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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)  2002-2018, University of Amsterdam
    7                              VU University 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:
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   15       notice, this list of conditions and the following disclaimer.
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   20       distribution.
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   25    FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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   34*/
   35
   36:- module(mimetype,
   37          [ file_mime_type/2,           % +Path, -Type
   38            file_content_type/2,        % +Path, -Type
   39            file_content_type/3         % +Path, ?MediaType, -Type
   40          ]).

Determine mime-type for a file

Simple library to guess the mime-type from the extension of a file. As various applications need to do this type ofinferencing it seems worthwhile to place this functionality in an extensible library.

To be done
- Consider content handling (using the Unix file command)
- Allow parameters? (e.g. text/html; charset=UTF-8) */
   52:- multifile
   53    mime:mime_extension/2,
   54    mime:text_mimetype/1,
   55    mime:charset/3.
 file_mime_type(+FileName, -MimeType) is semidet
True when MimeType is the mime-type to be used for sending FileName. The default rules can be overridden and extended using the hook mime:mime_extension/2.
Arguments:
MimeType- is a compound term of the form Type/SubType.
   65file_mime_type(File, MimeType) :-
   66    file_name_extension(_, Ext, File),
   67    (   current_prolog_flag(windows, true)
   68    ->  downcase_atom(Ext, Lower),
   69        mime_extension(Lower, MimeType)
   70    ;   mime_extension(Ext, M0)
   71    ->  MimeType = M0
   72    ;   downcase_atom(Ext, Lower),
   73        mime_extension(Lower, MimeType)
   74    ),
   75    !.
   76file_mime_type(File, MimeType) :-
   77    file_base_name(File, Base),
   78    downcase_atom(Base, Lower),
   79    name_mimetype(Lower, Mime),
   80    !,
   81    MimeType = Mime.
   82file_mime_type(_, MimeType) :-
   83    default_mimetype(MimeType).
 mime:mime_extension(+Ext, -MimeType) is semidet
Hook that is called by file_mime_type/2 before the default table is examined.
   90mime_extension(Ext, MimeType) :-
   91    (   mime:mime_extension(Ext, Mime)
   92    ->  MimeType = Mime
   93    ;   ext_mimetype(Ext, Mime)
   94    ->  MimeType = Mime
   95    ).
 default_mimetype(-MimeType) is semidet
If the mime-type cannot be determined from the file extension, this predicate is used as fallback. It takes the value from the Prolog flag default_mimetype. To change the default, use e.g.,
:- set_prolog_flag(default_mimetype, text/plain).

The initial default mime-type is application/unknown. Use the value - to denote there is no default.

