/*
 * Common support reconstructed from DES/UNDES V1.1.0 executables.
 * Original program copyright: (C) 1998 H.N.M. Dijkema, GPL.
 *
 * This is reconstructed source, not the original source text.  The helper
 * behaviour and strings below are derived directly from des.exe/undes.exe.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "des_common.h"

DES_INT32 desKnownVersions[] = {
    DES_FILE_VERSION,
    (DES_INT32) -1
};

const char *desProgramVersion =
    "DES/UNDES V1.1.0, (C) 1998 H.N.M. Dijkema (GPL)";

const char *desCopyrightText =
    "    Copyright (C) 1998 H.N.M. Dijkema\n"
    "\n"
    "    This product includes software developed by Eric Young (eay@mincom.oz.au)\n"
    "\n"
    "    This program is free software; you can redistribute it and/or modify\n"
    "    it under the terms of the GNU General Public License as published by\n"
    "    the Free Software Foundation; either version 2 of the License, or\n"
    "    (at your option) any later version.\n"
    "\n"
    "    This program is distributed in the hope that it will be useful,\n"
    "    but WITHOUT ANY WARRANTY; without even the implied warranty of\n"
    "    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the\n"
    "    GNU General Public License for more details.\n"
    "\n"
    "    You should have received a copy of the GNU General Public License\n"
    "    along with this program; if not, write to the Free Software\n"
    "    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA\n"
    "\n"
    "    You can contact the author by electronic mail, hnmdijkema@freemail.nl\n"
    "\n"
    "\n"
    "Acknowledgements\n"
    "----------------\n"
    "The author of CRYPTLIB, Peter Putmann of University of Auckland\n"
    "cryptl99.zip Free encryption library for DOS/UNIX/Windows\n"
    "\n"
    "The DES and 3DES encryption code was contributed by Eric Young\n"
    "<eay@psych.psy.uq.oz.au> and is part of his libdes package.\n"
    "The primary ftp site for the full libdes is\n"
    "   ftp://ftp.psy.uq.oz.au/pub/Crypto/DES/libdes-x.xx.tar.gz.\n"
    "\n";

void checkRead( int result )
{
    if( result == -1 )
    {
        fprintf( stderr, "\nFATAL   : error reading input stream\n" );
        perror( "MESSAGE " );
        exit( 3 );
    }
}

void checkWrite( FILE *stream )
{
    if( ferror( stream ) )
    {
        fprintf( stderr, "\nFATAL   : error writing output stream\n" );
        perror( "MESSAGE " );
        exit( 3 );
    }
}

void checkOpen( FILE *stream, const char *name )
{
    if( stream == NULL )
    {
        fprintf( stderr, "\nFATAL   : Cannot open '%s'\n", name );
        perror( "MESSAGE " );
        exit( 3 );
    }
}

void checkVersion( DES_INT32 version )
{
    int i = 0;

    while( desKnownVersions[ i ] != version &&
           desKnownVersions[ i ] != (DES_INT32) -1 )
        i++;

    if( desKnownVersions[ i ] == (DES_INT32) -1 )
    {
        fprintf( stderr,
                 "I don't know the version of this file, can't decrypt this\n" );
        exit( 1 );
    }
}

/*
 * The compiler output proves that the marker is formed from a signed 16-bit
 * word: abs(word), followed by negation and sign-extension to 32 bits.
 */
DES_INT32 negativeMarker( const unsigned char *p )
{
    DES_INT16 value;
    DES_UINT16 magnitude;
    DES_UINT16 negated;

    memcpy( &value, p, sizeof( value ) );

    /* Emulate 16-bit Turbo C arithmetic exactly, including -32768. */
    if( value < 0 )
        magnitude = (DES_UINT16) ( -(DES_INT32) value );
    else
        magnitude = (DES_UINT16) value;

    negated = (DES_UINT16) ( 0U - magnitude );
    memcpy( &value, &negated, sizeof( value ) );
    return( (DES_INT32) value );
}