/*

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 1.1 1999/09/26 20:53:33 deraadt Exp $");

#include "ssh.h"
#include "gmp.h"
#include "bufaux.h"
#include "xmalloc.h"
#include "getput.h"

/* Stores an MP_INT 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_mp_int(Buffer *buffer, MP_INT *value)
{
  int bits = mpz_sizeinbase(value, 2);
  int hex_size = mpz_sizeinbase(value, 16);
  char *buf = xmalloc(hex_size + 2);
  int i, oi, byte;
  char msg[2];
  
  /* Get the value of the number in hex.  Too bad that gmp does not allow
     us to get it in binary. */
  mpz_get_str(buf, 16, value);

  /* i is "input index", oi is "output index".  Both point to the same array,
     and start from the beginning.  "input index" moves twice as fast. */
  i = 0;
  oi = 0;
  /* Check for an odd number of hex digits.  Process the odd digit 
     separately. */
  if (hex_size & 1)
    {
      sscanf(buf, "%1x", &byte);
      buf[oi++] = byte;
      i = 1;
    }

  /* Convert the hex number into binary representation. */
  for (; i < hex_size; i += 2)
    {
      sscanf(buf + i, "%2x", &byte);
      buf[oi++] = byte;
    }
  
  assert(oi == ((bits + 7) / 8));
  /* 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, hex_size);
  xfree(buf);
}

/* Retrieves an MP_INT from the buffer. */

int buffer_get_mp_int(Buffer *buffer, MP_INT *value)
{
  int i, bits, bytes;
  char *hex;
  unsigned char buf[2];

  /* 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;
  /* Allocate space for a corresponding hex string. */
  hex = xmalloc(2 * bytes + 1);
  
  /* Read and convert the binary bytes into a hex string. */
  for (i = 0; i < bytes; i++)
    {
      unsigned char byte;
      buffer_get(buffer, (char *)&byte, 1);
      sprintf(hex + 2 * i, "%02x", byte);
    }
  /* Read the hex string into a mp-int. */
  mpz_set_str(value, hex, 16);
  /* Free the string. */
  xfree(hex);
  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);
}