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http_open.pl
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/* Part of SWI-Prolog
Author: Jan Wielemaker
E-mail: J.Wielemaker@vu.nl
WWW: http://www.swi-prolog.org
Copyright (c) 2002-2020, University of Amsterdam
VU University Amsterdam
CWI, Amsterdam
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in
the documentation and/or other materials provided with the
distribution.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.
*/
:- module(http_open,
[ http_open/3, % +URL, -Stream, +Options
http_set_authorization/2, % +URL, +Authorization
http_close_keep_alive/1 % +Address
]).
:- use_module(library(uri)).
:- use_module(library(readutil)).
:- use_module(library(socket)).
:- use_module(library(lists)).
:- use_module(library(option)).
:- use_module(library(error)).
:- use_module(library(base64)).
:- use_module(library(debug)).
:- use_module(library(aggregate)).
:- use_module(library(apply)).
:- use_module(library(http/http_header), [http_parse_header/2]).
:- use_module(library(http/http_stream)).
/** <module> HTTP client library
This library defines http_open/3, which opens a URL as a Prolog stream.
The functionality of the library can be extended by loading two
additional modules that act as plugins:
* library(http/http_ssl_plugin)
Loading this library causes http_open/3 to handle HTTPS connections.
Relevant options for SSL certificate handling are handed to
ssl_context/3. This plugin is loaded automatically if the scheme
`https` is requested using a default SSL context. See the plugin for
additional information regarding security.
* library(http/http_cookie)
Loading this library adds tracking cookies to http_open/3. Returned
cookies are collected in the Prolog database and supplied for
subsequent requests.
Here is a simple example to fetch a web-page:
==
?- http_open('http://www.google.com/search?q=prolog', In, []),
copy_stream_data(In, user_output),
close(In).
<!doctype html><head><title>prolog - Google Search</title><script>
...
==
The example below fetches the modification time of a web-page. Note that
Modified is '' (the empty atom) if the web-server does not provide a
time-stamp for the resource. See also parse_time/2.
==
modified(URL, Stamp) :-
http_open(URL, In,
[ method(head),
header(last_modified, Modified)
]),
close(In),
Modified \== '',
parse_time(Modified, Stamp).
==
Then next example uses Google search. It exploits library(uri) to manage
URIs, library(sgml) to load an HTML document and library(xpath) to
navigate the parsed HTML. Note that you may need to adjust the XPath
queries if the data returned by Google changes.
==
:- use_module(library(http/http_open)).
:- use_module(library(xpath)).
:- use_module(library(sgml)).
:- use_module(library(uri)).
google(For, Title, HREF) :-
uri_encoded(query_value, For, Encoded),
atom_concat('http://www.google.com/search?q=', Encoded, URL),
http_open(URL, In, []),
call_cleanup(
load_html(In, DOM, []),
close(In)),
xpath(DOM, //h3(@class=r), Result),
xpath(Result, //a(@href=HREF0, text), Title),
uri_components(HREF0, Components),
uri_data(search, Components, Query),
uri_query_components(Query, Parts),
memberchk(q=HREF, Parts).
==
An example query is below:
==
?- google(prolog, Title, HREF).
Title = 'SWI-Prolog',
HREF = 'http://www.swi-prolog.org/' ;
Title = 'Prolog - Wikipedia',
HREF = 'https://nl.wikipedia.org/wiki/Prolog' ;
Title = 'Prolog - Wikipedia, the free encyclopedia',
HREF = 'https://en.wikipedia.org/wiki/Prolog' ;
Title = 'Pro-Log is logistiek dienstverlener m.b.t. vervoer over water.',
HREF = 'http://www.pro-log.nl/' ;
Title = 'Learn Prolog Now!',
HREF = 'http://www.learnprolognow.org/' ;
Title = 'Free Online Version - Learn Prolog
...
==
@see load_html/3 and xpath/3 can be used to parse and navigate HTML
documents.
@see http_get/3 and http_post/4 provide an alternative interface that
convert the reply depending on the =|Content-Type|= header.
