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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)  2002-2025, University of Amsterdam
    7                              VU University 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(http_header,
   38          [ http_read_request/2,        % +Stream, -Request
   39            http_read_reply_header/2,   % +Stream, -Reply
   40            http_reply/2,               % +What, +Stream
   41            http_reply/3,               % +What, +Stream, +HdrExtra
   42            http_reply/4,               % +What, +Stream, +HdrExtra, -Code
   43            http_reply/5,               % +What, +Stream, +HdrExtra, +Context,
   44                                        % -Code
   45            http_reply/6,               % +What, +Stream, +HdrExtra, +Context,
   46                                        % +Request, -Code
   47            http_reply_header/3,        % +Stream, +What, +HdrExtra
   48            http_status_reply/4,        % +Status, +Out, +HdrExtra, -Code
   49            http_status_reply/5,        % +Status, +Out, +HdrExtra,
   50                                        % +Context, -Code
   51
   52            http_timestamp/2,           % ?Time, ?HTTPstring
   53
   54            http_post_data/3,           % +Stream, +Data, +HdrExtra
   55
   56            http_read_header/2,         % +Fd, -Header
   57            http_parse_header/2,        % +Codes, -Header
   58            http_parse_header_value/3,  % +Header, +HeaderValue, -MediaTypes
   59            http_join_headers/3,        % +Default, +InHdr, -OutHdr
   60            http_update_encoding/3,     % +HeaderIn, -Encoding, -HeaderOut
   61            http_update_connection/4,   % +HeaderIn, +Request, -Connection, -HeaderOut
   62            http_update_transfer/4      % +HeaderIn, +Request, -Transfer, -HeaderOut
   63          ]).   64:- autoload(html_write,
   65	    [ print_html/2, print_html/1, page/4, html/3,
   66	      html_print_length/2
   67	    ]).   68:- if(exists_source(http_exception)).   69:- autoload(http_exception,[map_exception_to_http_status/4]).   70:- endif.   71:- autoload(mimepack,[mime_pack/3]).   72:- autoload(mimetype,[file_mime_type/2]).   73:- autoload(library(apply),[maplist/2]).   74:- autoload(library(base64),[base64/2]).   75:- use_module(library(debug),[debug/3,debugging/1]).   76:- autoload(library(error),[syntax_error/1,domain_error/2]).   77:- autoload(library(lists),[append/3,member/2,select/3,delete/3]).   78:- autoload(library(memfile),
   79	    [ new_memory_file/1, open_memory_file/3,
   80	      free_memory_file/1, open_memory_file/4,
   81	      size_memory_file/3
   82	    ]).   83:- autoload(library(option),[option/3,option/2]).   84:- autoload(library(pairs),[pairs_values/2]).   85:- autoload(library(readutil),
   86	    [read_line_to_codes/2,read_line_to_codes/3]).   87:- autoload(library(sgml_write),[xml_write/3]).   88:- autoload(library(socket),[gethostname/1]).   89:- autoload(library(uri),
   90	    [ uri_components/2, uri_data/3, uri_encoded/3, uri_query_components/2
   91	    ]).   92:- autoload(library(url),[parse_url_search/2]).   93:- autoload(library(dcg/basics),
   94	    [ integer/3, atom/3, whites/2, blanks_to_nl/2, string/3,
   95	      number/3, blanks/2, float/3, nonblanks/3, eos/2
   96	    ]).   97:- autoload(library(date), [parse_time/3]).   98:- use_module(library(settings),[setting/4,setting/2]).   99
  100:- multifile
  101    http:status_page/3,             % +Status, +Context, -HTML
  102    http:status_reply/3,            % +Status, -Reply, +Options
  103    http:serialize_reply/2,         % +Reply, -Body
  104    http:post_data_hook/3,          % +Data, +Out, +HdrExtra
  105    http:mime_type_encoding/2.      % +MimeType, -Encoding
  106
  107% see http_update_transfer/4.
  108
  109:- setting(http:chunked_transfer, oneof([never,on_request,if_possible]),
  110           on_request, 'When to use Transfer-Encoding: Chunked').  111
  112
  113/** <module> Handling HTTP headers
  114
  115The library library(http/http_header) provides   primitives  for parsing
  116and composing HTTP headers. Its functionality  is normally hidden by the
  117other parts of the HTTP server and client libraries.
  118*/
  119
  120:- discontiguous
  121    term_expansion/2.  122
  123
  124                 /*******************************
  125                 *          READ REQUEST        *
  126                 *******************************/
  127
  128%!  http_read_request(+FdIn:stream, -Request) is det.
  129%
  130%   Read an HTTP request-header from FdIn and return the broken-down
  131%   request fields as +Name(+Value) pairs  in   a  list.  Request is
  132%   unified to =end_of_file= if FdIn is at the end of input.
  133
  134http_read_request(In, Request) :-
  135    catch(read_line_to_codes(In, Codes), E, true),
  136    (   var(E)
  137    ->  (   Codes == end_of_file
  138        ->  debug(http(header), 'end-of-file', []),
  139            Request = end_of_file
  140        ;   debug(http(header), 'First line: ~s', [Codes]),
  141            Request =  [input(In)|Request1],
  142            phrase(request(In, Request1), Codes),
  143            (   Request1 = [unknown(Text)|_]
  144            ->  string_codes(S, Text),
  145                syntax_error(http_request(S))
  146            ;   true
  147            )
  148        )
  149    ;   (   debugging(http(request))
  150        ->  message_to_string(E, Msg),
  151            debug(http(request), "Exception reading 1st line: ~s", [Msg])
  152        ;   true
  153        ),
  154        Request = end_of_file
  155    ).
  156
  157
  158%!  http_read_reply_header(+FdIn, -Reply)
  159%
  160%   Read the HTTP reply header. Throws   an exception if the current
  161%   input does not contain a valid reply header.
  162
  163http_read_reply_header(In, [input(In)|Reply]) :-
  164    read_line_to_codes(In, Codes),
  165    (   Codes == end_of_file
  166    ->  debug(http(header), 'end-of-file', []),
  167        throw(error(syntax(http_reply_header, end_of_file), _))
  168    ;   debug(http(header), 'First line: ~s~n', [Codes]),
  169        (   phrase(reply(In, Reply), Codes)
  170        ->  true
  171        ;   atom_codes(Header, Codes),
  172            syntax_error(http_reply_header(Header))
  173        )
  174    ).
  175
  176
  177                 /*******************************
  178                 *        FORMULATE REPLY       *
  179                 *******************************/
  180
  181%!  http_reply(+Data, +Out:stream) is det.
  182%!  http_reply(+Data, +Out:stream, +HdrExtra) is det.
  183%!  http_reply(+Data, +Out:stream, +HdrExtra, -Code) is det.
  184%!  http_reply(+Data, +Out:stream, +HdrExtra, +Context, -Code) is det.
  185%!  http_reply(+Data, +Out:stream, +HdrExtra, +Context, +Request, -Code) is det.
  186%
  187%   Compose  a  complete  HTTP  reply  from   the  term  Data  using
  188%   additional headers from  HdrExtra  to   the  output  stream Out.
  189%   ExtraHeader is a list of Field(Value). Data is one of:
  190%
  191%           * html(HTML)
  192%           HTML tokens as produced by html//1 from html_write.pl
  193%
  194%           * file(+MimeType, +FileName)
  195%           Reply content of FileName using MimeType
  196%
  197%           * file(+MimeType, +FileName, +Range)
  198%           Reply partial content of FileName with given MimeType
  199%
  200%           * tmp_file(+MimeType, +FileName)
  201%           Same as =file=, but do not include modification time
  202%
  203%           * bytes(+MimeType, +Bytes)
  204%           Send a sequence of Bytes with the indicated MimeType.
  205%           Bytes is either a string of character codes 0..255 or
  206%           list of integers in the range 0..255. Out-of-bound codes
  207%           result in a representation error exception.
  208%
  209%           * stream(+In, +Len)
  210%           Reply content of stream.
  211%
  212%           * cgi_stream(+In, +Len)
  213%           Reply content of stream, which should start with an
  214%           HTTP header, followed by a blank line.  This is the
  215%           typical output from a CGI script.
  216%
  217%           * Status
  218%           HTTP status report as defined by http_status_reply/4.
  219%
  220%   @param HdrExtra provides additional reply-header fields, encoded
  221%          as Name(Value). It can also contain a field
  222%          content_length(-Len) to _retrieve_ the
  223%          value of the Content-length header that is replied.
  224%   @param Code is the numeric HTTP status code sent
  225%
  226%   @tbd    Complete documentation
  227
  228http_reply(What, Out) :-
  229    http_reply(What, Out, [connection(close)], _).
  230
  231http_reply(Data, Out, HdrExtra) :-
  232    http_reply(Data, Out, HdrExtra, _Code).
  233
  234http_reply(Data, Out, HdrExtra, Code) :-
  235    http_reply(Data, Out, HdrExtra, [], Code).
  236
  237http_reply(Data, Out, HdrExtra, Context, Code) :-
  238    http_reply(Data, Out, HdrExtra, Context, [method(get)], Code).
  239
  240http_reply(Data, Out, HdrExtra, _Context, Request, Code) :-
  241    byte_count(Out, C0),
  242    memberchk(method(Method), Request),
  243    catch(http_reply_data(Data, Out, HdrExtra, Method, Code), E, true),
  244    !,
  245    (   var(E)
  246    ->  true
  247    ;   (   E = error(io_error(write,_), _)
  248        ;   E = error(socket_error(_,_), _)
  249        )
  250    ->  byte_count(Out, C1),
  251        Sent is C1 - C0,
  252        throw(error(http_write_short(Data, Sent), _))
  253    ;   E = error(timeout_error(write, _), _)
  254    ->  throw(E)
  255    ;   map_exception_to_http_status(E, Status, NewHdr, NewContext)
  256    ->  http_status_reply(Status, Out, NewHdr, NewContext, Request, Code)
  257    ;   throw(E)
  258    ).
  259http_reply(Status, Out, HdrExtra, Context, Request, Code) :-
  260    http_status_reply(Status, Out, HdrExtra, Context, Request, Code).
  261
  262:- if(\+current_predicate(map_exception_to_http_status/4)).  263map_exception_to_http_status(_E, _Status, _NewHdr, _NewContext) :-
  264    fail.
  265:- endif.  266
  267:- meta_predicate
  268    if_no_head(0, +),
  269    with_encoding(+, +, 0).  270
  271%!  http_reply_data(+Data, +Out, +HdrExtra, +Method, -Code) is semidet.
  272%
  273%   Fails if Data is not a defined   reply-data format, but a status
  274%   term. See http_reply/3 and http_status_reply/6.
  275%
  276%   @error Various I/O errors.
  277
  278http_reply_data(Data, Out, HdrExtra, Method, Code) :-
  279    http_reply_data_(Data, Out, HdrExtra, Method, Code),
  280    flush_output(Out).
  281
  282http_reply_data_(html(HTML), Out, HdrExtra, Method, Code) :-
  283    !,
  284    phrase(reply_header(html(HTML), HdrExtra, Code), Header),
  285    send_reply_header(Out, Header),
  286    if_no_head(with_encoding(Out, utf8, print_html(Out, HTML)), Method).
  287http_reply_data_(file(Type, File), Out, HdrExtra, Method, Code) :-
  288    !,
  289    phrase(reply_header(file(Type, File), HdrExtra, Code), Header),
  290    reply_file(Out, File, Header, Method).
  291http_reply_data_(gzip_file(Type, File), Out, HdrExtra, Method, Code) :-
  292    !,
  293    phrase(reply_header(gzip_file(Type, File), HdrExtra, Code), Header),
  294    reply_file(Out, File, Header, Method).
  295http_reply_data_(file(Type, File, Range), Out, HdrExtra, Method, Code) :-
  296    !,
  297    phrase(reply_header(file(Type, File, Range), HdrExtra, Code), Header),
  298    reply_file_range(Out, File, Header, Range, Method).
  299http_reply_data_(tmp_file(Type, File), Out, HdrExtra, Method, Code) :-
  300    !,
  301    phrase(reply_header(tmp_file(Type, File), HdrExtra, Code), Header),
  302    reply_file(Out, File, Header, Method).
  303http_reply_data_(bytes(Type, Bytes), Out, HdrExtra, Method, Code) :-
  304    !,
  305    phrase(reply_header(bytes(Type, Bytes), HdrExtra, Code), Header),
  306    send_reply_header(Out, Header),
  307    if_no_head(format(Out, '~s', [Bytes]), Method).
  308http_reply_data_(stream(In, Len), Out, HdrExtra, Method, Code) :-
  309    !,
  310    phrase(reply_header(cgi_data(Len), HdrExtra, Code), Header),
  311    copy_stream(Out, In, Header, Method, 0, end).
  312http_reply_data_(cgi_stream(In, Len), Out, HdrExtra, Method, Code) :-
  313    !,
  314    http_read_header(In, CgiHeader),
  315    seek(In, 0, current, Pos),
  316    Size is Len - Pos,
  317    http_join_headers(HdrExtra, CgiHeader, Hdr2),
  318    phrase(reply_header(cgi_data(Size), Hdr2, Code), Header),
  319    copy_stream(Out, In, Header, Method, 0, end).
  320
  321if_no_head(_, head) :-
  322    !.
  323if_no_head(Goal, _) :-
  324    call(Goal).
  325
  326with_encoding(Out, Encoding, Goal) :-
  327    stream_property(Out, encoding(Old)),
  328    (   Old == Encoding
  329    ->  call(Goal)
  330    ;   setup_call_cleanup(
  331            set_stream(Out, encoding(Encoding)),
  332            call(Goal),
  333            set_stream(Out, encoding(Old)))
  334    ).
  335
  336reply_file(Out, _File, Header, head) :-
  337    !,
  338    send_reply_header(Out, Header).
