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posix-api

Objective

This library provides minimal bindings to system calls for POSIX-compliant operating systems. All functions follow these design decisions:

  • String is not used anywhere. ByteArray (from primitive) is used for serialized data. It is also used in certain filesystem function variants used in contexts where the paths are only ever handed over to other filesystem functions. Addr (from primitive) is used for pointers to data whose type is unknown. Ptr is used for pointers to data whose type is known.
  • Functions should not throw errors. This library uses IO (Either Errno a) in places where some libraries would use IO a.
  • The numeric types from Foreign.C.Types and System.Posix.Types are used in the type signatures of functions so that a haskell function's type signature matches its underlying POSIX equivalent exactly.
  • Flags are newtypes over CInt (or whatever integral type matches the posix specification) rather than enumerations. The data constructors are exported, making the types extensible for operating system that have additional flags.
  • There is some platform-specific code in this library. POSIX-specified data structures do not have the same in-memory representation on all platforms. Consequently, some of the code to serialize data to its C-struct representation must be written differently on different platforms. This is seldom needed. A viable alternative would be using the FFI to perform this serialization. However, the approach of using per-platform haskell code lets the serialization code inline better.

Pull requests that add bindings to POSIX APIs in a way that agrees with these guidelines will be accepted. Unfortunately, there is some grey area when it comes to what a "minimal binding" to a function is. Discussion may sometimes be necessary to refine the guidelines.

Infelicities

This project currently includes some Linux-specific code. It in the the Linux.Socket. The plan is to eventually move the Linux.Socket module into its own library. Currently, a ton of POSIX APIs are missing. These should be included.