*/
:- multifile
http:encoding_filter/3, % +Encoding, +In0, -In
http:current_transfer_encoding/1, % ?Encoding
http:disable_encoding_filter/1, % +ContentType
http:http_protocol_hook/5, % +Protocol, +Parts, +StreamPair,
% -NewStreamPair, +Options
http:open_options/2, % +Parts, -Options
http:write_cookies/3, % +Out, +Parts, +Options
http:update_cookies/3, % +CookieLine, +Parts, +Options
http:authenticate_client/2, % +URL, +Action
http:http_connection_over_proxy/6.
:- meta_predicate
http_open(+,-,:).
:- predicate_options(http_open/3, 3,
[ authorization(compound),
final_url(-atom),
header(+atom, -atom),
headers(-list),
connection(+atom),
method(oneof([delete,get,put,head,post,patch,options])),
size(-integer),
status_code(-integer),
output(-stream),
timeout(number),
proxy(atom, integer),
proxy_authorization(compound),
bypass_proxy(boolean),
request_header(any),
user_agent(atom),
version(-compound),
% The option below applies if library(http/http_header) is loaded
post(any),
% The options below apply if library(http/http_ssl_plugin)) is loaded
pem_password_hook(callable),
cacert_file(atom),
cert_verify_hook(callable)
]).
%! user_agent(-Agent) is det.
%
% Default value for =|User-Agent|=, can be overruled using the
% option user_agent(Agent) of http_open/3.
user_agent('SWI-Prolog').
%! http_open(+URL, -Stream, +Options) is det.
%
% Open the data at the HTTP server as a Prolog stream. URL is
% either an atom specifying a URL or a list representing a
% broken-down URL as specified below. After this predicate
% succeeds the data can be read from Stream. After completion this
% stream must be closed using the built-in Prolog predicate
% close/1. Options provides additional options:
%
% * authenticate(+Boolean)
% If `false` (default `true`), do _not_ try to automatically
% authenticate the client if a 401 (Unauthorized) status code
% is received.
%
% * authorization(+Term)
% Send authorization. See also http_set_authorization/2. Supported
% schemes:
%
% - basic(+User, +Password)
% HTTP Basic authentication.
% - bearer(+Token)
% HTTP Bearer authentication.
% - digest(+User, +Password)
% HTTP Digest authentication. This option is only provided
% if the plugin library(http/http_digest) is also loaded.
%
% * connection(+Connection)
% Specify the =Connection= header. Default is =close=. The
% alternative is =|Keep-alive|=. This maintains a pool of
% available connections as determined by keep_connection/1.
% The library(http/websockets) uses =|Keep-alive, Upgrade|=.
% Keep-alive connections can be closed explicitly using
% http_close_keep_alive/1. Keep-alive connections may
% significantly improve repetitive requests on the same server,
% especially if the IP route is long, HTTPS is used or the
% connection uses a proxy.
%
% * final_url(-FinalURL)
% Unify FinalURL with the final destination. This differs from
% the original URL if the returned head of the original
% indicates an HTTP redirect (codes 301, 302 or 303). Without a
% redirect, FinalURL is the same as URL if URL is an atom, or a
% URL constructed from the parts.
%
% * header(Name, -AtomValue)
% If provided, AtomValue is unified with the value of the
% indicated field in the reply header. Name is matched
% case-insensitive and the underscore (_) matches the hyphen
% (-). Multiple of these options may be provided to extract
% multiple header fields. If the header is not available
% AtomValue is unified to the empty atom ('').
%
% * headers(-List)
% If provided, List is unified with a list of Name(Value) pairs
% corresponding to fields in the reply header. Name and Value
% follow the same conventions used by the header(Name,Value)
% option.
%
% * method(+Method)
% One of =get= (default), =head=, =delete=, =post=, =put= or
% =patch=.
% The =head= message can be
% used in combination with the header(Name, Value) option to
% access information on the resource without actually fetching
% the resource itself. The returned stream must be closed
% immediately.
%
% If post(Data) is provided, the default is =post=.
%
% * size(-Size)
% Size is unified with the integer value of =|Content-Length|=
% in the reply header.
%
% * version(-Version)
% Version is a _pair_ `Major-Minor`, where `Major` and `Minor`
% are integers representing the HTTP version in the reply header.
