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matrixssl-1-8-6-open/src/crypto/peersec/mpi.c  view on Meta::CPAN

/******************************************************************************/
/*
	Call only from mp_exptmod to make sure this fast version qualifies
*/
static int32 mp_exptmod_fast(psPool_t *pool, mp_int * G, mp_int * X,
				mp_int * P, mp_int * Y, int32 redmode)
{
	mp_int		M[TAB_SIZE], res;
	mp_digit	buf, mp;
	int32		err, bitbuf, bitcpy, bitcnt, mode, digidx, x, y, winsize;


/*
	use a pointer to the reduction algorithm.  This allows us to use
	one of many reduction algorithms without modding the guts of
	the code with if statements everywhere.
 */
	int32	(*redux)(mp_int*,mp_int*,mp_digit);

/*

matrixssl-1-8-6-open/src/crypto/peersec/mpi.c  view on Meta::CPAN

			goto LBL_RES;
		}
	}

/*
	set initial mode and bit cnt
 */
	mode   = 0;
	bitcnt = 1;
	buf    = 0;
	digidx = X->used - 1;
	bitcpy = 0;
	bitbuf = 0;

	for (;;) {
/*
		grab next digit as required
 */
		if (--bitcnt == 0) {
			/* if digidx == -1 we are out of digits so break */
			if (digidx == -1) {
				break;
			}
			/* read next digit and reset bitcnt */
			buf    = X->dp[digidx--];
			bitcnt = (int)DIGIT_BIT;
		}

		/* grab the next msb from the exponent */
		y     = (mp_digit)(buf >> (DIGIT_BIT - 1)) & 1;
		buf <<= (mp_digit)1;

/*
		if the bit is zero and mode == 0 then we ignore it
		These represent the leading zero bits before the first 1 bit