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first-chunk-stream

Buffer and transform the n first bytes of a stream

Install

$ npm install --save first-chunk-stream

Usage

const fs = require('fs');
const concatStream = require('concat-stream');
const firstChunkStream = require('first-chunk-stream');

// unicorn.txt => unicorn rainbow
fs.createReadStream('unicorn.txt')
	.pipe(firstChunkStream({chunkLength: 7}, function (chunk, enc, cb) {
		this.push(chunk.toUpperCase());
		cb();
	}))
	.pipe(concatStream(function (data) {
		if (data.length < 7) {
			throw new Error('Couldn\'t get the minimum required first chunk length');
		}

		console.log(data);
		//=> 'UNICORN rainbow'
	}));

API

firstChunkStream([options], transform)

Returns a FirstChunkStream instance.

options

The options object is passed to the Duplex stream constructor allowing you to customize your stream behavior. In addition you can specify the following option:

chunkLength

Type: number

How many bytes you want to buffer.

transform(chunk, encoding, callback)

Type: function

The function that gets the required options.chunkLength bytes.

Note that the buffer can have a smaller length than the required one. In that case, it will be due to the fact that the complete stream contents has a length less than the òptions.chunkLength value. You should check for this yourself if you strictly depend on the length.

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