Merge pull request #44 from kit-ty-kate/miou-unix-mini-optim

Calculate the default value of Miou_unix.{really_read,read,write} ?len only when necessary

lib/miou_unix.ml

@@ -133,7 +133,10 @@ let rec unsafe_read ({ fd; non_blocking } as file_descr) off len buf =
     blocking_read fd; go ()
 
 let read file_descr ?(off = 0) ?len buf =
-  let len = Option.value ~default:(Bytes.length buf - off) len in
+  let len = match len with
+    | None -> Bytes.length buf - off
+    | Some len -> len
+  in
   if off < 0 || len < 0 || off > Bytes.length buf - len then
     invalid_arg "Miou_unix.read";
   unsafe_read file_descr off len buf
@@ -145,7 +148,10 @@ let rec really_read_go file_descr off len buf =
     really_read_go file_descr (off + len') (len - len') buf
 
 let really_read file_descr ?(off = 0) ?len buf =
-  let len = Option.value ~default:(Bytes.length buf - off) len in
+  let len = match len with
+    | None -> Bytes.length buf - off
+    | Some len -> len
+  in
   if off < 0 || len < 0 || off > Bytes.length buf - len then
     invalid_arg "Miou_unix.really_read";
   if len > 0 then really_read_go file_descr off len buf
@@ -172,7 +178,10 @@ let rec unsafe_write ({ fd; non_blocking } as file_descr) off len str =
     blocking_write fd; go ()
 
 let write file_descr ?(off = 0) ?len str =
-  let len = Option.value ~default:(String.length str - off) len in
+  let len = match len with
+    | None -> String.length str - off
+    | Some len -> len
+  in
   if off < 0 || len < 0 || off > String.length str - len then
     invalid_arg "Miou_unix.write";
   unsafe_write file_descr off len str