pull-buckets

Segmentate an incoming stream into groups ("buckets") and reduce each group to a single value that is then passed downstream. Suitable for live-streams when using hte timeout option. (Makes sure bucket value is eventually emitted when no new data comes in for a while)

const buckets = require('pull-buckets')

function bucketKey(n) {
  return (n / 10) << 0
}

function createOrAdd(b, n) {
  b = b || {
    tens: bucketKey(n),
    l: [],
    sum: 0
  }
  b.sum += n
  b.l = b.l.concat([n])
  return b
}

function fitsBucket({tens}, n) {
  return bucketKey(n) == tens
}

pull(
  pull.values([1,2,10,11,20,25]),
  buckets(fitsBucket, createOrAdd),
  pull.log()
)

/* output: 
   {tens: 0, sum: 3, l: [ 1, 2 ]},
   {tens: 1, sum: 21, l: [ 10, 11 ]},
   {tens: 2, sum: 45, l: [ 20, 25 ]} 
*/

buckets(fitsBucket, add, opts)

returns a new pull through stream that accumulates items in buckets and passes buckets downstream once encountering an item that does not fit the current bucket.

IMPORTANT: because of this mechanics, the icoming stream needs to be a sorted stream in regards to whatever criteria fitsBucket (see below) implements.

fitsBucket(bucket, value)

returns true if the value fits into the given bucket, false otherwise

add(bucket, value)

if bucket is undefined, creates a fresh bucket and throws the given value into it. Othereise, accumulate the value in the existing bucket. Should manipulate bucket object in-place whenever ppssible. pull-buckets will make a copy of the bucket before sending it out.

Options:

• initial: an initial value for the first bucket
• timeout: emit the current bucket once last update is older than given milliseconds
• max_size: start a new bucket when this number of items where thrown into current bucket

License: MIT