TwitterImagePipeline/Project/TIPImageDiskCache.m

//
//  TIPImageDiskCache.m
//  TwitterImagePipeline
//
//  Created on 3/3/15.
//  Copyright (c) 2015 Twitter, Inc. All rights reserved.
//

#include <pthread.h>

#import "TIP_Project.h"
#import "TIPError.h"
#import "TIPFileUtils.h"
#import "TIPGlobalConfiguration+Project.h"
#import "TIPImageCacheEntry.h"
#import "TIPImageDiskCache.h"
#import "TIPImageDiskCacheTemporaryFile.h"
#import "TIPImagePipelineInspectionResult+Project.h"
#import "TIPPartialImage.h"
#import "TIPTiming.h"

NS_ASSUME_NONNULL_BEGIN

static NSString * const kPartialImageExtension = @"tmp";

static NSString * const kXAttributeContextTTLKey = @"TTL";
static NSString * const kXAttributeContextUpdateTLLOnAccessKey = @"uTTL";
static NSString * const kXAttributeContextTreatAsPlaceholderKey = @"pl";
static NSString * const kXAttributeContextURLKey = @"URL";
static NSString * const kXAttributeContextLastAccessKey = @"LAD";
static NSString * const kXAttributeContextLastModifiedKey = @"LMD";
static NSString * const kXAttributeContextExpectedSizeKey = @"clen";
static NSString * const kXAttributeContextDimensionXKey = @"dX";
static NSString * const kXAttributeContextDimensionYKey = @"dY";
static NSString * const kXAttributeContextAnimated = @"ANI";

static NSDictionary<NSString *, Class> *_XAttributesKeysToKindsMap(void);
static NSDictionary<NSString *, Class> *_XAttributesKeysToKindsMap()
{
    static NSDictionary *sMap;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        sMap = @{
                 kXAttributeContextTTLKey : [NSNumber class],
                 kXAttributeContextUpdateTLLOnAccessKey : [NSNumber class], // BOOL
                 kXAttributeContextTreatAsPlaceholderKey : [NSNumber class], // BOOL
                 kXAttributeContextURLKey : [NSURL class],
                 kXAttributeContextLastAccessKey : [NSDate class],
                 kXAttributeContextLastModifiedKey : [NSString class], // Only used for partial entries
                 kXAttributeContextExpectedSizeKey : [NSNumber class], // Only used for partial entries
                 kXAttributeContextDimensionXKey : [NSNumber class],
                 kXAttributeContextDimensionYKey : [NSNumber class],
                 kXAttributeContextAnimated : [NSNumber class], // BOOL
                 };
    });
    return sMap;
}

static NSDictionary<NSString *, Class> *_XAttributesKeysToKindsMapForCompleteEntry(void);
static NSDictionary<NSString *, Class> *_XAttributesKeysToKindsMapForCompleteEntry()
{
    static NSDictionary *sMap;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        NSMutableDictionary *attributes = [_XAttributesKeysToKindsMap() mutableCopy];
        [attributes removeObjectsForKeys:@[kXAttributeContextLastModifiedKey, kXAttributeContextExpectedSizeKey]];
        sMap = [attributes copy];
    });
    return sMap;
}

static NSDictionary * __nullable _XAttributesFromContext(TIPImageCacheEntryContext * __nullable context);
static TIPImageCacheEntryContext * __nullable _ContextFromXAttributes(NSDictionary *xattrs,
                                                                      BOOL notYetComplete);
static NSOperation *
_ImageDiskCacheManifestLoadOperation(NSMutableDictionary<NSString *, TIPImageDiskCacheEntry *> *manifest,
                                     NSMutableArray<NSString *> *falseEntryPaths,
                                     NSMutableArray<TIPImageDiskCacheEntry *> *entries,
                                     unsigned long long *totalSizeInOut,
                                     NSURL *entryURL,
                                     NSString *cachePath,
                                     NSDate *timestamp,
                                     NSOperationQueue *manifestCacheQueue,
                                     NSOperation *finalCacheOperation);
static BOOL _UpdateImageConditionCheck(const BOOL force,
                                       const BOOL oldWasPlaceholder,
                                       const BOOL newIsPlaceholder,
                                       const BOOL extraCondition,
                                       const CGSize newDimensions,
                                       const CGSize oldDimensions,
                                       NSURL * __nullable oldURL,
                                       NSURL * __nullable newURL);
static void _SortEntries(NSMutableArray<TIPImageDiskCacheEntry *> *entries);

