line-reader-plus

Line Reader Plus - know where your lines are located.

Processes stream chunks into lines using a separator and adds extra info: start/end byte position and row number. Very useful if after reading the lines you want to modify them.

Install

npm install line-reader-plus

Basic Usage

const fs = require("fs")
const LineReaderPlus = require("line-reader-plus")  

fs.createReadStream("pathToYourFile")
    .pipe(new LineReaderPlus())
    .on("data", (line) => {
        // line = {value: String, start: Int, end: Int, row: Int)            
    })

Custom Options

const fs = require("fs")
const LineReaderPlus = require("line-reader-plus")  

fs.createReadStream("pathToYourFile")
    .pipe(new LineReaderPlus("SeparateMe", "ascii", {highWaterMark: 8}))
    .on("data", (line) => {
        // line = {value: String, start: Int, end: Int, row: Int)           
    })

Notes

Option objectMode is always true. Meaning you cannot overwrite it. This is required in order to return objects in streams on("data") event. Otherwise all Transform stream options are acceptable and should work.

Benchmarks

I was curious how much does this processing affect stream performance and was pleasantly surprised:

8192 bytes in HEX x 10000 lines = ~160 MB
  3 tests completed.

With LineReadePlus x 4.50 ops/sec ±5.67% (26 runs sampled)
With Split2        x 2.50 ops/sec ±6.29% (17 runs sampled)*
RAW (no pipes)     x 7.55 ops/sec ±2.74% (40 runs sampled)

*No extra info, just splitting into lines.

What do you know, only ~40% slower than raw and faster than well established split2. But take the results with a grain of salt. There's plenty of OS level caching going on behind the scenes. Which means that speed might be quite off. To check it yourself, run: npm run benchmark

Testing

npm test

Linting

npm run lint