60 lines
1.7 KiB
C
60 lines
1.7 KiB
C
/* mpz_sizeinbase(x, base) -- return an approximation to the number of
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character the integer X would have printed in base BASE. The
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approximation is never too small.
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Copyright (C) 1991 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 General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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The GNU MP Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with the GNU MP Library; see the file COPYING. If not, write to
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the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, 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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size_t
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#ifdef __STDC__
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mpz_sizeinbase (const MP_INT *x, int base)
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#else
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mpz_sizeinbase (x, base)
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const MP_INT *x;
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int base;
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#endif
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{
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mp_size size = ABS (x->size);
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int lb_base, cnt;
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size_t totbits;
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/* Special case for X == 0. */
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if (size == 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, x->d[size - 1]);
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totbits = size * BITS_PER_MP_LIMB - cnt;
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if ((base & (base - 1)) == 0)
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{
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/* Special case for powers of 2, giving exact result. */
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count_leading_zeros (lb_base, base);
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lb_base = BITS_PER_MP_LIMB - lb_base - 1;
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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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