Add cyclic group abstraction, with test code. Separate off exponentation

[u/mdw/catacomb] / buf.c

diff --git a/buf.c b/buf.c
index 5e0a069..b4cbb71 100644 (file)
--- a/buf.c
+++ b/buf.c
@@ -1,6 +1,6 @@
 /* -*-c-*-
  *
- * $Id: buf.c,v 1.2 2003/11/10 22:18:30 mdw Exp $
+ * $Id: buf.c,v 1.3 2004/04/01 12:50:09 mdw Exp $
  *
  * Buffer handling
  *
@@ -30,6 +30,13 @@
 /*----- Revision history --------------------------------------------------* 
  *
  * $Log: buf.c,v $
+ * Revision 1.3  2004/04/01 12:50:09  mdw
+ * Add cyclic group abstraction, with test code.  Separate off exponentation
+ * functions for better static linking.  Fix a buttload of bugs on the way.
+ * Generally ensure that negative exponents do inversion correctly.  Add
+ * table of standard prime-field subgroups.  (Binary field subgroups are
+ * currently unimplemented but easy to add if anyone ever finds a good one.)
+ *
  * Revision 1.2  2003/11/10 22:18:30  mdw
  * Build fixes.
  *
@@ -56,6 +63,7 @@
 #include <string.h>
 
 #include "mp.h"
+#include "ec.h"
 #include "buf.h"
 
 /*----- Main code ---------------------------------------------------------*/
@@ -280,11 +288,13 @@ int buf_putu32(buf *b, uint32 w)
 mp *buf_getmp(buf *b)
 {
   uint16 sz;
+  size_t n;
   mp *m;
   if (buf_getu16(b, &sz) || buf_ensure(b, sz))
     return (0);
   m = mp_loadb(MP_NEW, BCUR(b), sz);
-  if (mp_octets(m) != sz) {
+  n = mp_octets(m);
+  if (n != sz && n != 0 && sz != 1) {
     mp_drop(m);
     return (0);
   }
@@ -306,6 +316,7 @@ int buf_putmp(buf *b, mp *m)
 {
   size_t sz = mp_octets(m);
   assert(sz < MASK16);
+  if (!sz) sz = 1;
   if (buf_putu16(b, sz) || buf_ensure(b, sz))
     return (-1);
   mp_storeb(m, BCUR(b), sz);
@@ -313,4 +324,45 @@ int buf_putmp(buf *b, mp *m)
   return (0);
 }
 
+/* --- @buf_getec@ --- *
+ *
+ * Arguments:  @buf *b@ = pointer to a buffer block
+ *             @ec *p@ = where to put the point
+ *
+ * Returns:    Zero if it worked, nonzero if it failed.
+ *
+ * Use:                Gets a multiprecision integer from a buffer.  The point must
+ *             be initialized.
+ */
+
+int buf_getec(buf *b, ec *p)
+{
+  mp *x = 0, *y = 0;
+  uint16 n;
+  if (buf_ensure(b, 2)) return (-1);
+  n = LOAD16(BCUR(b)); if (!n) { BSTEP(b, 2); EC_SETINF(p); return (0); }
+  if ((x = buf_getmp(b)) == 0 || (y = buf_getmp(b)) == 0) {
+    mp_drop(x); mp_drop(y); return (-1);
+  }
+  EC_DESTROY(p); p->x = x; p->y = y; p->z = 0;
+  return (0);
+}
+
+/* --- @buf_putec@ --- *
+ *
+ * Arguments:  @buf *b@ = pointer to a buffer block
+ *             @ec *p@ = an elliptic curve point
+ *
+ * Returns:    Zero if it worked, nonzero if there wasn't enough space.
+ *
+ * Use:                Puts an elliptic curve point to a buffer.
+ */
+
+int buf_putec(buf *b, ec *p)
+{
+  if (EC_ATINF(p)) return (buf_putu16(b, 0));
+  if (buf_putmp(b, p->x) || buf_putmp(b, p->y)) return (-1);
+  return (0);
+}
+
 /*----- That's all, folks -------------------------------------------------*/