// Widdows, Stephen
// Assignment: HW:3
// File: encrypt.cc

#include<iostream.h>
#include<fstream.h>
#include<stdio.h>

class BitFileIOs
{
     int in_code, out_code;
     unsigned char in_mask, out_mask;
     unsigned int comforter;
     FILE *input, *output;
     public:
          BitFileIOs (char *argv1, char *argv2);
          int InputBit();
          long InputBits(int n);
          void OutputBit(int bit);
          void OutputBits(unsigned long value, int n);
          void CloseOutput();
          void CloseInput();
};

BitFileIOs::BitFileIOs(char *argv1, char *argv2)
{
     if ((input = fopen (argv1, "rb")) == NULL)
     {
          cout << "Error in opening file " << argv1 << endl;
          exit(1);
     }
     if ((output = fopen (argv2, "wb")) == NULL)
     {
          cout << "Error in opening file " << argv2 << endl;
     }
     in_code = out_code = comforter = 0;
     in_mask = out_mask = 0x80;
}

int BitFileIOs::InputBit()
{
     int value;
     if (in_mask == 0x80)
     {
          in_code = getc(input);
          if (in_code == EOF)
          {
               cout << "Out of data." << endl;
               return (-1);
          }
          if (!(comforter++ & 0x0fff))
               cout << ".";
     }
     value = in_code & in_mask;
     in_mask >>= 1;
     if (in_mask == 0)
          in_mask = 0x80;
     return (value ? 1 : 0);
}

long BitFileIOs::InputBits(int n)
{
     unsigned long temp_mask = 1L << (n-1);
     unsigned long return_value = 0;
     temp_mask = 1L << (n-1);
     while (temp_mask != 0)
     {
          if (in_mask == 0x80)
          {
               in_code = getc(input);
               if (in_code == EOF)
               {
                    cout << "Out of data." << endl;
                    return (-1);
               }
               if (!(comforter++ & 0x0fff))
                    cout << ".";
          }
          if (in_code & in_mask)
               return_value |= temp_mask;
          in_mask >>= 1;
          temp_mask >>= 1;
          if (in_mask == 0)
               in_mask = 0x80;
     }
     return (return_value);
}

void BitFileIOs::OutputBit(int bit)
{
     if (bit)
          out_code |= out_mask;
     out_mask >>= 1;
     if (out_mask == 0)
     {
          putc (out_code, output);
          out_code = 0;
          out_mask = 0x80;
          if (!(comforter++ & 0x0fff))
               cout << ".";
     }
}

void BitFileIOs::OutputBits(unsigned long value, int count)
{
     unsigned long p;
     p = 1L << (count - 1);
     while (p != 0)
     {
          if (p & value)
               out_code |= out_mask;
          p >>= 1;
          if (out_mask == 0)
          {
               putc (out_code, output);
               out_mask = 0x80;
               out_code = 0;
               if (!(comforter++ & 0x0fff))
                    cout << ".";
          }
     }
}

void BitFileIOs::CloseOutput()
{
     if (out_mask != 0x80)
          putc (out_code, output);
     fclose (output);
}

void encrypt(BitFileIOs f, int arr[])
{
     int  bit = f.InputBit(), i;
     while (bit != -1)
     {
          for (i = 0; (i < 15) && (bit != -1); bit = f.InputBit())
          {
               arr[i] = bit;
               ++i;
          }
          if (bit != -1)
          {
               f.OutputBit(arr[11]);
               f.OutputBit(arr[12]);
               for (int j = 0; (j < 11); ++j)
                    f.OutputBit(arr[j]);
               f.OutputBit(arr[14]);
               f.OutputBit(arr[13]);
          }
          else
               for (i -= 1; i >= 0; --i)
                    f.OutputBit(arr[i]);
     }
}
     
void decrypt(BitFileIOs f, int arr[])
{
     int bit = f.InputBit(), i;
     while (bit != -1)
     {
          for (i = 0; (i < 15) && (bit != -1); bit = f.InputBit())
          {
               arr[i] = bit;
               ++i;
          }
          if (bit != -1)
          {
               for (int j = 2; (j < 13); ++j)
                    f.OutputBit(arr[j]);
               f.OutputBit(arr[0]);
               f.OutputBit(arr[1]);
               f.OutputBit(arr[14]);
               f.OutputBit(arr[13]);
          } 
          else
               for (i -= 1; i >= 0; --i)
                    f.OutputBit(arr[i]);
     }
} 

void main(int argc, char *argv[])
{
     int bit, arr[15];
     char choice;
     if (argc < 3)
     {
          cout << "Usage:" << *argv << " infile outfile" << endl;
          exit (1);
     }
     argv++; 
     BitFileIOs f(*argv, *(argv + 1)); 
     cout << "Do you want to (e)ncrypt a file or (d)ecrypt one? " << endl;
     cin >> choice;
     switch (choice)
     {
          case 'e':
               encrypt(f, arr);
               break;
          case 'd':
               decrypt(f, arr);
               break;
     } 
}