61 lines
1.9 KiB
C
61 lines
1.9 KiB
C
/* mpn_sizeinbase -- approximation to chars required for an mpn.
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THE FUNCTIONS IN THIS FILE ARE FOR INTERNAL USE ONLY. THEY'RE ALMOST
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CERTAIN TO BE SUBJECT TO INCOMPATIBLE CHANGES OR DISAPPEAR COMPLETELY IN
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FUTURE GNU MP RELEASES.
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Copyright 1991, 1993, 1994, 1995, 2001, 2002 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., 51 Franklin Street, Fifth Floor, Boston,
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MA 02110-1301, USA. */
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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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/* Same as mpz_sizeinbase, meaning exact for power-of-2 bases, and either
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exact or 1 too big for other bases. */
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size_t
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mpn_sizeinbase (mp_srcptr xp, mp_size_t xsize, int base)
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{
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int lb_base, cnt;
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mp_size_t totbits;
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ASSERT (xsize >= 0);
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ASSERT (base >= 2);
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ASSERT (base < numberof (__mp_bases));
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/* Special case for X == 0. */
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if (xsize == 0)
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return 1;
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/* Calculate the total number of significant bits of X. */
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count_leading_zeros (cnt, xp[xsize-1]);
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totbits = xsize * BITS_PER_MP_LIMB - cnt;
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if (POW2_P (base))
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{
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/* Special case for powers of 2, giving exact result. */
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lb_base = __mp_bases[base].big_base;
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return (totbits + lb_base - 1) / lb_base;
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}
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else
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return (size_t) (totbits * __mp_bases[base].chars_per_bit_exactly) + 1;
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}
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