throughout
Apply a through stream to the output side of another through stream,
preserving the first stream as input in the returned stream.

example
var through = require('through');
var throughout = require('throughput');
var doubler = through(function (buf) {
var dbuf = new Buffer(buf.length * 2);
for (var i = 0; i < dbuf.length; i++) {
dbuf[i] = buf[Math.floor(i/2)];
}
this.queue(dbuf);
});
var counter = through(
function (buf) {
this._count = (this._count || 0) + buf.length;
},
function () {
this.queue(this._count + '\n');
this.queue(null);
}
);
process.stdin
.pipe(throughout(doubler, counter))
.pipe(process.stdout)
;
rationale
If you want to transform just the output side of a through stream, this is
actually somewhat difficult and it's not immediately obvious why something like:var duplexer = require('duplexer');
function filterOutput (a, b) {
a.pipe(b);
return duplexer(a, b);
}
shouldn't just work. The worst part is that it does work, until you try to pipe the results to a slow endpoint that will throttle with pause and resume.
The problem is that both
duplexer
and .pipe()
will handle pause and resume
in a mutually exclusive way that will cause the stream to hang indefinitely if a
slow downstream consumer ever triggers a pause.If you try to use event-stream's .pipeline() function you will get the same problem.
methods
var throughout = require('throughout');
var c = throughout(a, b)
Pipe the output of a through streama
into the input of a through stream b
,
returning a new stream c
that writes its input to a
and forwards the output
from b
.install
With npm do:npm install throughout
license
MIT