/*	$Id: cfb_enc.c,v 1.1 1995/12/14 06:52:44 tholo Exp $	*/

/* Copyright (C) 1993 Eric Young - see README for more details */
#include "des_locl.h"

/* The input and output are loaded in multiples of 8 bits.
 * What this means is that if you hame numbits=12 and length=2
 * the first 12 bits will be retrieved from the first byte and half
 * the second.  The second 12 bits will come from the 3rd and half the 4th
 * byte.
 */
int des_cfb_encrypt(unsigned char *in, unsigned char *out, int numbits, long int length, struct des_ks_struct *schedule, des_cblock (*ivec), int encrypt)
{
  register u_int32_t d0,d1,v0,v1,n=(numbits+7)/8;
  register u_int32_t mask0,mask1;
  register long l=length;
  register int num=numbits;
  u_int32_t ti[2],to[2];
  unsigned char *iv;

  if (num > 64) return(0);
  if (num > 32)
    {
      mask0=0xffffffff;
      if (num == 64)
	mask1=mask0;
      else
	mask1=(1L<<(num-32))-1;
    }
  else
    {
      if (num == 32)
	mask0=0xffffffff;
      else
	mask0=(1L<<num)-1;
      mask1=0x00000000;
    }

  iv=(unsigned char *)ivec;
  c2l(iv,v0);
  c2l(iv,v1);
  if (encrypt)
    {
      while (l-- > 0)
	{
	  ti[0]=v0;
	  ti[1]=v1;
	  des_encrypt(ti,to,
		      schedule,DES_ENCRYPT);
	  c2ln(in,d0,d1,n);
	  in+=n;
	  d0=(d0^to[0])&mask0;
	  d1=(d1^to[1])&mask1;
	  l2cn(d0,d1,out,n);
	  out+=n;
	  if (num > 32)
	    {
	      v0=((v1>>(num-32))|(d0<<(64-num)))&0xffffffff;
	      v1=((d0>>(num-32))|(d1<<(64-num)))&0xffffffff;
	    }
	  else
	    {
	      v0=((v0>>num)|(v1<<(32-num)))&0xffffffff;
	      v1=((v1>>num)|(d0<<(32-num)))&0xffffffff;
	    }
	}
    }
  else
    {
      while (l-- > 0)
	{
	  ti[0]=v0;
	  ti[1]=v1;
	  des_encrypt(ti,to,
		      schedule,DES_ENCRYPT);
	  c2ln(in,d0,d1,n);
	  in+=n;
	  if (num > 32)
	    {
	      v0=((v1>>(num-32))|(d0<<(64-num)))&0xffffffff;
	      v1=((d0>>(num-32))|(d1<<(64-num)))&0xffffffff;
	    }
	  else
	    {
	      v0=((v0>>num)|(v1<<(32-num)))&0xffffffff;
	      v1=((v1>>num)|(d0<<(32-num)))&0xffffffff;
	    }
	  d0=(d0^to[0])&mask0;
	  d1=(d1^to[1])&mask1;
	  l2cn(d0,d1,out,n);
	  out+=n;
	}
    }
  iv=(unsigned char *)ivec;
  l2c(v0,iv);
  l2c(v1,iv);
  v0=v1=d0=d1=ti[0]=ti[1]=to[0]=to[1]=0;
  return(0);
}