unikernel/duniverse/ocaml-re/lib/parse_buffer.ml

@@ -0,0 +1,67 @@
+type t =
+  { str : string
+  ; mutable pos : int
+  }
+
+exception Parse_error
+
+let create str = { str; pos = 0 }
+let unget t = t.pos <- t.pos - 1
+let junk t = t.pos <- t.pos + 1
+let eos t = t.pos = String.length t.str
+let test t c = (not (eos t)) && t.str.[t.pos] = c
+
+let test2 t c c' =
+  t.pos + 1 < String.length t.str && t.str.[t.pos] = c && t.str.[t.pos + 1] = c'
+;;
+
+let accept t c =
+  let r = test t c in
+  if r then t.pos <- t.pos + 1;
+  r
+;;
+
+let get t =
+  let r = t.str.[t.pos] in
+  t.pos <- t.pos + 1;
+  r
+;;
+
+let accept_s t s' =
+  let len = String.length s' in
+  try
+    for j = 0 to len - 1 do
+      (* CR-someday rgrinberg: stop relying on bound checks *)
+      try if s'.[j] <> t.str.[t.pos + j] then raise_notrace Exit with
+      | _ -> raise_notrace Exit
+    done;
+    t.pos <- t.pos + len;
+    true
+  with
+  | Exit -> false
+;;
+
+let rec integer' t i =
+  if eos t
+  then Some i
+  else (
+    match get t with
+    | '0' .. '9' as d ->
+      let i' = (10 * i) + (Char.code d - Char.code '0') in
+      if i' < i then raise Parse_error;
+      integer' t i'
+    | _ ->
+      unget t;
+      Some i)
+;;
+
+let integer t =
+  if eos t
+  then None
+  else (
+    match get t with
+    | '0' .. '9' as d -> integer' t (Char.code d - Char.code '0')
+    | _ ->
+      unget t;
+      None)
+;;