lib/containers.js
function BlockData(index, buf, cb, count) {
  this.index = index;
  this.buf = buf;
  this.cb = cb;
  this.count = count | 0;
}
function BlockData(index, buf, cb, count) {
  this.index = index;
  this.buf = buf;
  this.cb = cb;
  this.count = count | 0;
}
function BlockData ( index , buf , cb , count ) { this . index = index ; this . buf = buf ; this . cb = cb ; this . count = count | 0 ; }
Helpers. 
An indexed block.

This can be used to preserve block order since compression and decompression
can cause some some blocks to be returned out of order.
Helpers . An indexed block .