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    1/*  Part of SWI-Prolog
    2
    3    Author:        Jan Wielemaker and Matt Lilley
    4    E-mail:        J.Wielemaker@vu.nl
    5    WWW:           http://www.swi-prolog.org
    6    Copyright (c)  2016, CWI Amsterdam
    7    All rights reserved.
    8
    9    Redistribution and use in source and binary forms, with or without
   10    modification, are permitted provided that the following conditions
   11    are met:
   12
   13    1. Redistributions of source code must retain the above copyright
   14       notice, this list of conditions and the following disclaimer.
   15
   16    2. Redistributions in binary form must reproduce the above copyright
   17       notice, this list of conditions and the following disclaimer in
   18       the documentation and/or other materials provided with the
   19       distribution.
   20
   21    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   22    "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   23    LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
   24    FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
   25    COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
   26    INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
   27    BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
   28    LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
   29    CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   30    LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
   31    ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   32    POSSIBILITY OF SUCH DAMAGE.
   33*/
   34
   35:- module(c14n2,
   36          [ xml_write_canonical/3       % +Stream, +Term, +Options
   37          ]).   38:- autoload(library(apply),[partition/4,maplist/3]).   39:- autoload(library(dicts),[dict_keys/2]).   40:- autoload(library(error),[instantiation_error/1,must_be/2]).   41:- autoload(library(lists),[member/2,append/2,select/3]).   42:- autoload(library(option),[option/3]).   43:- autoload(library(ordsets),[ord_subtract/3]).   44:- autoload(library(sgml_write),[xml_write/3]).

C14n2 canonical XML documents

C14n2 specifies a canonical XML document. This library writes such a document from an XML DOM as returned by the XML (or SGML) parser. The process takes two steps:

