/*

bufaux.c

Author: Tatu Ylonen <ylo@cs.hut.fi>

Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
                   All rights reserved

Created: Wed Mar 29 02:24:47 1995 ylo

Auxiliary functions for storing and retrieving various data types to/from
Buffers.

*/

#include "includes.h"
RCSID("$Id: bufaux.c,v 1.2 1999/09/28 04:45:36 provos Exp $");

#include "ssh.h"
#include <ssl/bn.h>
#include "bufaux.h"
#include "xmalloc.h"
#include "getput.h"

/* Stores an BIGNUM in the buffer with a 2-byte msb first bit count, followed
   by (bits+7)/8 bytes of binary data, msb first. */

void
buffer_put_bignum(Buffer *buffer, BIGNUM *value)
{
  int bits = BN_num_bits(value);
  int bin_size = (bits + 7) / 8;
  char *buf = xmalloc(bin_size);
  int oi;
  char msg[2];
  
  /* Get the value of in binary */
  oi = BN_bn2bin(value, buf);
  assert(oi == bin_size);

  /* Store the number of bits in the buffer in two bytes, msb first. */
  PUT_16BIT(msg, bits);
  buffer_append(buffer, msg, 2);
  /* Store the binary data. */
  buffer_append(buffer, buf, oi);
  /* Clear the temporary data. */
  memset(buf, 0, bin_size);
  xfree(buf);
}

/* Retrieves an BIGNUM from the buffer. */

int
buffer_get_bignum(Buffer *buffer, BIGNUM *value)
{
  int bits, bytes;
  unsigned char buf[2], *bin;

  /* Get the number for bits. */
  buffer_get(buffer, (char *)buf, 2);
  bits = GET_16BIT(buf);
  /* Compute the number of binary bytes that follow. */
  bytes = (bits + 7) / 8;
  bin = xmalloc(bytes);
  buffer_get(buffer, bin, bytes);
  BN_bin2bn(bin, bytes, value);
  xfree(bin);

  return 2 + bytes;
}

/* Returns an integer from the buffer (4 bytes, msb first). */

unsigned int buffer_get_int(Buffer *buffer)
{
  unsigned char buf[4];
  buffer_get(buffer, (char *)buf, 4);
  return GET_32BIT(buf);
}

/* Stores an integer in the buffer in 4 bytes, msb first. */

void buffer_put_int(Buffer *buffer, unsigned int value)
{
  char buf[4];
  PUT_32BIT(buf, value);
  buffer_append(buffer, buf, 4);
}

/* Returns an arbitrary binary string from the buffer.  The string cannot
   be longer than 256k.  The returned value points to memory allocated
   with xmalloc; it is the responsibility of the calling function to free
   the data.  If length_ptr is non-NULL, the length of the returned data
   will be stored there.  A null character will be automatically appended
   to the returned string, and is not counted in length. */

char *buffer_get_string(Buffer *buffer, unsigned int *length_ptr)
{
  unsigned int len;
  char *value;
  /* Get the length. */
  len = buffer_get_int(buffer);
  if (len > 256*1024)
    fatal("Received packet with bad string length %d", len);
  /* Allocate space for the string.  Add one byte for a null character. */
  value = xmalloc(len + 1);
  /* Get the string. */
  buffer_get(buffer, value, len);
  /* Append a null character to make processing easier. */
  value[len] = 0;
  /* Optionally return the length of the string. */
  if (length_ptr)
    *length_ptr = len;
  return value;
}

/* Stores and arbitrary binary string in the buffer. */

void buffer_put_string(Buffer *buffer, const void *buf, unsigned int len)
{
  buffer_put_int(buffer, len);
  buffer_append(buffer, buf, len);
}

/* Returns a character from the buffer (0 - 255). */

int buffer_get_char(Buffer *buffer)
{
  char ch;
  buffer_get(buffer, &ch, 1);
  return (unsigned char)ch;
}

/* Stores a character in the buffer. */

void buffer_put_char(Buffer *buffer, int value)
{
  char ch = value;
  buffer_append(buffer, &ch, 1);
}