* mpq/set_f.c: New file.

1 files changed, 105 insertions, 0 deletions

diff --git a/mpq/set_f.c b/mpq/set_f.c
new file mode 100644
index 000000000..672761e69
--- /dev/null
+++ b/mpq/set_f.c
@@ -0,0 +1,105 @@
+/* mpq_set_f -- set an mpq from an mpf.
+
+Copyright (C) 2000 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 Lesser General Public License as published by
+the Free Software Foundation; either version 2.1 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 Lesser General Public
+License for more details.
+
+You should have received a copy of the GNU Lesser 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
+mpq_set_f (mpq_ptr q, mpf_srcptr f)
+{
+  mp_size_t  fexp = EXP(f);
+  mp_ptr     fptr = PTR(f);
+  mp_size_t  fsize = SIZ(f);
+  mp_size_t  abs_fsize = ABS(fsize);
+  mp_limb_t  flow;
+
+  if (fsize == 0)
+    {
+      /* set q=0 */
+      q->_mp_num._mp_size = 0;
+      q->_mp_den._mp_size = 1;
+      q->_mp_den._mp_d[0] = 1;
+      return;
+    }
+
+  /* strip low zero limbs from f */
+  for (;;)
+    {
+      flow = *fptr;
+      if (flow != 0)
+        break;
+      fptr++, abs_fsize--;
+    }
+
+  if (fexp >= abs_fsize)
+    {
+      /* radix point is to the right of the limbs, no denominator */
+      mp_ptr  num_ptr;
+
+      MPZ_REALLOC (mpq_numref (q), fexp);
+      num_ptr = q->_mp_num._mp_d;
+      MPN_ZERO (num_ptr, fexp - abs_fsize);
+      MPN_COPY (num_ptr + fexp - abs_fsize, fptr, abs_fsize);
+
+      q->_mp_num._mp_size = fsize >= 0 ? fexp : -fexp;
+      q->_mp_den._mp_size = 1;
+      q->_mp_den._mp_d[0] = 1;
+    }
+  else
+    {
+      /* radix point is within or to the left of the limbs, use demominator */
+      mp_ptr     num_ptr, den_ptr;
+      mp_size_t  den_size;
+
+      den_size = abs_fsize - fexp;
+      MPZ_REALLOC (mpq_numref (q), abs_fsize);
+      MPZ_REALLOC (mpq_denref (q), den_size+1);
+      num_ptr = q->_mp_num._mp_d;
+      den_ptr = q->_mp_den._mp_d;
+
+      if (flow & 1)
+        {
+          /* no powers of two to strip from numerator */
+
+          MPN_COPY (num_ptr, fptr, abs_fsize);
+          MPN_ZERO (den_ptr, den_size);
+          den_ptr[den_size] = 1;
+        }
+      else
+        {
+          /* right shift numerator, adjust denominator accordingly */
+          int  shift;
+
+          den_size--;
+          count_trailing_zeros (shift, flow);
+ 
+          mpn_rshift (num_ptr, fptr, abs_fsize, shift);
+          abs_fsize -= (num_ptr[abs_fsize-1] == 0);
+
+          MPN_ZERO (den_ptr, den_size);
+          den_ptr[den_size] = MP_LIMB_T_HIGHBIT >> (shift-1);
+        }
+
+      q->_mp_num._mp_size = fsize >= 0 ? abs_fsize : -abs_fsize;
+      q->_mp_den._mp_size = den_size + 1;
+    }
+}