adding a hexstring function

Author: sangkilc

Makefile.dep

@@ -19,3 +19,4 @@ bin,ocamlbuild
 lib,unix
 lib,str
 lib,bitstring
+lib,batteries

myocamlbuild.ml

@@ -73,6 +73,7 @@ let _ = dispatch begin function
       tag_any
         ["pkg_str";
          "pkg_unix";
+         "pkg_batteries";
          "pkg_bitstring";
          "pkg_bitstring.syntax";
         ];

src/ocamlExploit.ml

@@ -57,6 +57,22 @@ let ( * ) str num =
 let int32_to_hexstring i =
   Printf.sprintf "%08lx" i
 
+let hexstring_to_string hexstr =
+  let hexchar prev curr =
+    int_of_string (Printf.sprintf "0x%c%c" prev curr) |> char_of_int
+  in
+  let len = String.length hexstr in
+  assert (len mod 2 = 0);
+  let str = String.make (len / 2) '\x00' in
+  let _ =
+    BatString.fold_left (fun (pos, prev) ch ->
+      match prev with
+        | None -> pos, Some ch
+        | Some prev -> str.[pos] <- (hexchar prev ch); pos+1, None
+    ) (0, None) hexstr
+  in
+  str
+
 let print str = print_endline str; flush stdout
 
 let explode s =

src/ocamlExploit.mli

@@ -39,6 +39,9 @@ val ( * ) : string -> int -> string
 (** 32bit int to hex *)
 val int32_to_hexstring : int32 -> string
 
+(** get a string from a hexstring *)
+val hexstring_to_string : string -> string
+
 (** simple print, but always flush *)
 val print : string -> unit