time-to-botec

Benchmark sampling in different programming languages
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limit.js (3918B)

      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 logger = require( 'debug' );
     24 var hasOwnProp = require( '@stdlib/assert/has-own-property' );
     25 
     26 
     27 // VARIABLES //
     28 
     29 var debug = logger( 'count-by-async:limit' );
     30 
     31 
     32 // MAIN //
     33 
     34 /**
     35 * Invokes an indicator function once for each element in a collection, limiting the number of concurrently pending functions.
     36 *
     37 * @private
     38 * @param {Collection} collection - input collection
     39 * @param {Options} opts - function options
     40 * @param {*} [opts.thisArg] - execution context
     41 * @param {PositiveInteger} [opts.limit] - maximum number of pending function invocations
     42 * @param {Function} indicator - indicator function
     43 * @param {Callback} done - function to invoke upon completion or upon encountering an error
     44 * @returns {void}
     45 */
     46 function limit( collection, opts, indicator, done ) {
     47 	var maxIndex;
     48 	var count;
     49 	var flg;
     50 	var lim;
     51 	var len;
     52 	var idx;
     53 	var out;
     54 	var i;
     55 
     56 	len = collection.length;
     57 	debug( 'Collection length: %d', len );
     58 
     59 	out = {};
     60 	if ( len === 0 ) {
     61 		debug( 'Finished processing a collection.' );
     62 		return done( null, out );
     63 	}
     64 	if ( len < opts.limit ) {
     65 		lim = len;
     66 	} else {
     67 		lim = opts.limit;
     68 	}
     69 	debug( 'Concurrency limit: %d', lim );
     70 	debug( 'Number of arguments: %d', indicator.length );
     71 
     72 	maxIndex = len - 1;
     73 	count = 0;
     74 	idx = -1;
     75 	for ( i = 0; i < lim; i++ ) {
     76 		// This guard is necessary to protect against synchronous functions which exhaust all collection elements...
     77 		if ( idx < maxIndex ) {
     78 			next(); // eslint-disable-line callback-return
     79 		}
     80 	}
     81 	/**
     82 	* Callback to invoke a provided function for the next element in a collection.
     83 	*
     84 	* @private
     85 	*/
     86 	function next() {
     87 		var v;
     88 		var j;
     89 
     90 		idx += 1;
     91 		j = idx;
     92 		v = collection[ j ];
     93 
     94 		debug( 'Collection element %d: %s.', j, JSON.stringify( v ) );
     95 		if ( indicator.length === 2 ) {
     96 			indicator.call( opts.thisArg, v, cb );
     97 		} else if ( indicator.length === 3 ) {
     98 			indicator.call( opts.thisArg, v, j, cb );
     99 		} else {
    100 			indicator.call( opts.thisArg, v, j, collection, cb );
    101 		}
    102 		/**
    103 		* Callback invoked once a provided function finishes processing a collection element.
    104 		*
    105 		* @private
    106 		* @param {*} [error] - error
    107 		* @param {*} [group] - group
    108 		* @returns {void}
    109 		*/
    110 		function cb( error, group ) {
    111 			if ( flg ) {
    112 				// Prevent further processing of collection elements:
    113 				return;
    114 			}
    115 			if ( error ) {
    116 				flg = true;
    117 				return clbk( error );
    118 			}
    119 			debug( 'Collection element %d group: %s.', j, group );
    120 
    121 			// Checking for an "own" property is necessary to guard against the edge case where an indicator function returns a group identifier which matches a method or property on the `Object` prototype.
    122 			if ( hasOwnProp( out, group ) ) {
    123 				out[ group ] += 1;
    124 			} else {
    125 				out[ group ] = 1;
    126 			}
    127 			clbk();
    128 		}
    129 	}
    130 
    131 	/**
    132 	* Callback invoked once ready to process the next collection element.
    133 	*
    134 	* @private
    135 	* @param {*} [error] - error
    136 	* @returns {void}
    137 	*/
    138 	function clbk( error ) {
    139 		if ( error ) {
    140 			debug( 'Encountered an error: %s', error.message );
    141 			return done( error );
    142 		}
    143 		count += 1;
    144 		debug( 'Processed %d of %d collection elements.', count, len );
    145 		if ( idx < maxIndex ) {
    146 			return next();
    147 		}
    148 		if ( count === len ) {
    149 			debug( 'Finished processing a collection.' );
    150 			return done( null, out );
    151 		}
    152 	}
    153 }
    154 
    155 
    156 // EXPORTS //
    157 
    158 module.exports = limit;