### view libtommath/bn_mp_sub.c @ 1490:9b87cbe931e3

build: Remove unused constructs: `space' and `AC_PROG_MAKE_SET' The makefile variable `space' is never used. The autoconf output variable `SET_MAKE' is never used, so the autoconf macro `AC_PROG_MAKE_SET' has been removed.
author Michael Witten Mon, 31 Jul 2017 23:55:52 +0000 8bba51a55704 f52919ffd3b1
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```#include <tommath_private.h>
#ifdef BN_MP_SUB_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
*
* The library is free for all purposes without any express
* guarantee it works.
*
* Tom St Denis, [email protected], http://libtom.org
*/

/* high level subtraction (handles signs) */
int
mp_sub (mp_int * a, mp_int * b, mp_int * c)
{
int     sa, sb, res;

sa = a->sign;
sb = b->sign;

if (sa != sb) {
/* subtract a negative from a positive, OR */
/* subtract a positive from a negative. */
/* In either case, ADD their magnitudes, */
/* and use the sign of the first number. */
c->sign = sa;
res = s_mp_add (a, b, c);
} else {
/* subtract a positive from a positive, OR */
/* subtract a negative from a negative. */
/* First, take the difference between their */
/* magnitudes, then... */
if (mp_cmp_mag (a, b) != MP_LT) {
/* Copy the sign from the first */
c->sign = sa;
/* The first has a larger or equal magnitude */
res = s_mp_sub (a, b, c);
} else {
/* The result has the *opposite* sign from */
/* the first number. */
c->sign = (sa == MP_ZPOS) ? MP_NEG : MP_ZPOS;
/* The second has a larger magnitude */
res = s_mp_sub (b, a, c);
}
}
return res;
}

#endif

/* ref:         \$Format:%D\$ */
/* git commit:  \$Format:%H\$ */
/* commit time: \$Format:%ai\$ */
```