1 files changed, 79 insertions, 0 deletions
diff --git a/src/get_z_exp.c b/src/get_z_exp.c
new file mode 100644
index 0000000..30a5f18
--- /dev/null
+++ b/src/get_z_exp.c
@@ -0,0 +1,79 @@
+/* mpfr_get_z_2exp -- get a multiple-precision integer and an exponent
+                      from a floating-point number
+
+Copyright 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Free Software Foundation, Inc.
+Contributed by the AriC and Caramel projects, INRIA.
+
+This file is part of the GNU MPFR Library.
+
+The GNU MPFR Library is free software; you can redistribute it and/or modify
+it under the terms of 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.
+
+The GNU MPFR 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 Lesser General Public
+License for more details.
+
+You should have received a copy of the GNU Lesser General Public License
+along with the GNU MPFR Library; see the file COPYING.LESSER.  If not, see
+http://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc.,
+51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. */
+
+#include "mpfr-impl.h"
+
+/* puts the significand of f into z, and returns 'exp' such that f = z * 2^exp
+ *
+ * 0 doesn't have an exponent, therefore the returned exponent in this case
+ * isn't really important. We choose to return __gmpfr_emin because
+ *   1) it is in the exponent range [__gmpfr_emin,__gmpfr_emax],
+ *   2) the smaller a number is (in absolute value), the smaller its
+ *      exponent is. In other words, the f -> exp function is monotonous
+ *      on nonnegative numbers. --> This is WRONG since the returned
+ *      exponent is not necessarily in the exponent range!
+ * Note that this is different from the C function frexp().
+ *
+ * For NaN and infinities, we choose to set z = 0 (neutral value).
+ * The exponent doesn't really matter, so let's keep __gmpfr_emin
+ * for consistency. The erange flag is set.
+ */
+
+mpfr_exp_t
+mpfr_get_z_2exp (mpz_ptr z, mpfr_srcptr f)
+{
+  mp_size_t fn;
+  int sh;
+
+  if (MPFR_UNLIKELY (MPFR_IS_SINGULAR (f)))
+    {
+      if (MPFR_UNLIKELY (MPFR_NOTZERO (f)))
+        MPFR_SET_ERANGE ();
+      mpz_set_ui (z, 0);
+      return __gmpfr_emin;
+    }
+
+  fn = MPFR_LIMB_SIZE(f);
+
+  /* check whether allocated space for z is enough */
+  if (MPFR_UNLIKELY (ALLOC (z) < fn))
+    MPZ_REALLOC (z, fn);
+
+  MPFR_UNSIGNED_MINUS_MODULO (sh, MPFR_PREC (f));
+  if (MPFR_LIKELY (sh))
+    mpn_rshift (PTR (z), MPFR_MANT (f), fn, sh);
+  else
+    MPN_COPY (PTR (z), MPFR_MANT (f), fn);
+
+  SIZ(z) = MPFR_IS_NEG (f) ? -fn : fn;
+
+  if (MPFR_UNLIKELY ((mpfr_uexp_t) MPFR_GET_EXP (f) - MPFR_EXP_MIN
+                     < (mpfr_uexp_t) MPFR_PREC (f)))
+    {
+      /* The exponent isn't representable in an mpfr_exp_t. */
+      MPFR_SET_ERANGE ();
+      return MPFR_EXP_MIN;
+    }
+
+  return MPFR_GET_EXP (f) - MPFR_PREC (f);
+}