git.distorted.org.uk Git - u/mdw/catacomb/blob - math/buf.c

   1 /* -*-c-*-
   2  *
   3  * Buffer handling
   4  *
   5  * (c) 2001 Straylight/Edgeware
   6  */
   7
   8 /*----- Licensing notice --------------------------------------------------*
   9  *
  10  * This file is part of Catacomb.
  11  *
  12  * Catacomb is free software; you can redistribute it and/or modify
  13  * it under the terms of the GNU Library General Public License as
  14  * published by the Free Software Foundation; either version 2 of the
  15  * License, or (at your option) any later version.
  16  *
  17  * Catacomb is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20  * GNU Library General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU Library General Public
  23  * License along with Catacomb; if not, write to the Free
  24  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
  25  * MA 02111-1307, USA.
  26  */
  27
  28 /*----- Header files ------------------------------------------------------*/
  29
  30 #include <string.h>
  31
  32 #include "mp.h"
  33 #include "ec.h"
  34 #include "buf.h"
  35
  36 /*----- Main code ---------------------------------------------------------*/
  37
  38 /* --- @buf_getmp@ --- *
  39  *
  40  * Arguments:   @buf *b@ = pointer to a buffer block
  41  *
  42  * Returns:     A multiprecision integer, or null if there wasn't one there.
  43  *
  44  * Use:         Gets a multiprecision integer from a buffer.
  45  */
  46
  47 mp *buf_getmp(buf *b)
  48 {
  49   uint16 sz;
  50   size_t n;
  51   mp *m;
  52   if (buf_getu16(b, &sz) || buf_ensure(b, sz))
  53     return (0);
  54   m = mp_loadb(MP_NEW, BCUR(b), sz);
  55   n = mp_octets(m);
  56   if (n != sz && n != 0 && sz != 1) {
  57     mp_drop(m);
  58     return (0);
  59   }
  60   BSTEP(b, sz);
  61   return (m);
  62 }
  63
  64 /* --- @buf_putmp@ --- *
  65  *
  66  * Arguments:   @buf *b@ = pointer to a buffer block
  67  *              @mp *m@ = a multiprecision integer
  68  *
  69  * Returns:     Zero if it worked, nonzero if there wasn't enough space.
  70  *
  71  * Use:         Puts a multiprecision integer to a buffer.
  72  */
  73
  74 int buf_putmp(buf *b, mp *m)
  75 {
  76   size_t sz = mp_octets(m);
  77   assert(sz < MASK16);
  78   if (!sz) sz = 1;
  79   if (buf_putu16(b, sz) || buf_ensure(b, sz))
  80     return (-1);
  81   mp_storeb(m, BCUR(b), sz);
  82   BSTEP(b, sz);
  83   return (0);
  84 }
  85
  86 /* --- @buf_getec@ --- *
  87  *
  88  * Arguments:   @buf *b@ = pointer to a buffer block
  89  *              @ec *p@ = where to put the point
  90  *
  91  * Returns:     Zero if it worked, nonzero if it failed.
  92  *
  93  * Use:         Gets a multiprecision integer from a buffer.  The point must
  94  *              be initialized.
  95  */
  96
  97 int buf_getec(buf *b, ec *p)
  98 {
  99   mp *x = 0, *y = 0;
 100   uint16 n;
 101   if (buf_ensure(b, 2)) return (-1);
 102   n = LOAD16(BCUR(b)); if (!n) { BSTEP(b, 2); EC_SETINF(p); return (0); }
 103   if ((x = buf_getmp(b)) == 0 || (y = buf_getmp(b)) == 0) {
 104     mp_drop(x); mp_drop(y); return (-1);
 105   }
 106   EC_DESTROY(p); p->x = x; p->y = y; p->z = 0;
 107   return (0);
 108 }
 109
 110 /* --- @buf_putec@ --- *
 111  *
 112  * Arguments:   @buf *b@ = pointer to a buffer block
 113  *              @ec *p@ = an elliptic curve point
 114  *
 115  * Returns:     Zero if it worked, nonzero if there wasn't enough space.
 116  *
 117  * Use:         Puts an elliptic curve point to a buffer.
 118  */
 119
 120 int buf_putec(buf *b, ec *p)
 121 {
 122   if (EC_ATINF(p)) return (buf_putu16(b, 0));
 123   if (buf_putmp(b, p->x) || buf_putmp(b, p->y)) return (-1);
 124   return (0);
 125 }
 126
 127 /*----- That's all, folks -------------------------------------------------*/