/*
    This file is part of Pretty Curved Privacy (pcp1).

    Copyright (C) 2013 T.Linden.

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program 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 General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.

    You can contact me by mail: <tlinden AT cpan DOT org>.
*/


#ifndef _HAVE_PCP_ZPADDING
#define _HAVE_PCP_ZPADDING

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <stdlib.h>
#include <limits.h>

#include "mem.h"

#ifdef DEBUG
#define ZPADCHAR 48
#else
#define ZPADCHAR 0
#endif

// prepends a binary stream with a number of
// \0's as required by the secret_box and
// secret_box_open functions of libsodium.
//
// parameters:
//
// padded:    destination array (ref)
// unpadded:  source array without padding
// padlen:    length of padding
// unpadlen:  length of source array
//
// turns "efa5" into "00000000efa5" with padlen 8
//
// if DEBUG is set, destination will be padded with
// the character '0', NOT the integer 0.
//
// allocates memory for padded and it is up to the
// user to free it after use.
//
// sample call:
//
// char unpadded[] = {0xef, 0xa5};
// unsigned char *padded;
// pcp_pad_prepend(&padded, unpadded, 8, 2);
//
// the result, padded, would be 10 bytes long, 8
// bytes for the leading zeros and 2 for the content
// of the original unpadded.
void pcp_pad_prepend(unsigned char **padded, unsigned char *unpadded,
		 size_t padlen, size_t unpadlen);

// removes zero's of a binary stream, which is
// the reverse of pcp_pad_prepend().
//
// parameters:
// 
// unpadded:   destination array (ref), with padding removed
// padded:     source array with padding
// padlen:     length of padding
// unpadlen:   length of source array
//
// turns "00000000efa5" into "efa5" with padlen 8
//
// allocates memory for unpadded and it is up to the
// user to free it after use.
//
// sample call:
//
// char padded[] = {0x0, 0x0, 0x0, 0x0, 0xef, 0xa5};
// unsigned char *unpadded;
// pcp_pad_remove(unpadded, padded, 4, 2);
//
// the result, unpadded would be 2 bytes long containing
// only the 2 bytes we want to have with zeros removed.
void pcp_pad_remove(unsigned char **unpadded, unsigned char *padded,
		size_t padlen, size_t unpadlen);


#endif // _HAVE_PCP_ZPADDING