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  • License MIT

Filtering streams.

Package Exports

  • streamfilter

This package does not declare an exports field, so the exports above have been automatically detected and optimized by JSPM instead. If any package subpath is missing, it is recommended to post an issue to the original package (streamfilter) to support the "exports" field. If that is not possible, create a JSPM override to customize the exports field for this package.

Readme

streamfilter

Filtering streams.

Build status Coverage Status NPM version Dependency Status devDependency Status Dependency Status Package Quality Code Climate

streamfilter is a function based filter for streams inspired per gulp-filter but no limited to Gulp nor to objectMode streams.

Installation

First, install streamfilter in your project:

npm install --save streamfilter

Getting started

There are 3 common usages:

Simple filter

import FilterStream from 'streamfilter';

const filter = new FilterStream((chunk, encoding, cb) => {
  const mustBeFiltered = chunk.length() > 128;
  if(mustBeFiltered) {
    cb(true);
    return;
  }
  cb(false);
});

// Print to stdout a filtered stdin
process.stdin
  .pipe(filter)
  .pipe(process.stdout);

Filter and restore

import FilterStream from 'streamfilter';

const filter = new FilterStream((chunk, encoding, cb) => {
  const mustBeFiltered = chunk.length() > 128;
  if(mustBeFiltered) {
    cb(true);
    return;
  }
  cb(false);
}, {
  restore: true
});

// Print accepted chunks in stdout
filter.pipe(process.stdout);

// Print filtered one to stderr
filter.restore.pipe(process.stderr);

Filter and restore as a passthrough stream

Let's reach total hype!

import FilterStream from 'streamfilter';
import { Transform } from 'stream';

// Filter values
const filter = new FilterStream((chunk, encoding, cb) => {
  const mustBeFiltered = chunk.length() > 128;
  if(mustBeFiltered) {
    cb(true);
    return;
  }
  cb(false);
}, {
  restore: true,
  passthrough: true
});

// Uppercase strings
const mySuperTransformStream = new Transform({
  transform: (chunk, encoding, cb) => cb(
    null,
    Buffer.from(
      chunk.toString(encoding).toUpperCase(),
      encoding,
    ),
  ),
});

// Pipe stdin
process.stdin.pipe(filter)
  // Edit kept chunks
  .pipe(mySuperTransformStream)
  // Restore filtered chunks
  .pipe(filter.restore)
  // and output!
  .pipe(process.stdout)

Note that in this case, this is your responsibility to end the restore stream by piping in another stream or ending him manually.

API

StreamFilter(filterCallback, options) ⇒ Stream

Filter piped in streams according to the given filterCallback that takes the following arguments: chunk the actual chunk, encoding the chunk encoding, filterResultCallbackthe function to call as the result of the filtering process withtruein argument to filter her orfalse` otherwise.

Options are passed in as is in the various stream instances spawned by this module. So, to use the objectMode, simply pass in the options.objectMode value set to true.

Kind: global function
Returns: Stream - The filtering stream

Param Type Description
filterCallback function Callback applying the filters
options Object Filtering options
options.passthrough boolean Set to true, this option change the restore stream nature from a readable stream to a passthrough one, allowing you to reuse the filtered chunks in an existing pipeline.
options.restore boolean Set to true, this option create a readable stream allowing you to use the filtered chunks elsewhere. The restore stream is exposed in the FilterStream instance as a restore named property.

Authors

License

MIT