stream-splicer
v2.0.1
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streaming pipeline with a mutable configuration
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stream-splicer
streaming pipeline with a mutable configuration
This module is similar to stream-combiner, but with a pipeline configuration that can be changed at runtime.
example
This example begins with an HTTP header parser that waits for an empty line to signify the end of the header. At that point, it switches to a streaming json parser to operate on the HTTP body.
var splicer = require('stream-splicer');
var through = require('through2');
var jsonStream = require('jsonstream2');
var split = require('split2');
var headerData = {};
var headers = through.obj(function (buf, enc, next) {
var line = buf.toString('utf8');
if (line === '') {
this.push(headerData);
pipeline.splice(1, 1, jsonStream.parse([ 'rows', true ]));
}
else {
var m = /^(\S+):(.+)/.exec(line);
var key = m && m[1].trim();
var value = m && m[2].trim();
if (m) headerData[key] = value;
}
next();
});
var pipeline = splicer([ split(), headers, jsonStream.stringify() ]);
process.stdin.pipe(pipeline).pipe(process.stdout);
intput:
GET / HTTP/1.1
Host: substack.net
User-Agent: echo
{"rows":["beep","boop"]}
output:
$ echo -ne 'GET / HTTP/1.1\nHost: substack.net\nUser-Agent: echo\n\n{"rows":["beep","boop"]}\n' | node example/header.js
[
{"Host":"substack.net","User-Agent":"echo"}
,
"beep"
,
"boop"
]
methods
var splicer = require('stream-splicer')
var pipeline = splicer(streams, opts)
Create a pipeline
duplex stream given an array of streams
. Each stream
will be piped to the next. Writes to pipeline
get written to the first stream
and data for reads from pipeline
come from the last stream.
For example, for streams [ a, b, c, d ]
, this pipeline is constructed
internally:
a.pipe(b).pipe(c).pipe(d)
Input will get written into a
. Output will be read from d
.
If any of the elements in streams
are arrays, they will be converted into
nested pipelines. This is useful if you want to expose a hookable pipeline with
grouped insertion points.
var pipeline = splicer.obj(streams, opts)
Create a pipeline
with opts.objectMode
set to true for convenience.
var removed = pipeline.splice(index, howMany, stream, ...)
Splice the pipeline starting at index
, removing howMany
streams and
replacing them with each additional stream
argument provided.
The streams that were removed from the splice and returned.
pipeline.push(stream, ...)
Push one or more streams to the end of the pipeline.
var stream = pipeline.pop()
Pop a stream from the end of the pipeline.
pipeline.unshift(stream, ...)
Unshift one or more streams to the begining of the pipeline.
var stream = pipeline.shift()
Shift a stream from the begining of the pipeline.
var stream = pipeline.get(index, ...)
Return the stream at index index, ...
. Indexes can be negative.
Multiple indexes will traverse into nested pipelines.
attributes
pipeline.length
The number of streams in the pipeline
install
With npm do:
npm install stream-splicer
license
MIT