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"
@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;
@property (copy, nonatomic) void (^completionBlock)(NSUInteger, NSUInteger);
@property (copy, nonatomic) void (^progressBlock)(NSUInteger, NSUInteger);
@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];
_options = SDWebImageLowPriority;
self.maxConcurrentDownloads = 3;
}
return self;
}
- (void)setMaxConcurrentDownloads:(NSUInteger)maxConcurrentDownloads {
self.manager.imageDownloader.maxConcurrentDownloads = maxConcurrentDownloads;
}
- (NSUInteger)maxConcurrentDownloads {
return self.manager.imageDownloader.maxConcurrentDownloads;
}
- (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, SDImageCacheType cacheType, BOOL finished) {
if (!finished) return;
self.finishedCount++;
if (image) {
if (self.progressBlock) {
self.progressBlock(self.finishedCount,[self.prefetchURLs count]);
}
#ifdef SD_VERBOSE
NSLog(@"Prefetched %d out of %d", self.finishedCount, self.prefetchURLs.count);
#endif
}
else {
if (self.progressBlock) {
self.progressBlock(self.finishedCount,[self.prefetchURLs count]);
}
#ifdef SD_VERBOSE
NSLog(@"Prefetched %d out of %d (Failed)", self.finishedCount, [self.prefetchURLs count]);
#endif
// Add last failed
self.skippedCount++;
}
if ([self.delegate respondsToSelector:@selector(imagePrefetcher:didPrefetchURL:finishedCount:totalCount:)]) {
[self.delegate imagePrefetcher:self
didPrefetchURL:self.prefetchURLs[index]
finishedCount:self.finishedCount
totalCount:self.prefetchURLs.count
];
}
if (self.prefetchURLs.count > self.requestedCount) {
dispatch_async(dispatch_get_main_queue(), ^{
[self startPrefetchingAtIndex:self.requestedCount];
});
}
else if (self.finishedCount + self.skippedCount == self.requestedCount) {
[self reportStatus];
if (self.completionBlock) {
self.completionBlock(self.finishedCount, self.skippedCount);
self.completionBlock = nil;
}
}
}];
}
- (void)reportStatus {
NSUInteger total = [self.prefetchURLs count];
#ifdef SD_VERBOSE
NSLog(@"Finished prefetching (%d successful, %d skipped, timeElasped %.2f)", total - self.skippedCount, self.skippedCount, CFAbsoluteTimeGetCurrent() - self.startedTime);
#endif
if ([self.delegate respondsToSelector:@selector(imagePrefetcher:didFinishWithTotalCount:skippedCount:)]) {
[self.delegate imagePrefetcher:self
didFinishWithTotalCount:(total - self.skippedCount)
skippedCount:self.skippedCount
];
}
}
- (void)prefetchURLs:(NSArray *)urls {
[self prefetchURLs:urls progress:nil completed:nil];
}
- (void)prefetchURLs:(NSArray *)urls progress:(void (^)(NSUInteger, NSUInteger))progressBlock completed:(void (^)(NSUInteger, NSUInteger))completionBlock {
[self cancelPrefetching]; // Prevent duplicate prefetch request
self.startedTime = CFAbsoluteTimeGetCurrent();
self.prefetchURLs = urls;
self.completionBlock = completionBlock;
self.progressBlock = progressBlock;
// 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