SDWebImagePrefetcher.m
5.02 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
/*
* 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, nonnull) SDWebImageManager *manager;
@property (strong, atomic, nullable) NSArray<NSURL *> *prefetchURLs; // may be accessed from different queue
@property (assign, nonatomic) NSUInteger requestedCount;
@property (assign, nonatomic) NSUInteger skippedCount;
@property (assign, nonatomic) NSUInteger finishedCount;
@property (assign, nonatomic) NSTimeInterval startedTime;
@property (copy, nonatomic, nullable) SDWebImagePrefetcherCompletionBlock completionBlock;
@property (copy, nonatomic, nullable) SDWebImagePrefetcherProgressBlock progressBlock;
@end
@implementation SDWebImagePrefetcher
+ (nonnull instancetype)sharedImagePrefetcher {
static dispatch_once_t once;
static id instance;
dispatch_once(&once, ^{
instance = [self new];
});
return instance;
}
- (nonnull instancetype)init {
return [self initWithImageManager:[SDWebImageManager new]];
}
- (nonnull instancetype)initWithImageManager:(SDWebImageManager *)manager {
if ((self = [super init])) {
_manager = manager;
_options = SDWebImageLowPriority;
_prefetcherQueue = dispatch_get_main_queue();
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 {
NSURL *currentURL;
@synchronized(self) {
if (index >= self.prefetchURLs.count) return;
currentURL = self.prefetchURLs[index];
self.requestedCount++;
}
[self.manager loadImageWithURL:currentURL options:self.options progress:nil completed:^(UIImage *image, NSData *data, NSError *error, SDImageCacheType cacheType, BOOL finished, NSURL *imageURL) {
if (!finished) return;
self.finishedCount++;
if (self.progressBlock) {
self.progressBlock(self.finishedCount,(self.prefetchURLs).count);
}
if (!image) {
// Add last failed
self.skippedCount++;
}
if ([self.delegate respondsToSelector:@selector(imagePrefetcher:didPrefetchURL:finishedCount:totalCount:)]) {
[self.delegate imagePrefetcher:self
didPrefetchURL:currentURL
finishedCount:self.finishedCount
totalCount:self.prefetchURLs.count
];
}
if (self.prefetchURLs.count > self.requestedCount) {
dispatch_async(self.prefetcherQueue, ^{
// we need dispatch to avoid function recursion call. This can prevent stack overflow even for huge urls list
[self startPrefetchingAtIndex:self.requestedCount];
});
} else if (self.finishedCount == self.requestedCount) {
[self reportStatus];
if (self.completionBlock) {
self.completionBlock(self.finishedCount, self.skippedCount);
self.completionBlock = nil;
}
self.progressBlock = nil;
}
}];
}
- (void)reportStatus {
NSUInteger total = (self.prefetchURLs).count;
if ([self.delegate respondsToSelector:@selector(imagePrefetcher:didFinishWithTotalCount:skippedCount:)]) {
[self.delegate imagePrefetcher:self
didFinishWithTotalCount:(total - self.skippedCount)
skippedCount:self.skippedCount
];
}
}
- (void)prefetchURLs:(nullable NSArray<NSURL *> *)urls {
[self prefetchURLs:urls progress:nil completed:nil];
}
- (void)prefetchURLs:(nullable NSArray<NSURL *> *)urls
progress:(nullable SDWebImagePrefetcherProgressBlock)progressBlock
completed:(nullable SDWebImagePrefetcherCompletionBlock)completionBlock {
[self cancelPrefetching]; // Prevent duplicate prefetch request
self.startedTime = CFAbsoluteTimeGetCurrent();
self.prefetchURLs = urls;
self.completionBlock = completionBlock;
self.progressBlock = progressBlock;
if (urls.count == 0) {
if (completionBlock) {
completionBlock(0,0);
}
} else {
// 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 {
@synchronized(self) {
self.prefetchURLs = nil;
self.skippedCount = 0;
self.requestedCount = 0;
self.finishedCount = 0;
}
[self.manager cancelAll];
}
@end