diff options
Diffstat (limited to 'vendor/gmp-6.3.0/mpq/md_2exp.c')
-rw-r--r-- | vendor/gmp-6.3.0/mpq/md_2exp.c | 110 |
1 files changed, 110 insertions, 0 deletions
diff --git a/vendor/gmp-6.3.0/mpq/md_2exp.c b/vendor/gmp-6.3.0/mpq/md_2exp.c new file mode 100644 index 0000000..b3378b3 --- /dev/null +++ b/vendor/gmp-6.3.0/mpq/md_2exp.c @@ -0,0 +1,110 @@ +/* mpq_mul_2exp, mpq_div_2exp - multiply or divide by 2^N */ + +/* +Copyright 2000, 2002, 2012, 2018 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 either: + + * the GNU Lesser General Public License as published by the Free + Software Foundation; either version 3 of the License, or (at your + option) any later version. + +or + + * the GNU General Public License as published by the Free Software + Foundation; either version 2 of the License, or (at your option) any + later version. + +or both in parallel, as here. + +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 General Public License +for more details. + +You should have received copies of the GNU General Public License and the +GNU Lesser General Public License along with the GNU MP Library. If not, +see https://www.gnu.org/licenses/. */ + +#include "gmp-impl.h" +#include "longlong.h" + + +/* The multiplier/divisor "n", representing 2^n, is applied by right shifting + "r" until it's odd (if it isn't already), and left shifting "l" for the + rest. */ + +static void +mord_2exp (mpz_ptr ldst, mpz_ptr rdst, mpz_srcptr lsrc, mpz_srcptr rsrc, + mp_bitcnt_t n) +{ + mp_size_t rsrc_size = SIZ(rsrc); + mp_size_t len = ABS (rsrc_size); + mp_ptr rsrc_ptr = PTR(rsrc); + mp_ptr p, rdst_ptr; + mp_limb_t plow; + + p = rsrc_ptr; + plow = *p; + while (n >= GMP_NUMB_BITS && plow == 0) + { + n -= GMP_NUMB_BITS; + p++; + plow = *p; + } + + /* no realloc here if rsrc==rdst, so p and rsrc_ptr remain valid */ + len -= (p - rsrc_ptr); + rdst_ptr = MPZ_REALLOC (rdst, len); + + if ((plow & 1) || n == 0) + { + /* need INCR when src==dst */ + if (p != rdst_ptr) + MPN_COPY_INCR (rdst_ptr, p, len); + } + else + { + unsigned long shift; + if (plow == 0) + shift = n; + else + { + count_trailing_zeros (shift, plow); + shift = MIN (shift, n); + } + mpn_rshift (rdst_ptr, p, len, shift); + len -= (rdst_ptr[len-1] == 0); + n -= shift; + } + SIZ(rdst) = (rsrc_size >= 0) ? len : -len; + + if (n) + mpz_mul_2exp (ldst, lsrc, n); + else if (ldst != lsrc) + mpz_set (ldst, lsrc); +} + + +void +mpq_mul_2exp (mpq_ptr dst, mpq_srcptr src, mp_bitcnt_t n) +{ + mord_2exp (NUM(dst), DEN(dst), NUM(src), DEN(src), n); +} + +void +mpq_div_2exp (mpq_ptr dst, mpq_srcptr src, mp_bitcnt_t n) +{ + if (SIZ(NUM(src)) == 0) + { + SIZ(NUM(dst)) = 0; + SIZ(DEN(dst)) = 1; + MPZ_NEWALLOC (DEN(dst), 1)[0] = 1; + return; + } + + mord_2exp (DEN(dst), NUM(dst), DEN(src), NUM(src), n); +} |