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/*
Copyright (C) 2010 William Hart
This file is part of FLINT.
FLINT is free software: you can redistribute it and/or modify it under
the terms of the GNU Lesser General Public License (LGPL) as published
by the Free Software Foundation; either version 3 of the License, or
(at your option) any later version. See <https://www.gnu.org/licenses/>.
*/
#include "mpn_extras.h"
#include "fmpz.h"
int
fmpz_bit_unpack(fmpz_t coeff, nn_srcptr arr, flint_bitcnt_t shift,
flint_bitcnt_t bits, int negate, int borrow)
{
ulong mask, sign;
ulong limbs = (shift + bits) / FLINT_BITS;
ulong rem_bits = (shift + bits) % FLINT_BITS;
/* determine if field is positive or negative */
if (rem_bits)
sign = ((((ulong) 1) << (rem_bits - 1)) & arr[limbs]);
else
sign = ((((ulong) 1) << (FLINT_BITS - 1)) & arr[limbs - 1]);
if (bits <= SMALL_FMPZ_BITCOUNT_MAX) /* fits into a small coeff */
{
_fmpz_demote(coeff);
/* mask for the given number of bits */
mask = (((ulong) 1) << bits) - (ulong) 1;
if (limbs + (rem_bits != 0) > 1) /* field crosses a limb boundary */
(*coeff) =
((arr[0] >> shift) + (arr[1] << (FLINT_BITS - shift))) & mask;
else /* field is in first limb only, mask it */
(*coeff) = (arr[0] >> shift) & mask;
/* sign extend */
if (sign)
(*coeff) += ((~(ulong) 0) << bits);
/* determine whether we need to return a borrow */
sign = (*coeff < (slong) 0 ? (ulong) 1 : (ulong) 0);
/* deal with borrow */
if (borrow)
{
(*coeff)++;
if ((*coeff) > COEFF_MAX)
{
fmpz v = *coeff;
*coeff = 0;
fmpz_set_ui(coeff, v);
}
}
/* negate the coeff if necessary */
if (negate)
fmpz_neg(coeff, coeff);
return (sign != (ulong) 0);
}
else /* large coefficient */
{
mpz_ptr mcoeff;
ulong * p;
ulong l, b;
mcoeff = _fmpz_promote(coeff);
/* the number of limbs to hold the bitfield _including_ b extra bits */
l = (bits - 1) / FLINT_BITS + 1;
b = bits % FLINT_BITS;
/* allocate space for l limbs only */
p = FLINT_MPZ_REALLOC_TIGHT(mcoeff, l);
/* shift in l limbs */
if (shift)
mpn_rshift(p, arr, l, shift);
else
flint_mpn_copyi(p, arr, l);
/* shift in any rem_bits that weren't already shifted */
if (limbs + (rem_bits != 0) > l)
p[l - 1] += (arr[limbs] << (FLINT_BITS - shift));
/* mask off the last limb, if not full */
if (b)
{
mask = (((ulong) 1) << b) - (ulong) 1;
p[l - 1] &= mask;
}
if (sign != (ulong) 0)
{
/* sign extend */
if (b)
p[l - 1] += ((~(ulong) 0) << b);
/* negate */
mpn_com(p, p, l);
if (!borrow)
mpn_add_1(p, p, l, 1);
/* normalise */
while (l && (p[l - 1] == (ulong) 0))
l--;
mcoeff->_mp_size = -l;
sign = 1;
}
else
{
/* deal with borrow */
if (borrow)
mpn_add_1(p, p, l, 1);
/* normalise */
while (l && (p[l - 1] == (ulong) 0))
l--;
mcoeff->_mp_size = l;
sign = 0;
}
/* negate if required */
if (negate)
mpz_neg(mcoeff, mcoeff);
/* coeff may fit in a small */
_fmpz_demote_val(coeff);
return sign;
}
}
void
fmpz_bit_unpack_unsigned(fmpz_t coeff, nn_srcptr arr,
flint_bitcnt_t shift, flint_bitcnt_t bits)
{
ulong limbs = (shift + bits) / FLINT_BITS;
ulong rem_bits = (shift + bits) % FLINT_BITS;
ulong mask;
if (bits <= SMALL_FMPZ_BITCOUNT_MAX) /* fits into a small coeff */
{
_fmpz_demote(coeff);
/* mask for the given number of bits */
mask = (((ulong) 1) << bits) - (ulong) 1;
if (limbs + (rem_bits != 0) > 1) /* field crosses a limb boundary */
(*coeff) =
((arr[0] >> shift) + (arr[1] << (FLINT_BITS - shift))) & mask;
else /* field is in first limb only, mask it */
(*coeff) = (arr[0] >> shift) & mask;
}
else /* large coefficient */
{
mpz_ptr mcoeff;
ulong * p;
ulong l, b;
mcoeff = _fmpz_promote(coeff);
/* the number of limbs to hold the bitfield _including_ b extra bits */
l = (bits - 1) / FLINT_BITS + 1;
b = bits % FLINT_BITS;
/* allocate space for l limbs only */
p = FLINT_MPZ_REALLOC_TIGHT(mcoeff, l);
/* shift in l limbs */
if (shift)
mpn_rshift(p, arr, l, shift);
else
flint_mpn_copyi(p, arr, l);
/* shift in any rem_bits that weren't already shifted */
if (limbs + (rem_bits != 0) > l)
p[l - 1] += (arr[limbs] << (FLINT_BITS - shift));
/* mask off the last limb, if not full */
if (b)
{
mask = (((ulong) 1) << b) - (ulong) 1;
p[l - 1] &= mask;
}
/* normalise */
while (l && (p[l - 1] == (ulong) 0))
l--;
mcoeff->_mp_size = l;
/* coeff may fit in a small */
_fmpz_demote_val(coeff);
}
}