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/*
* BigInt Binary Operators
* (C) 1999-2007 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/
#include <botan/bigint.h>
#include <botan/divide.h>
#include <botan/internal/mp_core.h>
#include <botan/internal/bit_ops.h>
#include <algorithm>
namespace Botan {
/*
* Addition Operator
*/
BigInt operator+(const BigInt& x, const BigInt& y)
{
const size_t x_sw = x.sig_words(), y_sw = y.sig_words();
BigInt z(x.sign(), std::max(x_sw, y_sw) + 1);
if((x.sign() == y.sign()))
bigint_add3(z.mutable_data(), x.data(), x_sw, y.data(), y_sw);
else
{
s32bit relative_size = bigint_cmp(x.data(), x_sw, y.data(), y_sw);
if(relative_size < 0)
{
bigint_sub3(z.mutable_data(), y.data(), y_sw, x.data(), x_sw);
z.set_sign(y.sign());
}
else if(relative_size == 0)
z.set_sign(BigInt::Positive);
else if(relative_size > 0)
bigint_sub3(z.mutable_data(), x.data(), x_sw, y.data(), y_sw);
}
return z;
}
/*
* Subtraction Operator
*/
BigInt operator-(const BigInt& x, const BigInt& y)
{
const size_t x_sw = x.sig_words(), y_sw = y.sig_words();
s32bit relative_size = bigint_cmp(x.data(), x_sw, y.data(), y_sw);
BigInt z(BigInt::Positive, std::max(x_sw, y_sw) + 1);
if(relative_size < 0)
{
if(x.sign() == y.sign())
bigint_sub3(z.mutable_data(), y.data(), y_sw, x.data(), x_sw);
else
bigint_add3(z.mutable_data(), x.data(), x_sw, y.data(), y_sw);
z.set_sign(y.reverse_sign());
}
else if(relative_size == 0)
{
if(x.sign() != y.sign())
bigint_shl2(z.mutable_data(), x.data(), x_sw, 0, 1);
}
else if(relative_size > 0)
{
if(x.sign() == y.sign())
bigint_sub3(z.mutable_data(), x.data(), x_sw, y.data(), y_sw);
else
bigint_add3(z.mutable_data(), x.data(), x_sw, y.data(), y_sw);
z.set_sign(x.sign());
}
return z;
}
/*
* Multiplication Operator
*/
BigInt operator*(const BigInt& x, const BigInt& y)
{
const size_t x_sw = x.sig_words(), y_sw = y.sig_words();
BigInt z(BigInt::Positive, x.size() + y.size());
if(x_sw == 1 && y_sw)
bigint_linmul3(z.mutable_data(), y.data(), y_sw, x.word_at(0));
else if(y_sw == 1 && x_sw)
bigint_linmul3(z.mutable_data(), x.data(), x_sw, y.word_at(0));
else if(x_sw && y_sw)
{
secure_vector<word> workspace(z.size());
bigint_mul(z.mutable_data(), z.size(), &workspace[0],
x.data(), x.size(), x_sw,
y.data(), y.size(), y_sw);
}
if(x_sw && y_sw && x.sign() != y.sign())
z.flip_sign();
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(is_power_of_2(mod))
return (n.word_at(0) & (mod - 1));
word remainder = 0;
for(size_t j = n.sig_words(); j > 0; --j)
remainder = bigint_modop(remainder, n.word_at(j-1), mod);
if(remainder && n.sign() == BigInt::Negative)
return mod - remainder;
return remainder;
}
/*
* Left Shift Operator
*/
BigInt operator<<(const BigInt& x, size_t shift)
{
if(shift == 0)
return x;
const size_t shift_words = shift / MP_WORD_BITS,
shift_bits = shift % MP_WORD_BITS;
const size_t x_sw = x.sig_words();
BigInt y(x.sign(), x_sw + shift_words + (shift_bits ? 1 : 0));
bigint_shl2(y.mutable_data(), x.data(), x_sw, shift_words, shift_bits);
return y;
}
/*
* Right Shift Operator
*/
BigInt operator>>(const BigInt& x, size_t shift)
{
if(shift == 0)
return x;
if(x.bits() <= shift)
return 0;
const size_t shift_words = shift / MP_WORD_BITS,
shift_bits = shift % MP_WORD_BITS,
x_sw = x.sig_words();
BigInt y(x.sign(), x_sw - shift_words);
bigint_shr2(y.mutable_data(), x.data(), x_sw, shift_words, shift_bits);
return y;
}
}
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