timed comparison of nsscanner to an array split parsing task.

scanner_test.m

//
//  main.m
//  Scratch
//
//  Created by Kim Hunter on 12/06/2014.
//  Copyright (c) 2014 Kim Hunter. All rights reserved.
//

// Here I do similar test while the code does some actual task in the loops
// The results: the nsscanner approach takes less than a tenth of the time
// of the naïve array splitting result.
//
// 2014-06-13 00:21:55.608 Scratch[2309:303] 11.123 avg: 5.459
// 2014-06-13 00:21:56.661 Scratch[2309:303] 1.052 avg: 0.573
// Program ended with exit code: 0
//

#import <Foundation/Foundation.h>
#import <QuartzCore/QuartzCore.h>

#define RUNS 20
int main(int argc, const char * argv[])
{
    NSString *filePath = [@"~/Desktop/scanner_test.txt" stringByExpandingTildeInPath];
    NSTask *t = [NSTask launchedTaskWithLaunchPath:@"/usr/bin/touch" arguments:@[filePath]];
    [t waitUntilExit];
    NSFileHandle *fh = [NSFileHandle fileHandleForWritingAtPath:filePath];
    @autoreleasepool {
        CFTimeInterval start, end;
        NSString *wordsString = [NSString stringWithContentsOfFile:@"/usr/share/dict/words" encoding:NSUTF8StringEncoding error:NULL];
        double total = 0.0;

        start = CACurrentMediaTime();
        for (int i = 0; i < RUNS; ++i)
        {
            NSArray *a = [wordsString componentsSeparatedByString:@"\n"];
            for (NSString *s in a)
            {
                if([s length])
                {
                    [fh writeData:[NSData dataWithBytes:[s UTF8String] length:[s length]]];
                }
            }
            total += CACurrentMediaTime() - start;
        }
        end = CACurrentMediaTime();
        NSLog(@"%.3lf avg: %.3lf", end - start, total/RUNS);

        total = 0.0;
        start = CACurrentMediaTime();
        for (int i = 0; i < RUNS; ++i)
        {

            NSScanner *scanner = [[NSScanner alloc] initWithString:wordsString];
            [scanner setCharactersToBeSkipped:nil];
            while (![scanner isAtEnd])
            {
                NSString *nextString = nil;

                [scanner scanUpToString:@"\r\n" intoString:&nextString];
                if ([nextString length])
                {
                    [fh writeData:[NSData dataWithBytes:[nextString UTF8String] length:[nextString length]]];
                }
                if ([scanner isAtEnd])
                {
                    break;
                }
                scanner.scanLocation += scanner.scanLocation;
            }
            total += CACurrentMediaTime() - start;
        }
        end = CACurrentMediaTime();
        NSLog(@"%.3lf avg: %.3lf", end - start, total/RUNS);

        
    }
    return 0;
}