This also comes with some changes to the specs as the old behaviour of
the Evaluator was incorrect. The Evaluator would bail after matching a
single node but instead it's meant to continue until it runs out of
parent nodes.
This currently supports index predicates (e.g. "foo[10]") and predicates
using paths (e.g. foo[bar/baz]). The usage of boolean operators and more
complex expressions has not yet been tested as these are not yet
supported in the first place.
This currently comes with exactly 0% test coverage. Once I've
implemented all required handler methods I'll be updating the current
evaluator tests to use the compiler instead. This removes the need for
writing an entirely new set of tests.
Currently the compiler is only capable of compiling basic expressions
such as "foo", "foo/bar" and "foo[@x="y"]/bar".
This change is broken up in to two parts:
1. Using a Hash to track if a node is already in a NodeSet
2. Only calling take_ownership when an owner is set
== Using a Hash
Previously various methods such as NodeSet#push and NodeSet#unshift
would call Array#include? (on the internal "nodes" Array) to see if a
node is already present in the set. This is quite problematic
performance wise, especially for large NodeSets. In fact, for the
attached benchmark the vast majority of the time was spent in
Array#include? calls.
Because a NodeSet demands ordering of nodes and must be able to access
them by index (something Set can't do without relying on Enumerable), a
Hash is used to separately keep track of what nodes are in a NodeSet.
This means that checking the presence of a node is simply a matter of
checking a Hash key's presence.
== Calling take_ownership
The if-check for the "owner" variable has been moved out of the
"take_ownership" method and into the methods that call "take_ownership".
This ensures the method isn't called in the first place if no owner is
present, at the cost of slightly more code repetition. The same applies
to the "remove_ownership" method.
== Conclusion
The combined result is a speedup of about 50x when running the attached
concurrent_time_bench.rb benchmark.
While the performance difference between the old and new approach is
pretty much negligible, it's simply not needed to use #shift/#unshift
here.
Thanks to Mon_Ouie from the #ruby IRC channel for suggesting this.
Without this the following could happen:
1. Thread A acquires the lock and sets the ownership to A.
2. Thread A yields and returns
3. Thread B tries to acquire the lock
4. At this exact moment Thread A calls the "synchronize" method again
and sees that the "owner" variable is still set to Thread A
5. Both thread A and B can now access the underlying data in parallel,
possibly leading to corrupted objects
This can be demonstrated using the following script:
require 'oga'
lru = Oga::LRU.new(64)
threads = 50.times.map do
Thread.new do
loop do
number = rand(100)
lru[number] = number
end
end
end
threads.each(&:join)
Run this for a while on either JRuby or Rubinius and you'll end up with
errors such as "ConcurrencyError: Detected invalid array contents due to
unsynchronized modifications with concurrent users" on JRuby or
"ArgumentError: negative array size" on Rubinius.
Resetting the owner variable ensures the above can never happen. Thanks
to @chrisseaton for bringing this up earlier today.
Prevents a superfluous end tag of a self-closing HTML tag from
closing its parent element prematurely, for example:
```html
<object><param></param><param></param></object>
```
(note <param> is self closing) being turned into:
```html
<object><param/></object><param/>
```
This is a Nokogiri extension (as far as I'm aware) but it's useful
enough to also include in Oga. Selectors such as "foo:nth(2)" are simply
compiled to XPath "descendant::foo[position() = 2]".
Fixes#123
```
element = Oga::XML::Element.new(:name => 'div')
some_node.replace(element)
```
You can also pass a `String` to `replace` and it will be replaced with
a `Oga::XML::Text` node
```
some_node.replace('this will replace the current node with a text node')
```
closes#115
Currently this only disabled the automatic insertion of closing tags, in
the future this may also disable other features if deemed worth the
effort.
Fixes#107
This ensures that entities such as "½" are decoded properly.
Previously this would be ignored as the regular expression used for this
only matched [a-zA-Z].
This was adapted from PR #111.
