Date parsing performance comparison

DateParsingPerformanceTests.m

#import <Foundation/Foundation.h>
#include <time.h>
#include <xlocale.h>
#import "sqlite3.h"
#import "ISO8601DateFormatter.h"

#define LOG_DATE 0

static NSUInteger count = 1000000;

typedef int64_t timestamp;

NSUInteger randomNumberInRange(NSUInteger start, NSUInteger end);

// Create a sample date using the ISO-8601 format.
// 2013-04-23T16:29:05Z
NSString* generateSampleDate();

// Create an array of <count> dates in the ISO-8601 format.
NSArray *generateSampleDates(NSUInteger count);

// Parse all given dates using SQLite's strftime function
void parseDatesUsingSQLite(NSArray *dates);

// Parse all given dates using NSDateFormatter
void parseDatesUsingNSDateFormatter(NSArray *dates);

// Use SQLite implementation directly
void parseDatesUsingSQLiteImpl(NSArray *dates);

// Use the library IS08601 written by Peter Hosey
void parseDatesUsingISO8601Parser(NSArray *dates);

// Use strptime and gmtime from time.h
void parseDatesUsingGMTime(NSArray *dates);


timestamp unixDate(int year, int month, int day, int hour, int minute, int second);

static NSDateFormatter *dateFormatter = nil;
static ISO8601DateFormatter *isoDateFormatter = nil;

int main()
{
    @autoreleasepool
    {
        printf("Generating sample data with %lu dates\n", count);
        NSArray *dates = generateSampleDates(count);
        printf("Sample data generation complete. Commencing tests...\n\n");

        NSDate *start = nil;
        NSDate *end = nil;

        start = [NSDate date];        
        parseDatesUsingSQLite(dates);
        end = [NSDate date];

        printf("sqlite3 took %4.3f seconds\n", [end timeIntervalSinceDate:start]);

        start = [NSDate date];
        parseDatesUsingNSDateFormatter(dates);
        end = [NSDate date];

        printf("NSDateFormatter took %4.3f seconds\n", [end timeIntervalSinceDate:start]);

    	start = [NSDate date];
        parseDatesUsingSQLiteImpl(dates);
        end = [NSDate date];

        printf("SQLite's implementation in C took %4.3f seconds\n", [end timeIntervalSinceDate:start]);

        start = [NSDate date];
        parseDatesUsingISO8601Parser(dates);
        end = [NSDate date];

        printf("ISO8601DateFormatter took %4.3f seconds\n", [end timeIntervalSinceDate:start]);


        start = [NSDate date];
        parseDatesUsingGMTime(dates);
        end = [NSDate date];

        printf("strptime/gmtime took %4.3f seconds\n", [end timeIntervalSinceDate:start]);
    }

    return 0;
}

NSArray *generateSampleDates(NSUInteger count)
{
    NSMutableArray *dates = [NSMutableArray array];

    for (int i = 0; i < count; i++)
    {
        [dates addObject:generateSampleDate()];
    }

    return dates;
}

NSString* generateSampleDate()
{
    NSUInteger year = randomNumberInRange(1980, 2013);
    NSUInteger month = randomNumberInRange(1, 12);
    NSUInteger date = randomNumberInRange(1, 28);
    NSUInteger hour = randomNumberInRange(0, 23);
    NSUInteger minute = randomNumberInRange(0, 59);
    NSUInteger second = randomNumberInRange(0, 59);

    NSString *dateString = [NSString stringWithFormat:@"%lu-%02lu-%02luT%02lu:%02lu:%02luZ",
        year,
        month, 
        date,
        hour,
        minute,
        second
    ];

    return dateString;
}

void parseDatesUsingSQLiteImpl(NSArray *dates)
{
	static const char *scanFormat = "%d-%d-%dT%d:%d:%d";
    int year, month, date, hour, minute, second;

    for (NSString *dateString in dates)
    {
        sscanf(dateString.UTF8String, scanFormat, &year, &month, &date, &hour, &minute, &second);
        timestamp interval = unixDate(year, month, date, hour, minute, second);
        NSDate *date = [NSDate dateWithTimeIntervalSince1970:interval];

        #if LOG_DATE
        NSLog(@"%@", date);
        #endif 
    }
}


void parseDatesUsingSQLite(NSArray *dates)
{
    sqlite3 *db = NULL;
    sqlite3_open(":memory:", &db);

    sqlite3_stmt *statement = NULL;
    sqlite3_prepare_v2(db, "SELECT strftime('%s', ?);", -1, &statement, NULL);

    for (NSString *dateString in dates)
    {
        sqlite3_bind_text(statement, 1, [dateString UTF8String], -1, SQLITE_STATIC);
        sqlite3_step(statement);
        timestamp value = sqlite3_column_int64(statement, 0);
        NSDate *date = [NSDate dateWithTimeIntervalSince1970:value];

        #if LOG_DATE
        NSLog(@"%@", date);
        #endif 
        
        sqlite3_clear_bindings(statement);
        sqlite3_reset(statement);
    }
}

void parseDatesUsingNSDateFormatter(NSArray *dates)
{
    if (dateFormatter == nil)
    {
        dateFormatter = [[NSDateFormatter alloc] init];
        [dateFormatter setDateFormat:@"yyyy-MM-dd'T'HH:mm:ss'Z'"];
        [dateFormatter setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:0]];        
    }

    for (NSString *dateString in dates)
    {
        NSDate *date = [dateFormatter dateFromString:dateString];

        #if LOG_DATE
        NSLog(@"%@", date);
        #endif 
    }
}

NSUInteger randomNumberInRange(NSUInteger start, NSUInteger end)
{
    NSUInteger span = end - start;
    return start + arc4random_uniform(span);
}

timestamp unixDate(int year, int month, int day, int hour, int minute, int second)
{
    int century, b, x1, x2;
    int64_t julianDay;
    
    if (month <= 2)
    {
        year--;
        month += 12;
    }

    century = year / 100;
    b = 2 - century + (century / 4);
    x1 = 36525 * (year + 4716) / 100;
    x2 = 306001 * (month + 1) / 10000;
    
    julianDay = (int64_t)((x1 + x2 + day + b - 1524.5 ) * 86400000);
    julianDay += (hour * 3600000) + (minute * 60000) + (int64_t)(second * 1000);
    int64_t unixTime = (julianDay / 1000) - (21086676 * (int64_t)10000);
    
    return unixTime;
}

void parseDatesUsingISO8601Parser(NSArray *dates)
{
    [NSTimeZone setDefaultTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:+0]];

    if (isoDateFormatter == nil)
    {
        isoDateFormatter = [[ISO8601DateFormatter alloc] init];
        isoDateFormatter.parsesStrictly = YES;
    }

    for (NSString *dateString in dates)
    {
        NSDate *date = [isoDateFormatter dateFromString:dateString];

        #if LOG_DATE
        NSLog(@"%@", date);
        #endif 
    }
}

void parseDatesUsingGMTime(NSArray *dates)
{
    struct tm  sometime;
    const char *formatString = "%Y-%m-%dT%H:%M:%SZ";
    for (NSString *date in dates)
    {
        strptime_l([date UTF8String], formatString, &sometime, NULL);
        NSDate *date = [NSDate dateWithTimeIntervalSince1970: timegm(&sometime)];

        #if LOG_DATE
        NSLog(@"%@", date);
        #endif 
    }
}