  339reply_file(Out, File, Header, _) :-
  340    setup_call_cleanup(
  341        open(File, read, In, [type(binary)]),
  342        copy_stream(Out, In, Header, 0, end),
  343        close(In)).
  344
  345reply_file_range(Out, _File, Header, _Range, head) :-
  346    !,
  347    send_reply_header(Out, Header).
  348reply_file_range(Out, File, Header, bytes(From, To), _) :-
  349    setup_call_cleanup(
  350        open(File, read, In, [type(binary)]),
  351        copy_stream(Out, In, Header, From, To),
  352        close(In)).
  353
  354copy_stream(Out, _, Header, head, _, _) :-
  355    !,
  356    send_reply_header(Out, Header).
  357copy_stream(Out, In, Header, _, From, To) :-
  358    copy_stream(Out, In, Header, From, To).
  359
  360copy_stream(Out, In, Header, From, To) :-
  361    (   From == 0
  362    ->  true
  363    ;   seek(In, From, bof, _)
  364    ),
  365    peek_byte(In, _),
  366    send_reply_header(Out, Header),
  367    (   To == end
  368    ->  copy_stream_data(In, Out)
  369    ;   Len is To - From,
  370        copy_stream_data(In, Out, Len)
  371    ).
  372
  373
  374%!  http_status_reply(+Status, +Out, +HdrExtra, -Code) is det.
  375%!  http_status_reply(+Status, +Out, +HdrExtra, +Context, -Code) is det.
  376%!  http_status_reply(+Status, +Out, +HdrExtra, +Context, +Request, -Code) is det.
  377%
  378%   Emit HTML non-200 status reports. Such  requests are always sent
  379%   as UTF-8 documents.
  380%
  381%   Status can be one of the following:
  382%      - authorise(Method)
  383%        Challenge authorization.  Method is one of
  384%        - basic(Realm)
  385%        - digest(Digest)
  386%      - authorise(basic,Realm)
  387%        Same as authorise(basic(Realm)).  Deprecated.
  388%      - bad_request(ErrorTerm)
  389%      - busy
  390%      - created(Location)
  391%      - forbidden(Url)
  392%      - moved(To)
  393%      - moved_temporary(To)
  394%      - no_content
  395%      - not_acceptable(WhyHtml)
  396%      - not_found(Path)
  397%      - method_not_allowed(Method, Path)
  398%      - not_modified
  399%      - resource_error(ErrorTerm)
  400%      - see_other(To)
  401%      - switching_protocols(Goal,Options)
  402%      - server_error(ErrorTerm)
  403%      - unavailable(WhyHtml)
  404
  405http_status_reply(Status, Out, Options) :-
  406    _{header:HdrExtra, context:Context, code:Code, method:Method} :< Options,
  407    http_status_reply(Status, Out, HdrExtra, Context, [method(Method)], Code).
  408
  409http_status_reply(Status, Out, HdrExtra, Code) :-
  410    http_status_reply(Status, Out, HdrExtra, [], Code).
  411
  412http_status_reply(Status, Out, HdrExtra, Context, Code) :-
  413    http_status_reply(Status, Out, HdrExtra, Context, [method(get)], Code).
  414
  415http_status_reply(Status, Out, HdrExtra, Context, Request, Code) :-
  416    option(method(Method), Request, get),
  417    parsed_accept(Request, Accept),
  418    status_reply_flush(Status, Out,
  419                       _{ context: Context,
  420                          method:  Method,
  421                          code:    Code,
  422                          accept:  Accept,
  423                          header:  HdrExtra
  424                        }).
  425
  426parsed_accept(Request, Accept) :-
  427    memberchk(accept(Accept0), Request),
  428    http_parse_header_value(accept, Accept0, Accept1),
  429    !,
  430    Accept = Accept1.
  431parsed_accept(_, [ media(text/html, [], 0.1,  []),
  432                   media(_,         [], 0.01, [])
  433                 ]).
  434
  435status_reply_flush(Status, Out, Options) :-
  436    status_reply(Status, Out, Options),
  437    !,
  438    flush_output(Out).
  439
  440%!  status_reply(+Status, +Out, +Options:dict)
  441%
  442%   Formulate a non-200 reply and send it to the stream Out.  Options
  443%   is a dict containing:
  444%
  445%     - header
  446%     - context
  447%     - method
  448%     - code
  449%     - accept
  450
  451% Replies without content
  452status_reply(no_content, Out, Options) :-
  453    !,
  454    phrase(reply_header(status(no_content), Options), Header),
  455    send_reply_header(Out, Header).
  456status_reply(switching_protocols(_Goal,SwitchOptions), Out, Options) :-
  457    !,
  458    (   option(headers(Extra1), SwitchOptions)
  459    ->  true
  460    ;   option(header(Extra1), SwitchOptions, [])
  461    ),
  462    http_join_headers(Options.header, Extra1, HdrExtra),
  463    phrase(reply_header(status(switching_protocols),
  464                        Options.put(header,HdrExtra)), Header),
  465    send_reply_header(Out, Header).
  466status_reply(authorise(basic, ''), Out, Options) :-
  467    !,
  468    status_reply(authorise(basic), Out, Options).
  469status_reply(authorise(basic, Realm), Out, Options) :-
  470    !,
  471    status_reply(authorise(basic(Realm)), Out, Options).
  472status_reply(not_modified, Out, Options) :-
  473    !,
  474    phrase(reply_header(status(not_modified), Options), Header),
  475    send_reply_header(Out, Header).
  476% aliases (compatibility)
  477status_reply(busy, Out, Options) :-
  478    status_reply(service_unavailable(busy), Out, Options).
  479status_reply(unavailable(Why), Out, Options) :-
  480    status_reply(service_unavailable(Why), Out, Options).
  481status_reply(resource_error(Why), Out, Options) :-
  482    status_reply(service_unavailable(Why), Out, Options).
  483% replies with content
  484status_reply(Status, Out, Options) :-
  485    status_has_content(Status),
  486    status_page_hook(Status, Reply, Options),
  487    serialize_body(Reply, Body),
  488    Status =.. List,
  489    append(List, [Body], ExList),
  490    ExStatus =.. ExList,
  491    phrase(reply_header(ExStatus, Options), Header),
  492    send_reply_header(Out, Header),
  493    reply_status_body(Out, Body, Options).
  494
  495%!  status_has_content(+StatusTerm, -HTTPCode)
  496%
  497%   True when StatusTerm  is  a  status   that  usually  comes  with  an
  498%   explanatory content message.
  499
  500status_has_content(created(_Location)).
  501status_has_content(moved(_To)).
  502status_has_content(moved_temporary(_To)).
  503status_has_content(gone(_URL)).
  504status_has_content(see_other(_To)).
  505status_has_content(bad_request(_ErrorTerm)).
  506status_has_content(authorise(_Method)).
  507status_has_content(forbidden(_URL)).
  508status_has_content(not_found(_URL)).
  509status_has_content(method_not_allowed(_Method, _URL)).
  510status_has_content(not_acceptable(_Why)).
  511status_has_content(server_error(_ErrorTerm)).
  512status_has_content(service_unavailable(_Why)).
  513
  514%!  serialize_body(+Reply, -Body) is det.
  515%
  516%   Serialize the reply as returned by status_page_hook/3 into a term:
  517%
  518%     - body(Type, Encoding, Content)
  519%     In this term, Type is the media type, Encoding is the
  520%     required wire encoding and Content a string representing the
  521%     content.
  522
  523serialize_body(Reply, Body) :-
  524    http:serialize_reply(Reply, Body),
  525    !.
  526serialize_body(html_tokens(Tokens), body(text/html, utf8, Content)) :-
  527    !,
  528    with_output_to(string(Content), print_html(Tokens)).
  529serialize_body(Reply, Reply) :-
  530    Reply = body(_,_,_),
  531    !.
  532serialize_body(Reply, _) :-
  533    domain_error(http_reply_body, Reply).
  534
  535reply_status_body(_, _, Options) :-
  536    Options.method == head,
  537    !.
  538reply_status_body(Out, body(_Type, Encoding, Content), _Options) :-
  539    (   Encoding == octet
  540    ->  format(Out, '~s', [Content])
  541    ;   setup_call_cleanup(
  542            set_stream(Out, encoding(Encoding)),
  543            format(Out, '~s', [Content]),
  544            set_stream(Out, encoding(octet)))
  545    ).
  546
  547%!  http:serialize_reply(+Reply, -Body) is semidet.
  548%
  549%   Multifile hook to serialize the result of http:status_reply/3
  550%   into a term
  551%
  552%     - body(Type, Encoding, Content)
  553%     In this term, Type is the media type, Encoding is the
  554%     required wire encoding and Content a string representing the
  555%     content.
  556
  557%!  status_page_hook(+Term, -Reply, +Options) is det.
  558%
  559%   Calls the following two hooks to generate an HTML page from a
  560%   status reply.
  561%
  562%     - http:status_reply(+Term, -Reply, +Options)
  563%       Provide non-HTML description of the (non-200) reply.
  564%       The term Reply is handed to serialize_body/2, calling
  565%       the hook http:serialize_reply/2.
  566%     - http:status_page(+Term, +Context, -HTML)
  567%     - http:status_page(+Code, +Context, -HTML)
  568%
  569%   @arg Term is the status term, e.g., not_found(URL)
  570%   @see http:status_page/3
  571
  572status_page_hook(Term, Reply, Options) :-
  573    Context = Options.context,
  574    functor(Term, Name, _),
  575    status_number_fact(Name, Code),
  576    (   Options.code = Code,
  577        http:status_reply(Term, Reply, Options)
  578    ;   http:status_page(Term, Context, HTML),
  579        Reply = html_tokens(HTML)
  580    ;   http:status_page(Code, Context, HTML), % deprecated
  581        Reply = html_tokens(HTML)
  582    ),
  583    !.
  584status_page_hook(created(Location), html_tokens(HTML), _Options) :-
  585    phrase(page([ title('201 Created')
  586                ],
  587                [ h1('Created'),
  588                  p(['The document was created ',
  589                     a(href(Location), ' Here')
  590                    ]),
  591                  \address
  592                ]),
  593           HTML).
  594status_page_hook(moved(To), html_tokens(HTML), _Options) :-
  595    phrase(page([ title('301 Moved Permanently')
  596                ],
  597                [ h1('Moved Permanently'),
  598                  p(['The document has moved ',
  599                     a(href(To), ' Here')
  600                    ]),
  601                  \address
  602                ]),
  603           HTML).
  604status_page_hook(moved_temporary(To), html_tokens(HTML), _Options) :-
  605    phrase(page([ title('302 Moved Temporary')
  606                ],
  607                [ h1('Moved Temporary'),
  608                  p(['The document is currently ',
  609                     a(href(To), ' Here')
  610                    ]),
  611                  \address
  612                ]),
  613           HTML).
  614status_page_hook(gone(URL), html_tokens(HTML), _Options) :-
  615    phrase(page([ title('410 Resource Gone')
  616                ],
  617                [ h1('Resource Gone'),
  618                  p(['The document has been removed ',
  619                     a(href(URL), ' from here')
  620                    ]),
  621                  \address
  622                ]),
  623           HTML).
  624status_page_hook(see_other(To), html_tokens(HTML), _Options) :-
  625    phrase(page([ title('303 See Other')
  626                 ],
  627                 [ h1('See Other'),
  628                   p(['See other document ',
  629                      a(href(To), ' Here')
  630                     ]),
  631                   \address
  632                 ]),
  633            HTML).
  634status_page_hook(bad_request(ErrorTerm), html_tokens(HTML), _Options) :-
  635    '$messages':translate_message(ErrorTerm, Lines, []),
  636    phrase(page([ title('400 Bad Request')
  637                ],
  638                [ h1('Bad Request'),
  639                  p(\html_message_lines(Lines)),
  640                  \address
  641                ]),
  642           HTML).
  643status_page_hook(authorise(_Method), html_tokens(HTML), _Options):-
  644    phrase(page([ title('401 Authorization Required')
  645                ],
  646                [ h1('Authorization Required'),
  647                  p(['This server could not verify that you ',
  648                     'are authorized to access the document ',
  649                     'requested.  Either you supplied the wrong ',
  650                     'credentials (e.g., bad password), or your ',
  651                     'browser doesn\'t understand how to supply ',
  652                     'the credentials required.'
  653                    ]),
  654                  \address
  655                ]),
  656           HTML).
  657status_page_hook(forbidden(URL), html_tokens(HTML), _Options) :-
  658    phrase(page([ title('403 Forbidden')
  659                ],
  660                [ h1('Forbidden'),
  661                  p(['You don\'t have permission to access ', URL,
  662                     ' on this server'
  663                    ]),
  664                  \address
  665                ]),
  666           HTML).
  667status_page_hook(not_found(URL), html_tokens(HTML), _Options) :-
  668    phrase(page([ title('404 Not Found')
  669                ],
  670                [ h1('Not Found'),
  671                  p(['The requested URL ', tt(URL),
  672                     ' was not found on this server'
  673                    ]),
  674                  \address
  675                ]),
  676           HTML).
  677status_page_hook(method_not_allowed(Method,URL), html_tokens(HTML), _Options) :-
  678    upcase_atom(Method, UMethod),
  679    phrase(page([ title('405 Method not allowed')
  680                ],
  681                [ h1('Method not allowed'),
  682                  p(['The requested URL ', tt(URL),
  683                     ' does not support method ', tt(UMethod), '.'
