Mercurial > dropbear
diff bn_mp_mul.c @ 2:86e0b50a9b58 libtommath-orig ltm-0.30-orig
ltm 0.30 orig import
author | Matt Johnston <matt@ucc.asn.au> |
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date | Mon, 31 May 2004 18:25:22 +0000 |
parents | |
children | d29b64170cf0 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/bn_mp_mul.c Mon May 31 18:25:22 2004 +0000 @@ -0,0 +1,48 @@ +/* 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, [email protected], http://math.libtomcrypt.org + */ +#include <tommath.h> + +/* high level multiplication (handles sign) */ +int mp_mul (mp_int * a, mp_int * b, mp_int * c) +{ + int res, neg; + neg = (a->sign == b->sign) ? MP_ZPOS : MP_NEG; + + /* use Toom-Cook? */ + if (MIN (a->used, b->used) >= TOOM_MUL_CUTOFF) { + res = mp_toom_mul(a, b, c); + /* use Karatsuba? */ + } else if (MIN (a->used, b->used) >= KARATSUBA_MUL_CUTOFF) { + res = mp_karatsuba_mul (a, b, c); + } else { + /* can we use the fast multiplier? + * + * The fast multiplier can be used if the output will + * have less than MP_WARRAY digits and the number of + * digits won't affect carry propagation + */ + int digs = a->used + b->used + 1; + + if ((digs < MP_WARRAY) && + MIN(a->used, b->used) <= + (1 << ((CHAR_BIT * sizeof (mp_word)) - (2 * DIGIT_BIT)))) { + res = fast_s_mp_mul_digs (a, b, c, digs); + } else { + res = s_mp_mul (a, b, c); + } + } + c->sign = neg; + return res; +}