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    1/*  Part of SWI-Prolog
    2
    3    Author:        Jan Wielemaker
    4    E-mail:        J.Wielemaker@vu.nl
    5    WWW:           http://www.swi-prolog.org
    6    Copyright (c)  2009-2014, VU University, Amsterdam
    7    All rights reserved.
    8
    9    Redistribution and use in source and binary forms, with or without
   10    modification, are permitted provided that the following conditions
   11    are met:
   12
   13    1. Redistributions of source code must retain the above copyright
   14       notice, this list of conditions and the following disclaimer.
   15
   16    2. Redistributions in binary form must reproduce the above copyright
   17       notice, this list of conditions and the following disclaimer in
   18       the documentation and/or other materials provided with the
   19       distribution.
   20
   21    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   22    "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   23    LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
   24    FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
   25    COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
   26    INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
   27    BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
   28    LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
   29    CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   30    LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
   31    ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   32    POSSIBILITY OF SUCH DAMAGE.
   33*/
   34
   35:- module(http_server_files,
   36          [ serve_files_in_directory/2  % +Alias, +HTTPRequest
   37          ]).   38:- use_module(library(http/http_path)).   39:- use_module(library(http/http_dispatch)).

Serve files needed by modules from the server

This module provides an infrastructure for serving resource-files such as icons, JavaScript, CSS files, etc. The default configuration serves the HTTP locations icons, css and js (see http_absolute_location/3)

The location for these services can be changed by adding rules for http:location/3. Directories providing additional or alternative resources can be achieved by adding rules for file_search_path/2. */

   53:- multifile
   54    http:location/3.                % Alias, Expansion, Options
   55:- dynamic
   56    http:location/3.                % Alias, Expansion, Options
   57
   58http:location(icons, root(icons), [ priority(-100) ]).
   59http:location(css,   root(css),   [ priority(-100) ]).
   60http:location(js,    root(js),    [ priority(-100) ]).
   61
   62:- multifile
   63    user:file_search_path/2.   64:- dynamic
   65    user:file_search_path/2.   66
   67user:file_search_path(icons, library('http/web/icons')).
   68user:file_search_path(css,   library('http/web/css')).
   69user:file_search_path(js,    library('http/web/js')).
   70
   71:- http_handler(icons(.), serve_files_in_directory(icons),
   72                [prefix, priority(-100)]).   73:- http_handler(css(.),   serve_files_in_directory(css),
   74                [prefix, priority(-100)]).   75:- http_handler(js(.),    serve_files_in_directory(js),
   76                [prefix, priority(-100)]).
 serve_files_in_directory(+Alias, +Request)
Serve files from the directory Alias from the path-info from Request. This predicate is used together with file_search_path/2. Note that multiple clauses for the same file_search_path alias can be used to merge files from different physical locations onto the same HTTP directory. Note that the handler must be declared as prefix. Below is an example serving images from http://<host>/img/... from the directory http/web/icons.
http:location(img, root(img), []).
user:file_search_path(icons, library('http/web/icons')).

:- http_handler(img(.), serve_files_in_directory(icons), [prefix]).

This predicate calls http_404/2 if the physical file cannot be located. If the requested path-name is unsafe (i.e., points outside the hierarchy defines by the file_search_path/2 declaration), this handlers returns a 403 Forbidden page.

See also
- http_reply_file/3
  103serve_files_in_directory(Alias, Request) :-
  104    memberchk(path_info(PathInfo), Request),
  105    !,
  106    Term =.. [Alias,PathInfo],
  107    (   catch(http_safe_file(Term, []),
  108              error(permission_error(read, file, _), _),
  109              fail)
  110    ->  (   absolute_file_name(Term, Path,
  111                               [ access(read),
  112                                 file_errors(fail)
  113                               ])
  114        ->  http_reply_file(Path,
  115                            [ unsafe(true),
  116                              static_gzip(true)
  117                            ], Request)
  118        ;   http_404([], Request)
  119        )
  120    ;   memberchk(path(Path), Request),
  121        throw(http_reply(forbidden(Path)))
  122    ).
  123serve_files_in_directory(_Alias, Request) :-
  124    memberchk(path(Path), Request),
  125    throw(http_reply(forbidden(Path)))