dropbear: bn_mp_mod_2d.c comparison

Import of libtommath 0.35 From ltm-0.35.tar.bz2 SHA1 of 3f193dbae9351e92d02530994fa18236f7fde01c

comparison

equal deleted inserted replaced

--1:000000000000
+:91fbc376f010
+#include <tommath.h>
+#ifdef BN_MP_MOD_2D_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, [email protected], http://math.libtomcrypt.org
+*/
+/* calc a value mod 2**b */
+int
+mp_mod_2d (mp_int * a, int b, mp_int * c)
+{
+int     x, res;
+/* if b is <= 0 then zero the int */
+if (b <= 0) {
+mp_zero (c);
+return MP_OKAY;
+}
+/* if the modulus is larger than the value than return */
+if (b >= (int) (a->used * DIGIT_BIT)) {
+res = mp_copy (a, c);
+return res;
+}
+/* copy */
+if ((res = mp_copy (a, c)) != MP_OKAY) {
+return res;
+}
+/* zero digits above the last digit of the modulus */
+for (x = (b / DIGIT_BIT) + ((b % DIGIT_BIT) == 0 ? 0 : 1); x < c->used; x++) {
+c->dp[x] = 0;
+}
+/* clear the digit that is not completely outside/inside the modulus */
+c->dp[b / DIGIT_BIT] &=
+(mp_digit) ((((mp_digit) 1) << (((mp_digit) b) % DIGIT_BIT)) - ((mp_digit) 1));
+mp_clamp (c);
+return MP_OKAY;
+}
+#endif

Mercurial > dropbear