%
% * range(+Range)
% Ask for partial content. Range is a term _|Unit(From,To)|_,
% where `From` is an integer and `To` is either an integer or
% the atom `end`. HTTP 1.1 only supports Unit = `bytes`. E.g.,
% to ask for bytes 1000-1999, use the option
% range(bytes(1000,1999))
%
% * redirect(+Boolean)
% If `false` (default `true`), do _not_ automatically redirect
% if a 3XX code is received. Must be combined with
% status_code(Code) and one of the header options to read the
% redirect reply. In particular, without status_code(Code) a
% redirect is mapped to an exception.
%
% * status_code(-Code)
% If this option is present and Code unifies with the HTTP
% status code, do *not* translate errors (4xx, 5xx) into an
% exception. Instead, http_open/3 behaves as if 2xx (success) is
% returned, providing the application to read the error document
% from the returned stream.
%
% * output(-Out)
% Unify the output stream with Out and do not close it. This can
% be used to upgrade a connection.
%
% * timeout(+Timeout)
% If provided, set a timeout on the stream using set_stream/2.
% With this option if no new data arrives within Timeout seconds
% the stream raises an exception. Default is to wait forever
% (=infinite=).
%
% * post(+Data)
% Issue a =POST= request on the HTTP server. Data is
% handed to http_post_data/3.
%
% * proxy(+Host:Port)
% Use an HTTP proxy to connect to the outside world. See also
% socket:proxy_for_url/3. This option overrules the proxy
% specification defined by socket:proxy_for_url/3.
%
% * proxy(+Host, +Port)
% Synonym for proxy(+Host:Port). Deprecated.
%
% * proxy_authorization(+Authorization)
% Send authorization to the proxy. Otherwise the same as the
% =authorization= option.
%
% * bypass_proxy(+Boolean)
% If =true=, bypass proxy hooks. Default is =false=.
%
% * request_header(Name = Value)
% Additional name-value parts are added in the order of
% appearance to the HTTP request header. No interpretation is
% done.
%
% * max_redirect(+Max)
% Sets the maximum length of a redirection chain. This is needed
% for some IRIs that redirect indefinitely to other IRIs without
% looping (e.g., redirecting to IRIs with a random element in them).
% Max must be either a non-negative integer or the atom `infinite`.
% The default value is `10`.
%
% * user_agent(+Agent)
% Defines the value of the =|User-Agent|= field of the HTTP
% header. Default is =SWI-Prolog=.
%
% The hook http:open_options/2 can be used to provide default
% options based on the broken-down URL. The option
% status_code(-Code) is particularly useful to query *REST*
% interfaces that commonly return status codes other than `200`
% that need to be be processed by the client code.
%
% @param URL is either an atom or string (url) or a list of _parts_.
%
% When provided, this list may contain the fields
% =scheme=, =user=, =password=, =host=, =port=, =path=
% and either =query_string= (whose argument is an atom)
% or =search= (whose argument is a list of
% =|Name(Value)|= or =|Name=Value|= compound terms).
% Only =host= is mandatory. The example below opens the
% URL =|http://www.example.com/my/path?q=Hello%20World&lang=en|=.
% Note that values must *not* be quoted because the
% library inserts the required quotes.
%
% ==
% http_open([ host('www.example.com'),
% path('/my/path'),
% search([ q='Hello world',
% lang=en
% ])
% ])
% ==
%
% @throws error(existence_error(url, Id),Context) is raised if the
% HTTP result code is not in the range 200..299. Context has the
% shape context(Message, status(Code, TextCode)), where `Code` is the
% numeric HTTP code and `TextCode` is the textual description thereof
% provided by the server. `Message` may provide additional details or
% may be unbound.
%
% @see ssl_context/3 for SSL related options if
% library(http/http_ssl_plugin) is loaded.
