merge-sort-stream

Merge sort two input streams to one sorted stream.

npm install merge-sort-stream

If you do not want to load all data into memory before doing the sort and the two input streams already are sorted then this module might help you.

Usage

Precondition, the two input streams should be readable with objectMode set to true and sorted regarding to the compare function.

var streamArray = require('stream-array');
var concat = require('concat-stream');
var mergeSortStream = require('merge-sort-stream');

function compare(a, b) { return b - a; }

var sortedA = streamArray([1,3,5,6,7]);
var sortedB = streamArray([2,3,4]);

var sorted = mergeSortStream(sortedA, sortedB, compare);

sorted.pipe(concat({encoding: 'object'}, function(array){
    console.log(array);
}));

// output to console will be [ 1, 2, 3, 3, 4, 5, 6, 7 ]

Streaming objects

If you have a streams of objects/points that have to be sorted regarding to the euclidean distance.

function euclidean(a, b) { return Math.sqrt(b.x*b.x+b.y*b.y) - Math.sqrt(a.x*a.x+a.y*a.y); }

var sortedA = streamArray([{x: 1, y: 1}, {x: 3, y: 3}]);
var sortedB = streamArray([{x: 4, y: 1}, {x: 5, y: 1}]);

var sorted = mergeSortStream(sortedA, sortedB, euclidean);

sorted.pipe(concat({encoding: 'object'}, function(array){
    console.log(array);
}));

// output to console will be [ { x: 1, y: 1 }, { x: 4, y: 1 }, { x: 3, y: 3 }, { x: 5, y: 1 } ]

Related module

If you are going to sort objects only based on a property, you should consider to use the well proven module sorted-union-stream.

License

MIT