--- /dev/null
+/* mpfr_round_raw_generic -- Generic rounding function
+
+Copyright 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 Free Software Foundation, Inc.
+Contributed by the Arenaire and Cacao 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 2.1 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.LIB. If not, write to
+the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston,
+MA 02110-1301, USA. */
+
+#ifndef flag
+# error "ERROR: flag must be defined (0 / 1)"
+#endif
+#ifndef use_inexp
+# error "ERROR: use_enexp must be defined (0 / 1)"
+#endif
+#ifndef mpfr_round_raw_generic
+# error "ERROR: mpfr_round_raw_generic must be defined"
+#endif
+
+/*
+ * If flag = 0, puts in y the value of xp (with precision xprec and
+ * sign 1 if negative=0, -1 otherwise) rounded to precision yprec and
+ * direction rnd_mode. Supposes x is not zero nor NaN nor +/- Infinity
+ * (i.e. *xp != 0). In that case, the return value is a possible carry
+ * (0 or 1) that may happen during the rounding, in which case the result
+ * is a power of two.
+ *
+ * If inexp != NULL, put in *inexp the inexact flag of the rounding (0, 1, -1).
+ * In case of even rounding when rnd = GMP_RNDN, put MPFR_EVEN_INEX (2) or
+ * -MPFR_EVEN_INEX (-2) in *inexp.
+ *
+ * If flag = 1, just returns whether one should add 1 or not for rounding.
+ *
+ * Note: yprec may be < MPFR_PREC_MIN; in particular, it may be equal
+ * to 1. In this case, the even rounding is done away from 0, which is
+ * a natural generalization. Indeed, a number with 1-bit precision can
+ * be seen as a denormalized number with more precision.
+ */
+
+int
+mpfr_round_raw_generic(
+#if flag == 0
+ mp_limb_t *yp,
+#endif
+ const mp_limb_t *xp, mp_prec_t xprec,
+ int neg, mp_prec_t yprec, mp_rnd_t rnd_mode
+#if use_inexp != 0
+ , int *inexp
+#endif
+ )
+{
+ mp_size_t xsize, nw;
+ mp_limb_t himask, lomask, sb;
+ int rw;
+#if flag == 0
+ int carry;
+#endif
+#if use_inexp == 0
+ int *inexp;
+#endif
+
+ if (use_inexp)
+ MPFR_ASSERTD(inexp != ((int*) 0));
+ MPFR_ASSERTD(neg == 0 || neg == 1);
+
+ if (flag && !use_inexp &&
+ (xprec <= yprec || MPFR_IS_LIKE_RNDZ (rnd_mode, neg)))
+ return 0;
+
+ xsize = (xprec-1)/BITS_PER_MP_LIMB + 1;
+ nw = yprec / BITS_PER_MP_LIMB;
+ rw = yprec & (BITS_PER_MP_LIMB - 1);
+
+ if (MPFR_UNLIKELY(xprec <= yprec))
+ { /* No rounding is necessary. */
+ /* if yp=xp, maybe an overlap: MPN_COPY_DECR is ok when src <= dst */
+ if (MPFR_LIKELY(rw))
+ nw++;
+ MPFR_ASSERTD(nw >= 1);
+ MPFR_ASSERTD(nw >= xsize);
+ if (use_inexp)
+ *inexp = 0;
+#if flag == 0
+ MPN_COPY_DECR(yp + (nw - xsize), xp, xsize);
+ MPN_ZERO(yp, nw - xsize);
+#endif
+ return 0;
+ }
+
+ if (use_inexp || !MPFR_IS_LIKE_RNDZ(rnd_mode, neg))
+ {
+ mp_size_t k = xsize - nw - 1;
+
+ if (MPFR_LIKELY(rw))
+ {
+ nw++;
+ lomask = MPFR_LIMB_MASK (BITS_PER_MP_LIMB - rw);
+ himask = ~lomask;
+ }
+ else
+ {
+ lomask = ~(mp_limb_t) 0;
+ himask = ~(mp_limb_t) 0;
+ }
+ MPFR_ASSERTD(k >= 0);
+ sb = xp[k] & lomask; /* First non-significant bits */
+ /* Rounding to nearest ? */
+ if (MPFR_LIKELY( rnd_mode == GMP_RNDN) )
+ {
+ /* Rounding to nearest */
