function ctor( options ) {
	var transform;
	var copts;
	var err;

	copts = assign( {}, DEFAULTS );
	if ( arguments.length ) {
		err = validate( copts, options );
		if ( err ) {
			throw err;
		}
	}
	if ( copts.transform ) {
		transform = copts.transform;
	} else {
		transform = _transform;
	}
	/**
	* Transform stream constructor.
	*
	* @private
	* @constructor
	* @param {Options} [options] - stream options
	* @param {boolean} [options.objectMode=false] - specifies whether a stream should operate in object mode
	* @param {(string|null)} [options.encoding=null] - specifies how `Buffer` objects should be decoded to `strings`
	* @param {NonNegativeNumber} [options.highWaterMark] - specifies the `Buffer` level for when `write()` starts returning `false`
	* @param {boolean} [options.allowHalfOpen=false] - specifies whether the stream should remain open even if one side ends
	* @param {boolean} [options.decodeStrings=true] - specifies whether to decode `strings` into `Buffer` objects when writing
	* @throws {TypeError} options argument must be an object
	* @throws {TypeError} must provide valid options
	* @returns {TransformStream} transform stream
	*
	* @example
	* var stdout = require( '@stdlib/streams/node/stdout' );
	*
	* var stream = new TransformStream();
	*
	* stream.pipe( stdout );
	*
	* stream.write( '1' );
	* stream.write( '2' );
	* stream.write( '3' );
	*
	* stream.end();
	*
	* // prints: '1\n2\n3\n'
	*/
	function TransformStream( options ) {
		var opts;
		var err;
		if ( !( this instanceof TransformStream ) ) {
			if ( arguments.length ) {
				return new TransformStream( options );
			}
			return new TransformStream();
		}
		opts = assign( {}, copts );
		if ( arguments.length ) {
			err = validate( opts, options );
			if ( err ) {
				throw err;
			}
		}
		debug( 'Creating a transform stream configured with the following options: %s.', JSON.stringify( opts ) );
		Transform.call( this, opts );
		this._destroyed = false;
		return this;
	}

	/**
	* Inherit from the `Transform` prototype.
	*/
	inherit( TransformStream, Transform );

	/**
	* Implements the `_transform` method.
	*
	* @private
	* @name _transform
	* @memberof TransformStream.prototype
	* @type {Function}
	* @param {(Buffer|string)} chunk - streamed chunk
	* @param {string} encoding - Buffer encoding
	* @param {Callback} clbk - callback to invoke after transforming the streamed chunk
	*/
	TransformStream.prototype._transform = transform; // eslint-disable-line no-underscore-dangle

	if ( copts.flush ) {
		/**
		* Implements the `_flush` method.
		*
		* @private
		* @name _flush
		* @memberof TransformStream.prototype
		* @type {Function}
		* @param {Callback} callback to invoke after performing flush tasks
		*/
		TransformStream.prototype._flush = copts.flush; // eslint-disable-line no-underscore-dangle
	}

	/**
	* Gracefully destroys a stream, providing backward compatibility.
	*
	* @private
	* @name destroy
	* @memberof TransformStream.prototype
	* @type {Function}
	* @param {Object} [error] - optional error message
	* @returns {TransformStream} stream instance
	*/
	TransformStream.prototype.destroy = destroy;

	return TransformStream;
}
Transform stream constructor factory.

@param {Options} [options] - stream options
@param {Function} [options.transform] - callback to invoke upon receiving a new chunk
@param {Function} [options.flush] - callback to invoke after receiving all chunks and prior to the stream closing
@param {boolean} [options.objectMode=false] - specifies whether a stream should operate in object mode
@param {(string|null)} [options.encoding=null] - specifies how `Buffer` objects should be decoded to `strings`
@param {NonNegativeNumber} [options.highWaterMark] - specifies the `Buffer` level for when `write()` starts returning `false`
@param {boolean} [options.allowHalfOpen=false] - specifies whether the stream should remain open even if one side ends
@param {boolean} [options.decodeStrings=true] - specifies whether to decode `strings` into `Buffer` objects when writing
@throws {TypeError} options argument must be an object
@throws {TypeError} must provide valid options
@returns {Function} Transform stream constructor

@example
var stdout = require( '@stdlib/streams/node/stdout' );

function transform( chunk, enc, clbk ) {
    clbk( null, chunk.toString()+'\n' );
}

var opts = {
    'transform': transform
};

var TransformStream = ctor( opts );

var stream = new TransformStream();

stream.pipe( stdout );

stream.write( '1' );
stream.write( '2' );
stream.write( '3' );

stream.end();

// prints: '1\n2\n3\n'