From: Stefano Zacchiroli <zack@upsilon.cc>
Date: Fri, 10 Jan 2003 09:10:09 +0000 (+0000)
Subject: implemented random id generation
X-Git-Tag: v0_3_99~49
X-Git-Url: http://matita.cs.unibo.it/gitweb/?a=commitdiff_plain;h=fc35d20e4e84902183ffbd4d903cdd55297eedfc;p=helm.git

implemented random id generation
---

diff --git a/helm/hbugs/common/hbugs_id_generator.ml b/helm/hbugs/common/hbugs_id_generator.ml
index 93d349b74..f535f4739 100644
--- a/helm/hbugs/common/hbugs_id_generator.ml
+++ b/helm/hbugs/common/hbugs_id_generator.ml
@@ -26,12 +26,40 @@
  *  http://helm.cs.unibo.it/
  *)
 
-let new_broker_id () =  (* TODO write a real id generator! *)
-  "FOO BROKER ID!"
-let new_client_id () =  (* TODO write a real id generator! *)
-  "FOO CLIENT ID!"
-let new_musing_id () =  (* TODO write a real id generator! *)
-  "FOO MUSING ID!"
-let new_tutor_id () =  (* TODO write a real id generator! *)
-  "FOO TUTOR ID!"
+let _ = Random.self_init ()
+
+let id_length = 32
+let min_ascii = 33
+let max_ascii = 126
+  (* characters forbidden inside an XML attribute value. Well, '>' and '''
+  aren't really forbidden, but are listed here ... just to be sure *)
+let forbidden_chars = (* i.e. [ '"'; '&'; '\''; '<'; '>' ] *)
+  [ 34; 38; 39; 60; 62 ]  (* assumption: is sorted! *)
+let chars_range = max_ascii - min_ascii + 1 - (List.length forbidden_chars)
+
+  (* return a random id char c such that 
+      (min_ascii <= Char.code c) &&
+      (Char.code c <= max_ascii) &&
+      (not (List.mem (Char.code c) forbidden_chars))
+  *)
+let random_id_char () =
+  let rec nth_char ascii shifts = function
+    | [] -> Char.chr (ascii + shifts)
+    | hd::tl when ascii + shifts < hd -> Char.chr (ascii + shifts)
+    | hd::tl (* when ascii + shifts >= hd *) -> nth_char ascii (shifts + 1) tl
+  in
+  nth_char (Random.int chars_range + min_ascii) 0 forbidden_chars
+
+  (* return a random id string which have length id_length *)
+let new_id () =
+  let str = String.create id_length in
+  for i = 0 to id_length - 1 do
+    String.set str i (random_id_char ())
+  done;
+  str
+
+let new_broker_id = new_id
+let new_client_id = new_id
+let new_musing_id = new_id
+let new_tutor_id = new_id