/* Part of SWI-Prolog Author: Jan Wielemaker E-mail: J.Wielemaker@vu.nl WWW: http://www.swi-prolog.org Copyright (c) 2007-2020, VU University Amsterdam CWI, Amsterdam All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ :- module(rdf_cache, [ rdf_set_cache_options/1, % +Options rdf_cache_file/3 % +URL, +RW, -File ]). :- autoload(library(error),[must_be/2,domain_error/2]). :- autoload(library(filesex),[make_directory_path/1]). /** Cache RDF triples The library library(semweb/rdf_cache) defines the caching strategy for triples sources. When using large RDF sources, caching triples greatly speedup loading RDF documents. The cache library implements two caching strategies that are controlled by rdf_set_cache_options/1. *|Local caching|* This approach applies to files only. Triples are cached in a sub-directory of the directory holding the source. This directory is called =|.cache|= (=|_cache|= on Windows). If the cache option =create_local_directory= is =true=, a cache directory is created if posible. *|Global caching|* This approach applies to all sources, except for unnamed streams. Triples are cached in directory defined by the cache option =global_directory=. When loading an RDF file, the system scans the configured cache files unless cache(false) is specified as option to rdf_load/2 or caching is disabled. If caching is enabled but no cache exists, the system will try to create a cache file. First it will try to do this locally. On failure it will try to configured global cache. */ :- dynamic cache_option/1. set_setfault_options :- assert(cache_option(enabled(true))), ( current_prolog_flag(windows, true) -> assert(cache_option(local_directory('_cache'))) ; assert(cache_option(local_directory('.cache'))) ). :- set_setfault_options. % _only_ when loading! %! rdf_set_cache_options(+Options) % % Change the cache policy. Provided options are: % % * enabled(Boolean) % If =true=, caching is enabled. % % * local_directory(Name). % Plain name of local directory. Default =|.cache|= % (=|_cache|= on Windows). % % * create_local_directory(Bool) % If =true=, try to create local cache directories % % * global_directory(Dir) % Writeable directory for storing cached parsed files. % % * create_global_directory(Bool) % If =true=, try to create the global cache directory. rdf_set_cache_options([]) :- !. rdf_set_cache_options([H|T]) :- !, rdf_set_cache_options(H), rdf_set_cache_options(T). rdf_set_cache_options(Opt) :- functor(Opt, Name, Arity), arg(1, Opt, Value), ( cache_option(Name, Type) -> must_be(Type, Value) ; domain_error(cache_option, Opt) ), functor(Gen, Name, Arity), retractall(cache_option(Gen)), expand_option(Opt, EOpt), assert(cache_option(EOpt)). cache_option(enabled, boolean). cache_option(local_directory, atom). cache_option(create_local_directory, boolean). cache_option(global_directory, atom). cache_option(create_global_directory, boolean). expand_option(global_directory(Local), global_directory(Global)) :- !, absolute_file_name(Local, Global). expand_option(Opt, Opt). %! rdf_cache_file(+URL, +ReadWrite, -File) is semidet. % % File is the cache file for URL. If ReadWrite is =read=, it % returns the name of an existing file. If =write= it returns % where a new cache file can be overwritten or created. rdf_cache_file(_URL, _, _File) :- cache_option(enabled(false)), !, fail. rdf_cache_file(URL, read, File) :- !, ( atom_concat('file://', Path, URL), cache_option(local_directory(Local)), file_directory_name(Path, Dir), local_cache_file(URL, LocalFile), atomic_list_concat([Dir, Local, LocalFile], /, File) ; cache_option(global_directory(Dir)), url_cache_file(URL, Dir, trp, read, File) ), access_file(File, read), !. rdf_cache_file(URL, write, File) :- !, ( atom_concat('file://', Path, URL), cache_option(local_directory(Local)), file_directory_name(Path, Dir), ( cache_option(create_local_directory(true)) -> RWDir = write ; RWDir = read ), ensure_dir(Dir, Local, RWDir, CacheDir), local_cache_file(URL, LocalFile), atomic_list_concat([CacheDir, LocalFile], /, File) ; cache_option(global_directory(Dir)), ensure_global_cache(Dir), url_cache_file(URL, Dir, trp, write, File) ), access_file(File, write), !. ensure_global_cache(Dir) :- exists_directory(Dir), !. ensure_global_cache(Dir) :- cache_option(create_global_directory(true)), make_directory_path(Dir), print_message(informational, rdf(cache_created(Dir))). /******************************* * LOCAL CACHE * *******************************/ %! local_cache_file(+FileURL, -File) is det. % % Return the name of the cache file for FileURL. The name is the % plain filename with the .trp extension. As the URL is a file % URL, it is guaranteed to be a valid filename. Assumes the % hosting OS can handle multiple exensions (=|.x.y|=) though. % These days thats even true on Windows. local_cache_file(URL, File) :- file_base_name(URL, Name), file_name_extension(Name, trp, File). /******************************* * GLOBAL CACHE * *******************************/ %! url_cache_file(+URL, +Dir, +Ext, +RW, -Path) is semidet. % % Determine location of cache-file for the given URL in Dir. If % Ext is provided, the returned Path is ensured to have the % specified extension. % % @param RW If =read=, no directories are created and the call % fails if URL is not in the cache. url_cache_file(URL, Dir, Ext, RW, Path) :- term_hash(URL, Hash0), Hash is Hash0 + 100000, % make sure > 4 characters format(string(Hex), '~16r', [Hash]), sub_atom(Hex, _, 2, 0, L1), ensure_dir(Dir, L1, RW, Dir1), sub_atom(Hex, _, 2, 2, L2), ensure_dir(Dir1, L2, RW, Dir2), url_to_file(URL, File), ensure_ext(File, Ext, FileExt), atomic_list_concat([Dir2, /, FileExt], Path). ensure_dir(D0, Sub, RW, Dir) :- atomic_list_concat([D0, /, Sub], Dir), ( exists_directory(Dir) -> true ; RW == write -> catch(make_directory(Dir), _, fail) ). ensure_ext(File, '', File) :- !. ensure_ext(File, Ext, File) :- file_name_extension(_, Ext, File), !. ensure_ext(File, Ext, FileExt) :- file_name_extension(File, Ext, FileExt). %! url_to_file(+URL, -File) % % Convert a URL in something that fits in a file, i.e. avoiding / % and :. We simply replace these by -. We could also use % www_form_encode/2, but confusion when to replace as well as the % fact that we loose the '.' (extension) makes this a less ideal % choice. We could also consider base64 encoding of the name. url_to_file(URL, File) :- atom_codes(URL, Codes), phrase(safe_file_name(Codes), FileCodes), atom_codes(File, FileCodes). safe_file_name([]) --> []. safe_file_name([H|T]) --> replace(H), !, safe_file_name(T). safe_file_name([H|T]) --> [H], safe_file_name(T). %! replace(+Code)// % % Replace a character code that cannot safely be put in a % filename. Should we use %XX? replace(0'/) --> "-". % directory separator replace(0'\\) --> "-". % not allowed in Windows filename replace(0':) --> "-". % idem replace(0'?) --> "-". % idem replace(0'*) --> "-". % idem /******************************* * MESSAGES * *******************************/ :- multifile prolog:message/3. prolog:message(rdf(cache_created(Dir))) --> [ 'Created RDF cache directory ~w'-[Dir] ].