factory.js (3591B)
1 /** 2 * @license Apache-2.0 3 * 4 * Copyright (c) 2018 The Stdlib Authors. 5 * 6 * Licensed under the Apache License, Version 2.0 (the "License"); 7 * you may not use this file except in compliance with the License. 8 * You may obtain a copy of the License at 9 * 10 * http://www.apache.org/licenses/LICENSE-2.0 11 * 12 * Unless required by applicable law or agreed to in writing, software 13 * distributed under the License is distributed on an "AS IS" BASIS, 14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 15 * See the License for the specific language governing permissions and 16 * limitations under the License. 17 */ 18 19 'use strict'; 20 21 // MODULES // 22 23 var hasOwnProp = require( '@stdlib/assert/has-own-property' ); 24 var copy = require( '@stdlib/utils/copy' ); 25 var ConstantStream = require( './main.js' ); 26 27 28 // MAIN // 29 30 /** 31 * Returns a function for creating readable streams which always stream the same value. 32 * 33 * @param {(string|Buffer|Uint8Array|*)} [value] - value to stream 34 * @param {Options} [options] - stream options 35 * @param {boolean} [options.objectMode=false] - specifies whether a stream should operate in object mode 36 * @param {(string|null)} [options.encoding=null] - specifies how `Buffer` objects should be decoded to `strings` 37 * @param {NonNegativeNumber} [options.highWaterMark] - specifies the maximum number of bytes to store in an internal buffer before pausing streaming 38 * @param {string} [options.sep='\n'] - separator used to join streamed data 39 * @param {NonNegativeInteger} [options.iter] - number of iterations 40 * @returns {Function} stream factory 41 * 42 * @example 43 * var opts = { 44 * 'sep': ',', 45 * 'objectMode': false, 46 * 'encoding': 'utf8', 47 * 'highWaterMark': 64 48 * }; 49 * 50 * var createStream = factory( opts ); 51 * 52 * // Create 10 identically configured streams... 53 * var streams = []; 54 * var i; 55 * for ( i = 0; i < 10; i++ ) { 56 * streams.push( createStream( i.toString() ) ); 57 * } 58 */ 59 function factory( value, options ) { 60 var nargs; 61 var opts; 62 var fcn; 63 var FLG; 64 65 nargs = arguments.length; 66 if ( nargs === 0 ) { 67 opts = {}; 68 FLG = true; 69 } else if ( nargs === 1 ) { 70 // Check (imperfectly!) whether we were provided an "options" object... 71 if ( 72 value !== null && 73 typeof value === 'object' && 74 ( 75 hasOwnProp( value, 'sep' ) || 76 hasOwnProp( value, 'iter' ) || 77 hasOwnProp( value, 'objectMode' ) || 78 hasOwnProp( value, 'encoding' ) || 79 hasOwnProp( value, 'highWaterMark' ) 80 ) 81 ) { 82 opts = copy( value, 1 ); 83 FLG = true; 84 } else { 85 opts = {}; 86 } 87 } else { // nargs > 1 88 opts = copy( options, 1 ); 89 } 90 if ( FLG ) { 91 fcn = createStream1; 92 } else { 93 fcn = createStream2; 94 } 95 return fcn; 96 97 /** 98 * Returns a readable stream which always streams the same value. 99 * 100 * @private 101 * @param {(string|Buffer|Uint8Array|*)} value - value to stream 102 * @throws {TypeError} in binary mode, value to stream must be a string, Buffer, or Uint8Array 103 * @throws {TypeError} options argument must be an object 104 * @throws {TypeError} must provide valid options 105 * @returns {ConstantStream} Stream instance 106 */ 107 function createStream1( value ) { 108 return new ConstantStream( value, opts ); 109 } 110 111 /** 112 * Returns a readable stream which always streams the same value. 113 * 114 * @private 115 * @throws {TypeError} in binary mode, value to stream must be a string, Buffer, or Uint8Array 116 * @throws {TypeError} options argument must be an object 117 * @throws {TypeError} must provide valid options 118 * @returns {ConstantStream} Stream instance 119 */ 120 function createStream2() { 121 return new ConstantStream( value, opts ); 122 } 123 } 124 125 126 // EXPORTS // 127 128 module.exports = factory;