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Diffstat (limited to 'gnu/lib/libgmp/mpz/fdiv_r_2exp.c')
-rw-r--r--gnu/lib/libgmp/mpz/fdiv_r_2exp.c88
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
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+/* 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);
+ }
+}