:- multifile
socket:proxy_for_url/3. % +URL, +Host, -ProxyList
http_open(URL, Stream, QOptions) :-
meta_options(is_meta, QOptions, Options0),
( atomic(URL)
-> parse_url_ex(URL, Parts)
; Parts = URL
),
autoload_https(Parts),
upgrade_ssl_options(Parts, Options0, Options),
add_authorization(Parts, Options, Options1),
findall(HostOptions, hooked_options(Parts, HostOptions), AllHostOptions),
foldl(merge_options_rev, AllHostOptions, Options1, Options2),
( option(bypass_proxy(true), Options)
-> try_http_proxy(direct, Parts, Stream, Options2)
; term_variables(Options2, Vars2),
findall(Result-Vars2,
try_a_proxy(Parts, Result, Options2),
ResultList),
last(ResultList, Status-Vars2)
-> ( Status = true(_Proxy, Stream)
-> true
; throw(error(proxy_error(tried(ResultList)), _))
)
; try_http_proxy(direct, Parts, Stream, Options2)
).
try_a_proxy(Parts, Result, Options) :-
parts_uri(Parts, AtomicURL),
option(host(Host), Parts),
( ( option(proxy(ProxyHost:ProxyPort), Options)
; is_list(Options),
memberchk(proxy(ProxyHost,ProxyPort), Options)
)
-> Proxy = proxy(ProxyHost, ProxyPort)
; socket:proxy_for_url(AtomicURL, Host, Proxy)
),
debug(http(proxy),
'http_open: Connecting via ~w to ~w', [Proxy, AtomicURL]),
( catch(try_http_proxy(Proxy, Parts, Stream, Options), E, true)
-> ( var(E)
-> !, Result = true(Proxy, Stream)
; Result = error(Proxy, E)
)
; Result = false(Proxy)
),
debug(http(proxy), 'http_open: ~w: ~p', [Proxy, Result]).
try_http_proxy(Method, Parts, Stream, Options0) :-
option(host(Host), Parts),
( Method == direct
-> parts_request_uri(Parts, RequestURI)
; parts_uri(Parts, RequestURI)
),
select_option(visited(Visited0), Options0, OptionsV, []),
Options = [visited([Parts|Visited0])|OptionsV],
parts_scheme(Parts, Scheme),
default_port(Scheme, DefPort),
url_part(port(Port), Parts, DefPort),
host_and_port(Host, DefPort, Port, HostPort),
( option(connection(Connection), Options0),
keep_alive(Connection),
get_from_pool(Host:Port, StreamPair),
debug(http(connection), 'Trying Keep-alive to ~p using ~p',
[ Host:Port, StreamPair ]),
catch(send_rec_header(StreamPair, Stream, HostPort,
RequestURI, Parts, Options),
error(E,_),
keep_alive_error(E))
-> true
; http:http_connection_over_proxy(Method, Parts, Host:Port,
SocketStreamPair, Options, Options1),
( catch(http:http_protocol_hook(Scheme, Parts,
SocketStreamPair,
StreamPair, Options),
Error,
( close(SocketStreamPair, [force(true)]),
throw(Error)))
-> true
; StreamPair = SocketStreamPair
),
send_rec_header(StreamPair, Stream, HostPort,
RequestURI, Parts, Options1)
),
return_final_url(Options).
http:http_connection_over_proxy(direct, _, Host:Port,
StreamPair, Options, Options) :-
!,
open_socket(Host:Port, StreamPair, Options).
http:http_connection_over_proxy(proxy(ProxyHost, ProxyPort), Parts, _,
StreamPair, Options, Options) :-
\+ ( memberchk(scheme(Scheme), Parts),
secure_scheme(Scheme)
),
!,
% We do not want any /more/ proxy after this
open_socket(ProxyHost:ProxyPort, StreamPair,
[bypass_proxy(true)|Options]).
http:http_connection_over_proxy(socks(SocksHost, SocksPort), _Parts, Host:Port,
StreamPair, Options, Options) :-
!,
tcp_connect(SocksHost:SocksPort, StreamPair, [bypass_proxy(true)]),
catch(negotiate_socks_connection(Host:Port, StreamPair),
Error,
( close(StreamPair, [force(true)]),
throw(Error)
)).
%! hooked_options(+Parts, -Options) is nondet.