Previous HTML such as this would be lexed incorrectly:
<div>
<ul>
<li>foo
</ul>
inside div
</div>
outside div
The lexer would see this as the following instead:
<div>
<ul>
<li>foo</li>
inside div
</ul>
outside div
</div>
This commit exposes the name of the closing tag to
XML::Lexer#on_element_end (omitted for self closing tags). This can be
used to automatically close nested tags that were left open, ensuring
the above HTML is lexer correctly.
The new setup ignores namespace prefixes as these are not used in HTML,
XML in turn won't even run the code to begin with since it doesn't allow
one to leave out closing tags.
By encoding single/double quotes we can potentially break input, so lets
stop doing this. This now ensures that this:
<foo>a"b</foo>
Is actually serialized back into the exact same instead of being
serialized into:
<foo>a"b</foo>
This allows for more fine grained control over when to close certain
elements. For example, an unclosed <tr> element should be closed first
when bumping into any element other than <td> or <th>. Using the old
NodeNameSet this would mean having to list every possible HTML element
out there. Using this new setup one can just create a whitelist of the
<td> and <th> elements.
When closing certain HTML elements the lexer should also close whatever
parent elements remain. For example, consider the following HTML:
<table>
<thead>
<tr>
<th>Foo
<th>Bar
<tbody>
...
</tbody>
</table>
Here the "<tbody>" element shouldn't only close the "<th>Bar" element
but also the parent "<tr>" and "<thead>" elements. This ensures we'd end
up with the following HTML:
<table>
<thead>
<tr>
<th>Foo</th>
<th>Bar</th>
</tr>
</thead>
<tbody>
...
</tbody>
</table>
Instead of garbage along the lines of this:
<table>
<thead>
<tr>
<th>Foo</th>
<th>Bar</th>
<tbody>
...
</tbody>
</table></tr></thead>
Fixes#99 (hopefully for good this time)
By using AST::Node#children directly with a splat we save ourselves an
extra method call. This in turn speeds up both the
xpath/evaluator/big_xml_average_bench.rb and
xpath/evaluator/node_matches_bench.rb benchmarks a little bit.
Using the benchmark xpath/evaluator/node_matches_bench.rb the results
prior to this commit were as following for 3 cases:
name only: 737633 i/s
namespace wildcard: 612196 i/s
name wildcard: 516030 i/s
With this commit said numbers have changed to the following:
name only: 746086 i/s
namespace wildcard: 1097168 i/s
name wildcard: 1151255 i/s
This results in the following increase of performance for each case:
name only: 1,011x (insignificant)
namespace wildcard: 1,79x
name wildcard: 2,23x
In the benchmark xpath/evaluator/big_xml_average_bench.rb the difference
isn't really noticable as said benchmark only queries elements by names,
of which the performance hasn't really improved.
This ensures that HTML such as this:
<li>foo
<li>bar
is parsed as this:
<li>foo</li>
<li>bar</li>
and not as this:
<li>
foo
<li>bar</li>
</li>
Fixes#97
This makes it easier to automatically insert preceding tokens when
starting a new element as we now have access to the name. Previously
on_element_start would be invoked first which doesn't receive an
argument.
The XML/HTML lexer is now capable of processing most invalid XML/HTML
(that I can think of at least). This is achieved by inserting missing
closing tags (where needed) and/or ignoring excessive closing tags. For
example, HTML such as this:
<a></a></p>
Results in the following tokens:
[:T_ELEM_START, nil, 1]
[:T_ELEM_NAME, 'a', 1]
[:T_ELEM_CLOSE, nil, 1]
In turn this HTML:
<a>
Results in these tokens:
[:T_ELEM_START, nil, 1]
[:T_ELEM_NAME, 'a', 1]
[:T_ELEM_CLOSE, nil, 1]
Fixes#84
Previously a single Ragel machine was used for processing HTML
script and style tags. This had the unfortunate side-effect that the
following was not parsed correctly (while being valid HTML):
<script>
var foo = "</style>";
</script>
The same applied to style tags:
<style>
/* </script> */
</style>
By using separate machines we can work around the above issue. The
downside is that this can produce multiple T_TEXT nodes, which have to
be stitched back together in the parser.
