refactor(pkg): reuse opam buffer for parsing

Signed-off-by: Rudi Grinberg <[email protected]>

<!-- ps-id: 112c662c-f54d-4ae3-b4bb-cf9b14c242b5 -->

Signed-off-by: Rudi Grinberg <[email protected]>

vendor/opam-file-format/opamLexer.mll

@@ -86,14 +86,24 @@ module HS =
   Weak.Make(struct include String let hash = Hashtbl.hash let equal = (=) end)
 let hm = HS.create 317
 
+let buf = Buffer.create 64
+let m = Mutex.create ()
 
 let buffer_rule r lb =
   let pos = lb.Lexing.lex_start_p in
-  let b = Buffer.create 64 in
-  r b lb ;
-  (* buffer start position, instead of last lexem position *)
-  lb.Lexing.lex_start_p <- pos;
-  HS.merge hm (Buffer.contents b)
+  Mutex.lock m;
+  Buffer.clear buf;
+  try
+    r buf lb ;
+    (* buffer start position, instead of last lexem position *)
+    lb.Lexing.lex_start_p <- pos;
+    let contents = Buffer.contents buf in
+    Mutex.unlock m;
+    HS.merge hm contents
+  with
+  e ->
+    Mutex.unlock m;
+    raise e
 }
 
 let eol = '\r'? '\n'