  684                    ]),
  685                  \address
  686                ]),
  687           HTML).
  688status_page_hook(not_acceptable(WhyHTML), html_tokens(HTML), _Options) :-
  689    phrase(page([ title('406 Not Acceptable')
  690                ],
  691                [ h1('Not Acceptable'),
  692                  WhyHTML,
  693                  \address
  694                ]),
  695           HTML).
  696status_page_hook(server_error(ErrorTerm), html_tokens(HTML), _Options) :-
  697    '$messages':translate_message(ErrorTerm, Lines, []),
  698    phrase(page([ title('500 Internal server error')
  699                ],
  700                [ h1('Internal server error'),
  701                  p(\html_message_lines(Lines)),
  702                  \address
  703                ]),
  704           HTML).
  705status_page_hook(service_unavailable(Why), html_tokens(HTML), _Options) :-
  706    phrase(page([ title('503 Service Unavailable')
  707                ],
  708                [ h1('Service Unavailable'),
  709                  \unavailable(Why),
  710                  \address
  711                ]),
  712           HTML).
  713
  714unavailable(busy) -->
  715    html(p(['The server is temporarily out of resources, ',
  716            'please try again later'])).
  717unavailable(error(Formal,Context)) -->
  718    { '$messages':translate_message(error(Formal,Context), Lines, []) },
  719    html_message_lines(Lines).
  720unavailable(HTML) -->
  721    html(HTML).
  722
  723html_message_lines([]) -->
  724    [].
  725html_message_lines([nl|T]) -->
  726    !,
  727    html([br([])]),
  728    html_message_lines(T).
  729html_message_lines([flush]) -->
  730    [].
  731html_message_lines([ansi(_Style,Fmt,Args)|T]) -->
  732    !,
  733    { format(string(S), Fmt, Args)
  734    },
  735    html([S]),
  736    html_message_lines(T).
  737html_message_lines([url(Pos)|T]) -->
  738    !,
  739    msg_url(Pos),
  740    html_message_lines(T).
  741html_message_lines([url(URL, Label)|T]) -->
  742    !,
  743    html(a(href(URL), Label)),
  744    html_message_lines(T).
  745html_message_lines([Fmt-Args|T]) -->
  746    !,
  747    { format(string(S), Fmt, Args)
  748    },
  749    html([S]),
  750    html_message_lines(T).
  751html_message_lines([Fmt|T]) -->
  752    !,
  753    { format(string(S), Fmt, [])
  754    },
  755    html([S]),
  756    html_message_lines(T).
  757
  758msg_url(File:Line:Pos) -->
  759    !,
  760    html([File, :, Line, :, Pos]).
  761msg_url(File:Line) -->
  762    !,
  763    html([File, :, Line]).
  764msg_url(File) -->
  765    html([File]).
  766
  767%!  http_join_headers(+Default, +Header, -Out)
  768%
  769%   Append headers from Default to Header if they are not
  770%   already part of it.
  771
  772http_join_headers([], H, H).
  773http_join_headers([H|T], Hdr0, Hdr) :-
  774    functor(H, N, A),
  775    functor(H2, N, A),
  776    member(H2, Hdr0),
  777    !,
  778    http_join_headers(T, Hdr0, Hdr).
  779http_join_headers([H|T], Hdr0, [H|Hdr]) :-
  780    http_join_headers(T, Hdr0, Hdr).
  781
  782
  783%!  http_update_encoding(+HeaderIn, -Encoding, -HeaderOut)
  784%
  785%   Allow for rewrite of the  header,   adjusting  the  encoding. We
  786%   distinguish three options. If  the   user  announces  `text', we
  787%   always use UTF-8 encoding. If   the user announces charset=utf-8
  788%   we  use  UTF-8  and  otherwise  we  use  octet  (raw)  encoding.
  789%   Alternatively we could dynamically choose for ASCII, ISO-Latin-1
  790%   or UTF-8.
  791
  792http_update_encoding(Header0, Encoding, Header) :-
  793    memberchk(content_type(Type), Header0),
  794    !,
  795    http_update_encoding(Type, Header0, Encoding, Header).
  796http_update_encoding(Header, octet, Header).
  797
  798http_update_encoding('text/event-stream', Header, utf8, Header) :-
  799    !.
  800http_update_encoding(Type0, Header0, utf8, [content_type(Type)|Header]) :-
  801    sub_atom(Type0, 0, _, _, 'text/'),
  802    !,
  803    select(content_type(_), Header0, Header),
  804    !,
  805    (   sub_atom(Type0, S, _, _, ';')
  806    ->  sub_atom(Type0, 0, S, _, B)
  807    ;   B = Type0
  808    ),
  809    atom_concat(B, '; charset=UTF-8', Type).
  810http_update_encoding(Type, Header, Encoding, Header) :-
  811    (   sub_atom_icasechk(Type, _, 'utf-8')
  812    ->  Encoding = utf8
  813    ;   http:mime_type_encoding(Type, Encoding)
  814    ->  true
  815    ;   mime_type_encoding(Type, Encoding)
  816    ->  true
  817    ;   Encoding = octet
  818    ).
  819
  820%!  mime_type_encoding(+MimeType, -Encoding) is semidet.
  821%
  822%   Encoding is the (default) character encoding for MimeType. Hooked by
  823%   http:mime_type_encoding/2.
  824
  825mime_type_encoding('application/json',                utf8).
  826mime_type_encoding('application/jsonrequest',         utf8).
  827mime_type_encoding('application/x-prolog',            utf8).
  828mime_type_encoding('application/n-quads',             utf8).
  829mime_type_encoding('application/n-triples',           utf8).
  830mime_type_encoding('application/sparql-query',        utf8).
  831mime_type_encoding('application/trig',                utf8).
  832mime_type_encoding('application/sparql-results+json', utf8).
  833mime_type_encoding('application/sparql-results+xml',  utf8).
  834
  835%!  http:mime_type_encoding(+MimeType, -Encoding) is semidet.
  836%
  837%   Encoding is the (default) character encoding   for MimeType. This is
  838%   used for setting the encoding for HTTP  replies after the user calls
  839%   format('Content-type: <MIME type>~n'). This hook   is  called before
  840%   mime_type_encoding/2. This default  defines  `utf8`   for  JSON  and
  841%   Turtle derived =|application/|= MIME types.
  842
  843
  844%!  http_update_connection(+CGIHeader, +Request, -Connection, -Header)
  845%
  846%   Merge keep-alive information from  Request   and  CGIHeader into
  847%   Header.
  848
  849http_update_connection(CgiHeader, Request, Connect,
  850                       [connection(Connect)|Rest]) :-
  851    select(connection(CgiConn), CgiHeader, Rest),
  852    !,
  853    connection(Request, ReqConnection),
  854    join_connection(ReqConnection, CgiConn, Connect).
  855http_update_connection(CgiHeader, Request, Connect,
  856                       [connection(Connect)|CgiHeader]) :-
  857    connection(Request, Connect).
  858
  859join_connection(Keep1, Keep2, Connection) :-
  860    (   downcase_atom(Keep1, 'keep-alive'),
  861        downcase_atom(Keep2, 'keep-alive')
  862    ->  Connection = 'Keep-Alive'
  863    ;   Connection = close
  864    ).
  865
  866
  867%!  connection(+Header, -Connection)
  868%
  869%   Extract the desired connection from a header.
  870
  871connection(Header, Close) :-
  872    (   memberchk(connection(Connection), Header)
  873    ->  Close = Connection
  874    ;   memberchk(http_version(1-X), Header),
  875        X >= 1
  876    ->  Close = 'Keep-Alive'
  877    ;   Close = close
  878    ).
  879
  880
  881%!  http_update_transfer(+Request, +CGIHeader, -Transfer, -Header)
  882%
  883%   Decide on the transfer encoding  from   the  Request and the CGI
  884%   header.    The    behaviour    depends      on    the    setting
  885%   http:chunked_transfer. If =never=, even   explicit  requests are
  886%   ignored. If =on_request=, chunked encoding  is used if requested
  887%   through  the  CGI  header  and  allowed    by   the  client.  If
  888%   =if_possible=, chunked encoding is  used   whenever  the  client
  889%   allows for it, which is  interpreted   as  the client supporting
  890%   HTTP 1.1 or higher.
  891%
  892%   Chunked encoding is more space efficient   and allows the client
  893%   to start processing partial results. The drawback is that errors
  894%   lead to incomplete pages instead of  a nicely formatted complete
  895%   page.
  896
  897http_update_transfer(Request, CgiHeader, Transfer, Header) :-
  898    setting(http:chunked_transfer, When),
  899    http_update_transfer(When, Request, CgiHeader, Transfer, Header).
  900
  901http_update_transfer(never, _, CgiHeader, none, Header) :-
  902    !,
  903    delete(CgiHeader, transfer_encoding(_), Header).
  904http_update_transfer(_, _, CgiHeader, none, Header) :-
  905    memberchk(location(_), CgiHeader),
  906    !,
  907    delete(CgiHeader, transfer_encoding(_), Header).
  908http_update_transfer(_, Request, CgiHeader, Transfer, Header) :-
  909    select(transfer_encoding(CgiTransfer), CgiHeader, Rest),
  910    !,
  911    transfer(Request, ReqConnection),
  912    join_transfer(ReqConnection, CgiTransfer, Transfer),
  913    (   Transfer == none
  914    ->  Header = Rest
  915    ;   Header = [transfer_encoding(Transfer)|Rest]
  916    ).
  917http_update_transfer(if_possible, Request, CgiHeader, Transfer, Header) :-
  918    transfer(Request, Transfer),
  919    Transfer \== none,
  920    !,
  921    Header = [transfer_encoding(Transfer)|CgiHeader].
  922http_update_transfer(_, _, CgiHeader, event_stream, CgiHeader) :-
  923    memberchk(content_type('text/event-stream'), CgiHeader),
  924    !.
  925http_update_transfer(_, _, CgiHeader, none, CgiHeader).
  926
  927join_transfer(chunked, chunked, chunked) :- !.
  928join_transfer(_, _, none).
  929
  930
  931%!  transfer(+Header, -Connection)
  932%
  933%   Extract the desired connection from a header.
  934
  935transfer(Header, Transfer) :-
  936    (   memberchk(transfer_encoding(Transfer0), Header)
  937    ->  Transfer = Transfer0
  938    ;   memberchk(http_version(1-X), Header),
  939        X >= 1
  940    ->  Transfer = chunked
  941    ;   Transfer = none
  942    ).
  943
  944
  945%!  content_length_in_encoding(+Encoding, +In, -Bytes)
  946%
  947%   Determine how many bytes are required to represent the data from
  948%   stream In using the given encoding.  Fails if the data cannot be
  949%   represented with the given encoding.
  950
  951content_length_in_encoding(Enc, Stream, Bytes) :-
  952    stream_property(Stream, position(Here)),
  953    setup_call_cleanup(
  954        open_null_stream(Out),
  955        ( set_stream(Out, encoding(Enc)),
  956          catch(copy_stream_data(Stream, Out), _, fail),
  957          flush_output(Out),
  958          byte_count(Out, Bytes)
  959        ),
  960        ( close(Out, [force(true)]),
  961          set_stream_position(Stream, Here)
  962        )).
  963
  964
  965                 /*******************************
  966                 *          POST SUPPORT        *
  967                 *******************************/
  968
  969%!  http_post_data(+Data, +Out:stream, +HdrExtra) is det.
  970%
  971%   Send data on behalf on an HTTP   POST request. This predicate is
  972%   normally called by http_post/4 from   http_client.pl to send the
  973%   POST data to the server.  Data is one of:
  974%
  975%     * html(+Tokens)
  976%     Result of html//1 from html_write.pl
  977%
  978%     * json(+Term)
  979%     Posting a JSON query and processing the JSON reply (or any other
  980%     reply understood by http_read_data/3) is simple as
  981%     =|http_post(URL, json(Term), Reply, [])|=, where Term is a JSON
  982%     term as described in json.pl and reply is of the same format if
  983%     the server replies with JSON, when using module =|:-
  984%     use_module(library(http/http_json))|=. Note that the module is
  985%     used in both http server and http client, see
  986%     library(http/http_json).
  987%
  988%     * xml(+Term)
  989%     Post the result of xml_write/3 using the Mime-type
  990%     =|text/xml|=
  991%
  992%     * xml(+Type, +Term)
  993%     Post the result of xml_write/3 using the given Mime-type
  994%     and an empty option list to xml_write/3.
  995%
  996%     * xml(+Type, +Term, +Options)
  997%     Post the result of xml_write/3 using the given Mime-type
  998%     and option list for xml_write/3.
  999%
 1000%     * file(+File)
 1001%     Send contents of a file. Mime-type is determined by
 1002%     file_mime_type/2.
 1003%
 1004%     * file(+Type, +File)
 1005%     Send file with content of indicated mime-type.
 1006%
 1007%     * memory_file(+Type, +Handle)
 1008%     Similar to file(+Type, +File), but using a memory file
 1009%     instead of a real file.  See new_memory_file/1.
 1010%
 1011%     * codes(+Codes)
 1012%     As codes(text/plain, Codes).
 1013%
 1014%     * codes(+Type, +Codes)
 1015%     Send Codes using the indicated MIME-type.
 1016%
 1017%     * bytes(+Type, +Bytes)
 1018%     Send Bytes using the indicated MIME-type.  Bytes is either a
 1019%     string of character codes 0..255 or list of integers in the
 1020%     range 0..255.  Out-of-bound codes result in a representation
 1021%     error exception.
 1022%
 1023%     * atom(+Atom)
 1024%     As atom(text/plain, Atom).
 1025%
 1026%     * atom(+Type, +Atom)
 1027%     Send Atom using the indicated MIME-type.
 1028%
 1029%     * string(+String)
 1030%     * string(+Type, +String)
 1031%     Similar to atom(Atom) and atom(Type,Atom), accepting a SWI-Prolog
 1032%     string.
 1033%
 1034%     * cgi_stream(+Stream, +Len) Read the input from Stream which,
 1035%     like CGI data starts with a partial HTTP header. The fields of
 1036%     this header are merged with the provided HdrExtra fields. The
 1037%     first Len characters of Stream are used.
