mpfr_rint, mpfr_trunc, mpfr_floor, mpfr_ceil, mpfr_round rewritten.

git-svn-id: svn://scm.gforge.inria.fr/svn/mpfr/trunk@1672 280ebfd0-de03-0410-8827-d642c229c3f4

1 files changed, 261 insertions, 0 deletions

diff --git a/rint.c b/rint.c
new file mode 100644
index 000000000..05875cda1
--- /dev/null
+++ b/rint.c
@@ -0,0 +1,261 @@
+/* mpfr_rint -- Round to an integer.
+
+Copyright (C) 1999-2002 Free Software Foundation, Inc.
+
+This file is part of the MPFR Library.
+
+The 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 2.1 of the License, or (at your
+option) any later version.
+
+The 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 MPFR 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"
+#include "mpfr.h"
+#include "mpfr-impl.h"
+
+int
+mpfr_rint (mpfr_ptr r, mpfr_srcptr u, mp_rnd_t rnd_mode)
+{
+  int sign;
+  mp_exp_t exp;
+
+  if (MPFR_IS_NAN(u))
+    {
+      MPFR_SET_NAN(r);
+      MPFR_RET_NAN;
+    }
+
+  MPFR_CLEAR_NAN(r);
+  MPFR_SET_SAME_SIGN(r, u);
+
+  if (MPFR_IS_INF(u))
+    {
+      MPFR_SET_INF(r);
+      MPFR_RET(0);  /* infinity is exact */
+    }
+
+  MPFR_CLEAR_INF(r);
+
+  if (MPFR_IS_ZERO(u))
+    {
+      MPFR_SET_ZERO(r);
+      MPFR_RET(0);  /* zero is exact */
+    }
+
+  sign = MPFR_SIGN(u);
+  exp = MPFR_EXP(u);
+
+  /* Single out the case where |u| < 1. */
+  if (exp <= 0)  /* 0 < |u| < 1 */
+    {
+      if ((rnd_mode == GMP_RNDD && sign < 0) ||
+          (rnd_mode == GMP_RNDU && sign > 0) ||
+          (rnd_mode == GMP_RNDN && exp == 0))
+        {
+          mp_limb_t *rp;
+          mp_size_t rm;
+
+          rp = MPFR_MANT(r);
+          rm = (MPFR_PREC(r) - 1) / BITS_PER_MP_LIMB;
+          rp[rm] = MP_LIMB_T_HIGHBIT;
+          MPN_ZERO(rp, rm);
+          MPFR_EXP(r) = 1;  /* |r| = 1 */
+          MPFR_RET(sign > 0 ? 2 : -2);
+        }
+      else
+        {
+          MPFR_SET_ZERO(r);  /* r = 0 */
+          MPFR_RET(sign > 0 ? -2 : 2);
+        }
+    }
+  else  /* exp > 0, |u| >= 1 */
+    {
+      mp_limb_t *up, *rp;
+      mp_size_t un, rn, ui;
+      int sh, idiff;
+      int uflags;
+
+      /*
+       * uflags will contain:
+       *   _ 0 if u is an integer representable in r,
+       *   _ 1 if u is an integer not representable in r,
+       *   _ 2 if u is not an integer.
+       */
+
+      up = MPFR_MANT(u);
+      rp = MPFR_MANT(r);
+
+      un = MPFR_ESIZE(u);
+      rn = MPFR_ESIZE(r);
+      sh = rn * BITS_PER_MP_LIMB - MPFR_PREC(r);
+
+      MPFR_EXP(r) = exp;
+
+      if ((exp - 1) / BITS_PER_MP_LIMB >= un)
+        {
+          ui = un;
+          idiff = 0;
+          uflags = 0;  /* u is an integer */
+        }
+      else
+        {
+          mp_size_t uj;
+
+          ui = (exp - 1) / BITS_PER_MP_LIMB + 1;  /* #limbs of the int part */
+          uj = un - ui;  /* lowest limb of the integer part */
+          idiff = exp % BITS_PER_MP_LIMB;  /* #int-part bits in up[uj] or 0 */
+
+          uflags = idiff == 0 || (up[uj] << idiff) == 0 ? 0 : 2;
+          if (uflags == 0)
+            while (uj > 0)
+              if (up[--uj] != 0)
+                {
+                  uflags = 2;
+                  break;
+                }
+        }
+
+      if (ui > rn)
+        {
+          MPFR_ASSERTN(rp != up && un > rn);
+          MPN_COPY(rp, up + (un - rn), rn);
+          /* In the rounding to the nearest mode, if the rounding bit
+             is 0, change the rounding mode to GMP_RNDZ. */
+          if (rnd_mode == GMP_RNDN &&
+              ((sh != 0 && (rp[0] & (MP_LIMB_T_ONE << (sh - 1))) == 0) ||
+               (sh == 0 && (up[un - rn - 1] & MP_LIMB_T_HIGHBIT) == 0)))
