Question

I built a program that parses the header and I would like to read the message body in case I receive a POST.

For headers, I have been able to look for to determine when the header ends. I am having more issues for the message body. Am I supposed to look at “Content-Length” field to know when to stop reading input? In my current code (below), it will not stop until I hit the red cross (stop loading page) in Firefox.

Here is the code:

size_t n;
unsigned char newChar;

int index = 0;
int capacity = 50;
char *option = (char *) malloc(sizeof(char) * capacity); 

while ( ( n = read( req->socket, &newChar, sizeof(newChar) ) ) > 0 ) {
  if (newChar == '\0' || newChar == '\n') break; // This is not working

  if (index == capacity) {
    capacity *= 2;
    option = (char *) realloc(option, sizeof(char) * capacity);
    assert(option != NULL);
  }
  option[index++] = newChar;
  fprintf(stderr, "%c", newChar);
}

if (index == capacity) {
  capacity *= 2;
  option = (char *) realloc(option, sizeof(char) * capacity);
  assert(option != NULL);
}
option[index] = '\0';

The correct input gets printed, but I wonder why it won’t stop until the stop loading button get pressed. I’d like to know if there is any other solution or if I please need to use the “Content-Length” field in the header.

Thank you very much,

Jary

Answer 1

There are a few things to consider. You’ll want to consider how you want to handle all of these cases perhaps?

• For HTTP protocol 1.0 the connection closing was used to signal the end of data.

• This was improved in HTTP 1.1 which supports persistant connections. For HTTP 1.1 typically you set or read the Content-Length header to know how much data to expect.

• Finally with HTTP 1.1 there is also the possibility of “Chunked” mode, you get the size as they come and you know you’ve reached the end when a chunk Size == 0 is found.

Also do you know about libcurl? It will certainly help you having to re-implement the wheel.