NS_INLINE NSString *_CreateTempFilePath()
{
    return [NSTemporaryDirectory() stringByAppendingPathComponent:[[NSUUID UUID] UUIDString]];
}

static NSOperationQueue *_ImageDiskCacheManifestCacheQueue(void); // serial
static NSOperationQueue *_ImageDiskCacheManifestIOQueue(void); // concurrent
static dispatch_queue_t _ImageDiskCacheManifestAccessQueue(void); // serial

@interface TIPImageDiskCache () <TIPLRUCacheDelegate>
@property (tip_atomic_direct) SInt64 atomicTotalSize;
- (NSString *)filePathForSafeIdentifier:(NSString *)safeIdentifier TIP_OBJC_DIRECT;
@end

TIP_OBJC_DIRECT_MEMBERS
@interface TIPImageDiskCache (Background)

- (nullable NSString *)_diskCache_copyImageEntryToTemporaryFile:(NSString *)unsafeIdentifier
                                                          error:(out NSError * __nullable * __nullable)errorOut;
- (nullable TIPImageDiskCacheEntry *)_diskCache_getImageEntry:(NSString *)unsafeIdentifier
                                                      options:(TIPImageDiskCacheFetchOptions)options
                                             targetDimensions:(CGSize)targetDimensions
                                            targetContentMode:(UIViewContentMode)targetContentMode
                                             decoderConfigMap:(nullable NSDictionary<NSString *, id> *)decoderConfigMap;
- (nullable TIPImageDiskCacheEntry *)_diskCache_getImageEntryDirectlyFromDisk:(NSString *)unsafeIdentifier
                                                                      options:(TIPImageDiskCacheFetchOptions)options
                                                             targetDimensions:(CGSize)targetDimensions
                                                            targetContentMode:(UIViewContentMode)targetContentMode
                                                             decoderConfigMap:(nullable NSDictionary<NSString *, id> *)decoderConfigMap;
- (nullable TIPImageDiskCacheEntry *)_diskCache_getImageEntryFromManifest:(NSString *)unsafeIdentifier
                                                                  options:(TIPImageDiskCacheFetchOptions)options
                                                         targetDimensions:(CGSize)targetDimensions
                                                        targetContentMode:(UIViewContentMode)targetContentMode
                                                         decoderConfigMap:(nullable NSDictionary<NSString *, id> *)decoderConfigMap;
- (void)_diskCache_updateImageEntry:(TIPImageCacheEntry *)entry
            forciblyReplaceExisting:(BOOL)forciblyReplaceExisting
                     safeIdentifier:(NSString *)safeIdentifier;
- (BOOL)_diskCache_touchImage:(NSString *)safeIdentifier
                       forced:(BOOL)forced;
- (void)_diskCache_touchEntry:(nullable TIPImageDiskCacheEntry *)entry
                       forced:(BOOL)forced
                      partial:(BOOL)partial;
- (void)_diskCache_finalizeTemporaryFile:(TIPImageDiskCacheTemporaryFile *)tempFile
                                 context:(TIPImageCacheEntryContext *)context;
- (void)_diskCache_clearAllImages;
- (void)_diskCache_ensureCacheDirectoryExists;
- (void)_diskCache_updateByteCountsAdded:(UInt64)bytesAdded
                                 removed:(UInt64)bytesRemoved;
- (BOOL)_diskCache_renameImageEntryWithOldIdentifier:(NSString *)oldIdentifier
                                       newIdentifier:(NSString *)newIdentifier
                                               error:(out NSError * __nullable * __nullable)errorOut;
- (void)_diskCache_populateEntryWithCompleteImage:(TIPImageDiskCacheEntry *)entry
                                 targetDimensions:(CGSize)targetDimensions
                                targetContentMode:(UIViewContentMode)targetContentMode
                                 decoderConfigMap:(nullable NSDictionary<NSString *, id> *)decoderConfigMap;
- (void)_diskCache_populateEntryWithPartialImage:(TIPImageDiskCacheEntry *)entry
                                decoderConfigMap:(nullable NSDictionary<NSString *, id> *)decoderConfigMap;
- (void)_diskCache_populateEntryWithTemporaryFile:(TIPImageDiskCacheEntry *)entry;
- (void)_diskCache_inspect:(TIPInspectableCacheCallback)callback;

