bug-fix: fixes issue #3 regarding timestamps

lib/cuid.ml

@@ -8,31 +8,43 @@ let alphabet = [
   "n"; "o"; "p"; "q"; "r"; "s"; "t"; "u"; "v"; "w"; "x"; "y"; "z"
 ]
 
+let floor_to_int number =
+  number
+  |> Core.Float.round_down
+  |> int_of_float
+
 let rec loop result number =
-  if number <= 0 then result else
-    let index   = number mod 36 in
-    let number' = number / 36 in
-    let digit   = List.nth alphabet index in
+  if number <= 0. then result else
+    let index   = Core.Float.mod_float number 36. in
+    let number' = Core.Float.(number / 36.) in
+    let digit   = List.nth alphabet (floor_to_int index) in
     let result' = digit ^ result in
     loop result' number'
 
 let base36 number =
-  let number' = abs number in
-  if number' < 36 then
-    List.nth alphabet number'
+  let number' = Core.Float.abs number in
+  if Core.Float.(number' < 36.) then
+    List.nth alphabet (floor_to_int number')
   else
     loop "" number'
 
-let adjust8 text =
-    let length = String.length text in
-    try
-      let buffer = String.make (8 - length) '0' in
-      buffer ^ text
-    with _ -> Core.String.sub text ~pos:(length - 8) ~len:8
+let adjust fill text =
+  let length = String.length text in
+  let size   = max 0 (fill - length) in
+  let buffer = String.make size '0' in
+  buffer ^ text
+
+let padding fill count text =
+  let adjusted = adjust fill text in
+  let length   = Core.String.length adjusted in
+  let offset   = length - count in
+  Core.String.sub adjusted ~pos:offset ~len:count
 
-let call     lambda = lambda ( )
-let padding4 text   = Core.String.sub text ~pos:4 ~len:4
-let digest   text   = Digest.to_hex (Digest.string text)
+let padding4 = padding 8 4
+let padding8 = padding 8 8
+
+let call   lambda = lambda ( )
+let digest text   = Digest.to_hex (Digest.string text)
 
 let sum text =
   let number = text
@@ -43,18 +55,17 @@ let sum text =
 
 let timestamp ( ) =
   ( )
-  |> Unix.gettimeofday
-  |> int_of_float
+  |> Unix.time
   |> base36
-  |> adjust8
+  |> padding8
 
 let counter ( ) =
   state := (if !state < maximum then !state else 0);
   incr state;
   !state
   |> pred
+  |> float_of_int
   |> base36
-  |> adjust8
   |> padding4
 
 let fingerprint =
@@ -63,17 +74,23 @@ let fingerprint =
   |> digest
   |> sum
   in (number + Unix.getpid ( ))
+  |> float_of_int
   |> base36
-  |> adjust8
   |> padding4
 
 let random ( ) =
   maximum
   |> Core.Random.int
+  |> float_of_int
   |> base36
-  |> adjust8
   |> padding4
 
+let __fields ( ) =
+  (call timestamp),
+  (call counter),
+  fingerprint,
+  (call random ^ call random)
+
 let generate ( ) =
   prefix ^
   (call timestamp) ^ (call counter) ^

lib/cuid.mli

@@ -1 +1,2 @@
+val __fields : unit -> string * string * string * string
 val generate : unit -> string

lib_test/cuids.ml

@@ -4,7 +4,12 @@ open Test_utils
 let __length_case ( ) =
   let cuid   = Cuid.generate ( ) in
   let length = String.length cuid in
-  check int "cuid length must be 25" length 25
+  check int "cuid length must be 25" length 25;
+  let (timestamp, counter, fingerprint, random) = Cuid.__fields ( ) in
+  check int "timestamp block length must be 8"    (String.length timestamp)  8;
+  check int "counter block length must be 4"     (String.length counter)     4;
+  check int "fingerprint block length must be 4" (String.length fingerprint) 4;
+  check int "random block length must be 8"      (String.length random)      8
 
 let __base36_case ( ) =
   let cuid   = Cuid.generate ( ) in
@@ -13,7 +18,10 @@ let __base36_case ( ) =
   check bool "cuid must contain valid base36 chars" (is_base36 cuid) true
 
 let __collision_case ( ) =
-  check bool "cuid must not collide" (does_collide ( )) false
+  let first = Cuid.generate ( ) in
+  check bool "cuid must not collide" (does_collide ( )) false;
+  let last   = Cuid.generate ( ) in
+  check bool "cuid must be monotonically increasing" (first < last) true
 
 let suite = [
   "length",    `Quick, __length_case;

lib_test/test_utils.ml

@@ -7,7 +7,7 @@ let is_base36 text =
 
 let does_collide ( ) =
   let collision  = ref false in
-  let iterations = 20000000 in
+  let iterations = 200000 in
   let cuids      = Hashtbl.create iterations in
   let rec loop index =
     if index > iterations then ( ) else (