Add query for existence of package

[hcoop/domtool2.git] / src / plugins / apt.sml

diff --git a/src/plugins/apt.sml b/src/plugins/apt.sml
index d2517e9..e97ec82 100644 (file)
--- a/src/plugins/apt.sml
+++ b/src/plugins/apt.sml
@@ -22,6 +22,31 @@ structure Apt :> APT = struct
 
 fun validName s = CharVector.all (fn ch => Char.isAlphaNum ch orelse ch = #"_" orelse ch = #"-" orelse ch = #".") s
                  andalso (size s > 0 andalso String.sub (s, 0) <> #"-")
+
+(* Copyed from the portal, doesn't exactly go out this in the most
+   direct way, or does it? *)
+
+fun exists name =
+    validName name andalso let
+       val proc = Unix.execute ("/usr/bin/apt-cache", ["show", name])
+       val inf = Unix.textInstreamOf proc
+
+       val _ = TextIO.inputLine inf (* in every let* lies an imperative program in disguise *)
+
+       fun loop _ =
+           case TextIO.inputLine inf of
+               NONE => false
+             | SOME line =>
+               if size line >= 9 andalso String.substring (line, 0, 9) = "Section: " then
+                   true
+               else if size line >= 13 andalso String.substring (line, 0, 13) = "Description: " then
+                   false
+               else
+                   loop ()
+    in
+       loop ()
+       before ignore (Unix.reap proc)
+    end
                           
 fun installed name =
     validName name