 1038%
 1039%     * form(+ListOfParameter)
 1040%     Send data of the MIME type application/x-www-form-urlencoded as
 1041%     produced by browsers issuing a POST request from an HTML form.
 1042%     ListOfParameter is a list of Name=Value or Name(Value).
 1043%
 1044%     * form_data(+ListOfData)
 1045%     Send data of the MIME type =|multipart/form-data|= as produced
 1046%     by browsers issuing a POST request from an HTML form using
 1047%     enctype =|multipart/form-data|=. ListOfData is the same as for
 1048%     the List alternative described below. Below is an example.
 1049%     Repository, etc. are atoms providing the value, while the last
 1050%     argument provides a value from a file.
 1051%
 1052%       ==
 1053%       ...,
 1054%       http_post([ protocol(http),
 1055%                   host(Host),
 1056%                   port(Port),
 1057%                   path(ActionPath)
 1058%                 ],
 1059%                 form_data([ repository = Repository,
 1060%                             dataFormat = DataFormat,
 1061%                             baseURI    = BaseURI,
 1062%                             verifyData = Verify,
 1063%                             data       = file(File)
 1064%                           ]),
 1065%                 _Reply,
 1066%                 []),
 1067%       ...,
 1068%       ==
 1069%
 1070%     * List
 1071%     If the argument is a plain list, it is sent using the MIME type
 1072%     multipart/mixed and packed using mime_pack/3. See mime_pack/3
 1073%     for details on the argument format.
 1074
 1075http_post_data(Data, Out, HdrExtra),
 1076    http:post_data_hook(Data, Out, HdrExtra) =>
 1077    true.
 1078http_post_data(html(HTML), Out, HdrExtra) =>
 1079    phrase(post_header(html(HTML), HdrExtra), Header),
 1080    send_request_header(Out, Header),
 1081    print_html(Out, HTML).
 1082http_post_data(xml(XML), Out, HdrExtra) =>
 1083    http_post_data(xml(text/xml, XML, []), Out, HdrExtra).
 1084http_post_data(xml(Type, XML), Out, HdrExtra) =>
 1085    http_post_data(xml(Type, XML, []), Out, HdrExtra).
 1086http_post_data(xml(Type, XML, Options), Out, HdrExtra) =>
 1087    setup_call_cleanup(
 1088        new_memory_file(MemFile),
 1089        (   setup_call_cleanup(
 1090                open_memory_file(MemFile, write, MemOut),
 1091                xml_write(MemOut, XML, Options),
 1092                close(MemOut)),
 1093            http_post_data(memory_file(Type, MemFile), Out, HdrExtra)
 1094        ),
 1095        free_memory_file(MemFile)).
 1096http_post_data(file(File), Out, HdrExtra) =>
 1097    (   file_mime_type(File, Type)
 1098    ->  true
 1099    ;   Type = text/plain
 1100    ),
 1101    http_post_data(file(Type, File), Out, HdrExtra).
 1102http_post_data(file(Type, File), Out, HdrExtra) =>
 1103    phrase(post_header(file(Type, File), HdrExtra), Header),
 1104    send_request_header(Out, Header),
 1105    setup_call_cleanup(
 1106        open(File, read, In, [type(binary)]),
 1107        copy_stream_data(In, Out),
 1108        close(In)).
 1109http_post_data(memory_file(Type, Handle), Out, HdrExtra) =>
 1110    phrase(post_header(memory_file(Type, Handle), HdrExtra), Header),
 1111    send_request_header(Out, Header),
 1112    setup_call_cleanup(
 1113        open_memory_file(Handle, read, In, [encoding(octet)]),
 1114        copy_stream_data(In, Out),
 1115        close(In)).
 1116http_post_data(codes(Codes), Out, HdrExtra) =>
 1117    http_post_data(codes(text/plain, Codes), Out, HdrExtra).
 1118http_post_data(codes(Type, Codes), Out, HdrExtra) =>
 1119    phrase(post_header(codes(Type, Codes), HdrExtra), Header),
 1120    send_request_header(Out, Header),
 1121    setup_call_cleanup(
 1122        set_stream(Out, encoding(utf8)),
 1123        format(Out, '~s', [Codes]),
 1124        set_stream(Out, encoding(octet))).
 1125http_post_data(bytes(Type, Bytes), Out, HdrExtra) =>
 1126    phrase(post_header(bytes(Type, Bytes), HdrExtra), Header),
 1127    send_request_header(Out, Header),
 1128    format(Out, '~s', [Bytes]).
 1129http_post_data(atom(Atom), Out, HdrExtra) =>
 1130    http_post_data(atom(text/plain, Atom), Out, HdrExtra).
 1131http_post_data(atom(Type, Atom), Out, HdrExtra) =>
 1132    phrase(post_header(atom(Type, Atom), HdrExtra), Header),
 1133    send_request_header(Out, Header),
 1134    setup_call_cleanup(
 1135        set_stream(Out, encoding(utf8)),
 1136        write(Out, Atom),
 1137        set_stream(Out, encoding(octet))).
 1138http_post_data(string(String), Out, HdrExtra) =>
 1139    http_post_data(atom(text/plain, String), Out, HdrExtra).
 1140http_post_data(string(Type, String), Out, HdrExtra) =>
 1141    phrase(post_header(string(Type, String), HdrExtra), Header),
 1142    send_request_header(Out, Header),
 1143    setup_call_cleanup(
 1144        set_stream(Out, encoding(utf8)),
 1145        write(Out, String),
 1146        set_stream(Out, encoding(octet))).
 1147http_post_data(cgi_stream(In, _Len), Out, HdrExtra) =>
 1148    debug(obsolete, 'Obsolete 2nd argument in cgi_stream(In,Len)', []),
 1149    http_post_data(cgi_stream(In), Out, HdrExtra).
 1150http_post_data(cgi_stream(In), Out, HdrExtra) =>
 1151    http_read_header(In, Header0),
 1152    http_update_encoding(Header0, Encoding, Header),
 1153    content_length_in_encoding(Encoding, In, Size),
 1154    http_join_headers(HdrExtra, Header, Hdr2),
 1155    phrase(post_header(cgi_data(Size), Hdr2), HeaderText),
 1156    send_request_header(Out, HeaderText),
 1157    setup_call_cleanup(
 1158        set_stream(Out, encoding(Encoding)),
 1159        copy_stream_data(In, Out),
 1160        set_stream(Out, encoding(octet))).
 1161http_post_data(form(Fields), Out, HdrExtra) =>
 1162    parse_url_search(Codes, Fields),
 1163    length(Codes, Size),
 1164    http_join_headers(HdrExtra,
 1165                      [ content_type('application/x-www-form-urlencoded')
 1166                      ], Header),
 1167    phrase(post_header(cgi_data(Size), Header), HeaderChars),
 1168    send_request_header(Out, HeaderChars),
 1169    format(Out, '~s', [Codes]).
 1170http_post_data(form_data(Data), Out, HdrExtra) =>
 1171    setup_call_cleanup(
 1172        new_memory_file(MemFile),
 1173        ( setup_call_cleanup(
 1174              open_memory_file(MemFile, write, MimeOut),
 1175              mime_pack(Data, MimeOut, Boundary),
 1176              close(MimeOut)),
 1177          size_memory_file(MemFile, Size, octet),
 1178          format(string(ContentType),
 1179                 'multipart/form-data; boundary=~w', [Boundary]),
 1180          http_join_headers(HdrExtra,
 1181                            [ mime_version('1.0'),
 1182                              content_type(ContentType)
 1183                            ], Header),
 1184          phrase(post_header(cgi_data(Size), Header), HeaderChars),
 1185          send_request_header(Out, HeaderChars),
 1186          setup_call_cleanup(
 1187              open_memory_file(MemFile, read, In, [encoding(octet)]),
 1188              copy_stream_data(In, Out),
 1189              close(In))
 1190        ),
 1191        free_memory_file(MemFile)).
 1192http_post_data(List, Out, HdrExtra), is_list(List) => % multipart-mixed
 1193    setup_call_cleanup(
 1194        new_memory_file(MemFile),
 1195        ( setup_call_cleanup(
 1196              open_memory_file(MemFile, write, MimeOut),
 1197              mime_pack(List, MimeOut, Boundary),
 1198              close(MimeOut)),
 1199          size_memory_file(MemFile, Size, octet),
 1200          format(string(ContentType),
 1201                 'multipart/mixed; boundary=~w', [Boundary]),
 1202          http_join_headers(HdrExtra,
 1203                            [ mime_version('1.0'),
 1204                              content_type(ContentType)
 1205                            ], Header),
 1206          phrase(post_header(cgi_data(Size), Header), HeaderChars),
 1207          send_request_header(Out, HeaderChars),
 1208          setup_call_cleanup(
 1209              open_memory_file(MemFile, read, In, [encoding(octet)]),
 1210              copy_stream_data(In, Out),
 1211              close(In))
 1212        ),
 1213        free_memory_file(MemFile)).
 1214
 1215%!  post_header(+Data, +HeaderExtra)//
 1216%
 1217%   Generate the POST header, emitting HeaderExtra, followed by the
 1218%   HTTP Content-length and Content-type fields.
 1219
 1220post_header(html(Tokens), HdrExtra) -->
 1221    header_fields(HdrExtra, Len),
 1222    content_length(html(Tokens), Len),
 1223    content_type(text/html),
 1224    "\r\n".
 1225post_header(file(Type, File), HdrExtra) -->
 1226    header_fields(HdrExtra, Len),
 1227    content_length(file(File), Len),
 1228    content_type(Type),
 1229    "\r\n".
 1230post_header(memory_file(Type, File), HdrExtra) -->
 1231    header_fields(HdrExtra, Len),
 1232    content_length(memory_file(File), Len),
 1233    content_type(Type),
 1234    "\r\n".
 1235post_header(cgi_data(Size), HdrExtra) -->
 1236    header_fields(HdrExtra, Len),
 1237    content_length(Size, Len),
 1238    "\r\n".
 1239post_header(codes(Type, Codes), HdrExtra) -->
 1240    header_fields(HdrExtra, Len),
 1241    content_length(codes(Codes, utf8), Len),
 1242    content_type(Type, utf8),
 1243    "\r\n".
 1244post_header(bytes(Type, Bytes), HdrExtra) -->
 1245    header_fields(HdrExtra, Len),
 1246    content_length(bytes(Bytes), Len),
 1247    content_type(Type),
 1248    "\r\n".
 1249post_header(atom(Type, Atom), HdrExtra) -->
 1250    header_fields(HdrExtra, Len),
 1251    content_length(atom(Atom, utf8), Len),
 1252    content_type(Type, utf8),
 1253    "\r\n".
 1254post_header(string(Type, String), HdrExtra) -->
 1255    header_fields(HdrExtra, Len),
 1256    content_length(string(String, utf8), Len),
 1257    content_type(Type, utf8),
 1258    "\r\n".
 1259
 1260
 1261                 /*******************************
 1262                 *       OUTPUT HEADER DCG      *
 1263                 *******************************/
 1264
 1265%!  http_reply_header(+Out:stream, +What, +HdrExtra) is det.
 1266%
 1267%   Create a reply header  using  reply_header//3   and  send  it to
 1268%   Stream.
 1269
 1270http_reply_header(Out, What, HdrExtra) :-
 1271    phrase(reply_header(What, HdrExtra, _Code), String),
 1272    !,
 1273    send_reply_header(Out, String).
 1274
 1275%!  reply_header(+Data, +HdrExtra, -Code)// is det.
 1276%
 1277%   Grammar that realises the HTTP handler for sending Data. Data is
 1278%   a  real  data  object  as  described   with  http_reply/2  or  a
 1279%   not-200-ok HTTP status reply. The   following status replies are
 1280%   defined.
 1281%
 1282%     * created(+URL, +HTMLTokens)
 1283%     * moved(+URL, +HTMLTokens)
 1284%     * moved_temporary(+URL, +HTMLTokens)
 1285%     * see_other(+URL, +HTMLTokens)
 1286%     * status(+Status)
 1287%     * status(+Status, +HTMLTokens)
 1288%     * authorise(+Method, +Realm, +Tokens)
 1289%     * authorise(+Method, +Tokens)
 1290%     * not_found(+URL, +HTMLTokens)
 1291%     * server_error(+Error, +Tokens)
 1292%     * resource_error(+Error, +Tokens)
 1293%     * service_unavailable(+Why, +Tokens)
 1294%
 1295%   @see http_status_reply/4 formulates the not-200-ok HTTP replies.
 1296
 1297reply_header(Data, Dict) -->
 1298    { _{header:HdrExtra, code:Code} :< Dict },
 1299    reply_header(Data, HdrExtra, Code).
 1300
 1301reply_header(string(String), HdrExtra, Code) -->
 1302    reply_header(string(text/plain, String), HdrExtra, Code).
 1303reply_header(string(Type, String), HdrExtra, Code) -->
 1304    vstatus(ok, Code, HdrExtra),
 1305    date(now),
 1306    header_fields(HdrExtra, CLen),
 1307    content_length(codes(String, utf8), CLen),
 1308    content_type(Type, utf8),
 1309    "\r\n".
 1310reply_header(bytes(Type, Bytes), HdrExtra, Code) -->
 1311    vstatus(ok, Code, HdrExtra),
 1312    date(now),
 1313    header_fields(HdrExtra, CLen),
 1314    content_length(bytes(Bytes), CLen),
 1315    content_type(Type),
 1316    "\r\n".
 1317reply_header(html(Tokens), HdrExtra, Code) -->
 1318    vstatus(ok, Code, HdrExtra),
 1319    date(now),
 1320    header_fields(HdrExtra, CLen),
 1321    content_length(html(Tokens, utf8), CLen),
 1322    content_type(text/html, utf8),
 1323    "\r\n".
