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/*************************************************
* MP Shift Algorithms Source File *
* (C) 1999-2006 The Botan Project *
*************************************************/
#include <botan/mp_core.h>
#include <botan/mem_ops.h>
namespace Botan {
extern "C" {
/*************************************************
* Single Operand Left Shift *
*************************************************/
void bigint_shl1(word x[], u32bit x_size, u32bit word_shift, u32bit bit_shift)
{
if(word_shift)
{
for(u32bit j = 1; j != x_size + 1; ++j)
x[(x_size - j) + word_shift] = x[x_size - j];
clear_mem(x, word_shift);
}
if(bit_shift)
{
word carry = 0;
for(u32bit j = word_shift; j != x_size + word_shift + 1; ++j)
{
word temp = x[j];
x[j] = (temp << bit_shift) | carry;
carry = (temp >> (MP_WORD_BITS - bit_shift));
}
}
}
/*************************************************
* Single Operand Right Shift *
*************************************************/
void bigint_shr1(word x[], u32bit x_size, u32bit word_shift, u32bit bit_shift)
{
if(x_size < word_shift)
{
clear_mem(x, x_size);
return;
}
if(word_shift)
{
for(u32bit j = 0; j != x_size - word_shift; ++j)
x[j] = x[j + word_shift];
for(u32bit j = x_size - word_shift; j != x_size; ++j)
x[j] = 0;
}
if(bit_shift)
{
word carry = 0;
for(u32bit j = x_size - word_shift; j > 0; --j)
{
word temp = x[j-1];
x[j-1] = (temp >> bit_shift) | carry;
carry = (temp << (MP_WORD_BITS - bit_shift));
}
}
}
/*************************************************
* Two Operand Left Shift *
*************************************************/
void bigint_shl2(word y[], const word x[], u32bit x_size,
u32bit word_shift, u32bit bit_shift)
{
for(u32bit j = 0; j != x_size; ++j)
y[j + word_shift] = x[j];
if(bit_shift)
{
word carry = 0;
for(u32bit j = word_shift; j != x_size + word_shift + 1; ++j)
{
word temp = y[j];
y[j] = (temp << bit_shift) | carry;
carry = (temp >> (MP_WORD_BITS - bit_shift));
}
}
}
/*************************************************
* Two Operand Right Shift *
*************************************************/
void bigint_shr2(word y[], const word x[], u32bit x_size,
u32bit word_shift, u32bit bit_shift)
{
if(x_size < word_shift) return;
for(u32bit j = 0; j != x_size - word_shift; ++j)
y[j] = x[j + word_shift];
if(bit_shift)
{
word carry = 0;
for(u32bit j = x_size - word_shift; j > 0; --j)
{
word temp = y[j-1];
y[j-1] = (temp >> bit_shift) | carry;
carry = (temp << (MP_WORD_BITS - bit_shift));
}
}
}
}
}
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