%
% Calls http:open_options/2 and if necessary upgrades old SSL
% cacerts_file(File) option to a cacerts(List) option to ensure proper
% merging of options.
hooked_options(Parts, Options) :-
http:open_options(Parts, Options0),
upgrade_ssl_options(Parts, Options0, Options).
upgrade_ssl_options(Parts, Options0, Options) :-
( requires_ssl(Parts)
-> ssl:upgrade_legacy_options(Options0, Options)
; Options = Options0
).
merge_options_rev(Old, New, Merged) :-
merge_options(New, Old, Merged).
is_meta(pem_password_hook). % SSL plugin callbacks
is_meta(cert_verify_hook).
http:http_protocol_hook(http, _, StreamPair, StreamPair, _).
default_port(https, 443) :- !.
default_port(wss, 443) :- !.
default_port(_, 80).
host_and_port(Host, DefPort, DefPort, Host) :- !.
host_and_port(Host, _, Port, Host:Port).
%! autoload_https(+Parts) is det.
%
% If the requested scheme is https or wss, load the HTTPS plugin.
autoload_https(Parts) :-
requires_ssl(Parts),
memberchk(scheme(S), Parts),
\+ clause(http:http_protocol_hook(S, _, StreamPair, StreamPair, _),_),
exists_source(library(http/http_ssl_plugin)),
!,
use_module(library(http/http_ssl_plugin)).
autoload_https(_).
requires_ssl(Parts) :-
memberchk(scheme(S), Parts),
secure_scheme(S).
secure_scheme(https).
secure_scheme(wss).
%! send_rec_header(+StreamPair, -Stream,
%! +Host, +RequestURI, +Parts, +Options) is det.
%
% Send header to Out and process reply. If there is an error or
% failure, close In and Out and return the error or failure.
send_rec_header(StreamPair, Stream, Host, RequestURI, Parts, Options) :-
( catch(guarded_send_rec_header(StreamPair, Stream,
Host, RequestURI, Parts, Options),
E, true)
-> ( var(E)
-> ( option(output(StreamPair), Options)
-> true
; true
)
; close(StreamPair, [force(true)]),
throw(E)
)
; close(StreamPair, [force(true)]),
fail
).
guarded_send_rec_header(StreamPair, Stream, Host, RequestURI, Parts, Options) :-
user_agent(Agent, Options),
method(Options, MNAME),
http_version(Version),
option(connection(Connection), Options, close),
debug(http(send_request), "> ~w ~w HTTP/~w", [MNAME, RequestURI, Version]),
debug(http(send_request), "> Host: ~w", [Host]),
debug(http(send_request), "> User-Agent: ~w", [Agent]),
debug(http(send_request), "> Connection: ~w", [Connection]),
format(StreamPair,
'~w ~w HTTP/~w\r\n\c
Host: ~w\r\n\c
User-Agent: ~w\r\n\c
Connection: ~w\r\n',
[MNAME, RequestURI, Version, Host, Agent, Connection]),
parts_uri(Parts, URI),
x_headers(Options, URI, StreamPair),
write_cookies(StreamPair, Parts, Options),
( option(post(PostData), Options)
-> http_header:http_post_data(PostData, StreamPair, [])
; format(StreamPair, '\r\n', [])
),
flush_output(StreamPair),
% read the reply header
read_header(StreamPair, Parts, ReplyVersion, Code, Comment, Lines),
update_cookies(Lines, Parts, Options),
do_open(ReplyVersion, Code, Comment, Lines, Options, Parts, Host,
StreamPair, Stream).
%! http_version(-Version:atom) is det.
%
% HTTP version we publish. We can only use 1.1 if we support
% chunked encoding.
http_version('1.1') :-
http:current_transfer_encoding(chunked),
!.
http_version('1.0').
method(Options, MNAME) :-
option(post(_), Options),
!,
option(method(M), Options, post),
( map_method(M, MNAME0)
-> MNAME = MNAME0
; domain_error(method, M)
).
method(Options, MNAME) :-
option(method(M), Options, get),
( map_method(M, MNAME0)
-> MNAME = MNAME0
; map_method(_, M)
-> MNAME = M
; domain_error(method, M)
).
map_method(delete, 'DELETE').
map_method(get, 'GET').
map_method(head, 'HEAD').
map_method(post, 'POST').
map_method(put, 'PUT').
map_method(patch, 'PATCH').
map_method(options, 'OPTIONS').
