/******************************************************************
 *
 * Description: Demonstrate the C bitwise operators.
 *
 * Author:      M.J. Leslie
 * Date:        18-Feb-96
 *
 * Syntax:    
 *       
 * Bugs:    
 *
 * Notes:       Compile and place in cgi-bin
 * 
 * History: 
 *      Ver Date      Comments
 *  --- ----      --------
 *  1.0 18-Feb-96 Initial release.
 *
 ******************************************************************/

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

/******************************************************************/

void ReadParms(char **Operator, 
               char **LeftOpHex, 
               char **RightOpHex);

void DecimalToBinary(int    Decimal, 
                     char **Binary);

void HexToDecimal(char     *Hex, 
                  long int *Decimal);

void CreateForm(int   LeftOpDec, 
            char *Operator, 
                int   RightOpDec, 
                int   AnswerDec);

void FormIP(int, char *, int);

void FormTable (int   LeftOpDec, 
            char *Operator, 
                int   RightOpDec, 
                int   AnswerDec);

void FormHeader(void);

void FormFooter(void);

void PerformCalc (long int  Left, 
                  char     *Operator, 
                  long int  Right, 
                  long unsigned int *Answer);

/******************************************************************/

main(int argc, char **argv)
{
  char *Operator;
  char *LeftOpHex;
  char *RightOpHex;

  long int LeftOpDec  = 0;
  long int RightOpDec = 0;
  long int AnswerDec;

  ReadParms(&Operator, &LeftOpHex, &RightOpHex); 

  /* ...    If we have parms, convert the values to decimal. */

  HexToDecimal(LeftOpHex, &LeftOpDec);

  HexToDecimal(RightOpHex, &RightOpDec);

  PerformCalc (LeftOpDec, Operator, RightOpDec, &AnswerDec);

  CreateForm  (LeftOpDec, Operator, RightOpDec, AnswerDec);

}

/******************************************************************/

void CreateForm(int   LeftOpDec, 
            char *Operator, 
                int   RightOpDec, 
                int   AnswerDec)
{

  FormHeader();

  FormIP(LeftOpDec, Operator, RightOpDec);

  FormTable( LeftOpDec, Operator, RightOpDec, AnswerDec);

  FormFooter();
}

/******************************************************************/

void FormIP(int LeftOpDec, char *Operator, int RightOpDec) 
{
  char       Options[]="<option> &  <option> |  <option> ^  <option> << <option> >> <option> ~  <option> &  <option> |  <option> ^  <option> << <option> >> <option> ~  ";
  char      *Ptr;
    
  puts("This page can be used to test the various bitwise operators.");
  puts("Just enter the Hex values and the operator, then press Execute");
  puts("to see the results.");

  puts("<center>");
  puts("<form action=\"/cgi-bin/mjl_bitwork\" method=get>");
  puts("<p>");
  printf("<input type=\"text\" name=\"LeftOp\" value=%02X size=8>",LeftOpDec);
  puts("<select name=\"Operation\">");

  /* ...        Find the supplied operator in "Options" */

  Ptr = strstr(Options, Operator);

  /* ...        Back up to the beginning of the <option> text. */

  Ptr -= 9;

  /* ...        And mark the end of string. */

  Ptr[72] = '\0';

  /* ...        O/P the options. */

  printf("%s\n", Ptr);

  puts("</select>");
  printf("<input type=\"text\" name=\"RightOp\" value=%02X size=8>", RightOpDec);
  puts("<input type=\"submit\" value=\"Execute\">");
  puts("</form>");
  puts("</center>");
}

/******************************************************************/

void FormTable(int   LeftOpDec, 
           char *Operator, 
               int   RightOpDec, 
               int   AnswerDec)
{
  char *LeftOpBin;
  char *RightOpBin;
  char *AnswerBin;

  DecimalToBinary(LeftOpDec,  &LeftOpBin);
  DecimalToBinary(RightOpDec, &RightOpBin);
  DecimalToBinary(AnswerDec,  &AnswerBin);

  puts("<center>");
  puts("<table border=1 bgcolor=\"ivory\">");
  puts("<tr align=center>");
  puts("<td>");
  puts("Hex");
  puts("</td>");
  puts("<td>");
  puts("Binary");
  puts("</td>");
  puts("</tr>");
  puts("<tr><td>");
  puts("<h3>");
  puts("<pre>");
  puts("     ");

  if (*Operator != '~')
  {
    printf("    %02X  \n", LeftOpDec);
  }

  printf(" %2s ",       Operator);
  printf("%02X \n",     RightOpDec);
  printf("    --\n");
  printf("  = %02X \n",  AnswerDec);

  puts("</pre>");
  puts("</h3>");
  puts("</td>");
  puts("<td>");
  puts("<h3>");
  puts("<pre>");
  puts("     ");

  if (*Operator != '~')
  {
    printf("    %s  \n", LeftOpBin);
  }

  printf(" %2s ",      Operator);
  printf("%s \n",      RightOpBin);
  printf("    ---------\n");
  printf("  = %s \n",  AnswerBin);
  puts("</pre>");
  puts("</h3>");
  puts("</tr></td>");
  puts("</table>");
  puts("</center>");
  puts("<p>");
}