+            rnd_mode = GMP_RNDZ;
+          if (uflags == 0)
+            { /* u is an integer; determine if it is representable */
+              if (sh != 0 && rp[0] << (BITS_PER_MP_LIMB - sh) != 0)
+                uflags = 1;  /* u is not representable in r */
+              else
+                {
+                  mp_size_t i;
+                  for (i = un - rn - 1; i >= 0; i--)
+                    if (up[i] != 0)
+                      {
+                        uflags = 1;  /* u is not representable in r */
+                        break;
+                      }
+                }
+            }
+          if (sh != 0)
+            rp[0] &= MP_LIMB_T_MAX << sh;
+        }
+      else
+        {
+          mp_size_t uj, rj;
+          int ush;
+
+          uj = un - ui;  /* lowest limb of the integer part in u */
+          rj = rn - ui;  /* lowest limb of the integer part in r */
+
+          MPN_ZERO(rp, rj);
+
+          if (rp != up)
+            MPN_COPY(rp + rj, up + uj, ui);
+
+          rp += rj;
+          rn = ui;
+
+          ush = idiff == 0 ? 0 : BITS_PER_MP_LIMB - idiff;
+          if (rj == 0 && ush < sh)
+            {
+              /* In the rounding to the nearest mode, if the rounding bit
+                 is 0, change the rounding mode to GMP_RNDZ. */
+              if (rnd_mode == GMP_RNDN &&
+                  (rp[0] & (MP_LIMB_T_ONE << (sh - 1))) == 0)
+                rnd_mode = GMP_RNDZ;  /* rounding bit is 0 */
+              if (uflags == 0)
+                { /* u is an integer; determine if it is representable */
+                  mp_limb_t mask;
+                  mask = (MP_LIMB_T_ONE << sh) - (MP_LIMB_T_ONE << ush);
+                  if ((rp[0] & mask) != 0)
+                    uflags = 1;  /* u is not representable in r */
+                }
+            }
+          else
+            {
+              sh = ush;
+              if (rnd_mode == GMP_RNDN &&
+                  ((ush != 0 &&
+                    (up[uj] & (MP_LIMB_T_ONE << (ush - 1))) == 0) ||
+                   (ush == 0 &&
+                    (uj == 0 || (up[uj - 1] & MP_LIMB_T_HIGHBIT) == 0))))
+                rnd_mode = GMP_RNDZ;  /* rounding bit is 0 */
+            }
+          if (sh != 0)
+            rp[0] &= MP_LIMB_T_MAX << sh;
+        }
+
+      if (uflags == 0)
+        MPFR_RET(0);
+
+      /* Note: if rnd_mode == GMP_RNDN, then round away from 0 (if
+         the rounding bit was 0 and rnd_mode == GMP_RNDN, rnd_mode
+         has been changed to GMP_RNDZ). */
+
+      if ((rnd_mode == GMP_RNDN ||
+           (rnd_mode == GMP_RNDD && sign < 0) ||
+           (rnd_mode == GMP_RNDU && sign > 0))
+          && mpn_add_1(rp, rp, rn, MP_LIMB_T_ONE << sh))
+        {
+          if (exp == __mpfr_emax)
+            return mpfr_set_overflow(r, rnd_mode, MPFR_SIGN(r)) >= 0 ?
+              uflags : -uflags;
+          else
+            {
+              MPFR_EXP(r)++;
+              rp[rn-1] = MP_LIMB_T_HIGHBIT;
+            }
+        }
+
+      MPFR_RET(rnd_mode == GMP_RNDU ||
+               (rnd_mode == GMP_RNDZ && sign < 0) ||
+               (rnd_mode == GMP_RNDN && sign > 0) ? uflags : -uflags);
+    }  /* exp > 0, |u| >= 1 */
+}
+
+#undef mpfr_round
+
+int
+mpfr_round (mpfr_ptr r, mpfr_srcptr u)
+{
+  return mpfr_rint(r, u, GMP_RNDN);
+}
+
+#undef mpfr_trunc
+
+int
+mpfr_trunc (mpfr_ptr r, mpfr_srcptr u)
+{
+  return mpfr_rint(r, u, GMP_RNDZ);
+}
+
+#undef mpfr_ceil
+
+int
+mpfr_ceil (mpfr_ptr r, mpfr_srcptr u)
+{
+  return mpfr_rint(r, u, GMP_RNDU);
+}
+
+#undef mpfr_floor
+
+int
+mpfr_floor (mpfr_ptr r, mpfr_srcptr u)
+{
+  return mpfr_rint(r, u, GMP_RNDD);
+}