/*************************************************
* Comparison Function *
*************************************************/
s32bit BigInt::cmp(const BigInt& n, bool check_signs) const
{
if(check_signs)
{
if(n.is_positive() && this->is_negative()) return -1;
if(n.is_negative() && this->is_positive()) return 1;
if(n.is_negative() && this->is_negative())
return (-bigint_cmp(data(), sig_words(), n.data(), n.sig_words()));
}
return bigint_cmp(data(), sig_words(), n.data(), n.sig_words());
}
/*************************************************
* Count how many bits are being used *
*************************************************/
u32bit BigInt::bits() const
{
if(sig_words() == 0)
return 0;
u32bit full_words = sig_words() - 1, top_bits = MP_WORD_BITS;
word top_word = word_at(full_words), mask = MP_WORD_TOP_BIT;
while(top_bits && ((top_word & mask) == 0))
{ mask >>= 1; top_bits--; }
return (full_words * MP_WORD_BITS + top_bits);
}
/*
* Modulo Operator
*/
word BigInt::operator%=(word mod)
{
if(mod == 0)
throw BigInt::DivideByZero();
if(is_power_of_2(mod))
{
word result = (word_at(0) & (mod - 1));
clear();
grow_to(2);
m_reg[0] = result;
return result;
}
word remainder = 0;
for(size_t j = sig_words(); j > 0; --j)
remainder = bigint_modop(remainder, word_at(j-1), mod);
clear();
grow_to(2);
if(remainder && sign() == BigInt::Negative)
m_reg[0] = mod - remainder;
else
m_reg[0] = remainder;
set_sign(BigInt::Positive);
return word_at(0);
}
/*
* Left Shift Operator
*/
BigInt& BigInt::operator<<=(size_t shift)
{
if(shift)
{
const size_t shift_words = shift / MP_WORD_BITS,
shift_bits = shift % MP_WORD_BITS,
words = sig_words();
grow_to(words + shift_words + (shift_bits ? 1 : 0));
bigint_shl1(mutable_data(), words, shift_words, shift_bits);
}
return (*this);
}
