time-to-botec

Benchmark sampling in different programming languages
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limit.js (4084B)

      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 indexOf = require( './../../../index-of' );
     25 
     26 
     27 // VARIABLES //
     28 
     29 var debug = logger( 'tabulate-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 tmp;
     55 	var i;
     56 
     57 	len = collection.length;
     58 	debug( 'Collection length: %d', len );
     59 
     60 	out = [];
     61 	if ( len === 0 ) {
     62 		debug( 'Finished processing a collection.' );
     63 		return done( null, out );
     64 	}
     65 	tmp = [];
     66 	if ( len < opts.limit ) {
     67 		lim = len;
     68 	} else {
     69 		lim = opts.limit;
     70 	}
     71 	debug( 'Concurrency limit: %d', lim );
     72 	debug( 'Number of arguments: %d', indicator.length );
     73 
     74 	maxIndex = len - 1;
     75 	count = 0;
     76 	idx = -1;
     77 	for ( i = 0; i < lim; i++ ) {
     78 		// This guard is necessary to protect against synchronous functions which exhaust all collection elements...
     79 		if ( idx < maxIndex ) {
     80 			next(); // eslint-disable-line callback-return
     81 		}
     82 	}
     83 	/**
     84 	* Callback to invoke a provided function for the next element in a collection.
     85 	*
     86 	* @private
     87 	*/
     88 	function next() {
     89 		var v;
     90 		var j;
     91 
     92 		idx += 1;
     93 		j = idx;
     94 		v = collection[ j ];
     95 
     96 		debug( 'Collection element %d: %s.', j, JSON.stringify( v ) );
     97 		if ( indicator.length === 2 ) {
     98 			indicator.call( opts.thisArg, v, cb );
     99 		} else if ( indicator.length === 3 ) {
    100 			indicator.call( opts.thisArg, v, j, cb );
    101 		} else {
    102 			indicator.call( opts.thisArg, v, j, collection, cb );
    103 		}
    104 		/**
    105 		* Callback invoked once a provided function finishes processing a collection element.
    106 		*
    107 		* @private
    108 		* @param {*} [error] - error
    109 		* @param {*} [group] - group
    110 		* @returns {void}
    111 		*/
    112 		function cb( error, group ) {
    113 			var i;
    114 			if ( flg ) {
    115 				// Prevent further processing of collection elements:
    116 				return;
    117 			}
    118 			if ( error ) {
    119 				flg = true;
    120 				return clbk( error );
    121 			}
    122 			debug( 'Collection element %d group: %s.', j, group );
    123 
    124 			// Determine if we've seen the group/category before. If not, cache a reference which points to its location in the output array; otherwise, update the running count.
    125 			i = indexOf( tmp, group );
    126 			if ( i === -1 ) {
    127 				tmp.push( group );
    128 				out.push( [ group, 1, 0 ] );
    129 			} else {
    130 				out[ i ][ 1 ] += 1;
    131 			}
    132 			clbk();
    133 		}
    134 	}
    135 
    136 	/**
    137 	* Callback invoked once ready to process the next collection element.
    138 	*
    139 	* @private
    140 	* @param {*} [error] - error
    141 	* @returns {void}
    142 	*/
    143 	function clbk( error ) {
    144 		var i;
    145 		if ( error ) {
    146 			debug( 'Encountered an error: %s', error.message );
    147 			return done( error );
    148 		}
    149 		count += 1;
    150 		debug( 'Processed %d of %d collection elements.', count, len );
    151 		if ( idx < maxIndex ) {
    152 			return next();
    153 		}
    154 		if ( count === len ) {
    155 			// Compute percentages...
    156 			for ( i = 0; i < out.length; i++ ) {
    157 				out[ i ][ 2 ] = out[ i ][ 1 ] / count;
    158 			}
    159 			debug( 'Finished processing a collection.' );
    160 			return done( null, out );
    161 		}
    162 	}
    163 }
    164 
    165 
    166 // EXPORTS //
    167 
    168 module.exports = limit;