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/* TomsFastMath, a fast ISO C bignum library.
*
* This project is meant to fill in where LibTomMath
* falls short. That is speed ;-)
*
* This project is public domain and free for all purposes.
*
* Tom St Denis, tomstdenis@gmail.com
*/
#define TFM_DEFINES
#include "fp_sqr_comba.c"
/* generic comba squarer */
void fp_sqr_comba(fp_int *A, fp_int *B)
{
int pa, ix, iz;
fp_digit c0, c1, c2;
fp_int tmp, *dst;
#ifdef TFM_ISO
fp_word tt;
#endif
/* get size of output and trim */
pa = A->used + A->used;
if (pa >= FP_SIZE) {
pa = FP_SIZE-1;
}
/* number of output digits to produce */
COMBA_START;
CLEAR_CARRY;
if (A == B) {
fp_zero(&tmp);
dst = &tmp;
} else {
fp_zero(B);
dst = B;
}
for (ix = 0; ix < pa; ix++) {
int tx, ty, iy;
fp_digit *tmpy, *tmpx;
/* get offsets into the two bignums */
ty = MIN(A->used-1, ix);
tx = ix - ty;
/* setup temp aliases */
tmpx = A->dp + tx;
tmpy = A->dp + ty;
/* this is the number of times the loop will iterrate,
while (tx++ < a->used && ty-- >= 0) { ... }
*/
iy = MIN(A->used-tx, ty+1);
/* now for squaring tx can never equal ty
* we halve the distance since they approach
* at a rate of 2x and we have to round because
* odd cases need to be executed
*/
iy = MIN(iy, (ty-tx+1)>>1);
/* forward carries */
CARRY_FORWARD;
/* execute loop */
for (iz = 0; iz < iy; iz++) {
SQRADD2(*tmpx++, *tmpy--);
}
/* even columns have the square term in them */
if ((ix&1) == 0) {
SQRADD(A->dp[ix>>1], A->dp[ix>>1]);
}
/* store it */
COMBA_STORE(dst->dp[ix]);
}
COMBA_FINI;
/* setup dest */
dst->used = pa;
fp_clamp (dst);
if (dst != B) {
fp_copy(dst, B);
}
}
/* $Source: /cvs/libtom/tomsfastmath/src/sqr/Attic/fp_sqr_comba_generic.c,v $ */
/* $Revision: 1.3 $ */
/* $Date: 2007/02/15 00:31:32 $ */
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