 1324reply_header(file(Type, File), HdrExtra, Code) -->
 1325    vstatus(ok, Code, HdrExtra),
 1326    date(now),
 1327    modified(file(File)),
 1328    header_fields(HdrExtra, CLen),
 1329    content_length(file(File), CLen),
 1330    content_type(Type),
 1331    "\r\n".
 1332reply_header(gzip_file(Type, File), HdrExtra, Code) -->
 1333    vstatus(ok, Code, HdrExtra),
 1334    date(now),
 1335    modified(file(File)),
 1336    header_fields(HdrExtra, CLen),
 1337    content_length(file(File), CLen),
 1338    content_type(Type),
 1339    content_encoding(gzip),
 1340    "\r\n".
 1341reply_header(file(Type, File, Range), HdrExtra, Code) -->
 1342    vstatus(partial_content, Code, HdrExtra),
 1343    date(now),
 1344    modified(file(File)),
 1345    header_fields(HdrExtra, CLen),
 1346    content_length(file(File, Range), CLen),
 1347    content_type(Type),
 1348    "\r\n".
 1349reply_header(tmp_file(Type, File), HdrExtra, Code) -->
 1350    vstatus(ok, Code, HdrExtra),
 1351    date(now),
 1352    header_fields(HdrExtra, CLen),
 1353    content_length(file(File), CLen),
 1354    content_type(Type),
 1355    "\r\n".
 1356reply_header(cgi_data(Size), HdrExtra, Code) -->
 1357    vstatus(ok, Code, HdrExtra),
 1358    date(now),
 1359    header_fields(HdrExtra, CLen),
 1360    content_length(Size, CLen),
 1361    "\r\n".
 1362reply_header(event_stream, HdrExtra, Code) -->
 1363    vstatus(ok, Code, HdrExtra),
 1364    date(now),
 1365    header_fields(HdrExtra, _),
 1366    "\r\n".
 1367reply_header(chunked_data, HdrExtra, Code) -->
 1368    vstatus(ok, Code, HdrExtra),
 1369    date(now),
 1370    header_fields(HdrExtra, _),
 1371    (   {memberchk(transfer_encoding(_), HdrExtra)}
 1372    ->  ""
 1373    ;   transfer_encoding(chunked)
 1374    ),
 1375    "\r\n".
 1376% non-200 replies without a body (e.g., 1xx, 204, 304)
 1377reply_header(status(Status), HdrExtra, Code) -->
 1378    vstatus(Status, Code),
 1379    header_fields(HdrExtra, Clen),
 1380    { Clen = 0 },
 1381    "\r\n".
 1382% non-200 replies with a body
 1383reply_header(Data, HdrExtra, Code) -->
 1384    { status_reply_headers(Data,
 1385                           body(Type, Encoding, Content),
 1386                           ReplyHeaders),
 1387      http_join_headers(ReplyHeaders, HdrExtra, Headers),
 1388      functor(Data, CodeName, _)
 1389    },
 1390    vstatus(CodeName, Code, Headers),
 1391    date(now),
 1392    header_fields(Headers, CLen),
 1393    content_length(codes(Content, Encoding), CLen),
 1394    content_type(Type, Encoding),
 1395    "\r\n".
 1396
 1397status_reply_headers(created(Location, Body), Body,
 1398                     [ location(Location) ]).
 1399status_reply_headers(moved(To, Body), Body,
 1400                     [ location(To) ]).
 1401status_reply_headers(moved_temporary(To, Body), Body,
 1402                     [ location(To) ]).
 1403status_reply_headers(gone(_URL, Body), Body, []).
 1404status_reply_headers(see_other(To, Body), Body,
 1405                     [ location(To) ]).
 1406status_reply_headers(authorise(Method, Body), Body,
 1407                     [ www_authenticate(Method) ]).
 1408status_reply_headers(not_found(_URL, Body), Body, []).
 1409status_reply_headers(forbidden(_URL, Body), Body, []).
 1410status_reply_headers(method_not_allowed(_Method, _URL, Body), Body, []).
 1411status_reply_headers(server_error(_Error, Body), Body, []).
 1412status_reply_headers(service_unavailable(_Why, Body), Body, []).
 1413status_reply_headers(not_acceptable(_Why, Body), Body, []).
 1414status_reply_headers(bad_request(_Error, Body), Body, []).
 1415
 1416
 1417%!  vstatus(+Status, -Code)// is det.
 1418%!  vstatus(+Status, -Code, +HdrExtra)// is det.
 1419%
 1420%   Emit the HTTP header for Status
 1421
 1422vstatus(_Status, Code, HdrExtra) -->
 1423    {memberchk(status(Code), HdrExtra)},
 1424    !,
 1425    vstatus(_NewStatus, Code).
 1426vstatus(Status, Code, _) -->
 1427    vstatus(Status, Code).
 1428
 1429vstatus(Status, Code) -->
 1430    "HTTP/1.1 ",
 1431    status_number(Status, Code),
 1432    " ",
 1433    status_comment(Status),
 1434    "\r\n".
 1435
 1436%!  status_number(?Status, ?Code)// is semidet.
 1437%
 1438%   Parse/generate the HTTP status  numbers  and   map  them  to the
 1439%   proper name.
 1440%
 1441%   @see See the source code for supported status names and codes.
 1442
 1443status_number(Status, Code) -->
 1444    { var(Status) },
 1445    !,
 1446    integer(Code),
 1447    { status_number(Status, Code) },
 1448    !.
 1449status_number(Status, Code) -->
 1450    { status_number(Status, Code) },
 1451    integer(Code).
 1452
 1453%!  status_number(+Status:atom, -Code:nonneg) is det.
 1454%!  status_number(-Status:atom, +Code:nonneg) is det.
 1455%
 1456%   Relates a symbolic  HTTP   status  names to their integer Code.
 1457%   Each code also needs a rule for status_comment//1.
 1458%
 1459%   @throws type_error    If Code is instantiated with something other than
 1460%                         an integer.
 1461%   @throws domain_error  If Code is instantiated with an integer
 1462%                         outside of the range [100-599] of defined
 1463%                         HTTP status codes.
 1464
 1465% Unrecognized status codes that are within a defined code class.
 1466% RFC 7231 states:
 1467%   "[...] a client MUST understand the class of any status code,
 1468%    as indicated by the first digit, and treat an unrecognized status code
 1469%    as being equivalent to the `x00` status code of that class [...]
 1470%   "
 1471% @see http://tools.ietf.org/html/rfc7231#section-6
 1472
 1473status_number(Status, Code) :-
 1474    nonvar(Status),
 1475    !,
 1476    status_number_fact(Status, Code).
 1477status_number(Status, Code) :-
 1478    nonvar(Code),
 1479    !,
 1480    (   between(100, 599, Code)
 1481    ->  (   status_number_fact(Status, Code)
 1482        ->  true
 1483        ;   ClassCode is Code // 100 * 100,
 1484            status_number_fact(Status, ClassCode)
 1485        )
 1486    ;   domain_error(http_code, Code)
 1487    ).
 1488
 1489status_number_fact(continue,                   100).
 1490status_number_fact(switching_protocols,        101).
 1491status_number_fact(ok,                         200).
 1492status_number_fact(created,                    201).
 1493status_number_fact(accepted,                   202).
 1494status_number_fact(non_authoritative_info,     203).
 1495status_number_fact(no_content,                 204).
 1496status_number_fact(reset_content,              205).
 1497status_number_fact(partial_content,            206).
 1498status_number_fact(multiple_choices,           300).
 1499status_number_fact(moved,                      301).
 1500status_number_fact(moved_temporary,            302).
 1501status_number_fact(see_other,                  303).
 1502status_number_fact(not_modified,               304).
 1503status_number_fact(use_proxy,                  305).
 1504status_number_fact(unused,                     306).
 1505status_number_fact(temporary_redirect,         307).
 1506status_number_fact(bad_request,                400).
 1507status_number_fact(authorise,                  401).
 1508status_number_fact(payment_required,           402).
 1509status_number_fact(forbidden,                  403).
 1510status_number_fact(not_found,                  404).
 1511status_number_fact(method_not_allowed,         405).
 1512status_number_fact(not_acceptable,             406).
 1513status_number_fact(request_timeout,            408).
 1514status_number_fact(conflict,                   409).
 1515status_number_fact(gone,                       410).
 1516status_number_fact(length_required,            411).
 1517status_number_fact(payload_too_large,          413).
 1518status_number_fact(uri_too_long,               414).
 1519status_number_fact(unsupported_media_type,     415).
 1520status_number_fact(expectation_failed,         417).
 1521status_number_fact(upgrade_required,           426).
 1522status_number_fact(server_error,               500).
 1523status_number_fact(not_implemented,            501).
 1524status_number_fact(bad_gateway,                502).
 1525status_number_fact(service_unavailable,        503).
 1526status_number_fact(gateway_timeout,            504).
 1527status_number_fact(http_version_not_supported, 505).
 1528
 1529
 1530%!  status_comment(+Code:atom)// is det.
 1531%
 1532%   Emit standard HTTP human-readable comment on the reply-status.
 1533
 1534status_comment(continue) -->
 1535    "Continue".
 1536status_comment(switching_protocols) -->
 1537    "Switching Protocols".
 1538status_comment(ok) -->
 1539    "OK".
 1540status_comment(created) -->
 1541    "Created".
 1542status_comment(accepted) -->
 1543    "Accepted".
 1544status_comment(non_authoritative_info) -->
 1545    "Non-Authoritative Information".
 1546status_comment(no_content) -->
 1547    "No Content".
 1548status_comment(reset_content) -->
 1549    "Reset Content".
 1550status_comment(created) -->
 1551    "Created".
 1552status_comment(partial_content) -->
 1553    "Partial content".
 1554status_comment(multiple_choices) -->
 1555    "Multiple Choices".
 1556status_comment(moved) -->
 1557    "Moved Permanently".
 1558status_comment(moved_temporary) -->
 1559    "Moved Temporary".
 1560status_comment(see_other) -->
 1561    "See Other".
 1562status_comment(not_modified) -->
 1563    "Not Modified".
 1564status_comment(use_proxy) -->
 1565    "Use Proxy".
 1566status_comment(unused) -->
 1567    "Unused".
 1568status_comment(temporary_redirect) -->
 1569    "Temporary Redirect".
 1570status_comment(bad_request) -->
 1571    "Bad Request".
 1572status_comment(authorise) -->
 1573    "Authorization Required".
 1574status_comment(payment_required) -->
 1575    "Payment Required".
 1576status_comment(forbidden) -->
 1577    "Forbidden".
 1578status_comment(not_found) -->
 1579    "Not Found".
 1580status_comment(method_not_allowed) -->
 1581    "Method Not Allowed".
 1582status_comment(not_acceptable) -->
 1583    "Not Acceptable".
 1584status_comment(request_timeout) -->
 1585    "Request Timeout".
 1586status_comment(conflict) -->
 1587    "Conflict".
 1588status_comment(gone) -->
 1589    "Gone".
 1590status_comment(length_required) -->
 1591    "Length Required".
 1592status_comment(payload_too_large) -->
 1593    "Payload Too Large".
 1594status_comment(uri_too_long) -->
 1595    "URI Too Long".
 1596status_comment(unsupported_media_type) -->
 1597    "Unsupported Media Type".
 1598status_comment(expectation_failed) -->
 1599    "Expectation Failed".
 1600status_comment(upgrade_required) -->
 1601    "Upgrade Required".
 1602status_comment(server_error) -->
 1603    "Internal Server Error".
 1604status_comment(not_implemented) -->
 1605    "Not Implemented".
 1606status_comment(bad_gateway) -->
 1607    "Bad Gateway".
 1608status_comment(service_unavailable) -->
 1609    "Service Unavailable".
 1610status_comment(gateway_timeout) -->
 1611    "Gateway Timeout".
 1612status_comment(http_version_not_supported) -->
 1613    "HTTP Version Not Supported".
 1614
 1615date(Time) -->
 1616    "Date: ",
 1617    (   { Time == now }
 1618    ->  now
 1619    ;   rfc_date(Time)
 1620    ),
 1621    "\r\n".
 1622
 1623modified(file(File)) -->
 1624    !,
 1625    { time_file(File, Time)
 1626    },
 1627    modified(Time).
 1628modified(Time) -->
 1629    "Last-modified: ",
 1630    (   { Time == now }
 1631    ->  now
 1632    ;   rfc_date(Time)
 1633    ),
 1634    "\r\n".
 1635
 1636
 1637%!  content_length(+Object, ?Len)// is det.
 1638%
 1639%   Emit the content-length field and (optionally) the content-range
 1640%   field.
 1641%
 1642%   @param Len Number of bytes specified
 1643
 1644content_length(file(File, bytes(From, To)), Len) -->
 1645    !,
 1646    { size_file(File, Size),
 1647      (   To == end
 1648      ->  Len is Size - From,
 1649          RangeEnd is Size - 1
 1650      ;   Len is To+1 - From,       % To is index of last byte
 1651          RangeEnd = To
 1652      )
 1653    },
 1654    content_range(bytes, From, RangeEnd, Size),
 1655    content_length(Len, Len).
 1656content_length(Reply, Len) -->
 1657    { length_of(Reply, Len)
 1658    },
 1659    "Content-Length: ", integer(Len),
 1660    "\r\n".
 1661
 1662:- meta_predicate
 1663    print_length(0, -, +, -). 1664
 1665:- det(length_of/2). 1666length_of(_, Len), integer(Len) => true.
 1667length_of(string(String, Encoding), Len) =>
 1668    length_of(codes(String, Encoding), Len).
 1669length_of(codes(String, Encoding), Len) =>
 1670    print_length(format(Out, '~s', [String]), Out, Encoding, Len).
 1671length_of(atom(Atom, Encoding), Len) =>
 1672    print_length(format(Out, '~a', [Atom]), Out, Encoding, Len).
 1673length_of(file(File), Len) =>
 1674    size_file(File, Len).