@end

typedef void(^TIPImageDiskCacheManifestPopulateEntriesCompletionBlock)(unsigned long long totalSize,
                                                                       NSArray<TIPImageDiskCacheEntry *> * __nullable entries,
                                                                       NSArray<NSString *> * __nullable falseEntryPaths);

TIP_OBJC_DIRECT_MEMBERS
@interface TIPImageDiskCache (Manifest)
- (void)_manifest_populateManifestWithCachePath:(NSString *)cachePath;
- (void)_manifest_populateEntriesWithCachePath:(NSString *)cachePath
                                    completion:(TIPImageDiskCacheManifestPopulateEntriesCompletionBlock)completionBlock;
- (void)_manifest_finalizePopulateManifest:(NSArray<TIPImageDiskCacheEntry *> *)entries
                                 totalSize:(unsigned long long)totalSize;
@end

@implementation TIPImageDiskCache
{
    TIPGlobalConfiguration *_globalConfig;
    dispatch_queue_t _manifestQueue;

    UInt64 _earlyRemovedBytesSize;
    TIPLRUCache *_manifest;
    pthread_mutex_t _manifestMutex;
    struct {
        BOOL manifestIsLoading:1;
    } _diskCache_flags;
}

- (TIPLRUCache *)manifest
{
    __block TIPLRUCache *manifest = nil;

    // Perform a thread safe double-NULL check.
    // This should keep perf up for the common case
    // with a slowdown in the rare case of accessing
    // manifest while it is still loading.

    // 1) thread safe get the manfiest
    dispatch_sync(_manifestQueue, ^{
        manifest = self->_manifest;
    });

    // nil manifest?
    if (!manifest) {

        // 2) thread safe wait until the loading completes via mutex
        //
        // This mutex will be locked by manifest loading which is
        // kicked of at "init" time and always ends with the mutex
        // being unlocked.
        // Performing a lock/unlock here ensures we wait for the manifest
        // before continuing
        pthread_mutex_lock(&_manifestMutex);
        pthread_mutex_unlock(&_manifestMutex);

        // 3) loading completed, thread safe get the non-nil manifest
        //    (unless there was an error, then we'll have an invalid disk cache w/ nil manifest)
        dispatch_sync(_manifestQueue, ^{
            manifest = self->_manifest;
        });
    }

    TIPAssert(manifest != nil);
    return (TIPLRUCache * _Nonnull)manifest; // TIPAssert() performed 1 line above
}

- (NSUInteger)totalCost
{
    return (NSUInteger)self.atomicTotalSize;
}

- (TIPImageCacheType)cacheType
{
    return TIPImageCacheTypeDisk;
}

- (instancetype)initWithPath:(NSString *)cachePath
{
    if (self = [super init]) {
        TIPAssert(cachePath != nil);
        _cachePath = [cachePath copy];
        _globalConfig = [TIPGlobalConfiguration sharedInstance];
        _manifestQueue = _ImageDiskCacheManifestAccessQueue();
        _diskCache_flags.manifestIsLoading = YES;
        pthread_mutex_init(&_manifestMutex, NULL);
        pthread_mutex_lock(&_manifestMutex);

        cachePath = _cachePath; // reassign local var to immutable ivar for async usage
        tip_dispatch_async_autoreleasing(_manifestQueue, ^{
            [self _manifest_populateManifestWithCachePath:cachePath];
        });
    }
    return self;
}

- (void)dealloc
{
    pthread_mutex_destroy(&_manifestMutex);

    // Don't delete the on disk cache, but do remove the cache's total bytes from our global count of total bytes
    const SInt64 totalSize = self.atomicTotalSize;
    const SInt16 totalCount = (SInt16)_manifest.numberOfEntries;
    TIPGlobalConfiguration *config = _globalConfig;
    tip_dispatch_async_autoreleasing(config.queueForDiskCaches, ^{
        config.internalTotalBytesForAllDiskCaches -= totalSize;
        config.internalTotalCountForAllDiskCaches -= totalCount;
    });
}

- (BOOL)renameImageEntryWithIdentifier:(NSString *)oldIdentifier
                          toIdentifier:(NSString *)newIdentifier
                                 error:(NSError * __nullable * __nullable)error
{
    __block BOOL success = NO;
    __block NSError *outerError;
    tip_dispatch_sync_autoreleasing(_globalConfig.queueForDiskCaches, ^{
        NSError *innerError;
        success = [self _diskCache_renameImageEntryWithOldIdentifier:oldIdentifier
                                                       newIdentifier:newIdentifier
                                                               error:&innerError];
        outerError = innerError;
    });
    if (error) {
        *error = outerError;
    }
    return success;
}

