C++ : String to Character Array conversion (non-Ascii characters removed)

Question

I have a payload string, which I want to convert it into character array and then remove any non-ASCII characters from it. Here is my code:

bool invalidChar (char c) 
{  
    return !(c>=0 && c <256);   
} 
void stripUnicode(string &str) 
{ 
    str.erase(remove_if(str.begin(),str.end(), invalidChar), str.end());  
}

Payload_input is a string consisting of ascii and non-ascii characters:

 stripUnicode(Payload_input) ;

     char input[Payload_input.length()];
    strcpy(input,Payload_input.c_str());



    char chunk1[Payload_input.length()];
    int counter1=0;

for(counter1=0; counter1< size; counter1++)
{
        chunk1[counter1]=input[counter1];
}

Now, here is my string payload which I want to convert into char array:

--90B452BFFF3F395ABDC878D8BEDBD152
Content-Disposition: form-data; name="uploaddir"

language/2BB5B9330E/C/
--90B452BFFF3F395ABDC878D8BEDBD152
Content-Disposition: form-data; name="filename"; filename="lottery[1]20110727082525.jpg"
Content-Type: text/plain
Content-Transfer-Encoding: binary

JFIFddDucky<http://ns.adobe.com/xap/1.0/<?xpacket begin="" id="W5M0MpCehiHzreSzNTczkc9d"?>

In the above string, the few characters after Content-Transfer-Encoding: binary appears in blocks (inside bloacks it is written 0001 etc) on linux terminal.

When I try to print the characters (cout << chunk1[counter1]) after stripping non-ASCII chararcters from the string then even some ASCII characters get omitted after line Content-Transfer-Encoding: binary .

Please point it out if there is something wrong with my code?

Answer 1

The problem is that on Linux char is always in the range -128-127, so your invalidChar function will return true for all the chars not strictly ASCII. If you want to check for extended ASCII (0-255) then your function is useless: every char value is in the extended ASCII set; however, since char is signed you need to check for negative values.