 1675length_of(memory_file(Handle), Len) =>
 1676    size_memory_file(Handle, Len, octet).
 1677length_of(html_tokens(Tokens), Len) =>
 1678    html_print_length(Tokens, Len).
 1679length_of(html(Tokens, Encoding), Len) =>
 1680    print_length(print_html(Out, Tokens), Out, Encoding, Len).
 1681length_of(bytes(Bytes), Len) =>
 1682    print_length(format(Out, '~s', [Bytes]), Out, octet, Len).
 1683length_of(Num, Len), integer(Num) =>
 1684    Len = Num.
 1685
 1686print_length(Goal, Out, Encoding, Len) :-
 1687    setup_call_cleanup(
 1688        open_null_stream(Out),
 1689        ( set_stream(Out, encoding(Encoding)),
 1690          call(Goal),
 1691          byte_count(Out, Len)
 1692        ),
 1693        close(Out)).
 1694
 1695%!  content_range(+Unit:atom, +From:int, +RangeEnd:int, +Size:int)// is det
 1696%
 1697%   Emit the =|Content-Range|= header  for   partial  content  (206)
 1698%   replies.
 1699
 1700content_range(Unit, From, RangeEnd, Size) -->
 1701    "Content-Range: ", atom(Unit), " ",
 1702    integer(From), "-", integer(RangeEnd), "/", integer(Size),
 1703    "\r\n".
 1704
 1705content_encoding(Encoding) -->
 1706    "Content-Encoding: ", atom(Encoding), "\r\n".
 1707
 1708transfer_encoding(Encoding) -->
 1709    "Transfer-Encoding: ", atom(Encoding), "\r\n".
 1710
 1711content_type(Type) -->
 1712    content_type(Type, _).
 1713
 1714content_type(Type, Charset) -->
 1715    ctype(Type),
 1716    charset(Charset),
 1717    "\r\n".
 1718
 1719ctype(Main/Sub) -->
 1720    !,
 1721    "Content-Type: ",
 1722    atom(Main),
 1723    "/",
 1724    atom(Sub).
 1725ctype(Type) -->
 1726    !,
 1727    "Content-Type: ",
 1728    atom(Type).
 1729
 1730charset(Var) -->
 1731    { var(Var) },
 1732    !.
 1733charset(utf8) -->
 1734    !,
 1735    "; charset=UTF-8".
 1736charset(CharSet) -->
 1737    "; charset=",
 1738    atom(CharSet).
 1739
 1740%!  header_field(-Name, -Value)// is det.
 1741%!  header_field(+Name, +Value) is det.
 1742%
 1743%   Process an HTTP request property. Request properties appear as a
 1744%   single line in an HTTP header.
 1745
 1746header_field(Name, Value) -->
 1747    { var(Name) },                 % parsing
 1748    !,
 1749    field_name(Name),
 1750    ":",
 1751    whites,
 1752    read_field_value(ValueChars),
 1753    blanks_to_nl,
 1754    !,
 1755    {   field_to_prolog(Name, ValueChars, Value)
 1756    ->  true
 1757    ;   atom_codes(Value, ValueChars),
 1758        domain_error(Name, Value)
 1759    }.
 1760header_field(Name, Value) -->
 1761    field_name(Name),
 1762    ": ",
 1763    field_value(Name, Value),
 1764    "\r\n".
 1765
 1766%!  read_field_value(-Codes)//
 1767%
 1768%   Read a field eagerly up to the next whitespace
 1769
 1770read_field_value([H|T]) -->
 1771    [H],
 1772    { \+ code_type(H, space) },
 1773    !,
 1774    read_field_value(T).
 1775read_field_value([]) -->
 1776    "".
 1777read_field_value([H|T]) -->
 1778    [H],
 1779    read_field_value(T).
 1780
 1781%!  send_reply_header(+Out, +String) is det.
 1782%!  send_request_header(+Out, +String) is det.
 1783%
 1784%   Low level routines to send a single HTTP request or reply line.
 1785
 1786send_reply_header(Out, String) :-
 1787    debug(http(send_reply), "< ~s", [String]),
 1788    format(Out, '~s', [String]).
 1789
 1790send_request_header(Out, String) :-
 1791    debug(http(send_request), "> ~s", [String]),
 1792    format(Out, '~s', [String]).
 1793
 1794%!  http_parse_header_value(+Field, +Value, -Prolog) is semidet.
 1795%
 1796%   Translate Value in a meaningful Prolog   term. Field denotes the
 1797%   HTTP request field for which we   do  the translation. Supported
 1798%   fields are:
 1799%
 1800%     * content_length
 1801%     Converted into an integer
 1802%     * status
 1803%     Converted into an integer
 1804%     * cookie
 1805%     Converted into a list with Name=Value by cookies//1.
 1806%     * set_cookie
 1807%     Converted into a term set_cookie(Name, Value, Options).
 1808%     Options is a list consisting of Name=Value or a single
 1809%     atom (e.g., =secure=)
 1810%     * host
 1811%     Converted to HostName:Port if applicable.
 1812%     * range
 1813%     Converted into bytes(From, To), where From is an integer
 1814%     and To is either an integer or the atom =end=.
 1815%     * accept
 1816%     Parsed to a list of media descriptions.  Each media is a term
 1817%     media(Type, TypeParams, Quality, AcceptExts). The list is
 1818%     sorted according to preference.
 1819%     * content_disposition
 1820%     Parsed into disposition(Name, Attributes), where Attributes is
 1821%     a list of Name=Value pairs.
 1822%     * content_type
 1823%     Parsed into media(Type/SubType, Attributes), where Attributes
 1824%     is a list of Name=Value pairs.
 1825%     * expires
 1826%     Parsed into a time stamp using http_timestamp/2.
 1827%
 1828%   As some fields are already parsed in the `Request`, this predicate
 1829%   is a no-op when called on an already parsed field.
 1830%
 1831%   @arg Value is either an atom, a list of codes or an already parsed
 1832%   header value.
 1833
 1834http_parse_header_value(Field, Value, Prolog) :-
 1835    known_field(Field, _, Type),
 1836    (   already_parsed(Type, Value)
 1837    ->  Prolog = Value
 1838    ;   parse_header_value_atom(Field, Value, Prolog)
 1839    ->  true
 1840    ;   to_codes(Value, Codes),
 1841        parse_header_value(Field, Codes, Prolog)
 1842    ).
 1843
 1844already_parsed(integer, V)    :- !, integer(V).
 1845already_parsed(list(Type), L) :- !, is_list(L), maplist(already_parsed(Type), L).
 1846already_parsed(Term, V)       :- subsumes_term(Term, V).
 1847
 1848
 1849%!  known_field(?FieldName, ?AutoConvert, -Type)
 1850%
 1851%   True if the value of FieldName is   by default translated into a
 1852%   Prolog data structure.
 1853
 1854known_field(content_length,      true,  integer).
 1855known_field(status,              true,  integer).
 1856known_field(expires,             false, number).
 1857known_field(cookie,              true,  list(_=_)).
 1858known_field(set_cookie,          true,  list(set_cookie(_Name,_Value,_Options))).
 1859known_field(host,                true,  _Host:_Port).
 1860known_field(range,               maybe, bytes(_,_)).
 1861known_field(accept,              maybe, list(media(_Type, _Parms, _Q, _Exts))).
 1862known_field(content_disposition, maybe, disposition(_Name, _Attributes)).
 1863known_field(content_type,        false, media(_Type/_Sub, _Attributes)).
 1864
 1865to_codes(In, Codes) :-
 1866    (   is_list(In)
 1867    ->  Codes = In
 1868    ;   atom_codes(In, Codes)
 1869    ).
 1870
 1871%!  field_to_prolog(+Field, +ValueCodes, -Prolog) is semidet.
 1872%
 1873%   Translate the value string into  a   sensible  Prolog  term. For
 1874%   known_fields(_,true), this must succeed. For   =maybe=,  we just
 1875%   return the atom if the translation fails.
 1876
 1877field_to_prolog(Field, Codes, Prolog) :-
 1878    known_field(Field, true, _Type),
 1879    !,
 1880    (   parse_header_value(Field, Codes, Prolog0)
 1881    ->  Prolog = Prolog0
 1882    ).
 1883field_to_prolog(Field, Codes, Prolog) :-
 1884    known_field(Field, maybe, _Type),
 1885    parse_header_value(Field, Codes, Prolog0),
 1886    !,
 1887    Prolog = Prolog0.
 1888field_to_prolog(_, Codes, Atom) :-
 1889    atom_codes(Atom, Codes).
 1890
 1891%!  parse_header_value_atom(+Field, +ValueAtom, -Value) is semidet.
 1892%
 1893%   As parse_header_value/3, but avoid translation to codes.
 1894
 1895parse_header_value_atom(content_length, Atom, ContentLength) :-
 1896    atomic(Atom),
 1897    atom_number(Atom, ContentLength).
 1898parse_header_value_atom(expires, Atom, Stamp) :-
 1899    http_timestamp(Stamp, Atom).
 1900
 1901%!  parse_header_value(+Field, +ValueCodes, -Value) is semidet.
 1902%
 1903%   Parse the value text of an HTTP   field into a meaningful Prolog
 1904%   representation.
 1905
 1906parse_header_value(content_length, ValueChars, ContentLength) :-
 1907    number_codes(ContentLength, ValueChars).
 1908parse_header_value(expires, ValueCodes, Stamp) :-
 1909    http_timestamp(Stamp, ValueCodes).
 1910parse_header_value(status, ValueChars, Code) :-
 1911    (   phrase(" ", L, _),
 1912        append(Pre, L, ValueChars)
 1913    ->  number_codes(Code, Pre)
 1914    ;   number_codes(Code, ValueChars)
 1915    ).
 1916parse_header_value(cookie, ValueChars, Cookies) :-
 1917    debug(cookie, 'Cookie: ~s', [ValueChars]),
 1918    phrase(cookies(Cookies), ValueChars).
 1919parse_header_value(set_cookie, ValueChars, SetCookie) :-
 1920    debug(cookie, 'SetCookie: ~s', [ValueChars]),
 1921    phrase(set_cookie(SetCookie), ValueChars).
 1922parse_header_value(host, ValueChars, Host) :-
 1923    (   append(HostChars, [0':|PortChars], ValueChars),
 1924        catch(number_codes(Port, PortChars), _, fail)
 1925    ->  atom_codes(HostName, HostChars),
 1926        Host = HostName:Port
 1927    ;   atom_codes(Host, ValueChars)
 1928    ).
 1929parse_header_value(range, ValueChars, Range) :-
 1930    phrase(range(Range), ValueChars).
 1931parse_header_value(accept, ValueChars, Media) :-
 1932    parse_accept(ValueChars, Media).
 1933parse_header_value(content_disposition, ValueChars, Disposition) :-
 1934    phrase(content_disposition(Disposition), ValueChars).
 1935parse_header_value(content_type, ValueChars, Type) :-
 1936    phrase(parse_content_type(Type), ValueChars).
 1937
 1938%!  field_value(+Name, +Value)//
 1939
 1940field_value(_, set_cookie(Name, Value, Options)) -->
 1941    !,
 1942    atom(Name), "=", atom(Value),
 1943    value_options(Options, cookie).
 1944field_value(_, disposition(Disposition, Options)) -->
 1945    !,
 1946    atom(Disposition), value_options(Options, disposition).
 1947field_value(www_authenticate, Auth) -->
 1948    auth_field_value(Auth).
 1949field_value(_, Atomic) -->
 1950    atom(Atomic).
 1951
 1952%!  auth_field_value(+AuthValue)//
 1953%
 1954%   Emit the authentication requirements (WWW-Authenticate field).
 1955
 1956auth_field_value(negotiate(Data)) -->
 1957    "Negotiate ",
 1958    { base64(Data, DataBase64),
 1959      atom_codes(DataBase64, Codes)
 1960    },
 1961    string(Codes).
 1962auth_field_value(negotiate) -->
 1963    "Negotiate".
 1964auth_field_value(basic) -->
 1965    !,
 1966    "Basic".
 1967auth_field_value(basic(Realm)) -->
 1968    "Basic Realm=\"", atom(Realm), "\"".
 1969auth_field_value(digest) -->
 1970    !,
 1971    "Digest".
 1972auth_field_value(digest(Details)) -->
 1973    "Digest ", atom(Details).
 1974
 1975%!  value_options(+List, +Field)//
 1976%
 1977%   Emit field parameters such as =|; charset=UTF-8|=.  There
 1978%   are three versions: a plain _key_ (`secure`), _token_ values
 1979%   and _quoted string_ values.  Seems we cannot deduce that from
 1980%   the actual value.
 1981
 1982value_options([], _) --> [].
 1983value_options([H|T], Field) -->
 1984    "; ", value_option(H, Field),
 1985    value_options(T, Field).
 1986
 1987value_option(secure=true, cookie) -->
 1988    !,
 1989    "secure".
 1990value_option(Name=Value, Type) -->
 1991    { string_option(Name, Type) },
 1992    !,
 1993    atom(Name), "=",
 1994    qstring(Value).
 1995value_option(Name=Value, Type) -->
 1996    { token_option(Name, Type) },
 1997    !,
 1998    atom(Name), "=", atom(Value).
 1999value_option(Name=Value, _Type) -->
 2000    atom(Name), "=",
 2001    option_value(Value).
 2002
 2003string_option(filename, disposition).
 2004
 2005token_option(path, cookie).
 2006
 2007option_value(Value) -->
 2008    { number(Value) },
 2009    !,
 2010    number(Value).
 2011option_value(Value) -->
 2012    { (   atom(Value)
 2013      ->  true
 2014      ;   string(Value)
 2015      ),
 2016      forall(string_code(_, Value, C),
 2017             token_char(C))
 2018    },
 2019    !,
 2020    atom(Value).
 2021option_value(Atomic) -->
 2022    qstring(Atomic).
