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author | rsc <devnull@localhost> | 2004-03-21 14:06:38 +0000 |
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committer | rsc <devnull@localhost> | 2004-03-21 14:06:38 +0000 |
commit | b3f61791f1e9095ce8ae9c6d6415b4ee94e2f7eb (patch) | |
tree | deaa85427ae73a045ddef39395bd286f9d3dc2ff /src/libmp/port/mpinvert.c | |
parent | 498bb22174aa2c76493e8c67b92949271131ebfb (diff) | |
download | plan9port-b3f61791f1e9095ce8ae9c6d6415b4ee94e2f7eb.tar.gz plan9port-b3f61791f1e9095ce8ae9c6d6415b4ee94e2f7eb.tar.bz2 plan9port-b3f61791f1e9095ce8ae9c6d6415b4ee94e2f7eb.zip |
Add libmp.
Diffstat (limited to 'src/libmp/port/mpinvert.c')
-rw-r--r-- | src/libmp/port/mpinvert.c | 21 |
1 files changed, 21 insertions, 0 deletions
diff --git a/src/libmp/port/mpinvert.c b/src/libmp/port/mpinvert.c new file mode 100644 index 00000000..ee263070 --- /dev/null +++ b/src/libmp/port/mpinvert.c @@ -0,0 +1,21 @@ +#include "os.h" +#include <mp.h> + +#define iseven(a) (((a)->p[0] & 1) == 0) + +// use extended gcd to find the multiplicative inverse +// res = b**-1 mod m +void +mpinvert(mpint *b, mpint *m, mpint *res) +{ + mpint *dc1, *dc2; // don't care + + dc1 = mpnew(0); + dc2 = mpnew(0); + mpextendedgcd(b, m, dc1, res, dc2); + if(mpcmp(dc1, mpone) != 0) + abort(); + mpmod(res, m, res); + mpfree(dc1); + mpfree(dc2); +} |