mirror of https://github.com/macssh/macssh.git
112 lines
2.7 KiB
C
112 lines
2.7 KiB
C
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/*
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Copyright (C) 1999, 2000 Free Software Foundation, Inc.
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This file is part of the GNU MP Library.
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The GNU MP Library is free software; you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or (at your
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option) any later version.
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The GNU MP Library is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
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License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with the GNU MP Library; see the file COPYING.LIB. If not, write to
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the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
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MA 02111-1307, USA.
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*/
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#include "gmp.h"
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#include "gmp-impl.h"
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#include "longlong.h"
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#define TWO64 18446744073709551616.0
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mp_limb_t
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#if __STDC__
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__MPN(udiv_qrnnd) (mp_limb_t n1, mp_limb_t n0, mp_limb_t d, mp_limb_t *r)
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#else
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__MPN(udiv_qrnnd) (n1, n0, d, r)
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mp_limb_t n1;
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mp_limb_t n0;
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mp_limb_t d;
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mp_limb_t *r;
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#endif
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{
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mp_limb_t q1, q2, q;
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mp_limb_t p1, p0;
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double di, dq;
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di = 1.0 / d;
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/* Generate upper 53 bits of quotient. Be careful here; the `double'
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quotient may be rounded to 2^64 which we cannot safely convert back
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to a 64-bit integer. */
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dq = (TWO64 * (double) n1 + (double) n0) * di;
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if (dq >= TWO64)
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q1 = 0xfffffffffffff800LL;
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else
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q1 = (mp_limb_t) dq;
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/* Multiply back in order to compare the product to the dividend. */
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umul_ppmm (p1, p0, q1, d);
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/* Was the 53-bit quotient greater that our sought quotient? Test the
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sign of the partial remainder to find out. */
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if (n1 < p1 || (n1 == p1 && n0 < p0))
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{
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/* 53-bit quotient too large. Partial remainder is negative.
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Compute the absolute value of the remainder in n1,,n0. */
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n1 = p1 - (n1 + (p0 < n0));
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n0 = p0 - n0;
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/* Now use the partial remainder as new dividend to compute more bits of
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quotient. This is an adjustment for the one we got previously. */
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q2 = (mp_limb_t) ((TWO64 * (double) n1 + (double) n0) * di);
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umul_ppmm (p1, p0, q2, d);
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q = q1 - q2;
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if (n1 < p1 || (n1 == p1 && n0 <= p0))
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{
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n0 = p0 - n0;
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}
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else
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{
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n0 = p0 - n0;
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n0 += d;
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q--;
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}
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}
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else
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{
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n1 = n1 - (p1 + (n0 < p0));
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n0 = n0 - p0;
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q2 = (mp_limb_t) ((TWO64 * (double) n1 + (double) n0) * di);
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umul_ppmm (p1, p0, q2, d);
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q = q1 + q2;
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if (n1 < p1 || (n1 == p1 && n0 < p0))
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{
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n0 = n0 - p0;
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n0 += d;
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q--;
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}
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else
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{
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n0 = n0 - p0;
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if (n0 >= d)
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{
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n0 -= d;
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q++;
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}
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}
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}
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*r = n0;
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return q;
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}
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