topsort-stream

Topological sort for streams

Example

var topsort = require('topsort-stream')
 
var dependencies = {
    c: ['b'],
    d: ['b', 'c']
}
 
var s = new require('stream').Readable({ objectMode: true })
 
s.pipe(topsort(function (data) {
     return {
         id: data,
         deps: dependencies[data] || []
     }
 }))
 .on('data', console.log.bind(console))
 
s.push('d')
s.push('c')
s.push('a')
s.push('b')
s.push(null)

Yields

a
b
c
d

'a' and 'b' where written to the destination stream after being read as they had no dependencies; 'a' first because it was read before 'b'. 'c' and 'd' depended on 'b' and written after; 'd' was written last becauese it dependend upon 'c'.

A real world example would be a gulp plugin that is passed a nodeResolver (see methods) that extracts the dependencies from metadata from the file content.

API

var topsort = require('topsort-stream')

methods

var t = topsort(function nodeResolver(data) { return { [id: Object,] [deps: Array] } })

• nodeResolver defines the dependency graph bit assigning identity and dependencies to data.

events

t inherits all all events from stream.Readable.

t.on('topsort-error:resolving-node', cb)

The event fires when there is an error resolving a node.

t.on('topsort-error:unresolved-nodes', cb)

The event fires when the readable side of the stream is closed before all dependencies have been resolved. The call back is fired with an array of the ids of dependant nodes.

Install

npm install topsort-stream

license

MIT