unicode-trie#
A data structure for fast Unicode character metadata lookup, ported from ICU
Background#
When implementing many Unicode algorithms such as text segmentation,
normalization, bidi processing, etc., fast access to character metadata
is crucial to good performance. There over a million code points in the
Unicode standard, many of which produce the same result when looked up,
so an array or hash table is not appropriate - those data structures are
fast but would require a lot of memory. The data is generally
grouped in ranges, so you could do a binary search, but that is not
fast enough for some applications.
The International Components for Unicode (ICU) project
came up with a data structure based on a Trie that provides fast access
to Unicode metadata. The range data is precompiled to a serialized
and flattened trie, which is then used at runtime to lookup the necessary
data. According to my own tests, this is generally at least 50% faster
than binary search, with not too much additional memory required.
Installation#
npm install unicode-trieBuilding a Trie#
Unicode Tries are generally precompiled from data in the Unicode database
for faster runtime performance. To build a Unicode Trie, use theUnicodeTrieBuilder class.
const UnicodeTrieBuilder = require('unicode-trie/builder');
const fs = require('fs');
// create a trie
let t = new UnicodeTrieBuilder();
// optional parameters for default value, and error value
// if not provided, both are set to 0
t = new UnicodeTrieBuilder(10, 999);
// set individual values and ranges
t.set(0x4567, 99);
t.setRange(0x40, 0xe7, 0x1234);
// you can lookup a value if you like
t.get(0x4567); // => 99
// get a compiled trie (returns a UnicodeTrie object)
const trie = t.freeze();
// write compressed trie to a binary file
fs.writeFileSync('data.trie', t.toBuffer());Using a precompiled Trie#
Once you've built a precompiled trie, you can load it into theUnicodeTrie class, which is a readonly representation of the
trie. From there, you can lookup values.
const UnicodeTrie = require('unicode-trie');
const fs = require('fs');
// load serialized trie from binary file
const data = fs.readFileSync('data.trie');
const trie = new UnicodeTrie(data);
// lookup a value
trie.get(0x4567); // => 99License#
MIT