribute it and/or modify +it under the terms of the GNU Library General Public License as published by +the Free Software Foundation; either version 2 of the License, or (at your +option) any later version. + +The GNU MP Library is distributed in the hope that it will be useful, but +WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY +or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public +License for more details. + +You should have received a copy of the GNU Library General Public License +along with the GNU MP Library; see the file COPYING.LIB. If not, write to +the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, +MA 02111-1307, USA. */ + +#include "gmp.h" +#include "gmp-impl.h" + +void +#if __STDC__ +mpz_fdiv_r_2exp (mpz_ptr res, mpz_srcptr in, unsigned long int cnt) +#else +mpz_fdiv_r_2exp (res, in, cnt) + mpz_ptr res; + mpz_srcptr in; + unsigned long int cnt; +#endif +{ + mp_size_t in_size = ABS (in->_mp_size); + mp_size_t res_size; + mp_size_t limb_cnt = cnt / BITS_PER_MP_LIMB; + mp_srcptr in_ptr = in->_mp_d; + + if (in_size > limb_cnt) + { + /* The input operand is (probably) greater than 2**CNT. */ + mp_limb_t x; + + x = in_ptr[limb_cnt] & (((mp_limb_t) 1 << cnt % BITS_PER_MP_LIMB) - 1); + if (x != 0) + { + res_size = limb_cnt + 1; + if (res->_mp_alloc < res_size) + _mpz_realloc (res, res_size); + + res->_mp_d[limb_cnt] = x; + } + else + { + res_size = limb_cnt; + MPN_NORMALIZE (in_ptr, res_size); + + if (res->_mp_alloc < res_size) + _mpz_realloc (res, res_size); + + limb_cnt = res_size; + } + } + else + { + /* The input operand is smaller than 2**CNT. We perform a no-op, + apart from that we might need to copy IN to RES. */ + res_size = in_size; + if (res->_mp_alloc < res_size) + _mpz_realloc (res, res_size); + + limb_cnt = res_size; + } + + if (res != in) + MPN_COPY (res->_mp_d, in->_mp_d, limb_cnt); + res->_mp_size = res_size; + if (in->_mp_size < 0 && res_size != 0) + { + /* Result should be 2^CNT - RES */ + mpz_t tmp; + MPZ_TMP_INIT (tmp, limb_cnt + 1); + mpz_set_ui (tmp, 1L); + mpz_mul_2exp (tmp, tmp, cnt); + mpz_sub (res, tmp, res); + } +} |