| /* 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 |
