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)  1998-2022, University of Amsterdam
    7                              CWI, Amsterdam
    8                              SWI-Prolog Solutions b.v.
    9    All rights reserved.
   10
   11    Redistribution and use in source and binary forms, with or without
   12    modification, are permitted provided that the following conditions
   13    are met:
   14
   15    1. Redistributions of source code must retain the above copyright
   16       notice, this list of conditions and the following disclaimer.
   17
   18    2. Redistributions in binary form must reproduce the above copyright
   19       notice, this list of conditions and the following disclaimer in
   20       the documentation and/or other materials provided with the
   21       distribution.
   22
   23    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   24    "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   25    LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
   26    FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
   27    COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
   28    INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
   29    BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
   30    LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
   31    CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   32    LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
   33    ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   34    POSSIBILITY OF SUCH DAMAGE.
   35*/
   36
   37:- module('$rc',
   38          [ open_resource/2,            % +Name, -Stream
   39            open_resource/3,            % +Name, +RW, -Stream
   40            current_resource/2          % :Name, ?File
   41          ]).   42
   43:- meta_predicate
   44    open_resource(:, -),
   45    open_resource(:, -, +),
   46    current_resource(:, ?).   47
   48:- dynamic
   49    user:resource/2,
   50    user:resource/3.   51:- multifile
   52    user:resource/2,
   53    user:resource/3.

 open_resource(:Name, -Stream) is det

 open_resource(:Name, -Stream, +Options) is det

open_resource(:Name, ?Class, -Stream) is det

Open resource with given Name, returning a Stream.

   61open_resource(Name, Handle) :-
   62    open_resource(Name, Handle, []).
   63
   64open_resource(Module:RcName, Stream, Options) :-
   65    is_list(Options),
   66    !,
   67    (   default_module(Module, RModule),
   68        current_resource(RModule:RcName, FileSpec)
   69    ->  absolute_file_name(FileSpec, File),
   70        open(File, read, Stream, Options)
   71    ;   '$rc_handle'(Zipper),
   72        zip_close(Zipper, Clone),
   73        tag_rc_name(Module, RcName, TaggedName),
   74        zipper_goto(Clone, file(TaggedName))
   75    ->  zipper_open_current(Clone, Stream,
   76                            [ release(true)
   77                            | Options
   78                            ]),
   79        zip_close_(Clone, _)
   80    ;   '$existence_error'(resource, Module:RcName)
   81    ).
   82open_resource(Name, _Class, Stream) :-
   83    open_resource(Name, Stream).
   84
   85tag_rc_name(user, RcName, RcName) :- !.
   86tag_rc_name(Module, RcName, TaggedName) :-
   87    atomic_list_concat([Module, ':', RcName], TaggedName).
   88tag_rc_name(_, RcName, RcName).

 current_resource(:Name, ?File) is nondet

List all currently declared resources. Should eventually deal with resources that are already part of the state.

   95current_resource(M:Name, File) :-
   96    current_module(M),
   97    (   current_predicate(M:resource/2),
   98        M:resource(Name, File)
   99    ;   current_predicate(M:resource/3),
  100        M:resource(Name, _Class, File)
  101    ).

 c_open_resource(:Name, +Mode, -Stream)

Callback for PL_open_resource().

  107:- public c_open_resource/3.  108:- meta_predicate c_open_resource(:, +, -).  109
  110c_open_resource(Name, Mode, Stream) :-
  111    atom_chars(Mode, Chars),
  112    (   Chars = [r|MChars]
  113    ->  mode_options(MChars, Options),
  114        open_resource(Name, Stream, Options)
  115    ;   '$domain_error'(open_resource_mode, Mode)
  116    ).
  117
  118mode_options([], []).
  119mode_options([t|Chars], [type(text)|T]) :-
  120    !,
  121    mode_options(Chars, T).
  122mode_options([b|Chars], [type(binary)|T]) :-
  123    !,
  124    mode_options(Chars, T).
  125mode_options([_|Chars], T) :-
  126    mode_options(Chars, T).
  127
  128
  129		 /*******************************
  130		 *      RESOURCES AS FILES	*
  131		 *******************************/
  132
  133:- register_iri_scheme(res, res_iri_hook, []).

 res_iri_hook(+Action, +IRI, -Stream) is det

Define the res:// IRI scheme, binding to the central resource DB. For speed, the first call calls index_rc/0 that creates a predicate associating IRIs to offsets in the central resource ZIP.

