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/*
* MP Misc Functions
* (C) 1999-2008 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/internal/mp_core.h>
#include <botan/internal/mp_madd.h>
#include <stdexcept>
namespace Botan {
/*
* Compare two MP integers
*/
s32bit bigint_cmp(const word x[], size_t x_size,
const word y[], size_t y_size)
{
if(x_size < y_size) { return (-bigint_cmp(y, y_size, x, x_size)); }
while(x_size > y_size)
{
if(x[x_size-1])
return 1;
x_size--;
}
for(size_t i = x_size; i > 0; --i)
{
if(x[i-1] > y[i-1])
return 1;
if(x[i-1] < y[i-1])
return -1;
}
return 0;
}
/*
* Do a 2-word/1-word Division
*/
word bigint_divop(word n1, word n0, word d)
{
if(d == 0)
throw Exception("bigint_divop divide by zero");
word high = n1 % d, quotient = 0;
for(size_t i = 0; i != MP_WORD_BITS; ++i)
{
word high_top_bit = (high & MP_WORD_TOP_BIT);
high <<= 1;
high |= (n0 >> (MP_WORD_BITS-1-i)) & 1;
quotient <<= 1;
if(high_top_bit || high >= d)
{
high -= d;
quotient |= 1;
}
}
return quotient;
}
/*
* Do a 2-word/1-word Modulo
*/
word bigint_modop(word n1, word n0, word d)
{
word z = bigint_divop(n1, n0, d);
word dummy = 0;
z = word_madd2(z, d, &dummy);
return (n0-z);
}
}
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