StopWatch.mm

//
//  StopWatch.m
//  FaceFront
//
//  Created by Yung-Luen Lan on 05/10/2016.
//  Copyright © 2016 Kneron. All rights reserved.
//
#import "StopWatch.h"
#import <Foundation/Foundation.h>

#include <string>
#include <map>
#include <mach/mach.h>
#include <mach/mach_time.h>

static std::map<std::string, uint64_t> totalDuration;
static std::map<std::string, uint64_t> sampleCount;
static std::map<std::string, uint64_t> beginTime;

void stopwatch_begin(const char *name) {
    uint64_t start = mach_absolute_time();
    std::string channel = name;
    beginTime[channel] = start;
    sampleCount[channel]++;
}

static double convert_mach_to_second(uint64_t mtime)
{
    static mach_timebase_info_data_t sTimebaseInfo;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        mach_timebase_info(&sTimebaseInfo);
    });
    return (double)mtime * sTimebaseInfo.numer / sTimebaseInfo.denom / 1000000000.0;
}

CFTimeInterval stopwatch_stop(const char *name, bool shouldLog)
{
    
    std::string channel = name;
    if (beginTime.find(channel) != beginTime.end()) {
        uint64_t end = mach_absolute_time();
        uint64_t elapsed = end - beginTime[channel];
        totalDuration[channel] += elapsed;
        beginTime.erase(channel);
        
        double current = convert_mach_to_second(elapsed);
        double total = convert_mach_to_second(totalDuration[channel]);
        NSLog(@"%llu timing %s: %lf seconds, total = %lf, avg = %lf.", sampleCount[channel], name, current, total, total / sampleCount[channel]);
        return convert_mach_to_second(elapsed);
    } else {
        return 0;
    }
}