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)  1998-2018, University of Amsterdam
    7                              CWI, Amsterdam
    8    All rights reserved.
    9
   10    Redistribution and use in source and binary forms, with or without
   11    modification, are permitted provided that the following conditions
   12    are met:
   13
   14    1. Redistributions of source code must retain the above copyright
   15       notice, this list of conditions and the following disclaimer.
   16
   17    2. Redistributions in binary form must reproduce the above copyright
   18       notice, this list of conditions and the following disclaimer in
   19       the documentation and/or other materials provided with the
   20       distribution.
   21
   22    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   23    "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   24    LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
   25    FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
   26    COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
   27    INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
   28    BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
   29    LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
   30    CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   31    LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
   32    ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   33    POSSIBILITY OF SUCH DAMAGE.
   34*/
   35
   36:- module('$rc',
   37          [ open_resource/2,            % +Name, -Stream
   38            open_resource/3,            % +Name, +RW, -Stream
   39            current_resource/2          % :Name, ?File
   40          ]).   41
   42:- meta_predicate
   43    open_resource(:, -),
   44    open_resource(:, -, +),
   45    current_resource(:, ?).   46
   47:- dynamic
   48    user:resource/2,
   49    user:resource/3.   50:- multifile
   51    user:resource/2,
   52    user:resource/3.   53
   54%!  open_resource(:Name, -Stream) is det.
   55%!  open_resource(:Name, -Stream, +Options) is det.
   56%!  open_resource(:Name, ?Class, -Stream) is det.
   57%
   58%   Open resource with given Name, returning a Stream.
   59
   60open_resource(Name, Handle) :-
   61    open_resource(Name, Handle, []).
   62
   63open_resource(Module:RcName, Stream, Options) :-
   64    is_list(Options),
   65    !,
   66    (   default_module(Module, RModule),
   67        current_resource(RModule:RcName, FileSpec)
   68    ->  absolute_file_name(FileSpec, File),
   69        open(File, read, Stream, Options)
   70    ;   '$rc_handle'(Zipper),
   71        tag_rc_name(Module, RcName, TaggedName),
   72        zipper_goto(Zipper, file(TaggedName))
   73    ->  zipper_open_current(Zipper, Stream,
   74                            [ release(true)
   75                            | Options
   76                            ])
   77    ;   '$existence_error'(resource, Module:RcName)
   78    ).
   79open_resource(Name, _Class, Stream) :-
   80    open_resource(Name, Stream).
   81
   82tag_rc_name(user, RcName, RcName) :- !.
   83tag_rc_name(Module, RcName, TaggedName) :-
   84    atomic_list_concat([Module, ':', RcName], TaggedName).
   85tag_rc_name(_, RcName, RcName).
   86
   87%!  current_resource(:Name, ?File) is nondet.
   88%
   89%   List all currently declared resources.   Should  eventually deal
   90%   with resources that are already part of the state.
   91
   92current_resource(M:Name, File) :-
   93    current_module(M),
   94    (   current_predicate(M:resource/2),
   95        M:resource(Name, File)
   96    ;   current_predicate(M:resource/3),
   97        M:resource(Name, _Class, File)
   98    ).
   99
  100%!  c_open_resource(:Name, +Mode, -Stream)
  101%
  102%   Callback for PL_open_resource().
  103
  104:- public c_open_resource/3.  105:- meta_predicate c_open_resource(:, +, -).  106
  107c_open_resource(Name, Mode, Stream) :-
  108    atom_chars(Mode, Chars),
  109    (   Chars = [r|MChars]
  110    ->  mode_options(MChars, Options),
  111        open_resource(Name, Stream, Options)
  112    ;   '$domain_error'(open_resource_mode, Mode)
  113    ).
  114
  115mode_options([], []).
  116mode_options([t|Chars], [type(text)|T]) :-
  117    !,
  118    mode_options(Chars, T).
  119mode_options([b|Chars], [type(binary)|T]) :-
  120    !,
  121    mode_options(Chars, T).
  122mode_options([_|Chars], T) :-
  123    mode_options(Chars, T).
  124
  125
  126		 /*******************************
  127		 *      RESOURCES AS FILES	*
  128		 *******************************/
  129
  130:- register_iri_scheme(res, res_iri_hook, []).  131
  132%!  res_iri_hook(+Action, +IRI, -Stream) is det.
  133%
  134%   Define the =|res://|= IRI scheme, binding   to  the central resource
  135%   DB. For speed, the  first  call   calls  index_rc/0  that  creates a
  136%   predicate associating IRIs to offsets in the central resource ZIP.
