In IP networks, all hosts must support what is known as fragmentation & reassembly. That is large packets exceeding the underlying maximum packet size for a link is packetized into smaller packets sized for the link, known as IP fragments.
Well it turns out theres a really nice data structure called a Hole Descriptor List which sorts a fragment into the corresponding hole in expected time of 1 compare due to fragments being received in almost sorted order for quick coalescing. The data structure is outlined in IP DATAGRAM REASSEMBLY ALGORITHMS (RFC815) by David D. Clark.
This implementation supports overlapping fragments and seen/duplicate fragment suppression.
An example driver program is included in driver.c to see how to use the API. We also have a small suite of unit tests and a basic fuzz tester (which has helped tremendously iron out bugs).