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/*  Project nGenEx
    Destroyer Studios LLC
    Copyright © 1997-2004. All Rights Reserved.

    SUBSYSTEM:    nGenEx.lib
    FILE:         Encrypt.cpp
    AUTHOR:       John DiCamillo


    OVERVIEW
    ========
    Simple Encryption / Decryption class
*/


#include "MemDebug.h"
#include "Encrypt.h"

// +--------------------------------------------------------------------+

void Print(const char* fmt, ...);

static long k[4] = {
   0x3B398E26,
   0x40C29501,
   0x614D7630,
   0x7F59409A
};

static void encypher(long* v)
{
   DWORD y=v[0];
   DWORD z=v[1];
   DWORD sum=0;
   DWORD delta=0x9e3779b9;                // a key schedule constant
   DWORD n=32;                            // num iterations

   while (n-->0) {                        // basic cycle start
      sum += delta;
      y += (z<<4)+k[0] ^ z+sum ^ (z>>5)+k[1];
      z += (y<<4)+k[2] ^ y+sum ^ (y>>5)+k[3];
   }

   v[0]=y;
   v[1]=z;
}

static void decypher(long* v)
{
   DWORD y=v[0];
   DWORD z=v[1];
   DWORD sum=0;
   DWORD delta=0x9e3779b9;                // a key schedule constant
   DWORD n=32;                            // num iterations

   sum=delta<<5;

   while (n-->0) {
      z-= (y<<4)+k[2] ^ y+sum ^ (y>>5)+k[3]; 
      y-= (z<<4)+k[0] ^ z+sum ^ (z>>5)+k[1];
      sum-=delta;
   }

   v[0]=y;
   v[1]=z;
}

// +-------------------------------------------------------------------+

Text 
Encryption::Encrypt(Text block)
{
   int len = block.length();

   if (len < 1)
      return Text();

   // pad to eight byte chunks
   if (len & 0x7) {
      len /= 8;
      len *= 8;
      len += 8;
   }

   BYTE* work = new(__FILE__,__LINE__) BYTE[len];
   ZeroMemory(work, len);
   CopyMemory(work, block.data(), block.length());

   long* v = (long*) work;
   for (int i = 0; i < len/8; i++) {
      encypher(v);
      v += 2;
   }

   Text cypher((const char*) work, len);
   delete [] work;
   return cypher;
}

// +-------------------------------------------------------------------+

Text 
Encryption::Decrypt(Text block)
{
   int  len    = block.length();

   if (len & 0x7) {
      Print("WARNING: attempt to decrypt odd length block (len=%d)\n", len);
      return Text();
   }

   BYTE* work = new(__FILE__,__LINE__) BYTE[len];
   CopyMemory(work, block.data(), len);

   long* v = (long*) work;
   for (int i = 0; i < len/8; i++) {
      decypher(v);
      v += 2;
   }

   Text clear((const char*) work, len);
   delete [] work;
   return clear;
}

// +-------------------------------------------------------------------+

static const char* codes = "abcdefghijklmnop";

Text 
Encryption::Encode(Text block)
{
   int   len  = block.length() * 2;
   char* work = new(__FILE__,__LINE__) char[len + 1];

   for (int i = 0; i < block.length(); i++) {
      BYTE b = (BYTE) (block.data()[i]);
      work[2*i]   = codes[b>>4 & 0xf];
      work[2*i+1] = codes[b    & 0xf];
   }

   work[len] = 0;

   Text code(work, len);
   delete [] work;
   return code;
}

// +-------------------------------------------------------------------+

Text 
Encryption::Decode(Text block)
{
   int   len  = block.length() / 2;
   char* work = new(__FILE__,__LINE__) char[len + 1];

   for (int i = 0; i < len; i++) {
      char u = block[2*i];
      char l = block[2*i + 1];

      work[i] = (u - codes[0]) << 4 |
                (l - codes[0]);
   }

   work[len] = 0;

   Text clear(work, len);
   delete [] work;
   return clear;
}