‚̧National Pizza Magistrate
    Wondering what‚Äôs next for npm?Check out our public roadmap! ¬Ľ

    @gmod/tribble-index

    2.0.5¬†‚Äʬ†Public¬†‚Äʬ†Published

    tribble-index

    Generated with nod Coverage Status NPM version Build Status Greenkeeper badge

    Read htsjdk Tribble indexes (e.g. *.vcf.idx files) using pure JavaScript. Supports only Tribble version 3 linear indexes right now.

    Install

    $ npm install --save @gmod/tribble-index
    

    Usage

    import TribbleIndexedFile from '@gmod/tribble-index'
    // or without ES6
    const { TribbleIndexedFile } = require('@gmod/tribble-index')
     
    const indexedFile = new TribbleIndexedFile({ path: 'path/to/data.vcf' })
    // by default, assumes tribble index at path/to/data.vcf.idx
    // can also provide `tribblePath` if the tribble is named differently
     
    async function doStuff() {
      // iterate over lines in the specified region, each of which
      // is structured as
      const lines = []
      await indexedFile.getLines('contigA', 3000, 3200, line => lines.push(line))
      // lines is now an array of strings, which are data lines.
      // commented (meta) lines are skipped.
      // line strings do not include any trailing whitespace characters.
      console.log(lines)
      // ↳ [ 'contigA\t3000\trs17883296\tG\tT\t100\tPASS\tNS=3;DP=14;AF=0.5;DB;H2\tGT:AP\t0|0:0.000,0.000']
     
      // get the approximate number of data lines in the file for the
      // given reference sequence, excluding header, comment, and whitespace lines
      console.log(await indexedFile.lineCount('contigA'))
      // ↳ 109
     
      // get the "header text" string from the file, which is the first contiguous
      // set of lines in the file that all start with a "meta" character (usually #)
      console.log(await indexedFile.getHeader())
      // ↳ ##fileformat=VCFv4.1
      // ↳ #CHROM POS ID REF ALT QUAL FILTER INFO FORMAT HG00096
     
      // or if you want a buffer instead, there is getHeaderBuffer()
      console.log(await indexedFile.getHeaderBuffer())
      // ↳ <Buffer 23 23 66 69 6c 65 66 6f 72 6d 61 74 3d 56 43 46 76 34 2e 31 0a 23 23 66 69 6c 65 ... >
    }

    Also supports a lower-level interface

    import fs from 'fs'
    import read from '@gmod/tribble-index'
    // or without ES6
    const fs = require('fs')
    const read = require('@gmod/tribble-index')
     
    fs.readFile('path/to/data.vcf.idx', (err, buffer) => {
      if (err) throw err
      const index = read(buffer)
     
      console.log(index)
      const blocks = index.getBlocks('contigA', 3000, 3200)
     
      // can now use these blocks from the index to read the file
      // regions of interest
      fs.open('path/to/data.vcf', 'r', (err2, fd) => {
        if (err2) throw err2
        blocks.forEach(({ length, offset }) => {
          const buffer2 = Buffer.alloc(length)
          fs.read(fd, buffer2, 0, length, offset, (err3, bytesRead, buffer3) => {
            if (err3) throw err3
            console.log('got file data', buffer3)
          })
        })
        fs.close(fd, err4 => {
          if (err4) throw err4
        })
      })
    })

    API

    Table of Contents

    getBlocks

    Get an array of { offset, length } objects describing regions of the indexed file containing data for the given range.

    Parameters

    • refName string name of the reference sequence
    • start integer start coordinate of the range of interest
    • end integer end coordinate of the range of interest

    getMetadata

    Returns an object like { fileMD5 fileName fileSize fileTimestamp firstDataOffset flags magic properties type version chromosomes}

    hasRefSeq

    Return true if the given reference sequence is present in the index, false otherwise

    Parameters

    Returns boolean

    read

    Parse the index from the given Buffer object. The buffer must contain the entire index.

    Parameters

    Returns (LinearIndex | IntervalTreeIndex) an index object supporting the getBlocks method

    constructor

    Parameters

    • args object
      • args.path string?
      • args.filehandle filehandle?
      • args.tribblePath string?
      • args.tribbleFilehandle filehandle?
      • args.metaChar string? character that denotes the beginning of a header line (optional, default '#')
      • args.columnNumbers object? object like {ref start end} defining the (1-based) columns in the file. end may be set to -1 if not present. default {ref: 1, start: 2, end: -1} (optional, default {ref:1,start:2,end:-1})
      • args.oneBasedClosed boolean? whether the indexed file uses one-based closed coordinates. default false (implying zero-based half-open coordinates) (optional, default false)
      • args.chunkSizeLimit number? maximum number of bytes to fetch in a single getLines call. default 2MiB (optional, default 2000000)
      • args.yieldLimit number? maximum number of lines to parse without yielding. this avoids having a large read prevent any other work getting done on the thread. default 300 lines. (optional, default 300)
      • args.renameRefSeqs function? optional function with sig string => string to transform reference sequence names for the purpose of indexing and querying. note that the data that is returned is not altered, just the names of the reference sequences that are used for querying. (optional, default n=>n)
      • args.blockCacheSize number? maximum size in bytes of the block cache. default 5MB (optional, default 5*2**20)

    checkLine

    Parameters

    • regionRefName string
    • regionStart number region start coordinate (0-based-half-open)
    • regionEnd number region end coordinate (0-based-half-open)
    • line

    Returns object like {startCoordinate, overlaps}. overlaps is boolean, true if line is a data line that overlaps the given region

    getReferenceSequenceNames

    get an array of reference sequence names

    reference sequence renaming is not applied to these names.

    Returns Promise for an array of string sequence names

    getHeaderBuffer

    get a buffer containing the "header" region of the file, which are the bytes up to the first non-meta line

    Returns Promise for a buffer

    getHeader

    get a string containing the "header" region of the file, is the portion up to the first non-meta line

    Returns Promise for a string

    lineCount

    return the approximate number of data lines in the given reference sequence returns -1 if the reference sequence is not found

    Parameters

    • refSeq string reference sequence name

    Returns Promise for number of data lines present on that reference sequence

    Academic Use

    This package was written with funding from the NHGRI as part of the JBrowse project. If you use it in an academic project that you publish, please cite the most recent JBrowse paper, which will be linked from jbrowse.org.

    License

    MIT © Robert Buels

    Install

    npm i @gmod/tribble-index

    DownloadsWeekly Downloads

    74

    Version

    2.0.5

    License

    MIT

    Unpacked Size

    50.6 kB

    Total Files

    11

    Last publish

    Collaborators

    • avatar
    • avatar
    • avatar
    • avatar
    • avatar