- (nullable NSString *)copyImageEntryFileForIdentifier:(NSString *)identifier
                                                 error:(out NSError * __autoreleasing __nullable * __nullable)error
{
    TIPAssert(identifier != nil);
    if (!identifier) {
        return nil;
    }

    __block NSError *outerError;
    __block NSString *tempFilePath;
    tip_dispatch_sync_autoreleasing(_globalConfig.queueForDiskCaches, ^{
        NSError *innerError;
        tempFilePath = [self _diskCache_copyImageEntryToTemporaryFile:identifier
                                                                error:&innerError];
        outerError = innerError;
    });
    if (error) {
        *error = outerError;
    }

    return tempFilePath;
}

- (nullable TIPImageDiskCacheEntry *)imageEntryForIdentifier:(NSString *)identifier
                                                     options:(TIPImageDiskCacheFetchOptions)options
                                            targetDimensions:(CGSize)targetDimensions
                                           targetContentMode:(UIViewContentMode)targetContentMode
                                            decoderConfigMap:(nullable NSDictionary<NSString *, id> *)decoderConfigMap
{
    if (!identifier) {
        return nil;
    }

    __block TIPImageDiskCacheEntry *entry;
    tip_dispatch_sync_autoreleasing(_globalConfig.queueForDiskCaches, ^{
        entry = [self _diskCache_getImageEntry:identifier
                                       options:options
                              targetDimensions:targetDimensions
                             targetContentMode:targetContentMode
                              decoderConfigMap:decoderConfigMap];
    });
    return entry;
}

- (void)updateImageEntry:(TIPImageCacheEntry *)entry forciblyReplaceExisting:(BOOL)force
{
    TIPAssert(entry.identifier != nil);
    if (!entry.identifier) {
        return;
    }

    tip_dispatch_async_autoreleasing(_globalConfig.queueForDiskCaches, ^{
        [self _diskCache_updateImageEntry:entry
                  forciblyReplaceExisting:force
                           safeIdentifier:TIPSafeFromRaw(entry.identifier)];
    });
}

- (void)clearImageWithIdentifier:(NSString *)identifier
{
    if (!identifier) {
        return;
    }

    tip_dispatch_async_autoreleasing(_globalConfig.queueForDiskCaches, ^{
        TIPLRUCache *manifest = [self diskCache_syncAccessManifest];
        TIPImageDiskCacheEntry *entry = (TIPImageDiskCacheEntry *)[manifest entryWithIdentifier:TIPSafeFromRaw(identifier)];
        [manifest removeEntry:entry];
    });
}

- (void)clearAllImages:(nullable void (^)(void))completion
{
    tip_dispatch_async_autoreleasing(_globalConfig.queueForDiskCaches, ^{
        [self _diskCache_clearAllImages];
        if (completion) {
            completion();
        }
    });
}

- (void)prune
{
    tip_dispatch_async_autoreleasing(_globalConfig.queueForDiskCaches, ^{
        [self->_globalConfig pruneAllCachesOfType:self.cacheType
                                withPriorityCache:nil];
    });
}

- (void)touchImageWithIdentifier:(NSString *)imageIdentifier
                orSaveImageEntry:(nullable TIPImageDiskCacheEntry *)entry
{
    if (entry) {
        TIPAssert(entry && [imageIdentifier isEqualToString:entry.identifier]);
        if (![imageIdentifier isEqualToString:entry.identifier]) {
            return;
        }
    } else {
        TIPAssert(!entry && imageIdentifier != nil);
        if (!imageIdentifier) {
            return;
        }
    }

    tip_dispatch_async_autoreleasing(_globalConfig.queueForDiskCaches, ^{
        NSString *safeIdentifier = TIPSafeFromRaw(imageIdentifier);
        if (![self _diskCache_touchImage:safeIdentifier forced:NO] && entry) {
            [self _diskCache_updateImageEntry:entry
                      forciblyReplaceExisting:NO
                               safeIdentifier:safeIdentifier];
        }
    });
}

- (TIPImageDiskCacheTemporaryFile *)openTemporaryFileForImageIdentifier:(NSString *)imageIdentifier
{
    TIPAssert(imageIdentifier != nil);
    if (!imageIdentifier) {
        return nil;
    }