Similar to comments (ea8b4aa92f) and CDATA
tags (8acc7fc743) processing instructions
are now lexed in separate chunks _with_ proper support for streaming
input.
Related issue: #93
Instead of using a single token (T_CDATA) for a CDATA tag the lexer now
uses 3 tokens:
1. T_CDATA_START
2. T_CDATA_BODY
3. T_CDATA_END
The T_CDATA_BODY token can occur multiple times and is turned into a
single value in the XML parser. This is similar to the way strings are
lexed.
By changing the way CDATA tags are lexed Oga can now lex CDATA tags
containing newlines when using an IO as input. For example, this would
previously fail:
Oga.parse_xml(StringIO.new("<![CDATA[\nfoo]]>"))
Because IO input reads input per line the input for the lexer would be
as following:
"<![CDATA[\n"
"foo]]>"
Related issues: #93
This cache is flushed whenever Element#register_namespace is called.
When this cache is flushed it's also recursively flushed for all child
elements. This makes calls to Element#register_namespace a bit more
expensive but in turn calls to Element#available_namespaces will be a
lot faster.
The results of these methods is now cached until a Node is moved into
another NodeSet. This reduces the time spent in the
xpath/evaluator/big_xml_average_bench.rb benchmark from roughly 10
seconds to roughly 5 seconds per iteration.
In HTML the text of a script/style tag should be left untouched, no
entities must be converted. Doing so would break Javascript such as the
following:
foo&&bar;
Such code is often the result of minifiers doing their dirty business.
This was broken by introducing the process of lazy decoding of XML/HTML
entities. The new setup works similar to how XML::Text#text decodes any
entities that may be present.
Fixes#91
When querying an XML document that explicitly defines the default XML
namespace the XPath evaluator now correctly matches all nodes within
that namespace if no namespace prefix is given in the query. Previously
this would always return an empty set.
Instead of trying to make this class thread-safe I'm going with the
option of simply declaring it unsafe to mutate instances of XML::Text
while reading it in parallel. This removes the need for Mutex
allocations and keeps the code simple.
Fixes#82
Currently all operators are left-associative with no particular precedence. This
causes a few specs to fail for now. Outside of that the new parser should be
able to parse the same input as the Racc based parser.
Removing this makes the process of parsing larger XML documents a bit faster.
The downside is that NodeSet#initialize will no longer filter out duplicate
nodes, though this is not something Oga itself relies upon.
Methods such as NodeSet#push still do ignore elements already present.
This was utterly broken, mainly due to me overlooking it. There are now 2 new
callbacks to handle this properly:
* on_attribute: to handle a single attribute/value pair
* on_attributes: to handle a collection of attributes (as returned by
on_attribute)
By default on_attribut returns a Hash, on_attributes in turn merges all
attribute hashes into a single one. This ensures that on_element _actually_
receives the attributes as a Hash, instead of an Array with random
nil/XML::Attribute values.
Using Array#+ for large sets (e.g. in the benchmarks) is _really_ slow.
Interesting enough Array#unshift uses as much memory as the Racc parser and is
about as fast, even though it has to move memory around.
Instead of decoding entities in the lexer we'll do this whenever XML::Text#text
is called. This removes the overhead from the parsing phase and ensures the
process is only triggered when actually needed. Note that calling #to_xml and/or
the #inspect methods on a Text (or parent) instance will also trigger the entity
conversion process.
The new entity decoding API supports both regular entities (e.g. &) as well
as codepoint based entities (both regular and hexadecimal codepoints).
To allow safe read-only access to Text instances from multiple threads a mutex
is used. This mutex ensures that only 1 thread can trigger the conversion
process.
