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cspell-trie

README.md

cspell-trie

Trie library for use with cspell

This library allows easily building of a Trie from a word list.

The resulting trie can then be compressed into a DAFSA|DAWG.

Tool

cspell-trie is both a tool and a library.

Give a list of words, cspell-trie will turn it into a trie file.

Installation

npm install -g cspell-trie

Usage

cspell-trie --help

Creating a trie file

cspell-trie create filename.txt -o filename.trie

Reading a trie file

cspell-trie reader filename.trie

File Format

Header

TrieXv1
base=10

The header has two parts.

  • TrieXv1 -- the identifiers
  • base -- offsets are stored using the base (10, 16, 32) are common. higher the base, the smaller the file. Max is 36

Data

The first line of data is always a *

Each line is a node in the Trie.

The format of each line is:

star [char index [, char index]*]

  • star - the presence of a star indicates that the node is the ending of a word.
  • char - a character that can be appended to the word followed by the node at index.
  • index - the offset in the list of nodes to continue appending

In other words, each line has an optional * followed by 0 or more (char, index) pairs. A missing index implies an index of 0, which is the end of word flag.

Example Line: *s1,e -- The word can stop here, or add an s and continue at node 1, or add an e

Example:

Word List:

  • walk
  • walked
  • walker
  • walking
  • walks
  • talk
  • talks
  • talked
  • talker
  • talking

becomes

Output: (Offsets are added for clarity, but do not exist in output)

Offset  Output
------- --------
        TrieXv1
        base=10
0       *
1       d,r
2       g
3       n2
4       *e1,i3,s
5       k4
6       l5
7       a6
8       t7,w7

The root of the trie is the last offset, 8. It is designed for the entire trie to be in memory, which is why the root is at the end. This allows for efficiently building the trie as the file loads line by line, because each line can only refer to previous lines.

How to walk the data to see if "talks" is in it.

  1. Start with the root at offset 8.
  2. t found goto 7
  3. a found goto 6
  4. l found goto 5
  5. k found goto 4
  6. s found stop (goto 0 is stop).