X-Git-Url: https://git.distorted.org.uk/u/mdw/catacomb/blobdiff_plain/b817bfc642225b8c3c0b6a7e42d1fb949b61a606..5278d9afdf1aff9fd6f64073ea42395d756ee58c:/mp-gcd.c

diff --git a/mp-gcd.c b/mp-gcd.c
index 5e663a1..40531c7 100644
--- a/mp-gcd.c
+++ b/mp-gcd.c
@@ -1,13 +1,13 @@
 /* -*-c-*-
  *
- * $Id: mp-gcd.c,v 1.7 2004/04/08 01:36:15 mdw Exp $
+ * $Id$
  *
  * Extended GCD calculation
  *
  * (c) 1999 Straylight/Edgeware
  */
 
-/*----- Licensing notice --------------------------------------------------* 
+/*----- Licensing notice --------------------------------------------------*
  *
  * This file is part of Catacomb.
  *
@@ -15,12 +15,12 @@
  * it under the terms of the GNU Library General Public License as
  * published by the Free Software Foundation; either version 2 of the
  * License, or (at your option) any later version.
- * 
+ *
  * Catacomb is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU Library General Public License for more details.
- * 
+ *
  * You should have received a copy of the GNU Library General Public
  * License along with Catacomb; if not, write to the Free
  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
@@ -50,7 +50,7 @@ void mp_gcd(mp **gcd, mp **xx, mp **yy, mp *a, mp *b)
   mp *x = MP_ONE, *X = MP_ZERO;
   mp *y = MP_ZERO, *Y = MP_ONE;
   mp *u, *v;
-  mp *q = MP_NEW;
+  mp *q = MP_NEW, *t, *spare = MP_NEW;
   unsigned f = 0;
 
 #define f_swap 1u
@@ -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@ --- *
@@ -74,20 +74,20 @@ void mp_gcd(mp **gcd, mp **xx, mp **yy, mp *a, mp *b)
    */
 
   if (MPX_UCMP(a->v, a->vl, <, b->v, b->vl)) {
-    { mp *t = a; a = b; b = t; }
+    t = a; a = b; b = t;
     f |= f_swap;
   }
 
   /* --- Check for zeroness --- */
 
-  if (MP_EQ(b, MP_ZERO)) {
+  if (MP_ZEROP(b)) {
 
     /* --- Store %$|a|$% as the GCD --- */
 
     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;
@@ -99,7 +99,7 @@ void mp_gcd(mp **gcd, mp **xx, mp **yy, mp *a, mp *b)
 
     if (f & f_ext) {
       if (f & f_swap) {
-	mp **t = xx; xx = yy; yy = t;
+	mp **tt = xx; xx = yy; yy = tt;
       }
       if (xx) {
 	if (*xx) MP_DROP(*xx);
@@ -118,34 +118,33 @@ 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)) {
-    mp *t;
+  /* --- Main extended Euclidean algorithm --- */
+
+  while (!MP_ZEROP(v)) {
     mp_div(&q, &u, u, v);
     if (f & f_ext) {
-      t = mp_mul(MP_NEW, X, q);
+      t = mp_mul(spare, X, q);
       t = mp_sub(t, x, t);
-      MP_DROP(x); x = X; X = t;
-      t = mp_mul(MP_NEW, Y, q);
+      spare = x; x = X; X = t;
+      t = mp_mul(spare, Y, q);
       t = mp_sub(t, y, t);
-      MP_DROP(y); y = Y; Y = t;
+      spare = y; y = Y; Y = t;
     }
     t = u; u = v; v = t;
   }
 
-  MP_DROP(q);
+  MP_DROP(q); if (spare) MP_DROP(spare);
   if (!gcd)
     MP_DROP(u);
   else {
@@ -166,7 +165,7 @@ void mp_gcd(mp **gcd, mp **xx, mp **yy, mp *a, mp *b)
     /* --- If @a@ and @b@ got swapped, swap the coefficients back --- */
 
     if (f & f_swap) {
-      mp *t = x; x = y; y = t;
+      t = x; x = y; y = t;
       t = a; a = b; b = t;
     }
 
@@ -178,11 +177,11 @@ 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 +189,10 @@ 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 +253,27 @@ 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;
@@ -267,8 +287,8 @@ static int gcd(dstr *v)
   mp_gcd(&gg, &xx, &yy, a, b);
   if (!MP_EQ(x, xx)) {
     fputs("\n*** mp_gcd(x) failed", stderr);
-    fputs("\na      = ", stderr); mp_writefile(a, stderr, 10);
-    fputs("\nb      = ", stderr); mp_writefile(b, stderr, 10);
+    fputs("\na	    = ", stderr); mp_writefile(a, stderr, 10);
+    fputs("\nb	    = ", stderr); mp_writefile(b, stderr, 10);
     fputs("\nexpect = ", stderr); mp_writefile(x, stderr, 10);
     fputs("\nresult = ", stderr); mp_writefile(xx, stderr, 10);
     fputc('\n', stderr);
@@ -276,8 +296,8 @@ static int gcd(dstr *v)
   }
   if (!MP_EQ(y, yy)) {
     fputs("\n*** mp_gcd(y) failed", stderr);
-    fputs("\na      = ", stderr); mp_writefile(a, stderr, 10);
-    fputs("\nb      = ", stderr); mp_writefile(b, stderr, 10);
+    fputs("\na	    = ", stderr); mp_writefile(a, stderr, 10);
+    fputs("\nb	    = ", stderr); mp_writefile(b, stderr, 10);
     fputs("\nexpect = ", stderr); mp_writefile(y, stderr, 10);
     fputs("\nresult = ", stderr); mp_writefile(yy, stderr, 10);
     fputc('\n', stderr);
@@ -296,8 +316,8 @@ static int gcd(dstr *v)
 
   if (!MP_EQ(g, gg)) {
     fputs("\n*** mp_gcd(gcd) failed", stderr);
-    fputs("\na      = ", stderr); mp_writefile(a, stderr, 10);
-    fputs("\nb      = ", stderr); mp_writefile(b, stderr, 10);
+    fputs("\na	    = ", stderr); mp_writefile(a, stderr, 10);
+    fputs("\nb	    = ", stderr); mp_writefile(b, stderr, 10);
     fputs("\nexpect = ", stderr); mp_writefile(g, stderr, 10);
     fputs("\nresult = ", stderr); mp_writefile(gg, stderr, 10);
     fputc('\n', stderr);
@@ -311,6 +331,7 @@ 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 } }
 };