/* -*-c-*-
*
- * $Id: gfshare.h,v 1.6 2000/12/06 20:30:10 mdw Exp $
+ * $Id$
*
* Secret sharing over %$\gf{2^8}$%
*
* MA 02111-1307, USA.
*/
-/*----- Revision history --------------------------------------------------*
- *
- * $Log: gfshare.h,v $
- * Revision 1.6 2000/12/06 20:30:10 mdw
- * Change secret sharing interface: present the secret at share
- * construction time.
- *
- * Revision 1.5 2000/06/24 19:11:47 mdw
- * Fix daft error in the comment for @gfshare_get@.
- *
- * Revision 1.4 2000/06/24 18:29:05 mdw
- * Interface change: allow shares to be extracted from a context on demand,
- * rather than building them all up-front.
- *
- * Revision 1.3 2000/06/18 23:12:15 mdw
- * Change typesetting of Galois Field names.
- *
- * Revision 1.2 2000/06/17 11:05:27 mdw
- * Add a commentary on the system.
- *
- * Revision 1.1 2000/06/17 10:56:30 mdw
- * Fast but nonstandard secret sharing system.
- *
- */
-
/*----- Notes on the system -----------------------------------------------*
*
* This uses a variant of Shamir's secret sharing system. Shamir's original
#define GFSHARE_INIT(t, sz) { t, 0, sz, 0 }
+#define GFSHARE_INDEX(s, i) ((s)->v[(i) * ((s)->sz + 1)])
+
/*----- Functions provided ------------------------------------------------*/
/* --- @gfshare_create@ --- *
extern void gfshare_get(gfshare */*s*/, unsigned /*x*/, void */*buf*/);
+/* --- @gfshare_addedp@ --- *
+ *
+ * Arguments: @gfshare *s@ = pointer to sharing context
+ * @unsigned x@ = which share number to check
+ *
+ * Returns: Nonzero if share @x@ has been added already, zero if it
+ * hasn't.
+ */
+
+extern int gfshare_addedp(gfshare */*s*/, unsigned /*x*/);
+
/* --- @gfshare_add@ --- *
*
* Arguments: @gfshare *s@ = pointer to sharing context