  137
  138res_iri_hook(open(Mode,Options), IRI, Stream) :-
  139    (   Mode == read
  140    ->  setup_call_cleanup(
  141            iri_zipper(IRI, Zipper),
  142            zipper_open_current(Zipper, Stream, Options),
  143            zip_close_(Zipper, _))
  144    ;   '$permission_error'(open, source_sink, IRI)
  145    ).
  146res_iri_hook(access(Mode), IRI0, True) :-
  147    (   read_mode(Mode),
  148        '$absolute_file_name'(IRI0, Canonical0),
  149        entry_name(Canonical0, Canonical),
  150        iri_offset(Canonical, _Offset)
  151    ->  access_ok(Mode, Canonical, True)
  152    ;   True = false
  153    ).
  154res_iri_hook(time, IRI, Time) :-
  155    setup_call_cleanup(
  156            iri_zipper_ex(IRI, Zipper),
  157            zipper_file_property(Zipper, _, time, Time),
  158            zip_close_(Zipper, _)).
  159res_iri_hook(size, IRI, Size) :-
  160    setup_call_cleanup(
  161            iri_zipper_ex(IRI, Zipper),
  162            zipper_file_property(Zipper, _, size, Size),
  163            zip_close_(Zipper, _)).
  164
  165read_mode(read).
  166read_mode(exists).
  167read_mode(file).
  168read_mode(directory).
  169
  170entry_name(Entry, Entry).
  171entry_name(Entry0, Entry) :-
  172    \+ sub_atom(Entry0, _, _, 0, /),
  173    atom_concat(Entry0, /, Entry).
  174
  175
  176%!  access_ok(+Access, +Entry, -Ok) is det.
  177%
  178%   This assumes directories are added with a trailing /
  179
  180access_ok(directory, Entry, True) :-
  181    !,
  182    (   sub_atom(Entry, _, _, 0, /)
  183    ->  True = true
  184    ;   True = false
  185    ).
  186access_ok(file, Entry, True) :-
  187    !,
  188    (   sub_atom(Entry, _, _, 0, /)
  189    ->  True = false
  190    ;   True = true
  191    ).
  192access_ok(_, _, true).
  193
  194%!  iri_zipper(+IRI, -Zipper) is semidet.
  195%!  iri_zipper_ex(+IRI, -Zipper) is det.
  196%
  197%   Find and position a zipper for IRI. Fails if this cannot be found.
  198
  199iri_zipper(IRI, Clone) :-
  200    '$absolute_file_name'(IRI, Canonical),
  201    iri_offset(Canonical, Offset),
  202    '$rc_handle'(Zipper),
  203    zip_clone(Zipper, Clone),
  204    zipper_goto(Clone, offset(Offset)).
  205
  206iri_zipper_ex(IRI, Zipper) :-
  207    iri_zipper(IRI, Zipper),
  208    !.
  209iri_zipper_ex(IRI, _Zipper) :-
  210    '$existence_error'(source_sink, IRI).
  211
  212%!  iri_offset(+IRI, -Offset) is semidet.
  213%
  214%   True when Offset is the zipper offset where we can find IRI.
  215
  216:- dynamic rc_index_db/2, rc_index_done/0.  217:- volatile rc_index_db/2, rc_index_done/0.  218
  219iri_offset(Entry, Offset) :-
  220    rc_index_done,
  221    !,
  222    rc_index_db(Entry, Offset).
  223iri_offset(Entry, Offset) :-
  224    with_mutex('$rc', index_rc),
  225    !,
  226    rc_index_db(Entry, Offset).
  227
  228index_rc :-
  229    rc_index_done,
  230    !.
  231index_rc :-
  232    '$rc_handle'(Zipper),
  233    setup_call_cleanup(
  234        zip_clone(Zipper, Clone),
  235        ( zipper_goto(Clone, first),
  236          index_rc(Clone)
  237        ),
  238        zip_close_(Clone, _)),
  239    asserta(rc_index_done).
  240
  241index_rc(Zipper) :-
  242    zipper_file_property(Zipper, Name, offset, Offset),
  243    atom_concat('res://', Name, IRI),
  244    assertz(rc_index_db(IRI, Offset)),
  245    (   zipper_goto(Zipper, next)
  246    ->  index_rc(Zipper)
  247    ;   true
  248    ).
  249
  250
  251%!  zipper_file_property(+Zipper, -Name, +Prop, -Value)
  252
  253zipper_file_property(Zipper, Name, Prop, Value) :-
  254    zip_file_info_(Zipper, Name, Info),
  255    zip_prop_arg(Prop, Arg),
  256    arg(Arg, Info, Value).
  257
  258zip_prop_arg(size,   2).
  259zip_prop_arg(time,   5).
  260zip_prop_arg(offset, 6)