%! x_headers(+Options, +URI, +Out) is det.
%
% Emit extra headers from request_header(Name=Value) options in
% Options.
%
% @tbd Use user/password fields
x_headers(Options, URI, Out) :-
x_headers_(Options, [url(URI)|Options], Out).
x_headers_([], _, _).
x_headers_([H|T], Options, Out) :-
x_header(H, Options, Out),
x_headers_(T, Options, Out).
x_header(request_header(Name=Value), _, Out) :-
!,
debug(http(send_request), "> ~w: ~w", [Name, Value]),
format(Out, '~w: ~w\r\n', [Name, Value]).
x_header(proxy_authorization(ProxyAuthorization), Options, Out) :-
!,
auth_header(ProxyAuthorization, Options, 'Proxy-Authorization', Out).
x_header(authorization(Authorization), Options, Out) :-
!,
auth_header(Authorization, Options, 'Authorization', Out).
x_header(range(Spec), _, Out) :-
!,
Spec =.. [Unit, From, To],
( To == end
-> ToT = ''
; must_be(integer, To),
ToT = To
),
debug(http(send_request), "> Range: ~w=~d-~w", [Unit, From, ToT]),
format(Out, 'Range: ~w=~d-~w\r\n', [Unit, From, ToT]).
x_header(_, _, _).
%! auth_header(+AuthOption, +Options, +HeaderName, +Out)
auth_header(basic(User, Password), _, Header, Out) :-
!,
format(codes(Codes), '~w:~w', [User, Password]),
phrase(base64(Codes), Base64Codes),
debug(http(send_request), "> ~w: Basic ~s", [Header, Base64Codes]),
format(Out, '~w: Basic ~s\r\n', [Header, Base64Codes]).
auth_header(bearer(Token), _, Header, Out) :-
!,
debug(http(send_request), "> ~w: Bearer ~w", [Header,Token]),
format(Out, '~w: Bearer ~w\r\n', [Header, Token]).
auth_header(Auth, Options, _, Out) :-
option(url(URL), Options),
add_method(Options, Options1),
http:authenticate_client(URL, send_auth_header(Auth, Out, Options1)),
!.
auth_header(Auth, _, _, _) :-
domain_error(authorization, Auth).
user_agent(Agent, Options) :-
( option(user_agent(Agent), Options)
-> true
; user_agent(Agent)
).
add_method(Options0, Options) :-
option(method(_), Options0),
!,
Options = Options0.
add_method(Options0, Options) :-
option(post(_), Options0),
!,
Options = [method(post)|Options0].
add_method(Options0, [method(get)|Options0]).
%! do_open(+HTTPVersion, +HTTPStatusCode, +HTTPStatusComment, +Header,
%! +Options, +Parts, +Host, +In, -FinalIn) is det.
%
% Handle the HTTP status once available. If 200-299, we are ok. If a
% redirect, redo the open, returning a new stream. Else issue an
% error.
%
% @error existence_error(url, URL)
% Redirections
do_open(_, Code, _, Lines, Options0, Parts, _, In, Stream) :-
redirect_code(Code),
option(redirect(true), Options0, true),
location(Lines, RequestURI),
!,
debug(http(redirect), 'http_open: redirecting to ~w', [RequestURI]),
close(In),
parts_uri(Parts, Base),
uri_resolve(RequestURI, Base, Redirected),
parse_url_ex(Redirected, RedirectedParts),
( redirect_limit_exceeded(Options0, Max)
-> format(atom(Comment), 'max_redirect (~w) limit exceeded', [Max]),
throw(error(permission_error(redirect, http, Redirected),
context(_, Comment)))
; redirect_loop(RedirectedParts, Options0)
-> throw(error(permission_error(redirect, http, Redirected),
context(_, 'Redirection loop')))
; true
),
redirect_options(Options0, Options),
http_open(RedirectedParts, Stream, Options).