    NSString *finalPath = [self filePathForSafeIdentifier:TIPSafeFromRaw(imageIdentifier)];
    TIPImageDiskCacheTemporaryFile *tempFile;
    tempFile = [[TIPImageDiskCacheTemporaryFile alloc] initWithIdentifier:imageIdentifier
                                                            temporaryPath:_CreateTempFilePath()
                                                                finalPath:finalPath
                                                                diskCache:self];
    return tempFile;
}

- (void)finalizeTemporaryFile:(TIPImageDiskCacheTemporaryFile *)tempFile
                  withContext:(TIPImageCacheEntryContext *)context
{
    TIPAssert(tempFile.imageIdentifier != nil);
    if (!tempFile.imageIdentifier) {
        return;
    }

    tip_dispatch_async_autoreleasing(_globalConfig.queueForDiskCaches, ^{
        [self _diskCache_finalizeTemporaryFile:tempFile
                                       context:context];
    });
}

- (void)clearTemporaryFilePath:(NSString *)filePath
{
    if (!filePath) {
        return;
    }

    tip_dispatch_async_autoreleasing(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_LOW, 0), ^{
        [[NSFileManager defaultManager] removeItemAtPath:filePath error:NULL];
    });
}

- (NSString *)filePathForSafeIdentifier:(NSString *)safeIdentifier
{
    TIPAssert(safeIdentifier != nil);
    if (!safeIdentifier) {
        return nil;
    }

    TIPAssert(_cachePath != nil);
    return [_cachePath stringByAppendingPathComponent:safeIdentifier];
}

#pragma mark TIPLRUCacheDelegate

- (void)tip_cache:(TIPLRUCache *)manifest didEvictEntry:(TIPImageDiskCacheEntry *)entry
{
    const NSUInteger size = entry.completeFileSize + entry.partialFileSize;
    _globalConfig.internalTotalCountForAllDiskCaches -= 1;
    [self _diskCache_updateByteCountsAdded:0 removed:size];

    NSFileManager *fm = [NSFileManager defaultManager];
    NSString *filePath = [self filePathForSafeIdentifier:entry.safeIdentifier];
    NSString *partialFilePath = [filePath stringByAppendingPathExtension:kPartialImageExtension];
    [fm removeItemAtPath:filePath error:NULL];
    [fm removeItemAtPath:partialFilePath error:NULL];

    TIPLogDebug(@"%@ Evicted '%@', complete:'%@', partial:'%@'", NSStringFromClass([self class]), entry.safeIdentifier, entry.completeImageContext.URL, entry.partialImageContext.URL);
}

#pragma mark Inspect

- (void)inspect:(TIPInspectableCacheCallback)callback
{
    tip_dispatch_async_autoreleasing(_globalConfig.queueForDiskCaches, ^{
        [self _diskCache_inspect:callback];
    });
}

@end

@implementation TIPImageDiskCache (Background)

- (void)_diskCache_updateByteCountsAdded:(UInt64)bytesAdded
                                 removed:(UInt64)bytesRemoved
{
    // are we decrementing our byte count before the manifest has finished loading?
    if (bytesRemoved > bytesAdded && _diskCache_flags.manifestIsLoading) {

        // this would cause the manifest to become negative
        // instead, delay the decrement until later and just deal with the increment

        _earlyRemovedBytesSize += bytesRemoved;

        TIPLogWarning(@"Decrementing disk cache size before the Manifest finished loading!  It's OK though, we'll delay the subtracting until later.  Added: %llu, Sub'd: %llu", bytesAdded, bytesRemoved);

        bytesRemoved = 0;
    }

    TIP_UPDATE_BYTES(self.atomicTotalSize, bytesAdded, bytesRemoved, @"Disk Cache Size");
    TIP_UPDATE_BYTES(_globalConfig.internalTotalBytesForAllDiskCaches, bytesAdded, bytesRemoved, @"All Disk Caches Size");
}

- (void)_diskCache_ensureCacheDirectoryExists
{
    [[NSFileManager defaultManager] createDirectoryAtPath:_cachePath
                              withIntermediateDirectories:YES
                                               attributes:nil
                                                    error:NULL];
}

