/************************************************* * MP Shift Algorithms Source File * * (C) 1999-2007 Jack Lloyd * *************************************************/ #include #include 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)); } } } } }