readable-stream/lib/_stream_passthrough.js

// Copyright Joyent, Inc. and other Node contributors.
//
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// "Software"), to deal in the Software without restriction, including
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//
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// a passthrough stream.
// basically just the most minimal sort of Transform stream.
// Every written chunk gets output as-is.
'use strict';

module.exports = PassThrough;

var Transform = require('./_stream_transform');

require('inherits')(PassThrough, Transform);

function PassThrough(options) {
  if (!(this instanceof PassThrough)) return new PassThrough(options);
  Transform.call(this, options);
}

PassThrough.prototype._transform = function (chunk, encoding, cb) {
  cb(null, chunk);
};