C: Addressing the case of partial headers when using select in the context of HTTP

This is in reference to a previous question of mine which was already answered:

C: Using a select call, when I am reading, how do I keep track of the data?

My protocol actually sends how much data it is about send initially before it sends any other data. But yesterday, when testing out this code of mine using a browser, I had this one question:

A lot of people suggested that I check for message length but take the scenario of a browser. The browser's HTTP Request does not have a size when it is first sent to the server. Now, assuming that I used a 256 byte buffer, how am I supposed to manage the data structure of this client if I keep receiving partial headers between each multiplexing action? Keep using realloc as I keep getting more data and then when I encounter a termination sequence ('\r\n'), assume that all data has been received?

What I mean is, have something like this:

typedef struct {
   int fd;
   char *data;
} CLIENT;

And then ke开发者_JAVA技巧ep using realloc on data? I was told to allocate a buffer size of the max protocol header but is that the only approach?

reallocing the buffer in sizes is fine. I'd pick a bit larger buffer than 256 - 1024 atleast or 4096. Allocating a max buffer size of a protocol like HTTP is not really feasible. You could also build an abstraction on top of your buffer that are able to read lines - much like fgets does on a FILE*

Keep in mind that reading a chunk might read the last part of the HTTP headers and a piece of the HTTP body if there's any , so you need to make sure you slice the buffer properly as you likely want to seperate the header from the body. You'll also have to look for the Content-Length: header, parse that, so you know how long the body will be.