  141res_iri_hook(open(Mode,Options), IRI, Stream) :-
  142    (   Mode == read
  143    ->  setup_call_cleanup(
  144            iri_zipper(IRI, Zipper),
  145            zipper_open_current(Zipper, Stream, Options),
  146            zip_close_(Zipper, _))
  147    ;   '$permission_error'(open, source_sink, IRI)
  148    ).
  149res_iri_hook(access(Mode), IRI0, True) :-
  150    (   read_mode(Mode),
  151        '$absolute_file_name'(IRI0, Canonical0),
  152        entry_name(Canonical0, Canonical),
  153        iri_offset(Canonical, _Offset)
  154    ->  access_ok(Mode, Canonical, True)
  155    ;   True = false
  156    ).
  157res_iri_hook(time, IRI, Time) :-
  158    setup_call_cleanup(
  159            iri_zipper_ex(IRI, Zipper),
  160            zipper_file_property(Zipper, _, time, Time),
  161            zip_close_(Zipper, _)).
  162res_iri_hook(size, IRI, Size) :-
  163    setup_call_cleanup(
  164            iri_zipper_ex(IRI, Zipper),
  165            zipper_file_property(Zipper, _, size, Size),
  166            zip_close_(Zipper, _)).
  167
  168read_mode(read).
  169read_mode(exists).
  170read_mode(file).
  171read_mode(directory).
  172
  173entry_name(Entry, Entry).
  174entry_name(Entry0, Entry) :-
  175    \+ sub_atom(Entry0, _, _, 0, /),
  176    atom_concat(Entry0, /, Entry).

 access_ok(+Access, +Entry, -Ok) is det

This assumes directories are added with a trailing /

  183access_ok(directory, Entry, True) :-
  184    !,
  185    (   sub_atom(Entry, _, _, 0, /)
  186    ->  True = true
  187    ;   True = false
  188    ).
  189access_ok(file, Entry, True) :-
  190    !,
  191    (   sub_atom(Entry, _, _, 0, /)
  192    ->  True = false
  193    ;   True = true
  194    ).
  195access_ok(_, _, true).

 iri_zipper(+IRI, -Zipper) is semidet

 iri_zipper_ex(+IRI, -Zipper) is det

Find and position a zipper for IRI. Fails if this cannot be found.

  202iri_zipper(IRI, Clone) :-
  203    '$absolute_file_name'(IRI, Canonical),
  204    iri_offset(Canonical, Offset),
  205    '$rc_handle'(Zipper),
  206    zip_clone(Zipper, Clone),
  207    zipper_goto(Clone, offset(Offset)).
  208
  209iri_zipper_ex(IRI, Zipper) :-
  210    iri_zipper(IRI, Zipper),
  211    !.
  212iri_zipper_ex(IRI, _Zipper) :-
  213    '$existence_error'(source_sink, IRI).

 iri_offset(+IRI, -Offset) is semidet

True when Offset is the zipper offset where we can find IRI.

  219:- dynamic rc_index_db/2, rc_index_done/0.  220:- volatile rc_index_db/2, rc_index_done/0.  221
  222iri_offset(Entry, Offset) :-
  223    rc_index_done,
  224    !,
  225    rc_index_db(Entry, Offset).
  226iri_offset(Entry, Offset) :-
  227    with_mutex('$rc', index_rc),
  228    !,
  229    rc_index_db(Entry, Offset).
  230
  231index_rc :-
  232    rc_index_done,
  233    !.
  234index_rc :-
  235    '$rc_handle'(Zipper),
  236    setup_call_cleanup(
  237        zip_clone(Zipper, Clone),
  238        ( zipper_goto(Clone, first),
  239          index_rc(Clone)
  240        ),
  241        zip_close_(Clone, _)),
  242    asserta(rc_index_done).
  243
  244index_rc(Zipper) :-
  245    zipper_file_property(Zipper, Name, offset, Offset),
  246    atom_concat('res://', Name, IRI),
  247    assertz(rc_index_db(IRI, Offset)),
  248    (   zipper_goto(Zipper, next)
  249    ->  index_rc(Zipper)
  250    ;   true
  251    ).

 zipper_file_property(+Zipper, -Name, +Prop, -Value)

  256zipper_file_property(Zipper, Name, Prop, Value) :-
  257    zip_file_info_(Zipper, Name, Info),
  258    zip_prop_arg(Prop, Arg),
  259    arg(Arg, Info, Value).
  260
  261zip_prop_arg(size,   2).
  262zip_prop_arg(time,   5).
  263zip_prop_arg(offset, 6)