  110:- create_prolog_flag(default_mimetype, application/unknown, [keep(true)]).  111
  112default_mimetype(MimeType) :-
  113    current_prolog_flag(default_mimetype, MimeType),
  114    MimeType = _/_.
 ext_mimetype(+Extension, -MimeType) is semidet
Built-in table of file-name extension to mime-type mappings.
To be done
- Update this list, e.g., from http://www.webmaster-toolkit.com/mime-types.shtml
  124                                        % plain text
  125ext_mimetype(txt,  text/plain).
  126                                        % markup
  127ext_mimetype(htm,  text/html).
  128ext_mimetype(html, text/html).
  129ext_mimetype(xhtml, application/'xhtml+xml').
  130ext_mimetype(sgml, text/'x-sgml').
  131ext_mimetype(sgm,  text/'x-sgml').
  132ext_mimetype(xml,  text/xml).
  133ext_mimetype(css,  text/css).
  134ext_mimetype(xsl,  text/xml).           % Unclear what this should be.
  135ext_mimetype(md,   text/markdown).
  136                                        % Other data markup
  137ext_mimetype(json, application/json).
  138ext_mimetype(yaml, application/yaml).   % Not official
  139                                        % semantic web stuff
  140ext_mimetype(rdf,  application/'rdf+xml').
  141ext_mimetype(rdfs, application/'rdf+xml').
  142ext_mimetype(owl,  application/'rdf+xml').
  143ext_mimetype(ttl,  application/turtle).
  144ext_mimetype(nt,   application/'n-triples').
  145ext_mimetype(nq,   application/'n-quads').
  146                                        % Prolog source
  147ext_mimetype(pl,   text/plain).
  148                                        % Other languages
  149ext_mimetype(c,    text/'x-c').
  150ext_mimetype(h,    text/'x-c').
  151ext_mimetype(cc,   text/'x-c').
  152ext_mimetype(py,   text/'x-python').
  153ext_mimetype(java, text/'x-java').
  154ext_mimetype(sh,   text/plain).
  155                                        % Packaged formats
  156ext_mimetype(gz,   application/'x-gzip').
  157ext_mimetype(zip,  application/zip).
  158ext_mimetype(tgz,  application/'x-gtar').
  159                                        % Some document formats
  160ext_mimetype(pdf,  application/pdf).
  161ext_mimetype(doc,  application/msword).
  162                                        % Java classes
  163ext_mimetype(class, application/'octet-stream').
  164ext_mimetype(jar,  application/'x-java-archive').
  165                                        % JavaScript
  166ext_mimetype(js,   text/javascript).
  167                                        % Visual Basic Script :-(
  168ext_mimetype(vbs,  text/vbscript).
  169                                        % Some image formats
  170ext_mimetype(jpg,  image/jpeg).
  171ext_mimetype(jpeg, image/jpeg).
  172ext_mimetype(gif,  image/gif).
  173ext_mimetype(png,  image/png).
  174ext_mimetype(tif,  image/tiff).
  175ext_mimetype(tiff, image/tiff).
  176ext_mimetype(xpm,  image/'x-xpixmap').
  177ext_mimetype(ico,  image/'x-ico').
  178ext_mimetype(svg,  image/'svg+xml').
  179                                        % Google earth
  180ext_mimetype(kml,  application/'vnd.google-earth.kml+xml').
  181ext_mimetype(kmz,  application/'vnd.google-earth.kmz').
  182
  183                                        % Flash
  184ext_mimetype(swf,  application/'x-shockwave-flash').
  185ext_mimetype(flv,  video/'x-flv').
  186                                        % MP3
  187ext_mimetype(mp3,  audio/mpeg).
  188                                        % Downloads
  189ext_mimetype(rpm,  application/'x-rpm').
  190ext_mimetype(exe,  application/'x-executable').
 name_mimetype(+DownCaseFileName, -MimeType) is semidet
Determine the mime-type of files based on the entire filename.
  196name_mimetype(makefile,       text/plain).
  197name_mimetype(configure,      text/plain).
  198name_mimetype('configure.in', text/plain).
  199name_mimetype('configure.ac', text/plain).
  200name_mimetype('makefile.in',  text/plain).
  201name_mimetype('makefile.am',  text/plain).
  202name_mimetype('readme.in',    text/plain).
 text_mimetype(+MimeType) is semidet
True when documents of MimeType are text documents and thus may need a charset specification.
  209text_mimetype(MimeType) :-
  210    mime:text_mimetype(MimeType),
  211    !.
  212text_mimetype(text/_).
 file_content_type(+File:atom, -ContentType:atom) is det
 file_content_type(+File:atom, ?MediaType, -ContentType:atom) is det
True if File should be served using ContentType: ContentType. It takes the following steps:
  1. Determine the media type using file_mime_type/2, unless already specified using file_content_type/3.
  2. Determine it is a text file using text_mimetype/1
  3. Use the charset from the Prolog flag default_charset

The behavior is controlled by several hooks and a flag.

  237file_content_type(File, ContentType) :-
  238    file_content_type(File, _, ContentType).
  239file_content_type(File, MediaType, ContentType) :-
  240    (   ground(MediaType)
  241    ->  true
  242    ;   file_mime_type(File, MediaType)
  243    ),
  244    (   text_mimetype(MediaType),
  245        (   mime:charset(File, MediaType, Charset0)
  246        ->  Charset = Charset0
  247        ;   default_charset(Charset)
  248        )
  249    ->  format(atom(ContentType), '~w; charset=~w', [MediaType, Charset])
  250    ;   format(atom(ContentType), '~w', [MediaType])
  251    ).
 mime:charset(+File, +MediaType, -Charset) is semidet
Hook that determines the Charset for File that has media type MediaType. This hook allows overruling file_content_type/2.
See also
- text_mimetype/1.
  260default_charset(Charset) :-
  261    current_prolog_flag(default_charset, Charset),
  262    Charset \== (-).
  263
  264set_default_charset :-
  265    current_prolog_flag(default_charset, _),
  266    !.
  267set_default_charset :-
  268    current_prolog_flag(encoding, utf8),
  269    !,
  270    set_prolog_flag(default_charset, 'UTF-8').
  271set_default_charset.
  272
  273:- initialization(set_default_charset).