mirror of
https://github.com/TomHarte/CLK.git
synced 2024-09-08 03:54:27 +00:00
76 lines
2.1 KiB
Objective-C
76 lines
2.1 KiB
Objective-C
//
|
|
// CSBestEffortUpdater.m
|
|
// Clock Signal
|
|
//
|
|
// Created by Thomas Harte on 16/06/2016.
|
|
// Copyright © 2016 Thomas Harte. All rights reserved.
|
|
//
|
|
|
|
#import "CSBestEffortUpdater.h"
|
|
|
|
#include <stdatomic.h>
|
|
|
|
@implementation CSBestEffortUpdater
|
|
{
|
|
// these are inherently handled only by thread-safe constructions
|
|
atomic_flag _updateIsOngoing;
|
|
dispatch_queue_t _serialDispatchQueue;
|
|
|
|
// these are permitted for modification on _serialDispatchQueue only
|
|
NSTimeInterval _previousTimeInterval;
|
|
NSTimeInterval _cyclesError;
|
|
BOOL _hasSkipped;
|
|
}
|
|
|
|
- (instancetype)init
|
|
{
|
|
if(self = [super init])
|
|
{
|
|
_serialDispatchQueue = dispatch_queue_create("Best Effort Updater", DISPATCH_QUEUE_SERIAL);
|
|
|
|
// This is a workaround for assigning the correct initial value within Objective-C's form.
|
|
atomic_flag initialFlagValue = ATOMIC_FLAG_INIT;
|
|
_updateIsOngoing = initialFlagValue;
|
|
}
|
|
return self;
|
|
}
|
|
|
|
- (void)update
|
|
{
|
|
// Always post an -openGLView:didUpdateToTime: if a previous one isn't still ongoing. This is the hook upon which the substantial processing occurs.
|
|
if(!atomic_flag_test_and_set(&_updateIsOngoing))
|
|
{
|
|
dispatch_async(_serialDispatchQueue, ^{
|
|
NSTimeInterval timeInterval = [NSDate timeIntervalSinceReferenceDate];
|
|
if(_previousTimeInterval > DBL_EPSILON && timeInterval > _previousTimeInterval)
|
|
{
|
|
NSTimeInterval timeToRunFor = timeInterval - _previousTimeInterval;
|
|
double cyclesToRunFor = timeToRunFor * self.clockRate + _cyclesError;
|
|
|
|
_cyclesError = fmod(cyclesToRunFor, 1.0);
|
|
NSUInteger integerCyclesToRunFor = (NSUInteger)MIN(cyclesToRunFor, self.clockRate * 0.5);
|
|
|
|
// treat 'unlimited' as running at a factor of 10
|
|
if(self.runAsUnlimited) integerCyclesToRunFor *= 10;
|
|
[self.delegate bestEffortUpdater:self runForCycles:integerCyclesToRunFor didSkipPreviousUpdate:_hasSkipped];
|
|
}
|
|
_previousTimeInterval = timeInterval;
|
|
_hasSkipped = NO;
|
|
atomic_flag_clear(&_updateIsOngoing);
|
|
});
|
|
}
|
|
else
|
|
{
|
|
dispatch_async(_serialDispatchQueue, ^{
|
|
_hasSkipped = YES;
|
|
});
|
|
}
|
|
}
|
|
|
|
- (void)flush
|
|
{
|
|
dispatch_sync(_serialDispatchQueue, ^{});
|
|
}
|
|
|
|
@end
|