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

[u/mdw/catacomb] / buf.c

/* -*-c-*-
 *
 * $Id: buf.c,v 1.3 2004/04/01 12:50:09 mdw Exp $
 *
 * Buffer handling
 *
 * (c) 2001 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: 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.
 *
 * Revision 1.1  2003/10/11 21:02:33  mdw
 * Import buf stuff from tripe.
 *
 * Revision 1.4  2001/06/19 22:09:54  mdw
 * Expose interface, for use in the proxy.
 *
 * Revision 1.3  2001/03/03 12:06:48  mdw
 * Use 16-bit lengths on MPs, since there's a packet limit of 64K anyway.
 *
 * Revision 1.2  2001/02/16 21:23:20  mdw
 * Various minor changes.  Check that MPs are in canonical form when
 * loading.
 *
 * Revision 1.1  2001/02/03 20:26:37  mdw
 * Initial checkin.
 *
 */

/*----- Header files ------------------------------------------------------*/

#include <string.h>

#include "mp.h"
#include "ec.h"
#include "buf.h"

/*----- Main code ---------------------------------------------------------*/

/* --- @buf_init@ --- *
 *
 * Arguments:	@buf *b@ = pointer to a buffer block
 *		@void *p@ = pointer to a buffer
 *		@size_t sz@ = size of the buffer
 *
 * Returns:	---
 *
 * Use:		Initializes the buffer block appropriately.
 */

void buf_init(buf *b, void *p, size_t sz)
{
  b->base = b->p = p;
  b->limit = b->p + sz;
  b->f = 0;
}

/* --- @buf_break@ --- *
 *
 * Arguments:	@buf *b@ = pointer to a buffer block
 *
 * Returns:	Some negative value.
 *
 * Use:		Marks a buffer as broken.
 */

int buf_break(buf *b) { b->f |= BF_BROKEN; return (-1); }

/* --- @buf_flip@ --- *
 *
 * Arguments:	@buf *b@ = pointer to a buffer block
 *
 * Returns:	---
 *
 * Use:		Flips a buffer so that if you've just been writing to it,
 *		you can now read from the bit you've written.
 */

void buf_flip(buf *b)
{
  b->limit = b->p;
  b->p = b->base;
}

/* --- @buf_ensure@ --- *
 *
 * Arguments:	@buf *b@ = pointer to a buffer block
 *		@size_t sz@ = size of data wanted
 *
 * Returns:	Zero if it worked, nonzero if there wasn't enough space.
 *
 * Use:		Ensures that there are @sz@ bytes still in the buffer.
 */

int buf_ensure(buf *b, size_t sz) { return (BENSURE(b, sz)); }

/* --- @buf_get@ --- *
 *
 * Arguments:	@buf *b@ = pointer to a buffer block
 *		@size_t sz@ = size of the buffer
 *
 * Returns:	Pointer to the place in the buffer.
 *
 * Use:		Reserves a space in the buffer of the requested size, and
 *		returns its start address.
 */

void *buf_get(buf *b, size_t sz)
{
  void *p;
  if (BENSURE(b, sz))
    return (0);
  p = BCUR(b);
  BSTEP(b, sz);
  return (p);
}

/* --- @buf_put@ --- *
 *
 * Arguments:	@buf *b@ = pointer to a buffer block
 *		@const void *p@ = pointer to a buffer
 *		@size_t sz@ = size of the buffer
 *
 * Returns:	Zero if it worked, nonzero if there wasn't enough space.
 *
 * Use:		Fetches data from some place and puts it in the buffer
 */

int buf_put(buf *b, const void *p, size_t sz)
{
  if (BENSURE(b, sz))
    return (-1);
  memcpy(BCUR(b), p, sz);
  BSTEP(b, sz);
  return (0);
}

/* --- @buf_getbyte@ --- *
 *
 * Arguments:	@buf *b@ = pointer to a buffer block
 *
 * Returns:	A byte, or less than zero if there wasn't a byte there.
 *
 * Use:		Gets a single byte from a buffer.
 */

int buf_getbyte(buf *b)
{
  if (BENSURE(b, 1))
    return (-1);
  return (*b->p++);
}

/* --- @buf_putbyte@ --- *
 *
 * Arguments:	@buf *b@ = pointer to a buffer block
 *		@int ch@ = byte to write
 *
 * Returns:	Zero if OK, nonzero if there wasn't enough space.
 *
 * Use:		Puts a single byte in a buffer.
 */

int buf_putbyte(buf *b, int ch)
{
  if (BENSURE(b, 1))
    return (-1);
  *b->p++ = ch;
  return (0);
}

/* --- @buf_getu16@ --- *
 *
 * Arguments:	@buf *b@ = pointer to a buffer block
 *		@uint16 *w@ = where to put the word
 *
 * Returns:	Zero if OK, or nonzero if there wasn't a word there.
 *
 * Use:		Gets a 16-bit word from a buffer.
 */

int buf_getu16(buf *b, uint16 *w)
{
  if (BENSURE(b, 2))
    return (-1);
  *w = LOAD16(b->p);
  BSTEP(b, 2);
  return (0);
}

/* --- @buf_putu16@ --- *
 *
 * Arguments:	@buf *b@ = pointer to a buffer block
 *		@uint16 w@ = word to write
 *
 * Returns:	Zero if OK, nonzero if there wasn't enough space.
 *
 * Use:		Puts a 16-but word in a buffer.
 */

int buf_putu16(buf *b, uint16 w)
{
  if (BENSURE(b, 2))
    return (-1);
  STORE16(b->p, w);
  BSTEP(b, 2);
  return (0);
}

/* --- @buf_getu32@ --- *
 *
 * Arguments:	@buf *b@ = pointer to a buffer block
 *		@uint32 *w@ = where to put the word
 *
 * Returns:	Zero if OK, or nonzero if there wasn't a word there.
 *
 * Use:		Gets a 32-bit word from a buffer.
 */

int buf_getu32(buf *b, uint32 *w)
{
  if (BENSURE(b, 4))
    return (-1);
  *w = LOAD32(b->p);
  BSTEP(b, 4);
  return (0);
}

/* --- @buf_putu32@ --- *
 *
 * Arguments:	@buf *b@ = pointer to a buffer block
 *		@uint32 w@ = word to write
 *
 * Returns:	Zero if OK, nonzero if there wasn't enough space.
 *
 * Use:		Puts a 32-but word in a buffer.
 */

int buf_putu32(buf *b, uint32 w)
{
  if (BENSURE(b, 4))
    return (-1);
  STORE32(b->p, w);
  BSTEP(b, 4);
  return (0);
}

/* --- @buf_getmp@ --- *
 *
 * Arguments:	@buf *b@ = pointer to a buffer block
 *
 * Returns:	A multiprecision integer, or null if there wasn't one there.
 *
 * Use:		Gets a multiprecision integer from a buffer.
 */

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);
  n = mp_octets(m);
  if (n != sz && n != 0 && sz != 1) {
    mp_drop(m);
    return (0);
  }
  BSTEP(b, sz);
  return (m);
}

/* --- @buf_putmp@ --- *
 *
 * Arguments:	@buf *b@ = pointer to a buffer block
 *		@mp *m@ = a multiprecision integer
 *
 * Returns:	Zero if it worked, nonzero if there wasn't enough space.
 *
 * Use:		Puts a multiprecision integer to a buffer.
 */

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);
  BSTEP(b, sz);
  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 -------------------------------------------------*/