diff --git a/Cargo.toml b/Cargo.toml
index 2085914f..bc13c81f 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -45,3 +45,4 @@ openssl = { version = "0.10.29", features = ["vendored"] }
native-tls = "0.2.4"
chrono = "0.4.11"
select = "0.4.3"
+roxmltree = "0.11.0"
diff --git a/README.md b/README.md
index 9d5faaaf..d8c4acd8 100644
--- a/README.md
+++ b/README.md
@@ -425,8 +425,9 @@ The modules that ship with Scryer Prolog are also called
* [`http/http_open`](src/lib/http/http_open.pl) Open a stream to
read answers from web servers. HTTPS is also supported.
* [`sgml`](src/lib/sgml.pl)
- `load_html/3` represents HTML documents as Prolog terms
- for convenient and efficient reasoning. See also `library(xpath)`.
+ `load_html/3` and `load_xml/3` represent HTML and XML documents
+ as Prolog terms for convenient and efficient reasoning. Use
+ `library(xpath)` to extract information from parsed documents.
* [`xpath`](src/lib/xpath.pl)
The predicate `xpath/3` is used for convenient reasoning about
HTML and XML documents, inspired by the XPath language. This
diff --git a/src/clause_types.rs b/src/clause_types.rs
index 5b4e56ff..7b7923c7 100644
--- a/src/clause_types.rs
+++ b/src/clause_types.rs
@@ -299,7 +299,8 @@ pub enum SystemClauseType {
Ed25519Verify,
Ed25519NewKeyPair,
Ed25519KeyPairPublicKey,
- LoadHTML
+ LoadHTML,
+ LoadXML,
}
impl SystemClauseType {
@@ -498,6 +499,7 @@ impl SystemClauseType {
&SystemClauseType::Ed25519NewKeyPair => clause_name!("$ed25519_new_keypair"),
&SystemClauseType::Ed25519KeyPairPublicKey => clause_name!("$ed25519_keypair_public_key"),
&SystemClauseType::LoadHTML => clause_name!("$load_html"),
+ &SystemClauseType::LoadXML => clause_name!("$load_xml"),
}
}
@@ -676,6 +678,7 @@ impl SystemClauseType {
("$ed25519_new_keypair", 1) => Some(SystemClauseType::Ed25519NewKeyPair),
("$ed25519_keypair_public_key", 2) => Some(SystemClauseType::Ed25519KeyPairPublicKey),
("$load_html", 3) => Some(SystemClauseType::LoadHTML),
+ ("$load_xml", 3) => Some(SystemClauseType::LoadXML),
_ => None,
}
}
diff --git a/src/lib/sgml.pl b/src/lib/sgml.pl
index 56825920..460646b7 100644
--- a/src/lib/sgml.pl
+++ b/src/lib/sgml.pl
@@ -1,18 +1,23 @@
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
- Predicates for parsing markup documents.
+ Predicates for parsing HTML and XML documents.
Written June 2020 by Markus Triska (triska@metalevel.at)
Part of Scryer Prolog.
- Currently, only a single predicate is provided:
+ Currently, two predicates are provided:
- load_html(+In, -Es, +Options)
- =============================
+ - load_html(+Source, -Es, +Options)
+ - load_xml(+Source, -Es, +Options)
- In must be a stream, specified as stream(S), and Es is unified with
- a list of elements of the form:
+ These predicates parse HTML and XML documents, respectively.
+
+ Source must be a stream, specified as stream(S), or a file,
+ specified as file(Name), where Name is a list of characters, or a
+ list of characters with the document contents.
+
+ Es is unified with the abstract syntax tree of the parsed document,
+ represented as a list of elements where each is of the form:
* a list of characters, representing text
-
* element(Name, Attrs, Children)
- Name is the name of the tag
- Attrs is a list of Key=Value pairs:
@@ -22,21 +27,62 @@
Currently, Options are ignored. In the future, more options may be
provided to control parsing.
- Use http_open/3 from library(http/http_open) to read answers from
- web servers via streams.
+ Example:
+
+ ?- load_html("Hello!", Es, []).
+
+ Yielding:
+
+ Es = [element(html,[],
+ [element(head,[],
+ [element(title,[],
+ ["Hello!"])]),
+ element(body,[],[])])].
library(xpath) provides convenient reasoning about parsed documents.
+ For example, to fetch the title of the document above, we can use:
+
+ ?- load_html("Hello!", Es, []),
+ xpath(Es, //title(text), T).
+
+ Yielding T = "Hello!".
