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diff --git a/helm/ocaml/getter/http_getter_storage.ml b/helm/ocaml/getter/http_getter_storage.ml
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+(* Copyright (C) 2004-2005, HELM Team.
+ * 
+ * This file is part of HELM, an Hypertextual, Electronic
+ * Library of Mathematics, developed at the Computer Science
+ * Department, University of Bologna, Italy.
+ * 
+ * HELM is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ * 
+ * HELM is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with HELM; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+ * MA  02111-1307, USA.
+ * 
+ * For details, see the HELM World-Wide-Web page,
+ * http://helm.cs.unibo.it/
+ *)
+
+(* $Id$ *)
+
+open Printf
+
+open Http_getter_misc
+open Http_getter_types
+
+exception Not_found'
+exception Resource_not_found of string * string  (** method, uri *)
+
+let index_fname = "INDEX"
+
+let trailing_slash_RE = Pcre.regexp "/$"
+let relative_RE_raw = "(^[^/]+(/[^/]+)*/?$)"
+let relative_RE = Pcre.regexp relative_RE_raw
+let file_scheme_RE_raw = "(^file://)"
+let extended_file_scheme_RE = Pcre.regexp "(^file:/+)"
+let file_scheme_RE = Pcre.regexp (relative_RE_raw ^ "|" ^ file_scheme_RE_raw)
+let http_scheme_RE = Pcre.regexp "^http://"
+let newline_RE = Pcre.regexp "\\n"
+let cic_scheme_sep_RE = Pcre.regexp ":/"
+let gz_suffix = ".gz"
+let gz_suffix_len = String.length gz_suffix
+
+let path_of_file_url url =
+  assert (Pcre.pmatch ~rex:file_scheme_RE url);
+  if Pcre.pmatch ~rex:relative_RE url then
+    url
+  else  (* absolute path, add heading "/" if missing *)
+    "/" ^ (Pcre.replace ~rex:extended_file_scheme_RE url)
+
+  (** associative list regular expressions -> url prefixes
+   * sorted with longest prefixes first *)
+let prefix_map = lazy (
+  let map_w_length =
+    List.map
+      (fun (uri_prefix, (url_prefix, attrs)) ->
+        let uri_prefix = normalize_dir uri_prefix in
+        let url_prefix = normalize_dir url_prefix in
+        let regexp = Pcre.regexp ("^(" ^ Pcre.quote uri_prefix ^ ")") in
+        (regexp, String.length uri_prefix, uri_prefix, url_prefix, attrs))
+      (Lazy.force Http_getter_env.prefixes)
+  in
+  let decreasing_length (_, len1, _, _, _) (_, len2, _, _, _) =
+    compare len2 len1 in
+  List.map
+    (fun (regexp, len, uri_prefix, url_prefix, attrs) ->
+      (regexp, strip_trailing_slash uri_prefix, url_prefix, attrs))
+    (List.fast_sort decreasing_length map_w_length))
+
+let lookup uri =
+  let matches =
+    List.filter (fun (rex, _, _, _) -> Pcre.pmatch ~rex uri)
+      (Lazy.force prefix_map) in
+  if matches = [] then raise (Unresolvable_URI uri);
+  matches
+
+let resolve_prefix uri =
+  match lookup uri with
+  | (rex, _, url_prefix, _) :: _ ->
+      Pcre.replace_first ~rex ~templ:url_prefix uri
+  | [] -> assert false
+
+let resolve_prefixes uri =
+  let matches = lookup uri in
+  List.map
+    (fun (rex, _, url_prefix, _) ->
+      Pcre.replace_first ~rex ~templ:url_prefix uri)
+    matches
+
+let get_attrs uri =
+  match lookup uri with
+  | (_, _, _, attrs) :: _ -> attrs
+  | [] -> assert false
+
+let is_legacy uri = List.exists ((=) `Legacy) (get_attrs uri)
+
+let is_read_only uri =
+  is_legacy uri || List.exists ((=) `Read_only) (get_attrs uri)
+
+let exists_http _ url =
+  Http_getter_wget.exists (url ^ gz_suffix) || Http_getter_wget.exists url
+
+let exists_file _ fname =
+  Sys.file_exists (fname ^ gz_suffix) || Sys.file_exists fname
+
+let resolve_http _ url =
+  try
+    List.find Http_getter_wget.exists [ url ^ gz_suffix; url ]
+  with Not_found -> raise Not_found'
+
+let resolve_file _ fname =
+  try
+    List.find Sys.file_exists [ fname ^ gz_suffix; fname ]
+  with Not_found -> raise Not_found'
+
+let strip_gz_suffix fname =
+  if extension fname = gz_suffix then
+    String.sub fname 0 (String.length fname - gz_suffix_len)
+  else
+    fname
+
+let remove_duplicates l =
+  Http_getter_misc.list_uniq (List.fast_sort Pervasives.compare l)
+
+let ls_file_single _ path_prefix =
+  let is_dir fname = (Unix.stat fname).Unix.st_kind = Unix.S_DIR in
+  let is_useless dir = try dir.[0] = '.' with _ -> false in
+  let entries = ref [] in
+  try
+    let dir_handle = Unix.opendir path_prefix in
+    (try
+      while true do
+        let entry = Unix.readdir dir_handle in
+        if is_useless entry then
+          ()
