Optimization: mpfr_trunc no longer used!

git-svn-id: svn://scm.gforge.inria.fr/svn/mpfr/trunk@1989 280ebfd0-de03-0410-8827-d642c229c3f4

1 files changed, 14 insertions, 7 deletions

diff --git a/isinteger.c b/isinteger.c
index ced0ec7c7..f79268eaf 100644
--- a/isinteger.c
+++ b/isinteger.c
@@ -29,8 +29,8 @@ mpfr_isinteger (mpfr_srcptr x)
 {
   mp_exp_t expo;
   mp_prec_t prec;
-  mpfr_t u;
-  int result;
+  mp_size_t xn;
+  mp_limb_t *xp;
 
   if (!MPFR_IS_FP(x))
     return 0;
@@ -46,11 +46,18 @@ mpfr_isinteger (mpfr_srcptr x)
   if (expo >= prec)
     return 1;
 
-  mpfr_init2(u,prec);
-  mpfr_trunc(u,x);
+  /* 0 < expo < prec */
 
-  result = (mpfr_cmp (x,u) == 0);
+  xn = (prec - 1) / BITS_PER_MP_LIMB;  /* index of last limb */
+  xn -= (mp_size_t) (expo / BITS_PER_MP_LIMB);
+  /* now the index of the last limb containing bits of the fractional part */
 
-  mpfr_clear (u);
-  return result;
+  xp = MPFR_MANT(x);
+  MPFR_ASSERTN(xn >= 0);
+  if (xp[xn] << (expo % BITS_PER_MP_LIMB) != 0)
+    return 0;
+  while (--xn >= 0)
+    if (xp[xn] != 0)
+      return 0;
+  return 1;
 }