Unix I/O functionality for GAP
This GAP package provides a link to the standard UNIX I/O functionality that is available through the C library. This part basically consists of functions on the GAP level that allow functions in the C library to be called. Built on top of this is a layer for buffered input/output which is implemented completely in the GAP language. It is intended to be used by programs for which it is not necessary to have full direct access to the operating system. On this level, quite a few convenience functions are implemented for interprocess communication like starting up pipelines of processes to filter data through them and to start up processes and then communicate with them. There is also support for creating network connections over TCP/IP and UDP. Building on this, the package contains an implementation of the client side of the HTTP protocol making it possible among other things to access web pages from within GAP. Another part of the package is a framework for object serialization. That is, GAP objects can be converted into a platform-independent byte sequence which can be stored to a file or sent over the network. The code takes complete care of arbitrarily self-referential data structures like lists containing themselves as an entry. The resulting byte strings can be read back into GAP and the original objects are rebuilt with exactly the same self-references. This works for most of the standard builtin types of GAP like numbers, permutations, polynomials, lists, and records and can be extended to nearly arbitrary GAP objects.