+ mp_limb_t rbmask = MPFR_LIMB_ONE << (BITS_PER_MP_LIMB - 1 - rw);
+ if (sb & rbmask) /* rounding bit */
+ sb &= ~rbmask; /* it is 1, clear it */
+ else
+ {
+ /* Rounding bit is 0, behave like rounding to 0 */
+ goto rnd_RNDZ;
+ }
+ while (MPFR_UNLIKELY(sb == 0) && k > 0)
+ sb = xp[--k];
+ /* rounding to nearest, with rounding bit = 1 */
+ if (MPFR_UNLIKELY(sb == 0)) /* Even rounding. */
+ {
+ /* sb == 0 && rnd_mode == GMP_RNDN */
+ sb = xp[xsize - nw] & (himask ^ (himask << 1));
+ if (sb == 0)
+ {
+ if (use_inexp)
+ *inexp = 2*MPFR_EVEN_INEX*neg-MPFR_EVEN_INEX;
+ /* ((neg!=0)^(sb!=0)) ? MPFR_EVEN_INEX : -MPFR_EVEN_INEX;*/
+ /* Since neg = 0 or 1 and sb=0*/
+#if flag == 1
+ return 0 /*sb != 0 && rnd_mode != GMP_RNDZ */;
+#else
+ MPN_COPY_INCR(yp, xp + xsize - nw, nw);
+ yp[0] &= himask;
+ return 0;
+#endif
+ }
+ else
+ {
+ /* sb != 0 && rnd_mode == GMP_RNDN */
+ if (use_inexp)
+ *inexp = MPFR_EVEN_INEX-2*MPFR_EVEN_INEX*neg;
+ /*((neg!=0)^(sb!=0))? MPFR_EVEN_INEX : -MPFR_EVEN_INEX; */
+ /*Since neg= 0 or 1 and sb != 0 */
+ goto rnd_RNDN_add_one_ulp;
+ }
+ }
+ else /* sb != 0 && rnd_mode == GMP_RNDN*/
+ {
+ if (use_inexp)
+ /* *inexp = (neg == 0) ? 1 : -1; but since neg = 0 or 1 */
+ *inexp = 1-2*neg;
+ rnd_RNDN_add_one_ulp:
+#if flag == 1
+ return 1; /*sb != 0 && rnd_mode != GMP_RNDZ;*/
+#else
+ carry = mpn_add_1 (yp, xp + xsize - nw, nw,
+ rw ?
+ MPFR_LIMB_ONE << (BITS_PER_MP_LIMB - rw)
+ : MPFR_LIMB_ONE);
+ yp[0] &= himask;
+ return carry;
+#endif
+ }
+ }
+ /* Rounding to Zero ? */
+ else if (MPFR_IS_LIKE_RNDZ(rnd_mode, neg))
+ {
+ /* rnd_mode == GMP_RNDZ */
+ rnd_RNDZ:
+ while (MPFR_UNLIKELY(sb == 0) && k > 0)
+ sb = xp[--k];
+ if (use_inexp)
+ /* rnd_mode == GMP_RNDZ and neg = 0 or 1 */
+ /* (neg != 0) ^ (rnd_mode != GMP_RNDZ)) ? 1 : -1);*/
+ *inexp = MPFR_UNLIKELY(sb == 0) ? 0 : (2*neg-1);
+#if flag == 1
+ return 0; /*sb != 0 && rnd_mode != GMP_RNDZ;*/
+#else
+ MPN_COPY_INCR(yp, xp + xsize - nw, nw);
+ yp[0] &= himask;
+ return 0;
+#endif
+ }
+ else
+ {
+ /* rnd_mode = Away */
+ while (MPFR_UNLIKELY(sb == 0) && k > 0)
+ sb = xp[--k];
+ if (MPFR_UNLIKELY(sb == 0))
+ {
+ /* sb = 0 && rnd_mode != GMP_RNDZ */
+ if (use_inexp)
+ /* (neg != 0) ^ (rnd_mode != GMP_RNDZ)) ? 1 : -1);*/
+ *inexp = 0;
+#if flag == 1
+ return 0;
+#else
+ MPN_COPY_INCR(yp, xp + xsize - nw, nw);
+ yp[0] &= himask;
+ return 0;
+#endif
+ }
+ else
+ {
+ /* sb != 0 && rnd_mode != GMP_RNDZ */
+ if (use_inexp)
+ /* (neg != 0) ^ (rnd_mode != GMP_RNDZ)) ? 1 : -1);*/
+ *inexp = 1-2*neg;
+#if flag == 1
+ return 1;
+#else
+ carry = mpn_add_1(yp, xp + xsize - nw, nw,
+ rw ? MPFR_LIMB_ONE << (BITS_PER_MP_LIMB - rw)
+ : 1);
+ yp[0] &= himask;
+ return carry;
+#endif
+ }
+ }
+ }
+ else
+ {
+ /* Roundind mode = Zero / No inexact flag */
+#if flag == 1
+ return 0 /*sb != 0 && rnd_mode != GMP_RNDZ*/;
+#else
+ if (MPFR_LIKELY(rw))
+ {
+ nw++;
+ himask = ~MPFR_LIMB_MASK (BITS_PER_MP_LIMB - rw);
+ }
+ else
+ himask = ~(mp_limb_t) 0;
+ MPN_COPY_INCR(yp, xp + xsize - nw, nw);
+ yp[0] &= himask;
+ return 0;
+#endif
+ }
+}
+
+#undef flag
+#undef use_inexp
+#undef mpfr_round_raw_generic
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