Stub out approach to implementing async libpq

postgresql-libpq.cabal

@@ -18,11 +18,22 @@ Copyright:           (c) 2010 Grant Monroe
                      (c) 2011 Leon P Smith
 Category:            Database
 Build-type:          Custom
--- Extra-source-files:
+
+-- Unfortunately cabal sdist isn't smart enough to catch all hs-source-dirs
+-- whether or not they are behind a conditional
+Extra-source-files:  unix/Database/PostgreSQL/LibPQ/*.hs
+                     windows/Database/PostgreSQL/LibPQ/*.hs
+
 Cabal-version:       >=1.8
 Library
   hs-source-dirs:      src
+  if os(windows)
+    hs-source-dirs:    windows
+  else
+    hs-source-dirs:    unix
+
   Exposed-modules:     Database.PostgreSQL.LibPQ
+                       Database.PostgreSQL.LibPQ.GHC
 
   Build-depends:       base >= 4 && < 5
                      , bytestring

unix/Database/PostgreSQL/LibPQ/GHC.hs

@@ -0,0 +1,38 @@
+------------------------------------------------------------------------------
+-- |
+-- Module:      Database.PostgreSQL.LibPQ.GHC
+-- Copyright:   (c) 2013 Leon P Smith
+-- License:     BSD3
+-- Maintainer:  Leon P Smith <leon@melding-monads.com>
+-- Stability:   experimental
+--
+-- On Unix,  this re-implements some of blocking libpq functions in terms of
+-- on-blocking libpq operations and GHC's IO manager.   This allows
+-- these operations to be interrupted by asynchronous exceptions,  and means
+-- that GHC's runtime is responsible for handling the concurrency instead
+-- of the OS kernel.
+--
+-- This module also re-exports the rest of libpq for convenience's sake.
+-- Thus taking advantage of these features should be as simple as importing
+-- @LibPQ.GHC@ instead of @LibPQ@.
+--
+-- On Windows,  this just re-exports the vanilla libpq bindings,  due to
+-- the lack of a satisfactory IO manager on that platform.
+--
+------------------------------------------------------------------------------
+
+module Database.PostgreSQL.LibPQ.GHC
+    ( module Database.PostgreSQL.LibPQ
+    , exec
+    , connectdb
+    ) where
+
+import Database.PostgreSQL.LibPQ hiding (exec, connectdb)
+import qualified Data.ByteString as B
+import qualified Database.PostgreSQL.LibPQ as LibPQ
+
+exec :: Connection -> B.ByteString -> IO (Maybe Result)
+exec = LibPQ.exec
+
+connectdb :: B.ByteString -> IO Connection
+connectdb = LibPQ.connectdb

windows/Database/PostgreSQL/LibPQ/GHC.hs

@@ -0,0 +1,28 @@
+------------------------------------------------------------------------------
+-- |
+-- Module:      Database.PostgreSQL.LibPQ.GHC
+-- Copyright:   (c) 2013 Leon P Smith
+-- License:     BSD3
+-- Maintainer:  Leon P Smith <leon@melding-monads.com>
+-- Stability:   experimental
+--
+-- On Unix,  this re-implements some of blocking libpq functions in terms of
+-- on-blocking libpq operations and GHC's IO manager.   This allows
+-- these operations to be interrupted by asynchronous exceptions,  and means
+-- that GHC's runtime is responsible for handling the concurrency instead
+-- of the OS kernel.
+--
+-- This module also re-exports the rest of libpq for convenience's sake.
+-- Thus taking advantage of these features should be as simple as importing
+-- @LibPQ.GHC@ instead of @LibPQ@.
+--
+-- On Windows,  this just re-exports the vanilla libpq bindings,  due to
+-- the lack of a satisfactory IO manager on that platform.
+--
+------------------------------------------------------------------------------
+
+module Database.PostgreSQL.LibPQ.GHC
+    ( module Database.PostgreSQL.LibPQ
+    ) where
+
+import Database.PostgreSQL.LibPQ