streamsearch

Description

streamsearch is a module for node.js that allows searching a stream using the Boyer-Moore-Horspool algorithm.

This module is based heavily on the Streaming Boyer-Moore-Horspool C++ implementation by Hongli Lai here.

Requirements

• node.js -- v10.0.0 or newer

Installation

npm install streamsearch

Example

  const { inspect } = require('util');

  const StreamSearch = require('streamsearch');

  const needle = Buffer.from('\r\n');
  const ss = new StreamSearch(needle, (isMatch, data, start, end) => {
    if (data)
      console.log('data: ' + inspect(data.toString('latin1', start, end)));
    if (isMatch)
      console.log('match!');
  });

  const chunks = [
    'foo',
    ' bar',
    '\r',
    '\n',
    'baz, hello\r',
    '\n world.',
    '\r\n Node.JS rules!!\r\n\r\n',
  ];
  for (const chunk of chunks)
    ss.push(Buffer.from(chunk));

  // output:
  //
  // data: 'foo'
  // data: ' bar'
  // match!
  // data: 'baz, hello'
  // match!
  // data: ' world.'
  // match!
  // data: ' Node.JS rules!!'
  // match!
  // data: ''
  // match!

API

Properties

• maxMatches - < integer > - The maximum number of matches. Defaults to Infinity.

• matches - < integer > - The current match count.

Functions

• (constructor)(< mixed >needle, < function >callback) - Creates and returns a new instance for searching for a Buffer or string needle. callback is called any time there is non-matching data and/or there is a needle match. callback will be called with the following arguments:

  1. isMatch - boolean - Indicates whether a match has been found

  2. data - mixed - If set, this contains data that did not match the needle.

  3. start - integer - The index in data where the non-matching data begins (inclusive).

  4. end - integer - The index in data where the non-matching data ends (exclusive).

  5. isSafeData - boolean - Indicates if it is safe to store a reference to data (e.g. as-is or via data.slice()) or not, as in some cases data may point to a Buffer whose contents change over time.

• destroy() - (void) - Emits any last remaining unmatched data that may still be buffered and then resets internal state.

• push(< Buffer >chunk) - integer - Processes chunk, searching for a match. The return value is the last processed index in chunk + 1.

• reset() - (void) - Resets internal state. Useful for when you wish to start searching a new/different stream for example.