SDWebImagePrefetcher.m
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/*
* This file is part of the SDWebImage package.
* (c) Olivier Poitrey <rs@dailymotion.com>
*
* For the full copyright and license information, please view the LICENSE
* file that was distributed with this source code.
*/
#import "SDWebImagePrefetcher.h"
#import "SDWebImageManager.h"
@interface SDWebImagePrefetcher ()
@property (strong, nonatomic) SDWebImageManager *manager;
@property (strong, nonatomic) NSArray *prefetchURLs;
@property (assign, nonatomic) NSUInteger requestedCount;
@property (assign, nonatomic) NSUInteger skippedCount;
@property (assign, nonatomic) NSUInteger finishedCount;
@property (assign, nonatomic) NSTimeInterval startedTime;
@end
@implementation SDWebImagePrefetcher
+ (SDWebImagePrefetcher *)sharedImagePrefetcher
{
static dispatch_once_t once;
static id instance;
dispatch_once(&once, ^{instance = self.new;});
return instance;
}
- (id)init
{
if ((self = [super init]))
{
_manager = SDWebImageManager.new;
_manager.imageDownloader.maxConcurrentDownloads = 3;
_options = SDWebImageLowPriority;
}
return self;
}
- (void)startPrefetchingAtIndex:(NSUInteger)index
{
if (index >= self.prefetchURLs.count) return;
self.requestedCount++;
[self.manager downloadWithURL:self.prefetchURLs[index] options:self.options progress:nil completed:^(UIImage *image, NSError *error, BOOL fromCache)
{
self.finishedCount++;
if (image)
{
NSLog(@"Prefetched %d out of %d", self.finishedCount, self.prefetchURLs.count);
}
else
{
NSLog(@"Prefetched %d out of %d (Failed)", self.finishedCount, [self.prefetchURLs count]);
// Add last failed
self.skippedCount++;
}
if (self.prefetchURLs.count > self.requestedCount)
{
[self startPrefetchingAtIndex:self.requestedCount];
}
else if (self.finishedCount == self.requestedCount)
{
[self reportStatus];
}
}];
}
- (void)reportStatus
{
NSUInteger total = [self.prefetchURLs count];
NSLog(@"Finished prefetching (%d successful, %d skipped, timeElasped %.2f)", total - self.skippedCount, self.skippedCount, CFAbsoluteTimeGetCurrent() - self.startedTime);
}
- (void)prefetchURLs:(NSArray *)urls
{
[self cancelPrefetching]; // Prevent duplicate prefetch request
self.startedTime = CFAbsoluteTimeGetCurrent();
self.prefetchURLs = urls;
// Starts prefetching from the very first image on the list with the max allowed concurrency
NSUInteger listCount = self.prefetchURLs.count;
for (NSUInteger i = 0; i < self.maxConcurrentDownloads && self.requestedCount < listCount; i++)
{
[self startPrefetchingAtIndex:i];
}
}
- (void)cancelPrefetching
{
self.prefetchURLs = nil;
self.skippedCount = 0;
self.requestedCount = 0;
self.finishedCount = 0;
[self.manager cancelAll];
}
@end