+        else if is_dir (path_prefix ^ "/" ^ entry) then
+          entries := normalize_dir entry :: !entries
+        else
+          entries := strip_gz_suffix entry :: !entries
+      done
+    with End_of_file -> Unix.closedir dir_handle);
+    remove_duplicates !entries
+  with Unix.Unix_error (_, "opendir", _) -> []
+
+let ls_http_single _ url_prefix =
+  try
+    let index = Http_getter_wget.get (normalize_dir url_prefix ^ index_fname) in
+    Pcre.split ~rex:newline_RE index
+  with Http_client_error _ -> raise Not_found'
+
+let get_file _ path =
+  if Sys.file_exists (path ^ gz_suffix) then
+    path ^ gz_suffix
+  else if Sys.file_exists path then
+    path
+  else
+    raise Not_found'
+
+let get_http uri url =
+  let scheme, path =
+    match Pcre.split ~rex:cic_scheme_sep_RE uri with
+    | [scheme; path] -> scheme, path
+    | _ -> assert false
+  in
+  let cache_name =
+    sprintf "%s%s/%s" (Lazy.force Http_getter_env.cache_dir) scheme path
+  in
+  if Sys.file_exists (cache_name ^ gz_suffix) then
+    cache_name ^ gz_suffix
+  else if Sys.file_exists cache_name then
+    cache_name
+  else begin  (* fill cache *)
+    Http_getter_misc.mkdir ~parents:true (Filename.dirname cache_name);
+    (try
+      Http_getter_wget.get_and_save (url ^ gz_suffix) (cache_name ^ gz_suffix);
+      cache_name ^ gz_suffix
+    with Http_client_error _ ->
+      (try
+        Http_getter_wget.get_and_save url cache_name;
+        cache_name
+      with Http_client_error _ ->
+        raise Not_found'))
+  end
+
+let remove_file _ path =
+  if Sys.file_exists (path ^ gz_suffix) then Sys.remove (path ^ gz_suffix);
+  if Sys.file_exists path then Sys.remove path
+
+let remove_http _ _ =
+  prerr_endline "Http_getter_storage.remove: not implemented for HTTP scheme";
+  assert false
+
+type 'a storage_method = {
+  name: string;
+  file: string -> string -> 'a; (* unresolved uri, resolved uri *)
+  http: string -> string -> 'a; (* unresolved uri, resolved uri *)
+}
+
+let normalize_root uri =  (* add trailing slash to roots *)
+  try
+    if uri.[String.length uri - 1] = ':' then uri ^ "/"
+    else uri
+  with Invalid_argument _ -> uri
+
+let invoke_method storage_method uri url =
+  try
+    if Pcre.pmatch ~rex:file_scheme_RE url then
+      storage_method.file uri (path_of_file_url url)
+    else if Pcre.pmatch ~rex:http_scheme_RE url then
+      storage_method.http uri url
+    else
+      raise (Unsupported_scheme url)
+  with Not_found' -> raise (Resource_not_found (storage_method.name, uri))
+
+let dispatch_single storage_method uri =
+  assert (extension uri <> gz_suffix);
+  let uri = normalize_root uri in
+  let url = resolve_prefix uri in
+  invoke_method storage_method uri url
+
+let dispatch_multi storage_method uri =
+  let urls = resolve_prefixes uri in
+  let rec aux = function
+    | [] -> raise (Resource_not_found (storage_method.name, uri))
+    | url :: tl ->
+        (try
+          invoke_method storage_method uri url
+        with Resource_not_found _ -> aux tl)
+  in
+  aux urls
+
+let exists =
+  dispatch_single { name = "exists"; file = exists_file; http = exists_http }
+
+let resolve =
+  dispatch_single { name = "resolve"; file = resolve_file; http = resolve_http }
+
+let ls_single =
+  dispatch_single { name = "ls"; file = ls_file_single; http = ls_http_single }
+
+let remove =
+  dispatch_single { name = "remove"; file = remove_file; http = remove_http }
+
+let filename ?(find = false) =
+  if find then
+    dispatch_multi { name = "filename"; file = get_file; http = get_http }
+  else
+    dispatch_single { name = "filename"; file = get_file; http = get_http }
+
+  (* ls_single performs ls only below a single prefix, but prefixes which have
+   * common prefix (sorry) with a given one may need to be considered as well
+   * for example: when doing "ls cic:/" we would like to see the "cic:/matita"
+   * directory *)
+let ls uri_prefix =
+(*   prerr_endline ("Http_getter_storage.ls " ^ uri_prefix); *)
+  let direct_results = ls_single uri_prefix in
+  List.fold_left
+    (fun results (_, uri_prefix', _, _) ->
+      if Filename.dirname uri_prefix' = strip_trailing_slash uri_prefix then
+        (Filename.basename uri_prefix' ^ "/") :: results
+      else
+        results)
+    direct_results
+    (Lazy.force prefix_map)
+
+let clean_cache () =
+  ignore (Sys.command
+    (sprintf "rm -rf %s/" (Lazy.force Http_getter_env.cache_dir)))
+