Reading from a socket until certain character is in buffer

Question

I am trying to read from a socket into a buffer until a certain character is reached using read(fd, buf, BUFFLEN) .

For example, the socket will receive two lots of information separated by a blank line in one read call.

Is it possible to put the read call in a loop so it stops when it reaches this blank line, then it can read the rest of the information later if it is required?

Answer 1

A simple approach would be to read a single byte at a time until the previous byte and the current byte are new-line characters, as two consecutive new-line characters is a blank line:

size_t buf_idx = 0;
char buf[BUFFLEN] = { 0 };

while (buf_idx < BUFFLEN && 1 == read(fd, &buf[buf_idx], 1)
{
    if (buf_idx > 0          && 
        '\n' == buf[buf_idx] &&
        '\n' == buf[buf_idx - 1])
    {
        break;
    }
    buf_idx++;
}

Any unread data will have to be read at some point if newly sent data is to be read.

Answer 2

You still need to read from the socket if you want to access this information later, otherwise it will be lost. I think best implementation would be to keep looping reading from the socket, while another process/thread is launched to perform any operation you want when a blank like is received.