*/

 xml_write_canonical(+Stream, +DOM, +Options) is det
Write an XML DOM using the canonical conventions as defined by C14n2. Namespace declarations in the canonical document depend on the original namespace declarations. For this reason the input document must be parsed (see load_structure/3) using the dialect xmlns and the option keep_prefix(true).
   64xml_write_canonical(Stream, DOM, Options) :-
   65    option(method(Method), Options, 'http://www.w3.org/TR/2001/REC-xml-c14n-20010315'),
   66    xml_canonical_dom(DOM, CDOM, xml{in_ns:ns{}, out_ns:ns{}, is_root:true, method:Method}),
   67    xml_write(Stream, CDOM,
   68              [ header(false),
   69                layout(false),
   70                net(false)
   71              ]).
   72
   73xml_canonical_dom(Var, _, _) :-
   74    var(Var),
   75    !,
   76    instantiation_error(Var).
   77xml_canonical_dom(DOM, CDOM, Options) :-
   78    is_list(DOM),
   79    !,
   80    xml_canonical_list(DOM, CDOM, Options).
   81xml_canonical_dom(element( Name,  Attrs,  Content),
   82                  element(CName, CAttrs, CContent),
   83                  Options) :-
   84    !,
   85    InNS0  = Options.in_ns,
   86    OutNS0 = Options.out_ns,
   87    Method = Options.method,
   88    % We must include namespaces which appear in attributes in this element, too, if using xml-exc-c14n
   89    % This means we need to know what they are
   90    findall(NS, (member(Attr, Attrs), Attr = (NS:_=_), NS \== xmlns), NamespacesInAttrs),
   91    take_ns(Attrs, Method, NamespacesInAttrs, Name, Attrs1, InNS0, InNS),
   92    partition(has_ns, Attrs1, AttrsWithNS0, AttrsSans0),
   93    sort(1, @<, AttrsWithNS0, AttrsWithNS1),
   94    sort(1, @<, AttrsSans0, AttrsSans),
   95    put_elemns(Name, CName, InNS, OutNS0, OutNS1, KillDefault),
   96    put_ns_attrs(AttrsWithNS1, AttrsWithNS, InNS, OutNS1, OutNS),
   97    ns_attrs(OutNS0, OutNS, NSAttrs),
   98    (  Options.is_root == true ->
   99           (  select(xmlns=DefaultNamespace, NSAttrs, NSAttrs0)
  100              % If there is a default namespace, it must come first, and I dont think sort/4 can sort on two keys at once
  101           -> findall(xmlns:NS=URI, member(xmlns:NS=URI, Attrs), RootNSAttrs, NSAttrs0),
  102              sort(2, @=<, RootNSAttrs, RootNSAttrs0),
  103              RootNSAttrs1 = [xmlns=DefaultNamespace|RootNSAttrs0]
  104           ;  Method == 'http://www.w3.org/2001/10/xml-exc-c14n#'
  105           -> RootNSAttrs1 = NSAttrs
  106           ;  findall(xmlns:NS=URI, member(xmlns:NS=URI, Attrs), RootNSAttrs, NSAttrs),
  107              sort(2, @<, RootNSAttrs, RootNSAttrs1)
  108           ),
  109           append([KillDefault, RootNSAttrs1, AttrsSans, AttrsWithNS], CAttrs)
  110    ;  append([KillDefault, NSAttrs, AttrsSans, AttrsWithNS], CAttrs)
  111    ),
  112    must_be(list, Content),
  113    xml_canonical_list(Content, CContent,
  114                       Options.put(_{in_ns:InNS, out_ns:OutNS, is_root:false})).
  115xml_canonical_dom(CDATA, CDATA, _) :-
  116    atomic(CDATA).
  117
  118has_ns(_NS:_Name=_Value).
  119
  120xml_canonical_list([], [], _).
  121xml_canonical_list([H0|T0], [H|T], Options) :-
  122    xml_canonical_dom(H0, H, Options),
  123    xml_canonical_list(T0, T, Options).
  124
  125take_ns([], _, _, _, [], NSList, NSList).
  126take_ns([H|T0], Method, NamespacesInAttrs, Name, T, NSList0, NSList) :-
  127    xml_ns(H, NS, URL),
  128    !,
  129    (  include_ns(Name, Method, NamespacesInAttrs, NS, URL)
  130    -> take_ns(T0, Method, NamespacesInAttrs, Name, T, NSList0.put(NS, URL), NSList)
  131    ;  take_ns(T0, Method, NamespacesInAttrs, Name, T, NSList0, NSList)
  132    ).
  133take_ns([H|T0], Method, NamespacesInAttrs, Name, [H|T], NSList0, NSList) :-
  134    take_ns(T0, Method, NamespacesInAttrs, Name, T, NSList0, NSList).
  135
  136include_ns(ns(Prefix, URI):_, 'http://www.w3.org/2001/10/xml-exc-c14n#', _, Prefix, URI):- !.
  137include_ns(_, 'http://www.w3.org/2001/10/xml-exc-c14n#', NamespacesInAttrs, _Prefix, URI):-
  138        memberchk(URI, NamespacesInAttrs).
  139include_ns(_, 'http://www.w3.org/TR/2001/REC-xml-c14n-20010315', _, _, _):- !.
  140
  141
  142put_ns_attrs([], [], _, OutNS, OutNS).
  143put_ns_attrs([Name=Value|T0], [CName=Value|T], InNS, OutNS0, OutNS) :-
  144    put_ns(Name, CName, InNS, OutNS0, OutNS1),
  145    put_ns_attrs(T0, T, InNS, OutNS1, OutNS).
  146
  147put_elemns(Name, Name, _InNS, OutNS0, OutNS1, [xmlns='']) :-
  148    atom(Name),
  149    dict_pairs(OutNS0, _, Pairs),
  150    memberchk(URL-'', Pairs),
  151    !,
  152    del_dict(URL, OutNS0, '', OutNS1).
  153put_elemns(Name, CName, InNS, OutNS0, OutNS, []) :-
  154    put_ns(Name, CName, InNS, OutNS0, OutNS).
  155
  156put_ns(ns(NS, URL):Name, CName, _InNS, OutNS, OutNS) :-
  157    get_dict(URL, OutNS, NS),
  158    !,
  159    make_cname(NS:Name, CName).
  160put_ns(ns(NS, URL):Name, CName, _InNS, OutNS0, OutNS) :-
  161    !,
  162    make_cname(NS:Name, CName),
  163    OutNS = OutNS0.put(URL, NS).
  164put_ns(URL:Name, CName, _InNS, OutNS, OutNS) :-
  165    get_dict(URL, OutNS, NS),
  166    !,
  167    make_cname(NS:Name, CName).
  168put_ns(URL:Name, CName, InNS, OutNS0, OutNS) :-
  169    dict_pairs(InNS, _, Pairs),
  170    memberchk(NS-URL, Pairs),
  171    !,
  172    make_cname(NS:Name, CName),
  173    OutNS = OutNS0.put(URL, NS).
  174put_ns(Name, Name, _, OutNS, OutNS).
  175
  176ns_attrs(OutNS, OutNS, []) :- !.
  177ns_attrs(OutNS0, OutNS, NSAttrs) :-
  178    !,
  179    dict_keys(OutNS, URLs),
  180    dict_keys(OutNS0, URLs0),
  181    ord_subtract(URLs, URLs0, NewURLs),
  182    maplist(ns_attr(OutNS), NewURLs, NSAttrs0),
  183    sort(NSAttrs0, NSAttrs).
  184
  185ns_attr(Dict, URL, NSAttr) :-
  186    ns_simplify(xmlns:Dict.URL=URL, NSAttr).
  187
  188ns_simplify(xmlns:''=URL, xmlns=URL) :- !.
  189ns_simplify(xmlns:NS=URL, XMLNS=URL) :-
  190    make_cname(xmlns:NS, XMLNS).
  191
  192xml_ns(xmlns=URL, '', URL) :- !.
  193xml_ns(xmlns:NS=URL, NS, URL) :- !.
  194xml_ns(Name=URL, NS, URL) :-
  195    atom(Name),
  196    atom_concat('xmlns:', NS, Name).
  197
  198make_cname('':Name, Name) :- !.
  199make_cname(NS:Name, CName) :-
  200    atomic_list_concat([NS,Name], :, CName)