1 files changed, 58 insertions, 0 deletions
diff --git a/distrib/compare/FilenameDescr.hs b/distrib/compare/FilenameDescr.hs
new file mode 100644
index 0000000000..5952058639
--- /dev/null
+++ b/distrib/compare/FilenameDescr.hs
@@ -0,0 +1,58 @@
+
+module FilenameDescr where
+
+import Data.Either
+
+import Utils
+import Tar
+
+-- We can't just compare plain filenames, because versions numbers of GHC
+-- and the libaries will vary. So we use FilenameDescr instead, which
+-- abstracts out the version numbers.
+type FilenameDescr = [FilenameDescrBit]
+data FilenameDescrBit = VersionOf String
+                      | FP String
+    deriving (Show, Eq, Ord)
+
+normalise :: FilenameDescr -> FilenameDescr
+normalise [] = []
+normalise [x] = [x]
+normalise (FP x1 : FP x2 : xs) = normalise (FP (x1 ++ x2) : xs)
+normalise (x : xs) = x : normalise xs
+
+-- Mapping from thing (e.g. "Cabal") to version (e.g. "1.10.0.0")
+type ThingVersionMap = [(String, String)]
+
+addThingVersion :: ThingVersionMap -> String -> String -> Maybe ThingVersionMap
+addThingVersion mapping thing version
+ = case lookup thing mapping of
+   Just version' ->
+       if version == version'
+       then Just mapping
+       else Nothing
+   Nothing ->
+       Just ((thing, version) : mapping)
+
+-- Sanity check that the FilenameDescr matches the filename in the tar line
+checkContent :: ThingVersionMap -> (FilenameDescr, TarLine) -> Errors
+checkContent mapping (fd, tl)
+ = let fn = tlFileName tl
+   in case flattenFilenameDescr mapping fd of
+      Right fn' ->
+          if fn' == fn
+          then []
+          else ["checkContent: Can't happen: filename mismatch: " ++ show fn]
+      Left errs ->
+          errs
+
+flattenFilenameDescr :: ThingVersionMap -> FilenameDescr
+                     -> Either Errors FilePath
+flattenFilenameDescr mapping fd = case partitionEithers (map f fd) of
+                                  ([], strs) -> Right (concat strs)
+                                  (errs, _) -> Left (concat errs)
+    where f (FP fp) = Right fp
+          f (VersionOf thing)
+           = case lookup thing mapping of
+             Just v -> Right v
+             Nothing -> Left ["Can't happen: thing has no version in mapping"]
+