Merge branch 'master' of git+ssh://metalzone.distorted.org.uk/~mdw/public-git/catacomb/

[u/mdw/catacomb] / mp-gcd.c

diff --git a/mp-gcd.c b/mp-gcd.c
index d997072..c78181f 100644 (file)
--- a/mp-gcd.c
+++ b/mp-gcd.c
@@ -118,19 +118,19 @@ void mp_gcd(mp **gcd, mp **xx, mp **yy, mp *a, mp *b)
     return;
   }
 
-  /* --- Take a reference to the arguments --- */
+  /* --- Force the signs on the arguments and take copies --- */
 
   a = MP_COPY(a);
   b = MP_COPY(b);
 
-  /* --- Make sure @a@ and @b@ are not both even --- */
-
   MP_SPLIT(a); a->f &= ~MP_NEG;
   MP_SPLIT(b); b->f &= ~MP_NEG;
 
   u = MP_COPY(a);
   v = MP_COPY(b);
 
+  /* --- Main extended Euclidean algorithm --- */
+
   while (!MP_ZEROP(v)) {
     mp *t;
     mp_div(&q, &u, u, v);
@@ -254,6 +254,27 @@ mp *mp_modinv(mp *d, mp *x, mp *p)
 
 #ifdef TEST_RIG
 
+static int modinv(dstr *v)
+{
+  int ok = 1;
+  mp *x = *(mp **)v[0].buf;
+  mp *m = *(mp **)v[1].buf;
+  mp *r = *(mp **)v[2].buf;
+
+  mp *y = mp_modinv(MP_NEW, x, m);
+  if (!MP_EQ(y, r)) {
+    fputs("\n*** mp_modinv failed", stderr);
+    fputs("\nx      = ", stderr); mp_writefile(x, stderr, 10);
+    fputs("\nm      = ", stderr); mp_writefile(m, stderr, 10);
+    fputs("\nexpect = ", stderr); mp_writefile(r, stderr, 10);
+    fputs("\nresult = ", stderr); mp_writefile(y, stderr, 10);
+    ok = 0;
+  }
+  MP_DROP(x); MP_DROP(m); MP_DROP(r); MP_DROP(y);
+  assert(mparena_count(MPARENA_GLOBAL) == 0);
+  return (ok);  
+}
+
 static int gcd(dstr *v)
 {
   int ok = 1;
@@ -311,6 +332,7 @@ static int gcd(dstr *v)
 
 static test_chunk tests[] = {
   { "gcd", gcd, { &type_mp, &type_mp, &type_mp, &type_mp, &type_mp, 0 } },
+  { "modinv", modinv, { &type_mp, &type_mp, &type_mp, 0 } },
   { 0, 0, { 0 } }
 };