time-to-botec

Benchmark sampling in different programming languages
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limit.js (3621B)

      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 
     25 
     26 // VARIABLES //
     27 
     28 var debug = logger( 'some-by-async:limit' );
     29 
     30 
     31 // MAIN //
     32 
     33 /**
     34 * Invokes a predicate function once for each element in a collection, limiting the number of concurrently pending functions.
     35 *
     36 * @private
     37 * @param {Collection} collection - input collection
     38 * @param {PositiveInteger} n - number of elements
     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} predicate - predicate function
     43 * @param {Callback} done - function to invoke upon completion or upon encountering an error
     44 * @returns {void}
     45 */
     46 function limit( collection, n, opts, predicate, done ) {
     47 	var maxIndex;
     48 	var count;
     49 	var flg;
     50 	var lim;
     51 	var len;
     52 	var idx;
     53 	var cnt;
     54 	var i;
     55 
     56 	len = collection.length;
     57 	debug( 'Collection length: %d', len );
     58 
     59 	if ( len === 0 ) {
     60 		debug( 'Finished processing a collection.' );
     61 		return done( null, false );
     62 	}
     63 	if ( len < opts.limit ) {
     64 		lim = len;
     65 	} else {
     66 		lim = opts.limit;
     67 	}
     68 	debug( 'Concurrency limit: %d', lim );
     69 	debug( 'Number of arguments: %d', predicate.length );
     70 
     71 	maxIndex = len - 1;
     72 	count = 0; // processed element count
     73 	idx = -1;
     74 	cnt = 0; // success count
     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 	/**
     83 	* Callback to invoke a provided function for the next element in a collection.
     84 	*
     85 	* @private
     86 	*/
     87 	function next() {
     88 		idx += 1;
     89 		debug( 'Collection element %d: %s.', idx, JSON.stringify( collection[ idx ] ) );
     90 		if ( predicate.length === 2 ) {
     91 			predicate.call( opts.thisArg, collection[ idx ], clbk );
     92 		} else if ( predicate.length === 3 ) {
     93 			predicate.call( opts.thisArg, collection[ idx ], idx, clbk );
     94 		} else {
     95 			predicate.call( opts.thisArg, collection[ idx ], idx, collection, clbk ); // eslint-disable-line max-len
     96 		}
     97 	}
     98 
     99 	/**
    100 	* Callback invoked once a provided function finishes processing a collection element.
    101 	*
    102 	* @private
    103 	* @param {*} [error] - error
    104 	* @param {*} [result] - test result
    105 	* @returns {void}
    106 	*/
    107 	function clbk( error, result ) {
    108 		if ( flg ) {
    109 			// Prevent further processing of collection elements:
    110 			return;
    111 		}
    112 		if ( error ) {
    113 			flg = true;
    114 			debug( 'Encountered an error: %s', error.message );
    115 			return done( error );
    116 		}
    117 		count += 1;
    118 		debug( 'Processed %d of %d collection elements.', count, len );
    119 
    120 		debug( 'Test result: %s', !!result );
    121 		if ( result && !flg ) {
    122 			cnt += 1;
    123 			if ( cnt === n ) {
    124 				flg = true;
    125 				debug( 'Finished processing a collection.' );
    126 				return done( null, true );
    127 			}
    128 		}
    129 		if ( idx < maxIndex ) {
    130 			return next();
    131 		}
    132 		if ( count === len ) {
    133 			debug( 'Finished processing a collection.' );
    134 			return done( null, false );
    135 		}
    136 	}
    137 }
    138 
    139 
    140 // EXPORTS //
    141 
    142 module.exports = limit;