85 lines
2.7 KiB
Prolog
85 lines
2.7 KiB
Prolog
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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Written June 2020 by Markus Triska (triska@metalevel.at)
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Part of Scryer Prolog.
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http_open(+Address, -Stream, +Options)
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======================================
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Yields Stream to read the body of an HTTP reply from Address.
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Address is a list of characters, and includes the method. Both HTTP
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and HTTPS are supported. Redirects are followed.
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Currently, Options must be the empty list. Options may be
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added in the future to give more control over the connection.
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We use HTTP/1.0 until we can read chunked transfer-encoding.
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Example:
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?- http_open("https://github.com/mthom/scryer-prolog", S, []).
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%@ S = '$stream'(0x7f86f94a6cd0)
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%@ ; false.
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- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
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:- module(http_open, [http_open/3]).
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:- use_module(library(sockets)).
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:- use_module(library(error)).
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:- use_module(library(format)).
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:- use_module(library(charsio)).
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:- use_module(library(dcgs)).
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:- use_module(library(lists), [member/2]).
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http_open(Address, Stream, Options) :-
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must_be(list, Options),
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must_be(list, Address),
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once(phrase((list(SchemeCs), "://", list(Rest)), Address)),
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atom_chars(Scheme, SchemeCs),
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chars_host_url(Rest, Host, URL),
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connect(Scheme, Host, Stream0),
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format(Stream0, "\
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GET ~s HTTP/1.0\r\n\
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Host: ~w\r\n\
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User-Agent: Scryer Prolog\r\n\
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Connection: close\r\n\r\n\
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", [URL,Host]),
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read_line_to_chars(Stream0, StatusLine, []),
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once(phrase(("HTTP/1.",(['0']|['1'])," ",[D1]), StatusLine, _)),
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read_header_lines(Stream0, HeaderLines),
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handle_response(D1, HeaderLines, Stream0, Stream).
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list([]) --> [].
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list([L|Ls]) --> [L], list(Ls).
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handle_response('2', _, Stream, Stream). % ok
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handle_response('3', HeaderLines, Stream0, Stream) :- % redirect
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close(Stream0),
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once((member(Line, HeaderLines),
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phrase(("Location: ",list(Location),"\r\n"), Line))),
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http_open(Location, Stream, []).
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% Status-Line = HTTP-Version SP Status-Code SP Reason-Phrase CRLF
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read_header_lines(Stream, Hs) :-
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read_line_to_chars(Stream, Cs, []),
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( Cs == "" -> Hs = []
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; Cs == "\r\n" -> Hs = []
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; Hs = [Cs|Rest],
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read_header_lines(Stream, Rest)
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).
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chars_host_url(Cs, Host, [/|Us]) :-
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( phrase((list(Hs),"/",list(Us)), Cs) ->
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true
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; Hs = Cs,
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Us = []
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),
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atom_chars(Host, Hs).
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connect(https, Host, Stream) :-
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socket_client_open(Host:443, Stream, [tls(true)]).
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connect(http, Host, Stream) :-
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socket_client_open(Host:80, Stream, []).
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