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A fast event-based XML parser.
- SAX-style/fold parser which triggers events for open/closetags, attributes, text, etc.
- Low memory use (see memory benchmarks below).
- Very fast (see speed benchmarks below).
- Itcheats like Hexml does(doesn't expand entities, or most of the XML standard).
- Written in pure Haskell.
- CDATA is supported as of version 0.2.
Please see the bottom of this file for guidelines on contributing to this library.
Thehexml Haskell library usesan XML parser written in C, so that is the baseline we're trying tobeat or match roughly.
TheXeno.SAX module is faster than Hexml for simply walking thedocument. Hexml actually does more work, allocating a DOM.Xeno.DOMis slighly slower or faster than Hexml depending on the document,although it is 2x slower on a 211KB document.
Memory benchmarks for Xeno:
Case Bytes GCs Check4kb/xeno/sax 2,376 0 OK31kb/xeno/sax 1,824 0 OK211kb/xeno/sax 56,832 0 OK4kb/xeno/dom 11,360 0 OK31kb/xeno/dom 10,352 0 OK211kb/xeno/dom 1,082,816 0 OKI memory benchmarked Hexml, but most of its allocation happens in C,which GHC doesn't track. So the data wasn't useful to compare.
Speed benchmarks:
benchmarking 4KB/hexml/domtime 6.317 μs (6.279 μs .. 6.354 μs) 1.000 R² (1.000 R² .. 1.000 R²)mean 6.333 μs (6.307 μs .. 6.362 μs)std dev 97.15 ns (77.15 ns .. 125.3 ns)variance introduced by outliers: 13% (moderately inflated)benchmarking 4KB/xeno/saxtime 5.152 μs (5.131 μs .. 5.179 μs) 1.000 R² (1.000 R² .. 1.000 R²)mean 5.139 μs (5.128 μs .. 5.161 μs)std dev 58.02 ns (41.25 ns .. 85.41 ns)benchmarking 4KB/xeno/domtime 10.93 μs (10.83 μs .. 11.14 μs) 0.994 R² (0.983 R² .. 0.999 R²)mean 11.35 μs (11.12 μs .. 11.91 μs)std dev 1.188 μs (458.7 ns .. 2.148 μs)variance introduced by outliers: 87% (severely inflated)benchmarking 31KB/hexml/domtime 9.405 μs (9.348 μs .. 9.480 μs) 0.999 R² (0.998 R² .. 0.999 R²)mean 9.745 μs (9.599 μs .. 10.06 μs)std dev 745.3 ns (598.6 ns .. 902.4 ns)variance introduced by outliers: 78% (severely inflated)benchmarking 31KB/xeno/saxtime 2.736 μs (2.723 μs .. 2.753 μs) 1.000 R² (1.000 R² .. 1.000 R²)mean 2.757 μs (2.742 μs .. 2.791 μs)std dev 76.93 ns (43.62 ns .. 136.1 ns)variance introduced by outliers: 35% (moderately inflated)benchmarking 31KB/xeno/domtime 5.767 μs (5.735 μs .. 5.814 μs) 0.999 R² (0.999 R² .. 1.000 R²)mean 5.759 μs (5.728 μs .. 5.810 μs)std dev 127.3 ns (79.02 ns .. 177.2 ns)variance introduced by outliers: 24% (moderately inflated)benchmarking 211KB/hexml/domtime 260.3 μs (259.8 μs .. 260.8 μs) 1.000 R² (1.000 R² .. 1.000 R²)mean 259.9 μs (259.7 μs .. 260.3 μs)std dev 959.9 ns (821.8 ns .. 1.178 μs)benchmarking 211KB/xeno/saxtime 249.2 μs (248.5 μs .. 250.1 μs) 1.000 R² (1.000 R² .. 1.000 R²)mean 251.5 μs (250.6 μs .. 253.0 μs)std dev 3.944 μs (3.032 μs .. 5.345 μs)benchmarking 211KB/xeno/domtime 543.1 μs (539.4 μs .. 547.0 μs) 0.999 R² (0.999 R² .. 1.000 R²)mean 550.0 μs (545.3 μs .. 553.6 μs)std dev 14.39 μs (12.45 μs .. 17.12 μs)variance introduced by outliers: 17% (moderately inflated)Easy as running the parse function:
> parse"<p key='val' x=\"foo\" k=\"\"><a><hr/>hi</a><b>sup</b>hi</p>"Right (Node"p" [("key","val"), ("x","foo"), ("k","")] [Element (Node"a"[] [Element (Node"hr"[][]),Text"hi"]) ,Element (Node"b"[] [Text"sup"]) ,Text"hi" ])
Quickly dumping XML:
>let input="Text<tag prop='value'>Hello, World!</tag><x><y prop=\"x\">Content!</y></x>Trailing."> dump input"Text"<tag prop="value">"Hello, World!"</tag><x><y prop="x">"Content!"</y></x>"Trailing."
Folding over XML:
> foldconst (\m _ _-> m+1)constconstconstconst0 input-- Count attributes.Right2
> fold (\m _-> m+1) (\m _ _-> m)constconstconstconst0 input-- Count elements.Right3
Most general XML processor:
process::Monadm=> (ByteString->m())--^ Open tag.-> (ByteString->ByteString->m())--^ Tag attribute.-> (ByteString->m())--^ End open tag.-> (ByteString->m())--^ Text.-> (ByteString->m())--^ Close tag.->ByteString--^ Input string.->m()
You can use any monad you want. IO, State, etc. For example,fold isimplemented like this:
fold openF attrF endOpenF textF closeF s str= execState (process (\name-> modify (\s'-> openF s' name)) (\key value-> modify (\s'-> attrF s' key value)) (\name-> modify (\s'-> endOpenF s' name)) (\text-> modify (\s'-> textF s' text)) (\name-> modify (\s'-> closeF s' name)) str) s
Theprocess is marked as INLINE, which means use-sites of it willinline, and your particular monad's type will be potentially erasedfor great performance.
See CONTRIBUTORS.md
All contributions and bug fixes are welcome and will be credited appropriately, as long as they are aligned with the goals of this library: speed and memory efficiency. In practical terms, patches and additional features should not introduce significant performance regressions.