Add binary xapi_gzip for testing Xapi_compression

ocaml/libs/xapi-compression/dune

@@ -1,6 +1,7 @@
 (library
   (name xapi_compression)
   (public_name xapi-compression)
+  (modules xapi_compression)
   (libraries
     forkexec
     threads
@@ -11,3 +12,10 @@
   )
 )
 
+(executable
+ (name xapi_gzip)
+ (modules xapi_gzip)
+ ; don't install this
+ ; (public_name xapi-gzip)
+ ; (package xapi-compression)
+ (libraries xapi_compression cmdliner))

ocaml/libs/xapi-compression/xapi_gzip.ml

@@ -0,0 +1,67 @@
+(*
+ * Copyright (C) Citrix Systems Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation; version 2.1 only. with the special
+ * exception on linking described in file LICENSE.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *)
+
+(* This is a minimal test CLI to exercise gzip for compression and
+   uncompression using the Gzip module; which in turn spawns a process via
+   Forkexecd *)
+
+module C = Cmdliner
+
+module Gzip = Xapi_compression.Make (struct let executable = "/bin/gzip" end)
+
+let help =
+  [
+    `P "These options are common to all commands."
+  ; `S "MORE HELP"
+  ; `P "Use `$(mname) $(i,COMMAND) --help' for help on a single command."
+  ]
+
+(** copy bytes from file descriptor [src] to [dst] *)
+let copy ~src ~dst =
+  let size = 1024 * 64 in
+  let buffer = Bytes.create size in
+  let rec loop () =
+    match Unix.read src buffer 0 size with
+    | 0 ->
+        ()
+    | n ->
+        ignore (Unix.write dst buffer 0 n) ;
+        loop ()
+  in
+  loop ()
+
+let gzip ~src ~dst = Gzip.compress dst (fun dst -> copy ~src ~dst)
+
+let gunzip ~src ~dst = Gzip.decompress_passive src (fun src -> copy ~src ~dst)
+
+let compress uncomp =
+  match uncomp with
+  | false ->
+      gzip ~src:Unix.stdin ~dst:Unix.stdout
+  | true ->
+      gunzip ~src:Unix.stdin ~dst:Unix.stdout
+
+let decompress =
+  let doc = "Decompress." in
+  C.Arg.(
+    value
+    & flag
+    & info ["decompress"; "uncompress"; "d"] ~docv:"DECOMPRESS" ~doc
+  )
+
+let main =
+  let doc = "Test compression and uncompression" in
+  C.Term.(const compress $ decompress, info "xapi-gzip" ~doc ~man:help)
+
+let () = if !Sys.interactive then () else C.Term.(exit @@ eval main)

ocaml/libs/xapi-compression/xapi_gzip.mli

@@ -0,0 +1 @@
+(* empty *)