Fixes#68
This basically re-applies the technique used for HTML <script> tags. With this
extra addition I decided to rename/normalize a few things so it's easier to add
any extra tags in the future. One downside of this setup is that the following
will not be parsed by Oga:
<style>
</script>
</style>
The same applies to script tags containing a literal </style> tag. Since this
particular case is rather unlikely to occur I'm OK with not supporting it as it
_does_ simplify the lexer quite a bit.
Fixes#80
When lexing input in HTML mode the lexer has to treat _all_ content of a
<script> tag as plain text. This ensures that the lexer can process input such
as "x <y" and "// <foo>" correctly.
Fixes#70.
This changes the behaviour of after_element when parsing documents using the SAX
parsing API. Previously it would always receive a nil argument, which is kinda
pointless. This commit changes that by making sure it receives a namespace name
(if any) and the element name.
This fixes#54.
The old XPath "position() = 1" would work in Nokogiri due to the way they
retrieve descendants. In Oga however this would simply always return the first
node.
To fix this Oga now counts the amount of preceding siblings that match the same
full name.
This means that "foo[1]" uses this AST:
(predicate (test nil "foo") (int 1))
Instead of this AST:
(test nil "foo" (int 1))
This makes it easier for the XPath evaluator to process predicates correctly.
This method can be used to compare two NodeSet instances. By using
XML::NodeSet#equal_nodes?() the need for exposing the "nodes" instance variable
is also removed.
This expression could be used to get all elements that _don't_ have any
namespace. The problem is that this can't be expressed as just a node test,
instead the resulting XPath would have to look something like the following:
X[local-name() = name()]
However, since the XPath predicates are already created for pseudo classes and
such, also injecting the above into it would be a real big pain. As such I've
decided not to support it.
Instead of using "descendant-or-self" Oga will use "descendant". This ensures
that expressions such as "foo *" don't return a set also including the "foo"
element.
Nokogiri solves this problem in a somewhat different way by using //foo//* for
the CSS expression "foo *". While this works in Nokogiri the expression
"descendant-or-self::node()" is slow as a snail in Oga (due to its nature of
retrieving _all_ nodes first). By using "descendant" we can work around this
problem.
When running XPath queries such as "self::node()" the result should be a set
containing the document itself. This in turn fixes expressions such as
descendant-or-self::node()/a.
This removes parsing support for selectors such as :nth-child(-n-6). According
to the CSS spec this isn't valid anyway (confirmed by testing it in Chromium).
As a result there's no point in supporting it in any way.
When lexing multi-line strings everything used to work fine as long as the input
were to be read as a whole. However, when using an IO instance all hell would
break loose. Due to the lexer reading IO instances on a per line basis,
sometimes Ragel would end up setting "ts" to NULL. For example, the following
input would break the lexer:
<foo class="\nbar" />
Due to the input being read per line, the following data would be sent to the
lexer:
<foo class="\n
bar" />
This would result in different (or NULL) pointers being used for building a
string, in turn resulting in memory allocation errors.
To work around this the string lexing setup has been broken into separate
machines for single and double quoted strings. The tokens used have also been
changed so that instead of just "T_STRING" there are now the following tokens:
* T_STRING_SQUOTE
* T_STRING_DQUOTE
* T_STRING_BODY
A string can have multiple T_STRING_BODY tokens (= multi-line strings, only the
case for IO inputs). These strings are stitched back together by the parser.
This fixes#58.
Processing of this axis along with a predicate wouldn't quite work out. Even if
the predicate returned false the node would still be matched (which should not
be the case).
Previously input such as "x > y" would result in the following token sequences:
T_IDENT, T_CHILD, T_IDENT
This commit changes this to the following:
T_IDENT, T_SPACE, T_CHILD, T_IDENT
This allows the parser to use T_SPACE as a terminal token, this in turn prevents
around 16 shift/reduce conflicts from arising.
This does mean that input such as " > y" or " x > y" is now invalid. This
however can be solved by simply _not_ adding leading/trailing whitespace to CSS
queries.
Yorick Peterse
Dan Fockler
Jakub Pawlowicz
Tero Tasanen
Dmitry Krasnoukhov