% Need authentication
do_open(_Version, Code, _Comment, Lines, Options0, Parts, _Host, In0, Stream) :-
authenticate_code(Code),
option(authenticate(true), Options0, true),
parts_uri(Parts, URI),
parse_headers(Lines, Headers),
http:authenticate_client(
URI,
auth_reponse(Headers, Options0, Options)),
!,
close(In0),
http_open(Parts, Stream, Options).
% Accepted codes
do_open(Version, Code, _, Lines, Options, Parts, Host, In0, In) :-
( option(status_code(Code), Options),
Lines \== []
-> true
; successful_code(Code)
),
!,
parts_uri(Parts, URI),
parse_headers(Lines, Headers),
return_version(Options, Version),
return_size(Options, Headers),
return_fields(Options, Headers),
return_headers(Options, Headers),
consider_keep_alive(Lines, Parts, Host, In0, In1, Options),
transfer_encoding_filter(Lines, In1, In),
% properly re-initialise the stream
set_stream(In, file_name(URI)),
set_stream(In, record_position(true)).
do_open(_, _, _, [], Options, _, _, _, _) :-
option(connection(Connection), Options),
keep_alive(Connection),
!,
throw(error(keep_alive(closed),_)).
% report anything else as error
do_open(_Version, Code, Comment, _, _, Parts, _, _, _) :-
parts_uri(Parts, URI),
( map_error_code(Code, Error)
-> Formal =.. [Error, url, URI]
; Formal = existence_error(url, URI)
),
throw(error(Formal, context(_, status(Code, Comment)))).
successful_code(Code) :-
between(200, 299, Code).
%! redirect_limit_exceeded(+Options:list(compound), -Max:nonneg) is semidet.
%
% True if we have exceeded the maximum redirection length (default 10).
redirect_limit_exceeded(Options, Max) :-
option(visited(Visited), Options, []),
length(Visited, N),
option(max_redirect(Max), Options, 10),
(Max == infinite -> fail ; N > Max).
%! redirect_loop(+Parts, +Options) is semidet.
%
% True if we are in a redirection loop. Note that some sites
% redirect once to the same place using cookies or similar, so we
% allow for two tries. In fact, we should probably test whether
% authorization or cookie headers have changed.
redirect_loop(Parts, Options) :-
option(visited(Visited), Options, []),
include(==(Parts), Visited, Same),
length(Same, Count),
Count > 2.
%! redirect_options(+Options0, -Options) is det.
%
% A redirect from a POST should do a GET on the returned URI. This
% means we must remove the method(post) and post(Data) options
% from the original option-list.
redirect_options(Options0, Options) :-
( select_option(post(_), Options0, Options1)
-> true
; Options1 = Options0
),
( select_option(method(Method), Options1, Options),
\+ redirect_method(Method)
-> true
; Options = Options1
).
redirect_method(delete).
redirect_method(get).
redirect_method(head).
%! map_error_code(+HTTPCode, -PrologError) is semidet.
%
% Map HTTP error codes to Prolog errors.
%
% @tbd Many more maps. Unfortunately many have no sensible Prolog
% counterpart.
map_error_code(401, permission_error).
map_error_code(403, permission_error).
map_error_code(404, existence_error).
map_error_code(405, permission_error).
map_error_code(407, permission_error).
map_error_code(410, existence_error).
redirect_code(301). % Moved Permanently
redirect_code(302). % Found (previously "Moved Temporary")
redirect_code(303). % See Other
redirect_code(307). % Temporary Redirect
authenticate_code(401).
%! open_socket(+Address, -StreamPair, +Options) is det.
%
% Create and connect a client socket to Address. Options
%
% * timeout(+Timeout)
% Sets timeout on the stream, *after* connecting the
% socket.
%
% @tbd Make timeout also work on tcp_connect/4.
