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    piece-table

    1.1.0 • Public • Published

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    PieceTable.js

    A JavaScript implementation of the piece table data structure

    A piece table is an efficient data structure for tracking edits to a text document. A detailed explanation can be found here.

    Overview

    A piece table consists of two buffers, the file buffer and the add buffer, and a table of "pieces", or windows into those buffers (the piece table). Each piece consists of a length, an offset, and a descriptor of which buffer the piece points to. The actual text of the document is represented by the series of pieces in the piece table. Initially, the file buffer consists of the full text of the document and the add buffer is empty. Insertions involve appending the new text to the add buffer and adding pieces to the piece table to reflect the addition. Deletion is performed simply by removing and editing pieces from the piece table. This has the added benefit of never losing data, allowing easy undo operations. Piece table operations are very efficient because they only ever append to the buffers, so no mid-array insertions or deletions are performed.

    Installation

    npm install --save piece-table

    Usage

    const PieceTable = require("piece-table");
     
    const document = new PieceTable("This is a document with some text.");
     
    document.insert("This is some more text to insert at offset 33.", 33);
     
    // Delete the previously inserted sentence
    document.delete(79, 46);
     
    var sequence = document.getSequence();
    // sequence == "This is a document with some text."
     
    var subString = document.stringAt(9, 8);
    // subString == "document"
     
    // PieceTable is an iterable:
    for (let character of document) {
        console.log(character);
        // 'T', 'h', 'i', 's', ...
    }

    API Documentation

    PieceTable

    Kind: global class

    new PieceTable(fileText)

    A piece table is an efficient data structure to track changes to a text. See https://www.cs.unm.edu/~crowley/papers/sds/node15.html for details

    Param Type Description
    fileText string the initial text of the piece table

    pieceTable.insert(str, offset)

    Inserts a string into the piece table

    Kind: instance method of PieceTable

    Param Type Description
    str string the string to insert
    offset number the offset at which to insert the string

    pieceTable.delete(offset, length)

    Deletes a string from the piece table

    Kind: instance method of PieceTable

    Param Type Description
    offset number the offset at which to begin deletion
    length number the number of characters to delete. If negative, deletes backwards

    pieceTable.getSequence() ⇒ string

    Gets the sequence as a string

    Kind: instance method of PieceTable
    Returns: string - The sequence

    pieceTable.stringAt(offset, length)

    Gets a string of a particular length from the piece table at a particular offset

    Kind: instance method of PieceTable

    Param Type Description
    offset number the offset from which to get the string
    length number the number of characters to return from the offset. If negative, looks backwards

    Install

    npm i piece-table

    DownloadsWeekly Downloads

    1

    Version

    1.1.0

    License

    MIT

    Last publish

    Collaborators

    • jdormit