I have been using mach_absolute_time() for all my timing functions so far. calculating how long between frames etc.
I now want to get the exact time touch input events happen using event.timestamp in the touch callbacks.
the problem is these two seem to use completely different timers. sure, you can get them both in seconds, but their origins are different and seemingly random...
is there any way to sync the two different timers?
or is there anyway to get access to the same timer that the touch input uses to generate that timestamp property? otherwise its next to useless.
Had some trouble with this myself. There isn't a lot of good documentation, so I went with experimentation. Here's what I was able to determine:
mach_absolute_time depends on the processor of the device. It returns ticks since the device was last rebooted (otherwise known as uptime). In order to get it in a human readable form, you have to modify it by the result from mach_timebase_info (a ratio), which will return billionth of seconds (or nanoseconds). To make this more usable I use a function like the one below:
#include <mach/mach_time.h>
int getUptimeInMilliseconds()
{
static const int64_t kOneMillion = 1000 * 1000;
static mach_timebase_info_data_t s_timebase_info;
if (s_timebase_info.denom == 0) {
(void) mach_timebase_info(&s_timebase_info);
}
// mach_absolute_time() returns billionth of seconds,
// so divide by one million to get milliseconds
return (int)((mach_absolute_time() * s_timebase_info.numer) / (kOneMillion * s_timebase_info.denom));
}
Get the initial difference between two i.e
what is returned by mach_absolute_time() initally when your application starts and also get the event.timestamp initially at the same time...
store the difference... it would remain same through out the time your application runs.. so you can use this time difference to convert one to another...
How about CFAbsoluteTimeGetCurrent?
Related
Before I spend a lot of time writing the only solution I can think of I was wondering if I'm doing it an inefficient way.
Once a support ticket is closed, a script is triggered, the script is passed an array of 'status-change-events' that happened from call open to close. So you might have 5 changes: new, open, active, stalled, resolved. Each one of these events has a timestamp associated with it.
What I need to do is calculate how much time the call was with us (new, open, active) and how much time it was with the customer (stalled). I also need to figure out how much of the 'us' time was within core hours 08:00 - 18:00 (and how many were non-core), and weekends/bank holidays count towards non-core hours.
My current idea is to for each status change, iterate over every second that occurred and check for core/non_core, and log it.
Here's some pseudo code:
time_since_last = ticket->creation_date
foreach events as event {
time_now = time_since_last
while (time_now < ticket->event_date) {
if ticket->status = stalled {
customer_fault_stalled++
} else {
work out if it was our fault or not
add to the appropriate counter etc
}
time_now++
}
}
Apologies if it's a little unclear, it's a fairly longwinded problem. Also I'm aware this may be slightly off of SO question guidelines, but I can't think of a better way of wording it and I need some advice before I spend days writing it this way.
I think you have the right idea, but recalculating the status of every ticket for every second of elapsed time will take a lot processing, and nothing will have changed for the vast majority of those one-second intervals
The way event simulations work, and the way I think you should write your application, is to create a list of all events where the status might change. So you will want to include all of the status change events for every ticket as well as the start and end of core time on all non-bank-holiday weekdays
That list of events is sorted by timestamp, after which you can just process each event as if your per-second counter has reached that time. The difference is that you no longer have to count through the many intervening seconds where nothing changes, and you should end up with a much more efficient application
I hope that's clear. You may find it easier to process each ticket separately, but the maximum gain will be achieved by processing all tickets simultaneously. You will still have a sorted sequence of events to process, but you will avoid having to reprocess the same core time start and end events over and over again
One more thing I noticed is that you can probably ignore any open status change events. I would guess that tickets either go from new to open and then active, or straight from new to resolved. So a switch between with your company and with the customer will never be made at an open event, and so they can be ignored. Please check this as I am only speaking from my intuition, and clearly know nothing about how your ticketing system has been designed
I would not iterate over the seconds. Depending on the cost of your calculations that could be quite costly. It would be better to calculate the borders between core/outside core.
use strict;
use warnings;
my $customer_time;
my $our_time_outside;
my $our_time_core;
foreach my $event ($ticket->events) {
my $current_ts = $event->start_ts;
while ($current_ts < $event->end_ts) {
if ($event->status eq 'stalled') {
$customer_time += $event->end_ts - $current_ts;
$current_ts = $event->end_ts;
}
elsif (is_core_hours($current_ts)) {
my $next_ts = min(end_of_core_hours($current_ts), $event->end_ts);
$our_time_core += $next_ts - $current_ts;
$current_ts = $next_ts;
}
else {
my $next_ts = min(start_of_core_hours($current_ts), $event->end_ts);
$our_time_outside += $next_ts - $current_ts;
$current_ts = $next_ts;
}
}
}
I can't see why you'd want to iterate over every second. That seems very wasteful.
Get a list of all of the events for a given ticket.
Add to the list any boundaries between core and non-core times.
Sort this list into chronological order.
For each consecutive pair of events in the list, subtract the later from the earlier to get a duration.
Add that duration to the appropriate bucket.
