time-to-botec

Benchmark sampling in different programming languages
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limit.js (3611B)

      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-right-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 and iterating from right to left.
     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 count;
     48 	var flg;
     49 	var lim;
     50 	var len;
     51 	var idx;
     52 	var cnt;
     53 	var i;
     54 
     55 	len = collection.length;
     56 	debug( 'Collection length: %d', len );
     57 
     58 	if ( len === 0 ) {
     59 		debug( 'Finished processing a collection.' );
     60 		return done( null, false );
     61 	}
     62 	if ( len < opts.limit ) {
     63 		lim = len;
     64 	} else {
     65 		lim = opts.limit;
     66 	}
     67 	debug( 'Concurrency limit: %d', lim );
     68 	debug( 'Number of arguments: %d', predicate.length );
     69 
     70 	count = 0; // processed element count
     71 	idx = len;
     72 	cnt = 0; // success count
     73 	for ( i = 0; i < lim; i++ ) {
     74 		// This guard is necessary to protect against synchronous functions which exhaust all collection elements...
     75 		if ( idx > 0 ) {
     76 			next(); // eslint-disable-line callback-return
     77 		}
     78 	}
     79 
     80 	/**
     81 	* Callback to invoke a provided function for the next element in a collection.
     82 	*
     83 	* @private
     84 	*/
     85 	function next() {
     86 		idx -= 1;
     87 		debug( 'Collection element %d: %s.', idx, JSON.stringify( collection[ idx ] ) );
     88 		if ( predicate.length === 2 ) {
     89 			predicate.call( opts.thisArg, collection[ idx ], clbk );
     90 		} else if ( predicate.length === 3 ) {
     91 			predicate.call( opts.thisArg, collection[ idx ], idx, clbk );
     92 		} else {
     93 			predicate.call( opts.thisArg, collection[ idx ], idx, collection, clbk ); // eslint-disable-line max-len
     94 		}
     95 	}
     96 
     97 	/**
     98 	* Callback invoked once a provided function finishes processing a collection element.
     99 	*
    100 	* @private
    101 	* @param {*} [error] - error
    102 	* @param {*} [result] - test result
    103 	* @returns {void}
    104 	*/
    105 	function clbk( error, result ) {
    106 		if ( flg ) {
    107 			// Prevent further processing of collection elements:
    108 			return;
    109 		}
    110 		if ( error ) {
    111 			flg = true;
    112 			debug( 'Encountered an error: %s', error.message );
    113 			return done( error );
    114 		}
    115 		count += 1;
    116 		debug( 'Processed %d of %d collection elements.', count, len );
    117 
    118 		debug( 'Test result: %s', !!result );
    119 		if ( result && !flg ) {
    120 			cnt += 1;
    121 			if ( cnt === n ) {
    122 				flg = true;
    123 				debug( 'Finished processing a collection.' );
    124 				return done( null, true );
    125 			}
    126 		}
    127 		if ( idx > 0 ) {
    128 			return next();
    129 		}
    130 		if ( count === len ) {
    131 			debug( 'Finished processing a collection.' );
    132 			return done( null, false );
    133 		}
    134 	}
    135 }
    136 
    137 
    138 // EXPORTS //
    139 
    140 module.exports = limit;