 2023
 2024qstring(Atomic) -->
 2025    { string_codes(Atomic, Codes) },
 2026    "\"",
 2027    qstring_codes(Codes),
 2028    "\"".
 2029
 2030qstring_codes([]) --> [].
 2031qstring_codes([H|T]) --> qstring_code(H), qstring_codes(T).
 2032
 2033qstring_code(C) --> {qstring_esc(C)}, !, "\\", [C].
 2034qstring_code(C) --> [C].
 2035
 2036qstring_esc(0'").
 2037qstring_esc(C) :- ctl(C).
 2038
 2039
 2040                 /*******************************
 2041                 *        ACCEPT HEADERS        *
 2042                 *******************************/
 2043
 2044:- dynamic accept_cache/2. 2045:- volatile accept_cache/2. 2046
 2047parse_accept(Codes, Media) :-
 2048    atom_codes(Atom, Codes),
 2049    (   accept_cache(Atom, Media0)
 2050    ->  Media = Media0
 2051    ;   phrase(accept(Media0), Codes),
 2052        keysort(Media0, Media1),
 2053        pairs_values(Media1, Media2),
 2054        assertz(accept_cache(Atom, Media2)),
 2055        Media = Media2
 2056    ).
 2057
 2058%!  accept(-Media)// is semidet.
 2059%
 2060%   Parse an HTTP Accept: header
 2061
 2062accept([H|T]) -->
 2063    blanks,
 2064    media_range(H),
 2065    blanks,
 2066    (   ","
 2067    ->  accept(T)
 2068    ;   {T=[]}
 2069    ).
 2070
 2071media_range(s(SortQuality,Spec)-media(Type, TypeParams, Quality, AcceptExts)) -->
 2072    media_type(Type),
 2073    blanks,
 2074    (   ";"
 2075    ->  blanks,
 2076        parameters_and_quality(TypeParams, Quality, AcceptExts)
 2077    ;   { TypeParams = [],
 2078          Quality = 1.0,
 2079          AcceptExts = []
 2080        }
 2081    ),
 2082    { SortQuality is float(-Quality),
 2083      rank_specialised(Type, TypeParams, Spec)
 2084    }.
 2085
 2086
 2087%!  content_disposition(-Disposition)//
 2088%
 2089%   Parse Content-Disposition value
 2090
 2091content_disposition(disposition(Disposition, Options)) -->
 2092    token(Disposition), blanks,
 2093    value_parameters(Options).
 2094
 2095%!  parse_content_type(-Type)//
 2096%
 2097%   Parse  Content-Type  value  into    a  term  media(Type/SubType,
 2098%   Parameters).
 2099
 2100parse_content_type(media(Type, Parameters)) -->
 2101    media_type(Type), blanks,
 2102    value_parameters(Parameters).
 2103
 2104
 2105%!  rank_specialised(+Type, +TypeParam, -Key) is det.
 2106%
 2107%   Although the specification linked  above   is  unclear, it seems
 2108%   that  more  specialised  types  must   be  preferred  over  less
 2109%   specialized ones.
 2110%
 2111%   @tbd    Is there an official specification of this?
 2112
 2113rank_specialised(Type/SubType, TypeParams, v(VT, VS, SortVP)) :-
 2114    var_or_given(Type, VT),
 2115    var_or_given(SubType, VS),
 2116    length(TypeParams, VP),
 2117    SortVP is -VP.
 2118
 2119var_or_given(V, Val) :-
 2120    (   var(V)
 2121    ->  Val = 0
 2122    ;   Val = -1
 2123    ).
 2124
 2125media_type(Type/SubType) -->
 2126    type(Type), "/", type(SubType).
 2127
 2128type(_) -->
 2129    "*",
 2130    !.
 2131type(Type) -->
 2132    token(Type).
 2133
 2134parameters_and_quality(Params, Quality, AcceptExts) -->
 2135    token(Name),
 2136    blanks, "=", blanks,
 2137    (   { Name == q }
 2138    ->  float(Quality), blanks,
 2139        value_parameters(AcceptExts),
 2140        { Params = [] }
 2141    ;   { Params = [Name=Value|T] },
 2142        parameter_value(Value),
 2143        blanks,
 2144        (   ";"
 2145        ->  blanks,
 2146            parameters_and_quality(T, Quality, AcceptExts)
 2147        ;   { T = [],
 2148              Quality = 1.0,
 2149              AcceptExts = []
 2150            }
 2151        )
 2152    ).
 2153
 2154%!  value_parameters(-Params:list) is det.
 2155%
 2156%   Accept (";" <parameter>)*, returning a list of Name=Value, where
 2157%   both Name and Value are atoms.
 2158
 2159value_parameters([H|T]) -->
 2160    ";",
 2161    !,
 2162    blanks, token(Name), blanks,
 2163    (   "="
 2164    ->  blanks,
 2165        (   token(Value)
 2166        ->  []
 2167        ;   quoted_string(Value)
 2168        ),
 2169        { H = (Name=Value) }
 2170    ;   { H = Name }
 2171    ),
 2172    blanks,
 2173    value_parameters(T).
 2174value_parameters([]) -->
 2175    [].
 2176
 2177parameter_value(Value) --> token(Value), !.
 2178parameter_value(Value) --> quoted_string(Value).
 2179
 2180
 2181%!  token(-Name)// is semidet.
 2182%
 2183%   Process an HTTP header token from the input.
 2184
 2185token(Name) -->
 2186    token_char(C1),
 2187    token_chars(Cs),
 2188    { atom_codes(Name, [C1|Cs]) }.
 2189
 2190token_chars([H|T]) -->
 2191    token_char(H),
 2192    !,
 2193    token_chars(T).
 2194token_chars([]) --> [].
 2195
 2196token_char(C) :-
 2197    \+ ctl(C),
 2198    \+ separator_code(C).
 2199
 2200ctl(C) :- between(0,31,C), !.
 2201ctl(127).
 2202
 2203separator_code(0'().
 2204separator_code(0')).
 2205separator_code(0'<).
 2206separator_code(0'>).
 2207separator_code(0'@).
 2208separator_code(0',).
 2209separator_code(0';).
 2210separator_code(0':).
 2211separator_code(0'\\).
 2212separator_code(0'").
 2213separator_code(0'/).
 2214separator_code(0'[).
 2215separator_code(0']).
 2216separator_code(0'?).
 2217separator_code(0'=).
 2218separator_code(0'{).
 2219separator_code(0'}).
 2220separator_code(0'\s).
 2221separator_code(0'\t).
 2222
 2223term_expansion(token_char(x) --> [x], Clauses) :-
 2224    findall((token_char(C)-->[C]),
 2225            (   between(0, 255, C),
 2226                token_char(C)
 2227            ),
 2228            Clauses).
 2229
 2230token_char(x) --> [x].
 2231
 2232%!  quoted_string(-Text)// is semidet.
 2233%
 2234%   True if input starts with a quoted string representing Text.
 2235
 2236quoted_string(Text) -->
 2237    "\"",
 2238    quoted_text(Codes),
 2239    { atom_codes(Text, Codes) }.
 2240
 2241quoted_text([]) -->
 2242    "\"",
 2243    !.
 2244quoted_text([H|T]) -->
 2245    "\\", !, [H],
 2246    quoted_text(T).
 2247quoted_text([H|T]) -->
 2248    [H],
 2249    !,
 2250    quoted_text(T).
 2251
 2252
 2253%!  header_fields(+Fields, ?ContentLength)// is det.
 2254%
 2255%   Process a sequence of  [Name(Value),   ...]  attributes  for the
 2256%   header. A term content_length(Len) is   special. If instantiated
 2257%   it emits the header. If not   it just unifies ContentLength with
 2258%   the argument of the content_length(Len)   term.  This allows for
 2259%   both sending and retrieving the content-length.
 2260
 2261header_fields([], _) --> [].
 2262header_fields([content_length(CLen)|T], CLen) -->
 2263    !,
 2264    (   { var(CLen) }
 2265    ->  ""
 2266    ;   header_field(content_length, CLen)
 2267    ),
 2268    header_fields(T, CLen).           % Continue or return first only?
 2269header_fields([status(_)|T], CLen) -->   % handled by vstatus//3.
 2270    !,
 2271    header_fields(T, CLen).
 2272header_fields([H|T], CLen) -->
 2273    { H =.. [Name, Value] },
 2274    header_field(Name, Value),
 2275    header_fields(T, CLen).
 2276
 2277
 2278%!  field_name(?PrologName)
 2279%
 2280%   Convert between prolog_name  and  HttpName.   Field  names  are,
 2281%   according to RFC 2616, considered  tokens   and  covered  by the
 2282%   following definition:
 2283%
 2284%   ==
 2285%   token          = 1*<any CHAR except CTLs or separators>
 2286%   separators     = "(" | ")" | "<" | ">" | "@"
 2287%                  | "," | ";" | ":" | "\" | <">
 2288%                  | "/" | "[" | "]" | "?" | "="
 2289%                  | "{" | "}" | SP | HT
 2290%   ==
 2291
 2292:- public
 2293    field_name//1. 2294
 2295field_name(Name) -->
 2296    { var(Name) },
 2297    !,
 2298    rd_field_chars(Chars),
 2299    { atom_codes(Name, Chars) }.
 2300field_name(mime_version) -->
 2301    !,
 2302    "MIME-Version".
 2303field_name(www_authenticate) -->
 2304    !,
 2305    "WWW-Authenticate".
 2306field_name(Name) -->
 2307    { atom_codes(Name, Chars) },
 2308    wr_field_chars(Chars).
 2309
 2310rd_field_chars_no_fold([C|T]) -->
 2311    [C],
 2312    { rd_field_char(C, _) },
 2313    !,
 2314    rd_field_chars_no_fold(T).
 2315rd_field_chars_no_fold([]) -->
 2316    [].
 2317
 2318rd_field_chars([C0|T]) -->
 2319    [C],
 2320    { rd_field_char(C, C0) },
 2321    !,
 2322    rd_field_chars(T).
 2323rd_field_chars([]) -->
 2324    [].
 2325
 2326%!  separators(-CharCodes) is det.
 2327%
 2328%   CharCodes is a list of separators according to RFC2616
 2329
 2330separators("()<>@,;:\\\"/[]?={} \t").
 2331
 2332term_expansion(rd_field_char('expand me',_), Clauses) :-
 2333
 2334    Clauses = [ rd_field_char(0'-, 0'_)
 2335              | Cls
 2336              ],
 2337    separators(SepString),
 2338    string_codes(SepString, Seps),
 2339    findall(rd_field_char(In, Out),
 2340            (   between(32, 127, In),
 2341                \+ memberchk(In, Seps),
 2342                In \== 0'-,         % 0'
 2343                code_type(Out, to_lower(In))),
 2344            Cls).
 2345
 2346rd_field_char('expand me', _).                  % avoid recursion
 2347
 2348wr_field_chars([C|T]) -->
 2349    !,
 2350    { code_type(C, to_lower(U)) },
 2351    [U],
 2352    wr_field_chars2(T).
 2353wr_field_chars([]) -->
 2354    [].
 2355
 2356wr_field_chars2([]) --> [].
 2357wr_field_chars2([C|T]) -->              % 0'
 2358    (   { C == 0'_ }
 2359    ->  "-",
 2360        wr_field_chars(T)
 2361    ;   [C],
 2362        wr_field_chars2(T)
 2363    ).
 2364
 2365%!  now//
 2366%
 2367%   Current time using rfc_date//1.
 2368
 2369now -->
 2370    { get_time(Time)
 2371    },
 2372    rfc_date(Time).
 2373
 2374%!  rfc_date(+Time)// is det.
 2375%
 2376%   Write time according to RFC1123 specification as required by the
 2377%   RFC2616 HTTP protocol specs.
 2378
 2379rfc_date(Time, String, Tail) :-
 2380    stamp_date_time(Time, Date, 'UTC'),
 2381    format_time(codes(String, Tail),
 2382                '%a, %d %b %Y %T GMT',
 2383                Date, posix).
 2384
 2385%!  http_timestamp(?Time:timestamp, ?Text:atom) is det.
 2386%
 2387%   Convert between a SWI-Prolog time stamp and  a string in HTTP format
 2388%   (RFC1123). When parsing, it  accepts   RFC1123,  RFC1036 and ASCTIME
 2389%   formats. See parse_time/3.
 2390%
 2391%   @error syntax_error(http_timestamp(Text)) if the string cannot
 2392%   be parsed.
 2393
 2394http_timestamp(Time, Text), nonvar(Text) =>
 2395    (   parse_time(Text, _Format, Time0)
 2396    ->  (   var(Time)
 2397        ->  Time = Time0
 2398        ;   Time =:= Time0
 2399        )
 2400    ;   syntax_error(http_timestamp(Text))
 2401    ).
 2402http_timestamp(Time, Atom), number(Time) =>
 2403    stamp_date_time(Time, Date, 'UTC'),
 2404    format_time(atom(Atom),
 2405                '%a, %d %b %Y %T GMT',
 2406                Date, posix).
 2407
 2408
 2409                 /*******************************
 2410                 *         REQUEST DCG          *
 2411                 *******************************/
 2412
 2413request(Fd, [method(Method),request_uri(ReqURI)|Header]) -->
 2414    method(Method),
 2415    blanks,
 2416    nonblanks(Query),
 2417    { atom_codes(ReqURI, Query),
 2418      request_uri_parts(ReqURI, Header, Rest)
 2419    },
 2420    request_header(Fd, Rest),
 2421    !.
 2422request(Fd, [unknown(What)|Header]) -->
 2423    string(What),
 2424    eos,
 2425    !,
 2426    {   http_read_header(Fd, Header)
 2427    ->  true
 2428    ;   Header = []
 2429    }.
 2430
 2431method(get)     --> "GET", !.
 2432method(put)     --> "PUT", !.
