CHUTIL: add utility function

Author: sipma

CodeHawk/CH/chutil/cHUtil.ml

@@ -6,7 +6,7 @@
 
    Copyright (c) 2005-2020 Kestrel Technology LLC
    Copyright (c) 2020      Henny B. Sipma
-   Copyright (c) 2021-2024 Aarno Labs LLC
+   Copyright (c) 2021-2025 Aarno Labs LLC
 
    Permission is hereby granted, free of charge, to any person obtaining a copy
    of this software and associated documentation files (the "Software"), to deal
@@ -91,6 +91,15 @@ let has_control_characters (s: string): bool =
   !found
 
 
+let startswith (s: string) (substr: string): bool =
+  let lens = String.length s in
+  let lensub = String.length substr in
+  if lens < lensub then
+    false
+  else
+    (String.sub s 0 lensub) = substr
+
+
 let hex_string (s: string): string =
   let ch = IO.input_string s in
   let h = ref "" in

CodeHawk/CH/chutil/cHUtil.mli

@@ -6,7 +6,7 @@
 
    Copyright (c) 2005-2020 Kestrel Technology LLC
    Copyright (c) 2020      Henny B. Sipma
-   Copyright (c) 2021-2024 Aarno Labs LLC
+   Copyright (c) 2021-2025 Aarno Labs LLC
 
    Permission is hereby granted, free of charge, to any person obtaining a copy
    of this software and associated documentation files (the "Software"), to deal
@@ -38,6 +38,8 @@ val string_nsplit: char -> string -> string list
 
 val has_control_characters: string -> bool
 
+val startswith: string -> string -> bool
+
 val byte_to_string: int -> string
 
 val value_from_byte: int -> int