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author | William Joye <wjoye@cfa.harvard.edu> | 2018-01-02 21:03:49 (GMT) |
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committer | William Joye <wjoye@cfa.harvard.edu> | 2018-01-02 21:03:49 (GMT) |
commit | 914501b5b992e7b6c7e0a4c958712a8ba9cab41c (patch) | |
tree | edbc059b9557d5fdb79e5a5c47889bc54708da53 /tcl8.6/libtommath/bn_fast_s_mp_sqr.c | |
parent | f88c190a01bc7f57e79dfaf91a3c0c48c2031549 (diff) | |
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upgrade to tcl/tk 8.6.8
Diffstat (limited to 'tcl8.6/libtommath/bn_fast_s_mp_sqr.c')
-rw-r--r-- | tcl8.6/libtommath/bn_fast_s_mp_sqr.c | 110 |
1 files changed, 110 insertions, 0 deletions
diff --git a/tcl8.6/libtommath/bn_fast_s_mp_sqr.c b/tcl8.6/libtommath/bn_fast_s_mp_sqr.c new file mode 100644 index 0000000..1abf24b --- /dev/null +++ b/tcl8.6/libtommath/bn_fast_s_mp_sqr.c @@ -0,0 +1,110 @@ +#include <tommath.h> +#ifdef BN_FAST_S_MP_SQR_C +/* LibTomMath, multiple-precision integer library -- Tom St Denis + * + * LibTomMath is a library that provides multiple-precision + * integer arithmetic as well as number theoretic functionality. + * + * The library was designed directly after the MPI library by + * Michael Fromberger but has been written from scratch with + * additional optimizations in place. + * + * The library is free for all purposes without any express + * guarantee it works. + * + * Tom St Denis, tomstdenis@gmail.com, http://math.libtomcrypt.com + */ + +/* the jist of squaring... + * you do like mult except the offset of the tmpx [one that + * starts closer to zero] can't equal the offset of tmpy. + * So basically you set up iy like before then you min it with + * (ty-tx) so that it never happens. You double all those + * you add in the inner loop + +After that loop you do the squares and add them in. +*/ + +int fast_s_mp_sqr (mp_int * a, mp_int * b) +{ + int olduse, res, pa, ix, iz; + mp_digit W[MP_WARRAY], *tmpx; + mp_word W1; + + /* grow the destination as required */ + pa = a->used + a->used; + if (b->alloc < pa) { + if ((res = mp_grow (b, pa)) != MP_OKAY) { + return res; + } + } + + /* number of output digits to produce */ + W1 = 0; + for (ix = 0; ix < pa; ix++) { + int tx, ty, iy; + mp_word _W; + mp_digit *tmpy; + + /* clear counter */ + _W = 0; + + /* 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, essentially + 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); + + /* execute loop */ + for (iz = 0; iz < iy; iz++) { + _W += ((mp_word)*tmpx++)*((mp_word)*tmpy--); + } + + /* double the inner product and add carry */ + _W = _W + _W + W1; + + /* even columns have the square term in them */ + if ((ix&1) == 0) { + _W += ((mp_word)a->dp[ix>>1])*((mp_word)a->dp[ix>>1]); + } + + /* store it */ + W[ix] = (mp_digit)(_W & MP_MASK); + + /* make next carry */ + W1 = _W >> ((mp_word)DIGIT_BIT); + } + + /* setup dest */ + olduse = b->used; + b->used = a->used+a->used; + + { + mp_digit *tmpb; + tmpb = b->dp; + for (ix = 0; ix < pa; ix++) { + *tmpb++ = W[ix] & MP_MASK; + } + + /* clear unused digits [that existed in the old copy of c] */ + for (; ix < olduse; ix++) { + *tmpb++ = 0; + } + } + mp_clamp (b); + return MP_OKAY; +} +#endif |