Annotation of OpenXM_contrib/gmp/mpf/add.c, Revision 1.1
1.1 ! maekawa 1: /* mpf_add -- Add two floats.
! 2:
! 3: Copyright (C) 1993, 1994, 1996 Free Software Foundation, Inc.
! 4:
! 5: This file is part of the GNU MP Library.
! 6:
! 7: The GNU MP Library is free software; you can redistribute it and/or modify
! 8: it under the terms of the GNU Library General Public License as published by
! 9: the Free Software Foundation; either version 2 of the License, or (at your
! 10: option) any later version.
! 11:
! 12: The GNU MP Library is distributed in the hope that it will be useful, but
! 13: WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
! 14: or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public
! 15: License for more details.
! 16:
! 17: You should have received a copy of the GNU Library General Public License
! 18: along with the GNU MP Library; see the file COPYING.LIB. If not, write to
! 19: the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
! 20: MA 02111-1307, USA. */
! 21:
! 22: #include "gmp.h"
! 23: #include "gmp-impl.h"
! 24:
! 25: void
! 26: #if __STDC__
! 27: mpf_add (mpf_ptr r, mpf_srcptr u, mpf_srcptr v)
! 28: #else
! 29: mpf_add (r, u, v)
! 30: mpf_ptr r;
! 31: mpf_srcptr u;
! 32: mpf_srcptr v;
! 33: #endif
! 34: {
! 35: mp_srcptr up, vp;
! 36: mp_ptr rp, tp;
! 37: mp_size_t usize, vsize, rsize;
! 38: mp_size_t prec;
! 39: mp_exp_t uexp;
! 40: mp_size_t ediff;
! 41: mp_limb_t cy;
! 42: int negate;
! 43: TMP_DECL (marker);
! 44:
! 45: usize = u->_mp_size;
! 46: vsize = v->_mp_size;
! 47:
! 48: /* Handle special cases that don't work in generic code below. */
! 49: if (usize == 0)
! 50: {
! 51: mpf_set (r, v);
! 52: return;
! 53: }
! 54: if (vsize == 0)
! 55: {
! 56: mpf_set (r, u);
! 57: return;
! 58: }
! 59:
! 60: /* If signs of U and V are different, perform subtraction. */
! 61: if ((usize ^ vsize) < 0)
! 62: {
! 63: __mpf_struct v_negated;
! 64: v_negated._mp_size = -vsize;
! 65: v_negated._mp_exp = v->_mp_exp;
! 66: v_negated._mp_d = v->_mp_d;
! 67: mpf_sub (r, u, &v_negated);
! 68: return;
! 69: }
! 70:
! 71: TMP_MARK (marker);
! 72:
! 73: /* Signs are now known to be the same. */
! 74: negate = usize < 0;
! 75:
! 76: /* Make U be the operand with the largest exponent. */
! 77: if (u->_mp_exp < v->_mp_exp)
! 78: {
! 79: mpf_srcptr t;
! 80: t = u; u = v; v = t;
! 81: usize = u->_mp_size;
! 82: vsize = v->_mp_size;
! 83: }
! 84:
! 85: usize = ABS (usize);
! 86: vsize = ABS (vsize);
! 87: up = u->_mp_d;
! 88: vp = v->_mp_d;
! 89: rp = r->_mp_d;
! 90: prec = r->_mp_prec;
! 91: uexp = u->_mp_exp;
! 92: ediff = u->_mp_exp - v->_mp_exp;
! 93:
! 94: /* If U extends beyond PREC, ignore the part that does. */
! 95: if (usize > prec)
! 96: {
! 97: up += usize - prec;
! 98: usize = prec;
! 99: }
! 100:
! 101: /* If V extends beyond PREC, ignore the part that does.
! 102: Note that this may make vsize negative. */
! 103: if (vsize + ediff > prec)
! 104: {
! 105: vp += vsize + ediff - prec;
! 106: vsize = prec - ediff;
! 107: }
! 108:
! 109: #if 0
! 110: /* Locate the least significant non-zero limb in (the needed parts
! 111: of) U and V, to simplify the code below. */
! 112: while (up[0] == 0)
! 113: up++, usize--;
! 114: while (vp[0] == 0)
! 115: vp++, vsize--;
! 116: #endif
! 117:
! 118: /* Allocate temp space for the result. Allocate
! 119: just vsize + ediff later??? */
! 120: tp = (mp_ptr) TMP_ALLOC (prec * BYTES_PER_MP_LIMB);
! 121:
! 122: if (ediff >= prec)
! 123: {
! 124: /* V completely cancelled. */
! 125: if (tp != up)
! 126: MPN_COPY (rp, up, usize);
! 127: rsize = usize;
! 128: }
! 129: else
! 130: {
! 131: /* uuuu | uuuu | uuuu | uuuu | uuuu */
! 132: /* vvvvvvv | vv | vvvvv | v | vv */
! 133:
! 134: if (usize > ediff)
! 135: {
! 136: /* U and V partially overlaps. */
! 137: if (vsize + ediff <= usize)
! 138: {
! 139: /* uuuu */
! 140: /* v */
! 141: mp_size_t size;
! 142: size = usize - ediff - vsize;
! 143: MPN_COPY (tp, up, size);
! 144: cy = mpn_add (tp + size, up + size, usize - size, vp, vsize);
! 145: rsize = usize;
! 146: }
! 147: else
! 148: {
! 149: /* uuuu */
! 150: /* vvvvv */
! 151: mp_size_t size;
! 152: size = vsize + ediff - usize;
! 153: MPN_COPY (tp, vp, size);
! 154: cy = mpn_add (tp + size, up, usize, vp + size, usize - ediff);
! 155: rsize = vsize + ediff;
! 156: }
! 157: }
! 158: else
! 159: {
! 160: /* uuuu */
! 161: /* vv */
! 162: mp_size_t size;
! 163: size = vsize + ediff - usize;
! 164: MPN_COPY (tp, vp, vsize);
! 165: MPN_ZERO (tp + vsize, ediff - usize);
! 166: MPN_COPY (tp + size, up, usize);
! 167: cy = 0;
! 168: rsize = size + usize;
! 169: }
! 170:
! 171: MPN_COPY (rp, tp, rsize);
! 172: rp[rsize] = cy;
! 173: rsize += cy;
! 174: uexp += cy;
! 175: }
! 176:
! 177: r->_mp_size = negate ? -rsize : rsize;
! 178: r->_mp_exp = uexp;
! 179: TMP_FREE (marker);
! 180: }
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