 2433method(head)    --> "HEAD", !.
 2434method(post)    --> "POST", !.
 2435method(delete)  --> "DELETE", !.
 2436method(patch)   --> "PATCH", !.
 2437method(options) --> "OPTIONS", !.
 2438method(trace)   --> "TRACE", !.
 2439
 2440%!  request_uri_parts(+RequestURI, -Parts, ?Tail) is det.
 2441%
 2442%   Process the request-uri, producing the following parts:
 2443%
 2444%     * path(-Path)
 2445%     Decode path information (always present)
 2446%     * search(-QueryParams)
 2447%     Present if there is a ?name=value&... part of the request uri.
 2448%     QueryParams is a Name=Value list.
 2449%     * fragment(-Fragment)
 2450%     Present if there is a #Fragment.
 2451
 2452request_uri_parts(ReqURI, [path(Path)|Parts], Rest) :-
 2453    uri_components(ReqURI, Components),
 2454    uri_data(path, Components, PathText),
 2455    uri_encoded(path, Path, PathText),
 2456    phrase(uri_parts(Components), Parts, Rest).
 2457
 2458uri_parts(Components) -->
 2459    uri_search(Components),
 2460    uri_fragment(Components).
 2461
 2462uri_search(Components) -->
 2463    { uri_data(search, Components, Search),
 2464      nonvar(Search),
 2465      catch(uri_query_components(Search, Query),
 2466            error(syntax_error(_),_),
 2467            fail)
 2468    },
 2469    !,
 2470    [ search(Query) ].
 2471uri_search(_) --> [].
 2472
 2473uri_fragment(Components) -->
 2474    { uri_data(fragment, Components, String),
 2475      nonvar(String),
 2476      !,
 2477      uri_encoded(fragment, Fragment, String)
 2478    },
 2479    [ fragment(Fragment) ].
 2480uri_fragment(_) --> [].
 2481
 2482%!  request_header(+In:stream, -Header:list) is det.
 2483%
 2484%   Read the remainder (after the request-uri)   of  the HTTP header
 2485%   and return it as a Name(Value) list.
 2486
 2487request_header(_, []) -->               % Old-style non-version header
 2488    blanks,
 2489    eos,
 2490    !.
 2491request_header(Fd, [http_version(Version)|Header]) -->
 2492    http_version(Version),
 2493    blanks,
 2494    eos,
 2495    !,
 2496    {   Version = 1-_
 2497    ->  http_read_header(Fd, Header)
 2498    ;   Header = []
 2499    }.
 2500
 2501http_version(Version) -->
 2502    blanks,
 2503    "HTTP/",
 2504    http_version_number(Version).
 2505
 2506http_version_number(Major-Minor) -->
 2507    integer(Major),
 2508    ".",
 2509    integer(Minor).
 2510
 2511
 2512                 /*******************************
 2513                 *            COOKIES           *
 2514                 *******************************/
 2515
 2516%!  cookies(-List)// is semidet.
 2517%
 2518%   Translate a cookie description into a list Name=Value.
 2519
 2520cookies([Name=Value|T]) -->
 2521    blanks,
 2522    cookie(Name, Value),
 2523    !,
 2524    blanks,
 2525    (   ";"
 2526    ->  cookies(T)
 2527    ;   { T = [] }
 2528    ).
 2529cookies(List) -->
 2530    string(Skipped),
 2531    ";",
 2532    !,
 2533    { print_message(warning, http(skipped_cookie(Skipped))) },
 2534    cookies(List).
 2535cookies([]) -->
 2536    blanks.
 2537
 2538cookie(Name, Value) -->
 2539    cookie_name(Name),
 2540    blanks, "=", blanks,
 2541    cookie_value(Value).
 2542
 2543cookie_name(Name) -->
 2544    { var(Name) },
 2545    !,
 2546    rd_field_chars_no_fold(Chars),
 2547    { atom_codes(Name, Chars) }.
 2548
 2549cookie_value(Value) -->
 2550    quoted_string(Value),
 2551    !.
 2552cookie_value(Value) -->
 2553    chars_to_semicolon_or_blank(Chars),
 2554    { atom_codes(Value, Chars)
 2555    }.
 2556
 2557chars_to_semicolon_or_blank([]), ";" -->
 2558    ";",
 2559    !.
 2560chars_to_semicolon_or_blank([]) -->
 2561    " ",
 2562    blanks,
 2563    eos,
 2564    !.
 2565chars_to_semicolon_or_blank([H|T]) -->
 2566    [H],
 2567    !,
 2568    chars_to_semicolon_or_blank(T).
 2569chars_to_semicolon_or_blank([]) -->
 2570    [].
 2571
 2572set_cookie(set_cookie(Name, Value, Options)) -->
 2573    ws,
 2574    cookie(Name, Value),
 2575    cookie_options(Options).
 2576
 2577cookie_options([H|T]) -->
 2578    ws,
 2579    ";",
 2580    ws,
 2581    cookie_option(H),
 2582    !,
 2583    cookie_options(T).
 2584cookie_options([]) -->
 2585    ws.
 2586
 2587ws --> " ", !, ws.
 2588ws --> [].
 2589
 2590
 2591%!  cookie_option(-Option)// is semidet.
 2592%
 2593%   True if input represents a valid  Cookie option. Officially, all
 2594%   cookie  options  use  the  syntax   <name>=<value>,  except  for
 2595%   =Secure= and =HttpOnly=.
 2596%
 2597%   @param  Option  Term of the form Name=Value
 2598%   @bug    Incorrectly accepts options without = for M$ compatibility.
 2599
 2600cookie_option(Name=Value) -->
 2601    rd_field_chars(NameChars), ws,
 2602    { atom_codes(Name, NameChars) },
 2603    (   "="
 2604    ->  ws,
 2605        chars_to_semicolon(ValueChars),
 2606        { atom_codes(Value, ValueChars)
 2607        }
 2608    ;   { Value = true }
 2609    ).
 2610
 2611chars_to_semicolon([H|T]) -->
 2612    [H],
 2613    { H \== 32, H \== 0'; },
 2614    !,
 2615    chars_to_semicolon(T).
 2616chars_to_semicolon([]), ";" -->
 2617    ws, ";",
 2618    !.
 2619chars_to_semicolon([H|T]) -->
 2620    [H],
 2621    chars_to_semicolon(T).
 2622chars_to_semicolon([]) -->
 2623    [].
 2624
 2625%!  range(-Range)// is semidet.
 2626%
 2627%   Process the range header value. Range is currently defined as:
 2628%
 2629%       * bytes(From, To)
 2630%       Where From is an integer and To is either an integer or
 2631%       the atom =end=.
 2632
 2633range(bytes(From, To)) -->
 2634    "bytes", whites, "=", whites, integer(From), "-",
 2635    (   integer(To)
 2636    ->  ""
 2637    ;   { To = end }
 2638    ).
 2639
 2640
 2641                 /*******************************
 2642                 *           REPLY DCG          *
 2643                 *******************************/
 2644
 2645%!  reply(+In, -Reply:list)// is semidet.
 2646%
 2647%   Process the first line of an HTTP   reply.  After that, read the
 2648%   remainder  of  the  header  and    parse  it.  After  successful
 2649%   completion, Reply contains the following fields, followed by the
 2650%   fields produced by http_read_header/2.
 2651%
 2652%       * http_version(Major-Minor)
 2653%       * status(Code, Status, Comment)
 2654%         `Code` is an integer between 100 and 599.
 2655%         `Status` is a Prolog internal name.
 2656%         `Comment` is the comment following the code
 2657%         as it appears in the reply's HTTP status line.
 2658%         @see status_number//2.
 2659
 2660reply(Fd, [http_version(HttpVersion), status(Code, Status, Comment)|Header]) -->
 2661    http_version(HttpVersion),
 2662    blanks,
 2663    (   status_number(Status, Code)
 2664    ->  []
 2665    ;   integer(Status)
 2666    ),
 2667    blanks,
 2668    string(CommentCodes),
 2669    blanks_to_nl,
 2670    !,
 2671    blanks,
 2672    { atom_codes(Comment, CommentCodes),
 2673      http_read_header(Fd, Header)
 2674    }.
 2675
 2676
 2677                 /*******************************
 2678                 *            READ HEADER       *
 2679                 *******************************/
 2680
 2681%!  http_read_header(+Fd, -Header) is det.
 2682%
 2683%   Read Name: Value lines from FD until an empty line is encountered.
 2684%   Field-name are converted to Prolog conventions (all lower, _ instead
 2685%   of -): Content-Type: text/html --> content_type(text/html)
 2686
 2687http_read_header(Fd, Header) :-
 2688    read_header_data(Fd, Text),
 2689    http_parse_header(Text, Header).
 2690
 2691read_header_data(Fd, Header) :-
 2692    read_line_to_codes(Fd, Header, Tail),
 2693    read_header_data(Header, Fd, Tail),
 2694    debug(http(header), 'Header = ~n~s~n', [Header]).
 2695
 2696read_header_data([0'\r,0'\n], _, _) :- !.
 2697read_header_data([0'\n], _, _) :- !.
 2698read_header_data([], _, _) :- !.
 2699read_header_data(_, Fd, Tail) :-
 2700    read_line_to_codes(Fd, Tail, NewTail),
 2701    read_header_data(Tail, Fd, NewTail).
 2702
 2703%!  http_parse_header(+Text:codes, -Header:list) is det.
 2704%
 2705%   Header is a list of Name(Value)-terms representing the structure
 2706%   of the HTTP header in Text.
 2707%
 2708%   @error domain_error(http_request_line, Line)
 2709
 2710http_parse_header(Text, Header) :-
 2711    phrase(header(Header), Text),
 2712    debug(http(header), 'Field: ~p', [Header]).
 2713
 2714header(List) -->
 2715    header_field(Name, Value),
 2716    !,
 2717    { mkfield(Name, Value, List, Tail)
 2718    },
 2719    blanks,
 2720    header(Tail).
 2721header([]) -->
 2722    blanks,
 2723    eos,
 2724    !.
 2725header(_) -->
 2726    string(S), blanks_to_nl,
 2727    !,
 2728    { string_codes(Line, S),
 2729      syntax_error(http_parameter(Line))
 2730    }.
 2731
 2732%!  address//
 2733%
 2734%   Emit the HTML for the server address on behalf of error and
 2735%   status messages (non-200 replies).  Default is
 2736%
 2737%       ==
 2738%       SWI-Prolog httpd at <hostname>
 2739%       ==
 2740%
 2741%   The address can be modified by   providing  a definition for the
 2742%   multifile predicate http:http_address//0.
 2743
 2744:- multifile
 2745    http:http_address//0. 2746
 2747address -->
 2748    http:http_address,
 2749    !.
 2750address -->
 2751    { gethostname(Host) },
 2752    html(address([ a(href('http://www.swi-prolog.org'), 'SWI-Prolog'),
 2753                   ' httpd at ', Host
 2754                 ])).
 2755
 2756mkfield(host, Host:Port, [host(Host),port(Port)|Tail], Tail) :- !.
 2757mkfield(Name, Value, [Att|Tail], Tail) :-
 2758    Att =.. [Name, Value].
 2759
 2760%!  http:http_address// is det.
 2761%
 2762%   HTML-rule that emits the location of  the HTTP server. This hook
 2763%   is called from address//0 to customise   the server address. The
 2764%   server address is emitted on non-200-ok replies.
 2765
 2766%!  http:status_page(+Status, +Context, -HTMLTokens) is semidet.
 2767%
 2768%   Hook called by http_status_reply/4  and http_status_reply/5 that
 2769%   allows for emitting custom error pages   for  the following HTTP
 2770%   page types:
 2771%
 2772%     - 201 - created(Location)
 2773%     - 301 - moved(To)
 2774%     - 302 - moved_temporary(To)
 2775%     - 303 - see_other(To)
 2776%     - 400 - bad_request(ErrorTerm)
 2777%     - 401 - authorise(AuthMethod)
 2778%     - 403 - forbidden(URL)
 2779%     - 404 - not_found(URL)
 2780%     - 405 - method_not_allowed(Method,URL)
 2781%     - 406 - not_acceptable(Why)
 2782%     - 500 - server_error(ErrorTerm)
 2783%     - 503 - unavailable(Why)
 2784%
 2785%   The hook is tried twice,  first   using  the  status term, e.g.,
 2786%   not_found(URL) and than with the code,   e.g.  `404`. The second
 2787%   call is deprecated and only exists for compatibility.
 2788%
 2789%   @arg    Context is the 4th argument of http_status_reply/5, which
 2790%           is invoked after raising an exception of the format
 2791%           http_reply(Status, HeaderExtra, Context).  The default
 2792%           context is `[]` (the empty list).
 2793%   @arg    HTMLTokens is a list of tokens as produced by html//1.
 2794%           It is passed to print_html/2.
 2795
 2796
 2797                 /*******************************
 2798                 *            MESSAGES          *
 2799                 *******************************/
 2800
 2801:- multifile
 2802    prolog:message//1,
 2803    prolog:error_message//1. 2804
 2805prolog:error_message(http_write_short(Data, Sent)) -->
 2806    data(Data),
 2807    [ ': remote hangup after ~D bytes'-[Sent] ].
 2808prolog:error_message(syntax_error(http_request(Request))) -->
 2809    [ 'Illegal HTTP request: ~s'-[Request] ].
 2810prolog:error_message(syntax_error(http_parameter(Line))) -->
 2811    [ 'Illegal HTTP parameter: ~s'-[Line] ].
 2812
 2813prolog:message(http(skipped_cookie(S))) -->
 2814    [ 'Skipped illegal cookie: ~s'-[S] ].
 2815
 2816data(bytes(MimeType, _Bytes)) -->
 2817    !,
 2818    [ 'bytes(~p, ...)'-[MimeType] ].
 2819data(Data) -->
 2820    [ '~p'-[Data] ]