- (nullable NSString *)_diskCache_copyImageEntryToTemporaryFile:(NSString *)unsafeIdentifier
                                                          error:(out NSError * __nullable * __nullable)errorOut
{
    NSString *temporaryFilePath = nil;
    NSError *fileCopyError = nil;
    NSString *filePath = [self diskCache_imageEntryFilePathForIdentifier:unsafeIdentifier
                                                hitShouldMoveEntryToHead:YES
                                                                 context:NULL];

    if (filePath) {
        NSFileManager *fm = [NSFileManager defaultManager];
        temporaryFilePath = [NSTemporaryDirectory() stringByAppendingPathComponent:[NSUUID UUID].UUIDString];
        [fm createDirectoryAtPath:temporaryFilePath.stringByDeletingLastPathComponent
      withIntermediateDirectories:YES
                       attributes:NULL
                            error:NULL];
        if (![fm copyItemAtPath:filePath toPath:temporaryFilePath error:&fileCopyError]) {
            temporaryFilePath = nil;
        }
    }

    if (!temporaryFilePath && !fileCopyError) {
        fileCopyError = [NSError errorWithDomain:NSPOSIXErrorDomain
                                            code:ENOENT
                                        userInfo:nil];
    }

    if (errorOut) {
        *errorOut = fileCopyError;
    }
    return temporaryFilePath;
}

- (nullable TIPImageDiskCacheEntry *)_diskCache_getImageEntry:(NSString *)unsafeIdentifier
                                                      options:(TIPImageDiskCacheFetchOptions)options
                                             targetDimensions:(CGSize)targetDimensions
                                            targetContentMode:(UIViewContentMode)targetContentMode
                                             decoderConfigMap:(nullable NSDictionary<NSString *, id> *)decoderConfigMap
{
    TIPImageDiskCacheEntry *entry = nil;
    if (_diskCache_flags.manifestIsLoading) {
        entry = [self _diskCache_getImageEntryDirectlyFromDisk:unsafeIdentifier
                                                       options:options
                                              targetDimensions:targetDimensions
                                             targetContentMode:targetContentMode
                                              decoderConfigMap:decoderConfigMap];
    } else {
        entry = [self _diskCache_getImageEntryFromManifest:unsafeIdentifier
                                                   options:options
                                          targetDimensions:targetDimensions
                                         targetContentMode:targetContentMode
                                          decoderConfigMap:decoderConfigMap];
    }

    return entry;
}

- (nullable TIPImageDiskCacheEntry *)_diskCache_getImageEntryDirectlyFromDisk:(NSString *)unsafeIdentifier
                                                                      options:(TIPImageDiskCacheFetchOptions)options
                                                             targetDimensions:(CGSize)targetDimensions
                                                            targetContentMode:(UIViewContentMode)targetContentMode
                                                             decoderConfigMap:(nullable NSDictionary<NSString *, id> *)decoderConfigMap
{
    TIPImageDiskCacheEntry *entry = nil;
    NSFileManager *fm = [NSFileManager defaultManager];
    NSString *safeIdentifer = TIPSafeFromRaw(unsafeIdentifier);
    NSString *filePath = [self filePathForSafeIdentifier:safeIdentifer];
    if ([fm fileExistsAtPath:filePath]) {
        const NSUInteger size = TIPFileSizeAtPath(filePath, NULL);
        if (size) {
            NSDictionary *xattributes = TIPGetXAttributesForFile(filePath, _XAttributesKeysToKindsMap());
            TIPImageCacheEntryContext *context = _ContextFromXAttributes(xattributes, NO);
            if ([context isKindOfClass:[TIPCompleteImageEntryContext class]]) {
                entry = [[TIPImageDiskCacheEntry alloc] init];
                entry.identifier = unsafeIdentifier;
                entry.completeImageContext = (id)context;
                entry.completeFileSize = size;
                if (TIP_BITMASK_HAS_SUBSET_FLAGS(options, TIPImageDiskCacheFetchOptionCompleteImage)) {
                    NSData *data = [NSData dataWithContentsOfURL:[NSURL fileURLWithPath:filePath]
                                                         options:(context.isAnimated) ? NSDataReadingMappedIfSafe : 0
                                                           error:NULL];
                    TIPImageContainer *image = [TIPImageContainer imageContainerWithData:data
                                                                        targetDimensions:targetDimensions
                                                                       targetContentMode:targetContentMode
                                                                        decoderConfigMap:decoderConfigMap
                                                                          codecCatalogue:nil];
                    if (image) {
                        entry.completeImage = image;
                        entry.completeImageData = data;
                    } else {
                        entry = nil;
                    }
                }
            }
        }
    }
    return entry;
}