% @tbd This is the same as do_connect/4 in http_client.pl
open_socket(Address, StreamPair, Options) :-
debug(http(open), 'http_open: Connecting to ~p ...', [Address]),
tcp_connect(Address, StreamPair, Options),
stream_pair(StreamPair, In, Out),
debug(http(open), '\tok ~p ---> ~p', [In, Out]),
set_stream(In, record_position(false)),
( option(timeout(Timeout), Options)
-> set_stream(In, timeout(Timeout))
; true
).
return_version(Options, Major-Minor) :-
option(version(Major-Minor), Options, _).
return_size(Options, Headers) :-
( memberchk(content_length(Size), Headers)
-> option(size(Size), Options, _)
; true
).
return_fields([], _).
return_fields([header(Name, Value)|T], Headers) :-
!,
( Term =.. [Name,Value],
memberchk(Term, Headers)
-> true
; Value = ''
),
return_fields(T, Headers).
return_fields([_|T], Lines) :-
return_fields(T, Lines).
return_headers(Options, Headers) :-
option(headers(Headers), Options, _).
%! parse_headers(+Lines, -Headers:list(compound)) is det.
%
% Parse the header lines for the headers(-List) option. Invalid
% header lines are skipped, printing a warning using
% pring_message/2.
parse_headers([], []) :- !.
parse_headers([Line|Lines], Headers) :-
catch(http_parse_header(Line, [Header]), Error, true),
( var(Error)
-> Headers = [Header|More]
; print_message(warning, Error),
Headers = More
),
parse_headers(Lines, More).
%! return_final_url(+Options) is semidet.
%
% If Options contains final_url(URL), unify URL with the final
% URL after redirections.
return_final_url(Options) :-
option(final_url(URL), Options),
var(URL),
!,
option(visited([Parts|_]), Options),
parts_uri(Parts, URL).
return_final_url(_).
%! transfer_encoding_filter(+Lines, +In0, -In) is det.
%
% Install filters depending on the transfer encoding. If In0 is a
% stream-pair, we close the output side. If transfer-encoding is
% not specified, the content-encoding is interpreted as a synonym
% for transfer-encoding, because many servers incorrectly depend
% on this. Exceptions to this are content-types for which
% disable_encoding_filter/1 holds.
transfer_encoding_filter(Lines, In0, In) :-
transfer_encoding(Lines, Encoding),
!,
transfer_encoding_filter_(Encoding, In0, In).
transfer_encoding_filter(Lines, In0, In) :-
content_encoding(Lines, Encoding),
content_type(Lines, Type),
\+ http:disable_encoding_filter(Type),
!,
transfer_encoding_filter_(Encoding, In0, In).
transfer_encoding_filter(_, In, In).
transfer_encoding_filter_(Encoding, In0, In) :-
stream_pair(In0, In1, Out),
( nonvar(Out)
-> close(Out)
; true
),
( http:encoding_filter(Encoding, In1, In)
-> true
; domain_error(http_encoding, Encoding)
).
content_type(Lines, Type) :-
member(Line, Lines),
phrase(field('content-type'), Line, Rest),
!,
atom_codes(Type, Rest).
%! http:disable_encoding_filter(+ContentType) is semidet.
%
% Do not use the =|Content-encoding|= as =|Transfer-encoding|=
% encoding for specific values of ContentType. This predicate is
% multifile and can thus be extended by the user.
http:disable_encoding_filter('application/x-gzip').
http:disable_encoding_filter('application/x-tar').
http:disable_encoding_filter('x-world/x-vrml').
http:disable_encoding_filter('application/zip').
http:disable_encoding_filter('application/x-gzip').
http:disable_encoding_filter('application/x-zip-compressed').
http:disable_encoding_filter('application/x-compress').
http:disable_encoding_filter('application/x-compressed').
http:disable_encoding_filter('application/x-spoon').
%! transfer_encoding(+Lines, -Encoding) is semidet.
%
% True if Encoding is the value of the =|Transfer-encoding|=
% header.
transfer_encoding(Lines, Encoding) :-
what_encoding(transfer_encoding, Lines, Encoding).
what_encoding(What, Lines, Encoding) :-
member(Line, Lines),
phrase(encoding_(What, Debug), Line, Rest),
!,
atom_codes(Encoding, Rest),
debug(http(What), '~w: ~p', [Debug, Rest]).
encoding_(content_encoding, 'Content-encoding') -->
field('content-encoding').
encoding_(transfer_encoding, 'Transfer-encoding') -->
field('transfer-encoding').
%! content_encoding(+Lines, -Encoding) is semidet.
%
% True if Encoding is the value of the =|Content-encoding|=
% header.