And the usual caveats for dealing with dates and times apply here:
Use a library (I recommend DateTime together with DateTime::Duration)
Convert all of your timestamps to UTC as soon as you get them. Only convert back to local time just before displaying them to the user.
I'm using libspotify SDK, C library for win32.
I think to have a right setup, every session callback is registered. I don't understand why i can't receive the call for end_of_track, while music_delivery continues to be called with zero padding 22050 long frames.
I attempt to start playing first loading the track with sp_session_load; till it returns SP_ERROR_IS_LOADING I post a message on my message queue (synchronization method I've used, PostMessage win32 API) in order to reload again with same API sp_session_load. As soon as it returns SP_ERROR_OK I use the sp_session_play and the music_delivery starts immediately, with correct frames.
I don't know why at the end of track the libspotify runtime then start sending zero padded frames, instead of calling end_of_track callback.
In other conditions it works perfectly: I've used the sp_track obtained from a album browse, so the track is fully loaded at the moment I load to the current session for playing: with this track, it works fine with end_of_track called correctly. In the case with padding error, I search the track using its Spotify URI and got the results; in this case the track metadata are not still ready (at the play attempt) so I used that kind of "polling" on sp_session_load with PostMessage.
Can anybody help me?
I ran into the same problem and I think the issue was that I was consuming the data too fast without giving other threads time to do any work since I was spending all of my time in the music_delivery callback. I found that if I add some throttling and notify the main thread that it can wake up to do some processing, the extra zeros at the end of track is reduced to one delivery of 22,050 frames (or 500ms at 44.1kHz).
Here is an example of what I added to my callback, heavily borrowed from the jukebox.c example provided with the SDK:
/* Buffer 1 second of data, then notify the main thread to do some processing */
if (g_throttle > format->sample_rate) {
pthread_mutex_lock(&g_notify_mutex);
g_notify_do = 1;
pthread_cond_signal(&g_notify_cond);
pthread_mutex_unlock(&g_notify_mutex);
// Reset the throttle counter
g_throttle = 0;
return 0;
}
As I said, there was still 22,050 frames of zeros delivered before the track stopped, but I believe libspotify may purposely do this to ensure that the duration calculated by the number of frames received (song_duration_ms = total_frames_delivered / sample_rate * 1000) is greater than or equal to the duration reported by sp_track_duration. In my case, the track I was trying to stream was 172,000ms in duration, without the extra padding the duration calculated is 171,796ms, but with the padding it was 172,296ms.
Hope this helps.
In my app I apply filters for the image. I want to add UIProgressView as it takes about couple of seconds to complete the editing. How to add a UIProgressView for such method and also update how many percent it is completed? I have gone through many examples for UIProgressView but they are for Http request and loading network data. How to implement that for custom method ?
I guess you need to use Operation Queue for this.
[NSThread detachNewThreadSelector:#selector(showProgressView:) toTarget:self withObject:nil];
This has worked for me I hope it works for you too.. Have a happy Coding.!!
If you have control over how much of the editing is completed, like any delegate events you can update the progress just like network calls or others. Even if you don't have such events, you might be having some inner methods, which can give you a delta of the total progress happened.
Then you can have a method which takes in this delta, add it to existing progress.
- (void)updateProgress:(CGFloat)delta
{
[self.progressView setProgress:self.progressView.progress+delta];
self.progressLabel.text = [NSString stringWithFormat:#"Completed : %.0f",self.progressView.progress*100];
}
It's difficult to answer this without knowing what data you have available to you, but essentially, you need to have a method that gets called at a consistent periodic time interval until the image filter gets applied. A trick for doing this would be if you could come up with a time estimate for a filter and then just use an NSTimer to fire a method until that time is complete. Although if you could figure out an exact time for it to filter, that would obviously be preferable.
From there you need to set the progress of the progress view to that time over the amount of time total like so...
self.progressView.progress = (float) progress
Keep in mind though that the progress view is a percent, so you will need to store two values to compare (divide over each other) 1) the total amount of time 2) the total amount of time passed. You can just do this though by setting up a float progress in your user #interface.
I have not been able to find this information anywhere. How long can a string be send with the TTL version of the redpark cable?
The following delegate method is called twice when I print something thorough serial from my Arduino, an example of a string is this: 144;480,42;532,40;20e
- (void) readBytesAvailable:(UInt32)length{
When I use the new function methods of retrieving available data [getStringFromBytesAvailable] I will only get 144;480,42;532,40; and then the whole function is called again and the string now contains the rest of the string: 20e
The following method is working for appending the two strings, but only if the rate of data transmission is 'slow' (1 time a second, I would prefer minimum 10 times a second).
-
(void) readBytesAvailable:(UInt32)length{
if(string && [string rangeOfString:#"e"].location == NSNotFound){
string = [string stringByAppendingString:[rscMgr getStringFromBytesAvailable]];
NSLog(string);
finishedReading = YES;
}
else{
string = [rscMgr getStringFromBytesAvailable];
}
if (finishedReading == YES)
{
//do stuff
}
finishedReading = NO;
string = nil;
}
}
But can you tell my why the methods is called twice if I write a "long" string, and how to avoid this issue?
