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+/* 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.h"
+#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;
+}