Simple readline algorithm for Networking

Are there any simple standardized way of reading a full line from a socket that mallocs the memory for you? If so, what are they? If not, is there a way to do it in approximately O(1) time (obviously not including the time for the memory allocation).

Tons of people use these functions every day, so why is it any different to want to do this in C?
Because C has no infrastructure in which to do anything automatic.  Enjoy your portable assembler.