diff options
Diffstat (limited to 'vendor/gmp-6.3.0/mpf/get_ui.c')
-rw-r--r-- | vendor/gmp-6.3.0/mpf/get_ui.c | 101 |
1 files changed, 101 insertions, 0 deletions
diff --git a/vendor/gmp-6.3.0/mpf/get_ui.c b/vendor/gmp-6.3.0/mpf/get_ui.c new file mode 100644 index 0000000..e7b9333 --- /dev/null +++ b/vendor/gmp-6.3.0/mpf/get_ui.c @@ -0,0 +1,101 @@ +/* mpf_get_ui -- mpf to ulong conversion + +Copyright 2001, 2002, 2004 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" + + +/* Any fraction bits are truncated, meaning simply discarded. + + For values bigger than a ulong, the low bits are returned (the low + absolute value bits actually), like mpz_get_ui, but this isn't + documented. + + Notice this is equivalent to mpz_set_f + mpz_get_ui. + + + Implementation: + + The limb just above the radix point for us to extract is ptr[size-exp]. + + We need to check that the size-exp index falls in our available data + range, 0 to size-1 inclusive. We test this without risk of an overflow + involving exp by requiring size>=exp (giving size-exp >= 0) and exp>0 + (giving size-exp <= size-1). + + Notice if size==0 there's no fetch, since of course size>=exp and exp>0 + can only be true if size>0. So there's no special handling for size==0, + it comes out as 0 the same as any other time we have no data at our + target index. + + For nails, the second limb above the radix point is also required, this + is ptr[size-exp+1]. + + Again we need to check that size-exp+1 falls in our data range, 0 to + size-1 inclusive. We test without risk of overflow by requiring + size+1>=exp (giving size-exp+1 >= 0) and exp>1 (giving size-exp+1 <= + size-1). + + And again if size==0 these second fetch conditions are not satisfied + either since size+1>=exp and exp>1 are only true if size>0. + + The code is arranged with exp>0 wrapping the exp>1 test since exp>1 is + mis-compiled by alpha gcc prior to version 3.4. It re-writes it as + exp-1>0, which is incorrect when exp==MP_EXP_T_MIN. By having exp>0 + tested first we ensure MP_EXP_T_MIN doesn't reach exp>1. */ + +unsigned long +mpf_get_ui (mpf_srcptr f) __GMP_NOTHROW +{ + mp_size_t size; + mp_exp_t exp; + mp_srcptr fp; + mp_limb_t fl; + + exp = EXP (f); + size = SIZ (f); + fp = PTR (f); + + fl = 0; + if (exp > 0) + { + /* there are some limbs above the radix point */ + + size = ABS (size); + if (size >= exp) + fl = fp[size-exp]; + +#if BITS_PER_ULONG > GMP_NUMB_BITS + if (exp > 1 && size+1 >= exp) + fl += (fp[size-exp+1] << GMP_NUMB_BITS); +#endif + } + + return (unsigned long) fl; +} |