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

[u/mdw/catacomb] / group-string.c

diff --git a/group-string.c b/group-string.c
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+/* -*-c-*-
+ *
+ * $Id: group-string.c,v 1.1 2004/04/01 12:50:09 mdw Exp $
+ *
+ * String I/O for group elements
+ *
+ * (c) 2004 Straylight/Edgeware
+ */
+
+/*----- Licensing notice --------------------------------------------------* 
+ *
+ * This file is part of Catacomb.
+ *
+ * Catacomb is free software; you can redistribute it and/or modify
+ * 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,
+ * MA 02111-1307, USA.
+ */
+
+/*----- Revision history --------------------------------------------------* 
+ *
+ * $Log: group-string.c,v $
+ * Revision 1.1  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.)
+ *
+ */
+
+/*----- Header files ------------------------------------------------------*/
+
+#include "group.h"
+
+/*----- Main code ---------------------------------------------------------*/
+
+/* --- @group_readstring@ --- *
+ *
+ * Arguments:  @group *g@ = an abstract group
+ *             @ge *d@ = destination group element
+ *             @const char *p@ = where the string is
+ *             @char **end@ = where to put the end pointer
+ *
+ * Returns:    Zero on success, nonzero on failure.
+ *
+ * Use:                Parses a group element from a string.
+ */
+
+int group_readstring(group *g, ge *d, const char *p, char **end)
+{
+  mptext_stringctx ms;
+
+  ms.buf = (/*unconst*/ char *)p;
+  ms.lim = (/*unconst*/ char *)p + strlen(p);
+  if (G_READ(g, d, &mptext_stringops, &ms))
+    return (-1);
+  if (end) *end = ms.buf;
+  return (0);
+}
+
+/* --- @group_writestring@ --- *
+ *
+ * Arguments:  @group *g@ = an abstract group
+ *             @ge *x@ = a group element
+ *             @char *p@ = where the string should go
+ *             @size_t sz@ = how long the buffer is
+ *
+ * Returns:    Zero on success, nonzero on failure.
+ *
+ * Use:                Writes a group element to a string buffer.
+ */
+
+int group_writestring(group *g, ge *x, char *p, size_t sz)
+{
+  mptext_stringctx ms;
+
+  ms.buf = p;
+  ms.lim = p + sz - 1;
+  if (G_WRITE(g, x, &mptext_stringops, &ms))
+    return (-1);
+  *ms.buf = 0;
+  return (0);
+}
+
+/*----- That's all, folks -------------------------------------------------*/