Since your program fragment runs faster then the time it takes to send a string, you need to capture the bytes and append them to a string.
If the serial data is terminated with a carriage return you can test for it to know when you have received the entire string.
Then you can allow your Arduino to send 10 times a second.
That is just how serial ports work. You can't and don't need to avoid those issues. There is no attempt at any level of the SW/HW to keep your serial data stream intact, so making any assumptions about that in your code is just wrong. Serial data is just a stream of bytes, with no concept of packetization. So you have to deal with the fact that you might have to read partial data and read the rest later.
The serialPortConfig within the redparkSerial header file provided by RedPark does, in fact, give you more configuration control than you may realize. The readBytesAvailable:length method is abstracted, and is only called when one of two conditions is met: rxForwardingTimeout value is exceeded with data in the primary buffer (default set to 100 ms) or rxForwardCount is reached (default set to 16 characters).
So, in your case it looks like you've still got data in your buffer after your initial read, which means that the readBytesAvailable:length method will be called again (from the main run loop) to retrieve the remaining data. I would propose playing around with the rxForwardingTimeout and rxForwardCount until it performs as you'd expect.
As already mentioned, though, I'd recommend adding a flag (doesn't have to be carriage return) to at least the end of your packet, for identification.
Also, some good advice here: How do you design a serial command protocol for an embedded system?
Good luck!
I'm looking for a reliable way to get the time. It can't be tampered with and it needs to work offline. So no internet time , no user time setup in settings and no BSD uptime time since last reboot. I was wondering since GPS works using atomic clock, whether I could access that information.
Thank you
This works to get the GPS time:
#import <CoreLocation/CoreLocation.h>
CLLocation* gps = [[CLLocation alloc]
initWithLatitude:(CLLocationDegrees) 0.0
longitude:(CLLocationDegrees) 0.0];
NSDate* now = gps.timestamp;
It doesn't seem to be tamper-proof though.
I tried this code on an iPhone 4 in airplane mode (iOS 6.1), and even then it gives a time all right. But unfortunately this time seems to change with the system clock. Ugh.
Funny thing that I found (still in airplane mode) is that if you tamper with the system clock (after turning to off Time & Date's Set Automatically), and then turn Set Automatically back to on, the machine restores the real (original) time without a hitch. this works even after cycling the phone's power. So it seems that there is something like a tamper-proof time the device maintains internally. But how to access this?
P.S. A discussion of this from 2010. The author of the penultimate comment tried this in a fallout shelter: so it's clear the phone is not getting the pristine time from any external source.
Addendum, July 2013
Found a few more posts (here, here and here) about another kind of time measure: system kernel boot time. It's accessed through a call something like this: sysctlbyname("kern.boottime", &boottime, &size, NULL, 0);. Unfortunately it too changes with the user-adjusted data and time, even without reboot. Another function gettimeofday() is similarly dependent on user-defined time.
NSDate and it's CF counterpart are all based on the user controllable time, and thereby aren't tamper proof.
As far as I know, there is no open API for either GPS time or carrier time directly. However, you can check the mach_absolute_time to get untampered time since last boot up, and perhaps use it to at least be aware of how much time has passed since the app has been awoken (without having the potential for that time to be tampered with while the app is running).
mach_absolute_time depends on the processor of the device. It returns ticks since the device was last rebooted (otherwise known as uptime). In order to get it in a human readable form, you have to modify it by the result from mach_timebase_info (a ratio), which will return billionth of seconds (or nanoseconds). To make this more usable I use a function like the one below:
#include <mach/mach_time.h>
int getUptimeInMilliseconds()
{
static const int64_t kOneMillion = 1000 * 1000;
static mach_timebase_info_data_t s_timebase_info;
if (s_timebase_info.denom == 0) {
(void) mach_timebase_info(&s_timebase_info);
}
// mach_absolute_time() returns billionth of seconds,
// so divide by one million to get milliseconds
return (int)((mach_absolute_time() * s_timebase_info.numer) / (kOneMillion * s_timebase_info.denom));
}
Even if you can get hold of the time from GPS you should be aware that GPS time is not quite the same as UTC. The GPS receiver in the iPhone might take care of that for you though.
This gets you the current date and time:
NSDate *now = [NSDate date];
This will be as reliable as you can get. The internal clock on the iPhone will be updated when it can get access to an NTP server. If the phone uses GPS as a time sync source it'll also be used to update the same system-wide clock which is accessible via the above method.
The CoreFoundation equivalent is something like:
CFAbsoluteTime now = CFAbsoluteTimeGetCurrent();
Which returns the CoreFoundation equivalent of the normal UNIX seconds-since-epoch timestamp.
The gold standard of timekeeping are the various government time observatories in the U.S. and worldwide. They provide Atomic time. That is used world wide. Apple should be using that. If the want to sync w/ the cell towers, there should be an Alternate internal time. If the tower or GPS system malfunctions all are left with incorrect time.