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/*************************************************
* BigInt Binary Operators Source File *
* (C) 1999-2005 The Botan Project *
*************************************************/
#include <botan/bigint.h>
#include <botan/numthry.h>
#include <botan/mp_core.h>
#include <botan/bit_ops.h>
namespace Botan {
/*************************************************
* Addition Operator *
*************************************************/
BigInt operator+(const BigInt& x, const BigInt& y)
{
if((x.sign() == y.sign()))
{
BigInt z(x.sign(), std::max(x.sig_words(), y.sig_words()) + 1);
bigint_add3(z.get_reg(), x.data(), x.sig_words(),
y.data(), y.sig_words());
return z;
}
else if(x.is_positive())
return (x - y.abs());
else
return (y - x.abs());
}
/*************************************************
* Subtraction Operator *
*************************************************/
BigInt operator-(const BigInt& x, const BigInt& y)
{
s32bit relative_size = bigint_cmp(x.data(), x.sig_words(),
y.data(), y.sig_words());
if(relative_size == 0 && (x.sign() == y.sign())) return 0;
if(relative_size == 0 && (x.sign() != y.sign())) return (x << 1);
BigInt z(BigInt::Positive, std::max(x.sig_words(), y.sig_words()) + 1);
if(relative_size == -1)
{
if(x.sign() == y.sign())
bigint_sub3(z.get_reg(), y.data(), y.sig_words(),
x.data(), x.sig_words());
else
bigint_add3(z.get_reg(), x.data(), x.sig_words(),
y.data(), y.sig_words());
z.set_sign(y.reverse_sign());
}
if(relative_size == 1)
{
if(x.sign() == y.sign())
bigint_sub3(z.get_reg(), x.data(), x.sig_words(),
y.data(), y.sig_words());
else
bigint_add3(z.get_reg(), x.data(), x.sig_words(),
y.data(), y.sig_words());
z.set_sign(x.sign());
}
return z;
}
/*************************************************
* Multiplication Operator *
*************************************************/
BigInt operator*(const BigInt& x, const BigInt& y)
{
if(x.is_zero() || y.is_zero())
return 0;
BigInt::Sign sign = BigInt::Positive;
if(x.sign() != y.sign())
sign = BigInt::Negative;
const u32bit x_sw = x.sig_words();
const u32bit y_sw = y.sig_words();
if(x_sw == 1 || y_sw == 1)
{
BigInt z(sign, x_sw + y_sw);
if(x_sw == 1)
bigint_linmul3(z.get_reg(), y.data(), y_sw, x.word_at(0));
else
bigint_linmul3(z.get_reg(), x.data(), x_sw, y.word_at(0));
return z;
}
BigInt z(sign, x.size() + y.size());
bigint_mul3(z.get_reg(), z.size(),
x.data(), x.size(), x_sw,
y.data(), y.size(), y_sw);
return z;
}
/*************************************************
* Division Operator *
*************************************************/
BigInt operator/(const BigInt& x, const BigInt& y)
{
BigInt q, r;
divide(x, y, q, r);
return q;
}
/*************************************************
* Modulo Operator *
*************************************************/
BigInt operator%(const BigInt& n, const BigInt& mod)
{
if(mod.is_zero())
throw BigInt::DivideByZero();
if(mod.is_negative())
throw Invalid_Argument("BigInt::operator%: modulus must be > 0");
if(n.is_positive() && mod.is_positive() && n < mod)
return n;
BigInt q, r;
divide(n, mod, q, r);
return r;
}
/*************************************************
* Modulo Operator *
*************************************************/
word operator%(const BigInt& n, word mod)
{
if(mod == 0)
throw BigInt::DivideByZero();
if(power_of_2(mod))
return (n.word_at(0) & (mod - 1));
word remainder = 0;
u32bit size = n.sig_words();
for(u32bit j = size; j > 0; j--)
remainder = bigint_modop(remainder, n.word_at(j-1), mod);
return remainder;
}
/*************************************************
* Left Shift Operator *
*************************************************/
BigInt operator<<(const BigInt& x, u32bit shift)
{
if(shift == 0) return x;
const u32bit shift_words = shift / MP_WORD_BITS,
shift_bits = shift % MP_WORD_BITS;
BigInt y(x.sign(), x.sig_words() + shift_words + (shift_bits ? 1 : 0));
bigint_shl2(y.get_reg(), x.data(), x.sig_words(), shift_words, shift_bits);
return y;
}
/*************************************************
* Right Shift Operator *
*************************************************/
BigInt operator>>(const BigInt& x, u32bit shift)
{
if(shift == 0) return x;
if(x.bits() <= shift) return 0;
const u32bit shift_words = shift / MP_WORD_BITS,
shift_bits = shift % MP_WORD_BITS;
BigInt y(x.sign(), x.sig_words() - shift_words);
bigint_shr2(y.get_reg(), x.data(), x.sig_words(), shift_words, shift_bits);
return y;
}
}
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