Add ISO 7064 Mod 97, 10 algorithm

lib/iso7064/dune

@@ -1,4 +1,4 @@
 (library
  (name iso7064)
- (modules mod_37_2)
+ (modules mod_37_2 mod_97_10)
  (libraries tools))

lib/iso7064/mod_97_10.ml

@@ -0,0 +1,27 @@
+exception Invalid_format
+exception Invalid_checksum
+
+let to_base10 number =
+  let res = ref "" in
+  String.iter
+    (fun x -> res := !res ^ string_of_int (int_of_char x - int_of_char '0'))
+    number;
+  !res
+
+let checksum number = int_of_string (to_base10 number) mod 97
+
+let calc_check_digits number =
+  Printf.sprintf "%02d" (98 - checksum (number ^ "00"))
+
+let validate number =
+  try
+    let valid = checksum number = 1 in
+    if not valid then raise Invalid_checksum;
+    number
+  with _ -> raise Invalid_format
+
+let is_valid number =
+  try
+    ignore (validate number);
+    true
+  with Invalid_format | Invalid_checksum -> false

lib/iso7064/mod_97_10.mli

@@ -0,0 +1,27 @@
+(*
+The ISO 7064 Mod 97, 10 algorithm.
+
+The Mod 97, 10 algorithm evaluates the whole number as an integer which is
+valid if the number modulo 97 is 1. As such it has two check digits.
+*)
+
+(* Exception raised when the checksum is invalid *)
+exception Invalid_checksum
+
+(* Exception raised when the format is invalid *)
+exception Invalid_format
+
+(* Convert a base36 number to base10 *)
+val to_base10 : string -> string
+
+(* Calculate the checksum of a number *)
+val checksum : string -> int
+
+(* Calculate the extra digits that should be appended to the number to make it a valid number *)
+val calc_check_digits : string -> string
+
+(* Check whether the check digit is valid *)
+val validate : string -> string
+
+(* Check whether the number is valid *)
+val is_valid : string -> bool

test/iso7064/dune

@@ -2,3 +2,8 @@
  (name test_mod_37_2)
  (libraries alcotest iso7064)
  (modules test_mod_37_2))
+
+(test
+ (name test_mod_97_10)
+ (libraries alcotest iso7064)
+ (modules test_mod_97_10))

test/iso7064/test_mod_97_10.ml

@@ -0,0 +1,32 @@
+let test_to_base10 () =
+  let result = Iso7064.Mod_97_10.to_base10 "16122348495643231" in
+  Alcotest.(check string) "to_base10" "16122348495643231" result
+
+let test_checksum () =
+  let result = Iso7064.Mod_97_10.checksum "16122348495643231" in
+  Alcotest.(check int) "checksum" 31 result
+
+let test_calc_check_digits () =
+  let result = Iso7064.Mod_97_10.calc_check_digits "4354111611551114" in
+  Alcotest.(check string) "calc_check_digits" "31" result
+
+let test_validate () =
+  let result = Iso7064.Mod_97_10.validate "71616009861" in
+  Alcotest.(check string) "validate" "71616009861" result
+
+let test_is_valid () =
+  let result = Iso7064.Mod_97_10.is_valid "030633417226" in
+  Alcotest.(check bool) "is_valid" true result;
+  let result = Iso7064.Mod_97_10.is_valid "G123489654321Z" in
+  Alcotest.(check bool) "is_valid" false result
+
+let suite =
+  [
+    ("test_to_base10", `Quick, test_to_base10)
+  ; ("test_checksum", `Quick, test_checksum)
+  ; ("test_calc_check_digits", `Quick, test_calc_check_digits)
+  ; ("test_validate", `Quick, test_validate)
+  ; ("test_is_valid", `Quick, test_is_valid)
+  ]
+
+let () = Alcotest.run "Mod_37_2" [ ("suite", suite) ]