Bop, an ultra fast Boyer-Moore parser/matcher optimized for string and buffer patterns (<= 255 bytes), then it is ideal for parsing multipart/form-data streams, that have a pattern / boundary length < ~70 bytes.
Given a m-length pattern and n-length data, and σ-length alphabet ( σ = 256 ):
$ npm install bop [-g]
var Bop = ;
$cd bop/$npm test
$ cd bop/$ npm run bench
Create an instance with a Buffer or String pattern.
// orBuffer | String pattern
Arguments within [ ] are optional.
/** List all pattern occurrences into a String or Buffer data.* It returns a new array of indexes, or populates an array* passed as the last argument.** NOTE: it is faster using Buffers.*/Bop# : Array/** Change the pattern to search.*/Bop# : Buffer
var assert =Bop =pattern = 'hellofolks\r\n\r\n'text = 'hehe' + pattern +'loremipsumhellofolks\r\n' + pattern// create a Bop instance that parses the patternbop =// parse data from beginningresults = bopbresults = null;// change patternbop;// re-parse data passing a Buffer instead of a Stringbresults = bop;// results are the sameassert;// parser results ( starting indexes ) [ 4, 40 ]console;
Parser uses 3 Buffers 256-bytes long to build shifting tables, then:
- Pattern parsing / table creation space and time complexity is O(σ).
- Very low memory footprint.
- Ultra fast to preprocess pattern ( = tables creation ).
$ node bench/small-pattern-data-rate
for default it:
- uses a pattern string of 57 bytes/chars.
- builds a data buffer of 700 MB in memory.
- uses a redundancy/distance factor for pattern strings equal to 2. The bigger the value, the lesser are occurrences of pattern string into the text buffer.
# with [testBufferSizeInMB] [distanceFactor] [aStringPattern]$ node bench/small-pattern-data-rate.js 700 4 "that'sallfolks"
Parser uses 3 arrays to build shifting tables for big patterns, then:
- there will be an high memory consumption, due to the use of arrays.
- it will take a long time to preprocess pattern ( = tables creation ).
$ node bench/big-pattern-data-rate
- it uses a very big pattern ( 20 MBytes ).
- it builds a data buffer of 300 MBytes, copying the same pattern 12 times.
See bench dir.
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