X-Git-Url: https://git.distorted.org.uk/u/mdw/catacomb/blobdiff_plain/b817bfc642225b8c3c0b6a7e42d1fb949b61a606..80be023065ced106a4078a36371c135a60d2bd6c:/mp-gcd.c

diff --git a/mp-gcd.c b/mp-gcd.c
index 5e663a1..c78181f 100644
--- a/mp-gcd.c
+++ b/mp-gcd.c
@@ -1,6 +1,6 @@
 /* -*-c-*-
  *
- * $Id: mp-gcd.c,v 1.7 2004/04/08 01:36:15 mdw Exp $
+ * $Id$
  *
  * Extended GCD calculation
  *
@@ -63,9 +63,9 @@ void mp_gcd(mp **gcd, mp **xx, mp **yy, mp *a, mp *b)
   if (xx || yy)
     f |= f_ext;
 
-  if (a->f & MP_NEG)
+  if (MP_NEGP(a))
     f |= f_aneg;
-  if (b->f & MP_NEG)
+  if (MP_NEGP(b))
     f |= f_bneg;
 
   /* --- Ensure that @a@ is larger than @b@ --- *
@@ -87,7 +87,7 @@ void mp_gcd(mp **gcd, mp **xx, mp **yy, mp *a, mp *b)
     if (gcd) {
       if (*gcd) MP_DROP(*gcd);
       a = MP_COPY(a);
-      if (a->f & MP_NEG) {
+      if (MP_NEGP(a)) {
 	MP_SPLIT(a);
 	a->f &= ~MP_NEG;
 	f |= f_aneg;
@@ -118,20 +118,20 @@ 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);
 
-  while (MP_LEN(v)) {
+  /* --- Main extended Euclidean algorithm --- */
+
+  while (!MP_ZEROP(v)) {
     mp *t;
     mp_div(&q, &u, u, v);
     if (f & f_ext) {
@@ -178,11 +178,11 @@ void mp_gcd(mp **gcd, mp **xx, mp **yy, mp *a, mp *b)
      */
 
     if (yy) {
-      if (y->f & MP_NEG) {
+      if (MP_NEGP(y)) {
 	do {
 	  y = mp_add(y, y, a);
 	  x = mp_sub(x, x, b);
-	} while (y->f & MP_NEG);
+	} while (MP_NEGP(y));
       } else {
 	while (MP_CMP(y, >=, a)) {
 	  y = mp_sub(y, y, a);
@@ -190,10 +190,10 @@ void mp_gcd(mp **gcd, mp **xx, mp **yy, mp *a, mp *b)
 	}
       }
     } else {
-      if (x->f & MP_NEG) {
+      if (MP_NEGP(x)) {
 	do
 	  x = mp_add(x, x, b);
-	while (x->f & MP_NEG);
+	while (MP_NEGP(x));
       } else {
 	while (MP_CMP(x, >=, b))
 	  x = mp_sub(x, x, b);
@@ -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 } }
 };