/******************************************************************/

void DecimalToBinary(int    Decimal, 
                     char **Binary)
{
  int Index = 128;                     /* Just look at the 8 
                        * low order bits */
 
  *Binary = (char *) malloc(10);
  
  **Binary = '\0';           

  while(Index)
  {
    if (Index == 8) strcat(*Binary, " ");     /*  Put a space between the
                         *  Bytes */

    if(Decimal / Index)
    {
      strcat(*Binary, "1");
      Decimal -= Index;
    }
    else
    {
      strcat(*Binary,"0");
    }
    Index /= 2;
  }
}

/******************************************************************/

void ReadParms(char **Operator, 
               char **LeftOpHex, 
               char **RightOpHex)
{
  char  Defaults[]="LeftOp=00&Operation=%26&RightOp=00";
  char *Ptr;
  char *TmpPtr;

  if ((TmpPtr = getenv("QUERY_STRING")) == NULL)
  {   
    Ptr = Defaults;
  }
  else
  {
    Ptr = (char *) malloc(strlen(TmpPtr)+1);
    strcpy(Ptr, TmpPtr);
  }    

  /* ...        If no parms have been passed, supply a few defaults. */

  if (*Ptr == '\0')
  {
    Ptr = Defaults;
  }
 
  /*    QUERY_STRING will look like.
   * 
   * LeftOp=0&Operation=%26&RightOp=0
   *
   */
    
  strtok(Ptr, "=&");
  *LeftOpHex  = (char *) strtok(NULL, "=&");
  if (strlen(*LeftOpHex) > 2)
  {
    *(*LeftOpHex+2) = '\0';
  }
  strtok(NULL, "=&");
  *Operator   = (char *) strtok(NULL, "=&");
  strtok(NULL, "=&");
  *RightOpHex = (char *) strtok(NULL, "=&");
  if (strlen(*RightOpHex) > 2)
  {
    *(*RightOpHex+2) = '\0';
  }

  /* ...        CGI passes 'special characters in their Hex form, This will 
     ...        change them back to their character forms. */

  /* ...        This does not cope with rouge operators. */

  if (!strcmp(*Operator, "%26"))    *Operator = "&";
  if (!strcmp(*Operator, "%7C"))    *Operator = "|";
  if (!strcmp(*Operator, "%5E"))    *Operator = "^";
  if (!strcmp(*Operator, "%3C%3C")) *Operator = "<<";
  if (!strcmp(*Operator, "%3E%3E")) *Operator = ">>";
  if (!strcmp(*Operator, "%7E"))    *Operator = "~";
}

/******************************************************************/

void HexToDecimal(char     *Hex, 
                  long int *Decimal)
{
  *Decimal = strtol(Hex, NULL, 16);
}

/******************************************************************/

void PerformCalc (long int  Left, 
                  char     *Operator, 
                  long int  Right, 
                  long unsigned int *Answer)
{
  switch(Operator[0])
  {
    case '&':
    {
      *Answer = Left & Right;
      break;
    }
    case '|':
    {
      *Answer = Left | Right;
      break;
    }
    case '^':
    {
      *Answer = Left ^ Right;
      break;
    }
    case '<':
    {
      *Answer = Left << Right;
      break;
    }
    case '>':
    {
      *Answer = Left >> Right;
      break;
    }
    case '~':
    {
      *Answer = ~Right;
      break;
    }
    default:
    {
      *Answer = 0;
      break;
    }
  }

  /* We are only interested in the 2 low order bytes. */

  *Answer &= 255;

}

/******************************************************************/

void FormHeader(void)
{
   puts("Content-type: text/html");
   puts("");                            /* BLANK LINE IS REQUIRED       */

   puts("<TITLE>Bitwise Simulator</TITLE>");
   puts("<body background=/C_ref/GRAPHICS/bg1.gif>");
   puts("<hr>");
   puts("<center>");
   puts("<h1>Bitwise Simulator</h1>");
   puts("</center>");
   puts("<hr>");
   puts("<p>");
}

/******************************************************************/

void FormFooter(void)
{
  puts("<hr>");
  puts("<h2>See Also:</h2>");
  puts("<img src=/C_ref/GRAPHICS/whiteball.gif>");
  puts("<a href=/C_ref/C/CONCEPT/bitwise.html>Bitwise Operators</a>.");
  puts("<P>");
  puts("<hr>");
  puts("<p>");
  puts("<center>");
  puts("<table border=2 width=80% bgcolor=\"ivory\">");
  puts("<tr align=center>");
  puts("<td width=25%>");
  puts("<a href=http:/C_ref/C/cref.html>Top</a>");
  puts("</td><td width=25%>");
  puts("<a href=http:/C_ref/C/master_index.html>Master Index</a>");
  puts("</td><td width=25%>");
  puts("<a href=http:/C_ref/C/SYNTAX/keywords.html>Keywords</a>");
  puts("</td><td width=25%>");
  puts("<a href=http:/C_ref/C/FUNCTIONS/function.ref.html>Functions</a>");
  puts("</td>");
  puts("</tr>");
  puts("</table>");
  puts("</center>");
  puts("<p>");
  puts("<hr>");
  puts("<address><a href=/C_ref/address.html>Martin Leslie</a> ");
  puts("18-Feb-96</address><p>");
}