You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
77 lines
2.3 KiB
Markdown
77 lines
2.3 KiB
Markdown
# 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](http://site.icu-project.org) (ICU) project
|
|
came up with a data structure based on a [Trie](http://en.wikipedia.org/wiki/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-trie
|
|
|
|
## Building a Trie
|
|
|
|
Unicode Tries are generally precompiled from data in the Unicode database
|
|
for faster runtime performance. To build a Unicode Trie, use the
|
|
`UnicodeTrieBuilder` class.
|
|
|
|
```coffeescript
|
|
UnicodeTrieBuilder = require 'unicode-trie/builder'
|
|
|
|
# create a trie
|
|
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)
|
|
trie = t.freeze()
|
|
|
|
# write compressed trie to a binary file
|
|
fs.writeFile 'data.trie', t.toBuffer()
|
|
```
|
|
|
|
## Using a precompiled Trie
|
|
|
|
Once you've built a precompiled trie, you can load it into the
|
|
`UnicodeTrie` class, which is a readonly representation of the
|
|
trie. From there, you can lookup values.
|
|
|
|
```coffeescript
|
|
UnicodeTrie = require 'unicode-trie'
|
|
fs = require 'fs'
|
|
|
|
# load serialized trie from binary file
|
|
data = fs.readFileSync 'data.trie'
|
|
trie = new UnicodeTrie data
|
|
|
|
# lookup a value
|
|
trie.get 0x4567 # => 99
|
|
```
|
|
|
|
## License
|
|
|
|
MIT
|