git.distorted.org.uk Git - u/mdw/catacomb/blob - group-string.c

   1 /* -*-c-*-
   2  *
   3  * $Id: group-string.c,v 1.1 2004/04/01 12:50:09 mdw Exp $
   4  *
   5  * String I/O for group elements
   6  *
   7  * (c) 2004 Straylight/Edgeware
   8  */
   9
  10 /*----- Licensing notice --------------------------------------------------*
  11  *
  12  * This file is part of Catacomb.
  13  *
  14  * Catacomb is free software; you can redistribute it and/or modify
  15  * it under the terms of the GNU Library General Public License as
  16  * published by the Free Software Foundation; either version 2 of the
  17  * License, or (at your option) any later version.
  18  *
  19  * Catacomb is distributed in the hope that it will be useful,
  20  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  21  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  22  * GNU Library General Public License for more details.
  23  *
  24  * You should have received a copy of the GNU Library General Public
  25  * License along with Catacomb; if not, write to the Free
  26  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
  27  * MA 02111-1307, USA.
  28  */
  29
  30 /*----- Revision history --------------------------------------------------*
  31  *
  32  * $Log: group-string.c,v $
  33  * Revision 1.1  2004/04/01 12:50:09  mdw
  34  * Add cyclic group abstraction, with test code.  Separate off exponentation
  35  * functions for better static linking.  Fix a buttload of bugs on the way.
  36  * Generally ensure that negative exponents do inversion correctly.  Add
  37  * table of standard prime-field subgroups.  (Binary field subgroups are
  38  * currently unimplemented but easy to add if anyone ever finds a good one.)
  39  *
  40  */
  41
  42 /*----- Header files ------------------------------------------------------*/
  43
  44 #include "group.h"
  45
  46 /*----- Main code ---------------------------------------------------------*/
  47
  48 /* --- @group_readstring@ --- *
  49  *
  50  * Arguments:   @group *g@ = an abstract group
  51  *              @ge *d@ = destination group element
  52  *              @const char *p@ = where the string is
  53  *              @char **end@ = where to put the end pointer
  54  *
  55  * Returns:     Zero on success, nonzero on failure.
  56  *
  57  * Use:         Parses a group element from a string.
  58  */
  59
  60 int group_readstring(group *g, ge *d, const char *p, char **end)
  61 {
  62   mptext_stringctx ms;
  63
  64   ms.buf = (/*unconst*/ char *)p;
  65   ms.lim = (/*unconst*/ char *)p + strlen(p);
  66   if (G_READ(g, d, &mptext_stringops, &ms))
  67     return (-1);
  68   if (end) *end = ms.buf;
  69   return (0);
  70 }
  71
  72 /* --- @group_writestring@ --- *
  73  *
  74  * Arguments:   @group *g@ = an abstract group
  75  *              @ge *x@ = a group element
  76  *              @char *p@ = where the string should go
  77  *              @size_t sz@ = how long the buffer is
  78  *
  79  * Returns:     Zero on success, nonzero on failure.
  80  *
  81  * Use:         Writes a group element to a string buffer.
  82  */
  83
  84 int group_writestring(group *g, ge *x, char *p, size_t sz)
  85 {
  86   mptext_stringctx ms;
  87
  88   ms.buf = p;
  89   ms.lim = p + sz - 1;
  90   if (G_WRITE(g, x, &mptext_stringops, &ms))
  91     return (-1);
  92   *ms.buf = 0;
  93   return (0);
  94 }
  95
  96 /*----- That's all, folks -------------------------------------------------*/