Convert html form textarea to normal text

Projects Networking, Protocols, and Devices
1

If I send text from an textarea to my Arduino Webserver, I get this:

Hello%2C+this+is+a+test.%0D%0ALine+2%0D%0ALine+3

But I would like to write normal text to a file on the SD card, like this:

Hello, this is a test
Line 2
Line 3

Is there conversion code somewhere ?

I use an Arduino Mega 2560 with Ethernet Shield.
My webpages are located on the SD card.
My form textarea is:

<form method=get action=?>
<textarea name="4" rows="2" cols="40"></textarea> 
<input type=submit value=submit>
</form>

The name "4" is the command.

Edit: The name "4" was a bad idea, because it is an numer. I changed it to "D". The number "4" causes a conflict when prefilling the textarea with text.

2

It is url encoded. You must decode it. Here are the conversions:

3

Thanks SurferTim,

After reading that, it was not hard.
I wrote a function to decode it. After the function I also write a "\r\n" to the file.

void URLdecode (char *pText)
{
  // The text is converted in the same string.
  // So no extra memory is needed.

  uint8_t hex;
  
  char *pRead = pText;
  char *pWrite = pText;
  
  while (*pRead != '\0')
  {
    if (*pRead == '+')
    {
      // A '+' character is a space.
      *pWrite++ = ' ';
      pRead++;
    }
    else if (*pRead == '%')
    {
      // Read two hexadecimal digits
      // Assume the hexadecimal notation is in capitals.
      // No testing is done for illegal characters.
      // If the buffer was full, the line could be truncated,
      // so testing is done for the end of line.
      pRead++;
      if (*pRead < 'A')
        hex = (*pRead - '0') * 16;
      else
        hex = (*pRead - 'A' + 10) * 16;
      
      if (*pRead != '\0')
        pRead++;
        
      if (*pRead < 'A')
        hex += (*pRead - '0');
      else
        hex += (*pRead - 'A' + 10);
      
      *pWrite++ = hex;  
      
      if (*pRead != '\0')
        pRead++;
    }
    else
    {
      *pWrite++ = *pRead++;
    }
  }
  *pWrite = '\0';
}
4

Nice! I cheat by using sscanf.

void urlDecode(char* urlPtr) {
  char charBuf[3] = {0,0,0};
  
  for(int i=0;i<strlen(urlPtr);i++) {
    
    if(urlPtr[i] == '%') {
      int newLen = strlen(urlPtr);
      charBuf[0] = urlPtr[i+1];
      charBuf[1] = urlPtr[i+2];

      sscanf(charBuf,"%x",&urlPtr[i]);

      for(int x=i+1;x< (newLen-1);x++) {
        urlPtr[x] = urlPtr[x+2];  
      }
    }
    else if(urlPtr[i] == '+') urlPtr[i] = ' ';
  }
}