249 lines
6.9 KiB
JavaScript
249 lines
6.9 KiB
JavaScript
/**
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* @license Apache-2.0
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*
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* Copyright (c) 2018 The Stdlib Authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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'use strict';
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// MODULES //
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var Transform = require( 'readable-stream' ).Transform;
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var string2buffer = require( '@stdlib/buffer/from-string' );
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var copy = require( '@stdlib/utils/copy' );
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var inherit = require( '@stdlib/utils/inherit' );
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var Buffer = require( '@stdlib/buffer/ctor' );
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var setNonEnumerable = require( '@stdlib/utils/define-nonenumerable-property' );
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var setNonEnumerableReadOnly = require( '@stdlib/utils/define-nonenumerable-read-only-property' );
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var nextTick = require( '@stdlib/utils/next-tick' );
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var DEFAULTS = require( './defaults.json' );
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var validate = require( './validate.js' );
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var debug = require( './debug.js' );
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// FUNCTIONS //
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/**
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* Implements the `_transform` method.
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*
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* @private
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* @param {(Uint8Array|Buffer|string)} chunk - streamed chunk
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* @param {string} encoding - Buffer encoding
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* @param {Callback} clbk - callback to invoke after transforming the streamed chunk
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*/
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function transform( chunk, encoding, clbk ) {
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/* eslint-disable no-invalid-this */
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var len;
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this._idx += 1;
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debug( 'Received a new chunk. Chunk: %s. Encoding: %s. Index: %d.', chunk.toString(), encoding, this._idx );
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if ( this._encoding === 'utf8' ) {
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if ( this._init ) {
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chunk = this._sep + chunk;
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} else {
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this._init = true;
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}
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} else if ( this._init ) {
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chunk = new Buffer( chunk, encoding ); // eslint-disable-line no-buffer-constructor
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len = this._sep.length + chunk.length;
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chunk = Buffer.concat( [ this._sep, chunk ], len ); // TODO: replace with stdlib pkg
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chunk = chunk.toString( this._encoding );
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} else {
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this._init = true;
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}
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this.push( chunk, this._encoding );
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clbk();
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/* eslint-enable no-invalid-this */
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}
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/**
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* Implements the `_flush` method.
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*
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* @private
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* @param {Callback} clbk - callback to invoke after performing flush tasks
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*/
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function flush( clbk ) {
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debug( 'Flushing the stream...' );
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clbk(); // TODO: consider supporting an option to append a final separator
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}
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/**
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* Gracefully destroys a stream, providing backward compatibility.
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*
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* @private
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* @param {Object} [error] - optional error message
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* @returns {JoinStream} Stream instance
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*/
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function destroy( error ) {
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/* eslint-disable no-invalid-this */
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var self;
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if ( this._destroyed ) {
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debug( 'Attempted to destroy an already destroyed stream.' );
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return this;
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}
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self = this;
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this._destroyed = true;
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nextTick( close );
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return this;
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/**
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* Closes a stream.
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*
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* @private
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*/
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function close() {
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if ( error ) {
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debug( 'Stream was destroyed due to an error. Error: %s.', JSON.stringify( error ) );
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self.emit( 'error', error );
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}
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debug( 'Closing the stream...' );
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self.emit( 'close' );
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}
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/* eslint-enable no-invalid-this */
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}
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// MAIN //
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/**
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* Join stream constructor.
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*
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* @constructor
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* @param {Options} [options] - stream options
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* @param {string} [options.sep='\n'] - separator used to join streamed data
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* @param {boolean} [options.objectMode=false] - specifies whether the stream should operate in object mode
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* @param {(string|null)} [options.encoding=null] - specifies how `Buffer` objects should be decoded to `strings`
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* @param {NonNegativeNumber} [options.highWaterMark] - specifies the `Buffer` level for when `write()` starts returning `false`
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* @param {boolean} [options.allowHalfOpen=false] - specifies whether the stream should remain open even if one side ends
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* @param {boolean} [options.readableObjectMode=false] - specifies whether the readable side should be in object mode
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* @throws {TypeError} options argument must be an object
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* @throws {TypeError} must provide valid options
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* @returns {JoinStream} join stream
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*
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* @example
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* var inspectStream = require( '@stdlib/streams/node/inspect-sink' );
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*
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* function log( chunk ) {
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* console.log( chunk );
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* }
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*
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* var stream = new JoinStream();
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*
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* stream.pipe( inspectStream( log ) );
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*
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* stream.write( '1' );
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* stream.write( '2' );
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* stream.write( '3' );
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*
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* stream.end();
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*
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* // prints: '1\n2\n3'
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*/
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function JoinStream( options ) {
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var opts;
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var err;
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if ( !( this instanceof JoinStream ) ) {
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if ( arguments.length ) {
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return new JoinStream( options );
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}
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return new JoinStream();
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}
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opts = copy( DEFAULTS );
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if ( arguments.length ) {
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err = validate( opts, options );
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if ( err ) {
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throw err;
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}
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}
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// The stream's writable state should always be in object mode to prevent incoming data from being buffered (concatenated) and thus lose separation...
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opts.writableObjectMode = true;
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// The stream converts each chunk into a string so no need to encode strings written to the join stream as Buffer objects:
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opts.decodeStrings = false;
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// Make the stream a Transform stream:
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debug( 'Creating a transform stream configured with the following options: %s.', JSON.stringify( opts ) );
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Transform.call( this, opts );
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// Destruction state:
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setNonEnumerable( this, '_destroyed', false );
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// Cache the encoding:
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setNonEnumerableReadOnly( this, '_encoding', ( opts.encoding === null ) ? 'utf8' : opts.encoding );
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// Cache the separator:
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if ( this._encoding !== 'utf8' ) {
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opts.sep = string2buffer( opts.sep, this._encoding );
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}
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setNonEnumerableReadOnly( this, '_sep', opts.sep );
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// Flag indicating if the stream has received streamed data:
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setNonEnumerable( this, '_init', false );
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// Chunk counter:
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setNonEnumerable( this, '_idx', -1 );
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return this;
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}
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/*
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* Inherit from the `Transform` prototype.
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*/
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inherit( JoinStream, Transform );
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/**
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* Implements the `_transform` method.
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*
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* @private
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* @name _transform
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* @memberof JoinStream.prototype
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* @type {Function}
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* @param {(Buffer|string)} chunk - streamed chunk
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* @param {string} encoding - Buffer encoding
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* @param {Callback} clbk - callback to invoke after transforming the streamed chunk
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*/
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setNonEnumerableReadOnly( JoinStream.prototype, '_transform', transform );
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/**
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* Implements the `_flush` method.
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*
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* @private
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* @name _flush
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* @memberof JoinStream.prototype
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* @type {Function}
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* @param {Callback} clbk - callback to invoke after performing flush tasks
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*/
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setNonEnumerableReadOnly( JoinStream.prototype, '_flush', flush );
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/**
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* Gracefully destroys a stream, providing backward compatibility.
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*
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* @name destroy
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* @memberof JoinStream.prototype
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* @type {Function}
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* @param {Object} [error] - optional error message
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* @returns {JoinStream} Stream instance
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*/
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setNonEnumerableReadOnly( JoinStream.prototype, 'destroy', destroy );
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// EXPORTS //
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module.exports = JoinStream;
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