roxmltree

Represents an XML 1.0 document as a read-only tree.

Why read-only?

Because in some cases all you need is to retrieve some data from an XML document. And for such cases, we can make a lot of optimizations.

As for roxmltree, it's fast not only because it's read-only, but also because it uses xmlparser, which is many times faster than xml-rs. See the Performance section for details.

Parsing behavior

Sadly, XML can be parsed in many different ways. roxmltree tries to mimic the behavior of Python's lxml.

Unlike lxml, roxmltree does support comments outside the root element.

Fo more details see docs/parsing.md.

Alternatives

* Rust-based for now.

Feature/Crate	roxmltree	xmltree	elementtree	sxd-document	treexml
Element namespace resolving	✔	✔	✔	~1
Attribute namespace resolving	✔			✔
Entity references	✔	⚠	⚠	⚠	⚠
Character references	✔	✔	✔	✔	✔
Attribute-Value normalization	✔
Comments	✔			✔
Processing instructions	✔	⚠		✔
UTF-8 BOM	✔	⚠	⚠	⚠	⚠
Non UTF-8 input
Complete DTD support
Position preserving2	✔
xml:space
Tree modifications		✔	✔	✔	✔
Writing		✔	✔	✔	✔
No unsafe	✔	✔	~3		✔
Size overhead4	~62KiB	~80KiB	~96KiB	~130KiB	~110KiB
Dependencies	1	2	18	2	14
Tested version	0.4.0	0.8.0	0.5.0	0.2.6	0.7.0
License	MIT / Apache-2.0	MIT	BSD-3-Clause	MIT	MIT

Legend:

• ✔ - supported
• ⚠ - parsing error
• ~ - partial
• nothing - not supported

Notes:

1. No default namespace propagation.
2. roxmltree keeps all node and attribute positions in the original document, so you can easily retrieve it if you need it. See examples/print_pos.rs for details.
3. In the string_cache crate.
4. Binary size overhead according to cargo-bloat.

Performance

test large_roxmltree     ... bench:   5,609,303 ns/iter (+/- 105,511)
test large_sdx_document  ... bench:  10,299,996 ns/iter (+/- 315,027)
test large_xmltree       ... bench:  32,797,800 ns/iter (+/- 134,016)
test large_treexml       ... bench:  31,380,063 ns/iter (+/- 71,732)
test large_elementtree   ... bench:  32,121,979 ns/iter (+/- 264,842)

test medium_roxmltree    ... bench:   1,208,790 ns/iter (+/- 4,041)
test medium_sdx_document ... bench:   3,601,921 ns/iter (+/- 14,758)
test medium_treexml      ... bench:  10,975,247 ns/iter (+/- 22,692)
test medium_xmltree      ... bench:  11,601,320 ns/iter (+/- 46,216)
test medium_elementtree  ... bench:  11,550,227 ns/iter (+/- 17,991)

test tiny_roxmltree      ... bench:       8,002 ns/iter (+/- 73)
test tiny_sdx_document   ... bench:      26,835 ns/iter (+/- 47)
test tiny_xmltree        ... bench:      47,199 ns/iter (+/- 110)
test tiny_treexml        ... bench:      50,399 ns/iter (+/- 55)
test tiny_elementtree    ... bench:      51,569 ns/iter (+/- 165)

roxmltree uses xmlparser internally, while sdx-document uses its own implementation and xmltree, elementtree and treexml use the xml-rs crate. Here is a comparison between xmlparser and xml-rs:

test large_xmlparser     ... bench:   2,149,545 ns/iter (+/- 2,689)
test large_xmlrs         ... bench:  28,252,304 ns/iter (+/- 27,852)

test medium_xmlparser    ... bench:     517,778 ns/iter (+/- 1,842)
test medium_xmlrs        ... bench:  10,237,568 ns/iter (+/- 13,497)

test tiny_xmlparser      ... bench:       4,283 ns/iter (+/- 29)
test tiny_xmlrs          ... bench:      45,832 ns/iter (+/- 50)

Note: tree crates may use different xml-rs crate versions.

You can try it yourself by running cargo bench in the benches dir.

Safety

• This library must not panic. Any panic should be considered a critical bug and reported.
• This library forbids unsafe code.

Non-goals

• Complete XML support.
• Tree modification and writing.
• XPath/XQuery.

API

This library uses Rust's idiomatic API based on iterators. In case you are more familiar with browser/JS DOM APIs - you can check out tests/dom-api.rs to see how it can be converted into a Rust one.

Dependency

Rust >= 1.18

License

Licensed under either of

• Apache License v2.0
• MIT license

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.