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