How to send() an image by saving it in char string in ANSI C? Problem with casting

Question

I'm writing my own server in ANSI C (on Linux) and I've got one problem with sending images to a web browser. I'm using the function "send()" to send it and it required a char *. So I was reading a file char by char (using fgetc), I used fread and fgets, but everything had a problem with casting the content(int in most cases) to a bufor - some bytes still were missing (e.g 2008 was send instead of 2020). I think there is some problem with conversion, but I used sprintf and wchar_t and it is still not working.

I've got a function:

void send_www(char *buff, int cd){      
if(send (cd, buff, strlen(buff), 0) < 0) {
        perror ("send()");
        exit (1);

which I use here:

//  while (fread(znak, sizeof(char), i,  handler) != 0) {
    for (j = 0; j < i; j++) {
    a = fgetc(handler);
    sprintf(znak, "%ls", a);
    send_www(znak, cd);
    }

where i is the length of the image file, znak is the char* (in this version wchar_t*). You can also see my earlier try of using fread.

Answer 1

You are using strlen(). strlen() stops and returns the size after it reaches a \0 byte. Images and binary data are allowed to have a byte valued zero anywhere, so strlen() is useless in those cases.

You need to modify your function to:

send_www(unsigned char *buff, size_t buf_len int cd);

And pass the image size to it, so you can safely send() it with the appropriate size.

In your case, it seems you are sure it is a wchar_t string, use the appropriate function, wcslen(), not strlen() :)