+
+ Use http_open/3 from library(http/http_open) to read answers from
+ web servers via streams.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
-:- module(sgml, [load_html/3]).
+:- module(sgml, [load_html/3,
+ load_xml/3]).
:- use_module(library(iso_ext)).
:- use_module(library(error)).
+:- use_module(library(dcgs)).
+:- use_module(library(pio)).
-load_html(stream(Stream), [E], Options) :-
+load_html(Source, Es, Options) :-
+ load_structure_(Source, Es, Options, html).
+load_xml(Source, Es, Options) :-
+ load_structure_(Source, Es, Options, xml).
+
+list([]) --> [].
+list([L|Ls]) --> [L], list(Ls).
+
+load_structure_([], [], _, _).
+load_structure_([C|Cs], [E], Options, What) :-
+ load_(What, [C|Cs], E, Options).
+load_structure_(file(Fs), [E], Options, What) :-
+ must_be(list, Options),
+ must_be(list, Fs),
+ atom_chars(File, Fs),
+ once(phrase_from_file(list(Cs), File)),
+ load_(What, Cs, E, Options).
+load_structure_(stream(Stream), [E], Options, What) :-
must_be(list, Options),
read_to_end(Stream, Cs),
- '$load_html'(Cs, E, []).
+ load_(What, Cs, E, Options).
+
+load_(html, Cs, E, Options) :- '$load_html'(Cs, E, Options).
+load_(xml, Cs, E, Options) :- '$load_xml'(Cs, E, Options).
read_to_end(Stream, Cs) :-
'$get_n_chars'(Stream, 4096, Cs0),
diff --git a/src/machine/system_calls.rs b/src/machine/system_calls.rs
index 75fd9a31..97c16867 100644
--- a/src/machine/system_calls.rs
+++ b/src/machine/system_calls.rs
@@ -53,6 +53,7 @@ use crate::openssl::nid::Nid;
use crate::native_tls::TlsConnector;
extern crate select;
+use roxmltree;
pub fn get_key() -> KeyEvent {
let key;
@@ -5568,11 +5569,71 @@ impl MachineState {
self.unify(self[temp_v!(2)], result);
}
+ &SystemClauseType::LoadXML => {
+ let string = self.heap_pstr_iter(self[temp_v!(1)]).to_string();
+ match roxmltree::Document::parse(&string) {
+ Ok(doc) => { let result = self.xml_node_to_term(indices, doc.root_element());
+ self.unify(self[temp_v!(2)], result);
+ }
+ _ => { self.fail = true;
+ return Ok(());
+ }
+ }
+ }
};
return_from_clause!(self.last_call, self)
}
+ pub(super)
+ fn xml_node_to_term(
+ &mut self,
+ indices: &mut IndexStore,
+ node: roxmltree::Node,
+ ) -> Addr {
+ if node.has_children() {
+ let mut avec = Vec::new();
+ for attr in node.attributes() {
+ let chars = clause_name!(String::from(attr.name()), indices.atom_tbl);
+ let name = self.heap.to_unifiable(
+ HeapCellValue::Atom(chars, None)
+ );
+
+ let value = self.heap.put_complete_string(&attr.value());
+
+ avec.push(HeapCellValue::Addr(Addr::HeapCell(self.heap.h())));
+
+ self.heap.push(HeapCellValue::NamedStr(2, clause_name!("="), None));
+ self.heap.push(HeapCellValue::Addr(name));
+ self.heap.push(HeapCellValue::Addr(value));
+ }
+ let attrs = Addr::HeapCell(self.heap.to_list(avec.into_iter()));
+
+ let mut cvec = Vec::new();
+ for child in node.children() {
+ cvec.push(self.xml_node_to_term(indices, child));
+ }
+ let children = Addr::HeapCell(self.heap.to_list(cvec.into_iter()));
+
+ let chars = clause_name!(String::from(node.tag_name().name()), indices.atom_tbl);
+ let tag = self.heap.to_unifiable(
+ HeapCellValue::Atom(chars, None)
+ );
+
+ let result = Addr::HeapCell(self.heap.h());
+
+ self.heap.push(HeapCellValue::NamedStr(3, clause_name!("element"), None));
+ self.heap.push(HeapCellValue::Addr(tag));
+ self.heap.push(HeapCellValue::Addr(attrs));
+ self.heap.push(HeapCellValue::Addr(children));
+
+ result
+ } else {
+ let string = String::from(node.text().unwrap());
+ self.heap.put_complete_string(&string)
+ }
+ }
+
pub(super)
fn html_node_to_term(
&mut self,