- (nullable TIPImageDiskCacheEntry *)_diskCache_getImageEntryFromManifest:(NSString *)unsafeIdentifier
                                                                  options:(TIPImageDiskCacheFetchOptions)options
                                                         targetDimensions:(CGSize)targetDimensions
                                                        targetContentMode:(UIViewContentMode)targetContentMode
                                                         decoderConfigMap:(nullable NSDictionary<NSString *, id> *)decoderConfigMap
{
    TIPLRUCache *manifest = [self diskCache_syncAccessManifest];
    NSString *safeIdentifer = TIPSafeFromRaw(unsafeIdentifier);
    TIPImageDiskCacheEntry *entry = (TIPImageDiskCacheEntry *)[manifest entryWithIdentifier:safeIdentifer];
    if (entry) {
        // Validate TTL
        NSDate *now = [NSDate date];
        NSDate *lastAccess = nil;
        const NSUInteger oldCost = entry.completeFileSize + entry.partialFileSize;

        lastAccess = entry.partialImageContext.lastAccess;
        if (lastAccess && [now timeIntervalSinceDate:lastAccess] > entry.partialImageContext.TTL) {
            entry.partialImageContext = nil;
            entry.partialImage = nil;
            entry.partialFileSize = 0;
        }
        lastAccess = entry.completeImageContext.lastAccess;
        if (lastAccess && [now timeIntervalSinceDate:lastAccess] > entry.completeImageContext.TTL) {
            entry.completeImageContext = nil;
            entry.completeImage = nil;
            entry.completeFileSize = 0;
        }

        // Resolve changes to entry
        const NSUInteger newCost = entry.completeFileSize + entry.partialFileSize;
        if (!newCost) {
            [manifest removeEntry:entry];
            entry = nil;
        } else {
            [self _diskCache_updateByteCountsAdded:newCost removed:oldCost];
            TIPAssert(newCost <= oldCost); // removing the cache image and/or partial image only ever removes bytes
        }

        if (entry) {
            // Update entry
            if (![entry.identifier isEqualToString:unsafeIdentifier]) {
                // Entries read from disk can have hashed identifiers.
                // If the safe identifiers match but the unsafe ones don't,
                // we can safely update the existing entry's identifier.
                entry.identifier = unsafeIdentifier;
            }
            [self _diskCache_touchImage:safeIdentifer forced:NO];

            // Mutate and return a copy
            entry = [entry copy];

            if (TIP_BITMASK_HAS_SUBSET_FLAGS(options, TIPImageDiskCacheFetchOptionCompleteImage)) {
                [self _diskCache_populateEntryWithCompleteImage:entry
                                               targetDimensions:targetDimensions
                                              targetContentMode:targetContentMode
                                               decoderConfigMap:decoderConfigMap];
            }

            if (TIP_BITMASK_HAS_SUBSET_FLAGS(options, TIPImageDiskCacheFetchOptionPartialImage) || (TIP_BITMASK_HAS_SUBSET_FLAGS(options, TIPImageDiskCacheFetchOptionPartialImageIfNoCompleteImage) && !entry.completeImageContext)) {
                [self _diskCache_populateEntryWithPartialImage:entry
                                              decoderConfigMap:decoderConfigMap];
            }

            if (TIP_BITMASK_HAS_SUBSET_FLAGS(options, TIPImageDiskCacheFetchOptionTemporaryFile) || (TIP_BITMASK_HAS_SUBSET_FLAGS(options, TIPImageDiskCacheFetchOptionTemporaryFileIfNoCompleteImage) && !entry.completeImageContext)) {
                [self _diskCache_populateEntryWithTemporaryFile:entry];
            }
        }
    }

    return entry;
}

- (void)_diskCache_populateEntryWithCompleteImage:(TIPImageDiskCacheEntry *)entry
                                 targetDimensions:(CGSize)targetDimensions
                                targetContentMode:(UIViewContentMode)targetContentMode
                                 decoderConfigMap:(nullable NSDictionary<NSString *, id> *)decoderConfigMap
{
    if (entry.completeImageContext) {
        NSString *filePath = [self filePathForSafeIdentifier:entry.safeIdentifier];
        TIPAssertMessage(filePath != nil, @"entry.identifier = %@", entry.identifier);
        if (filePath) {
            const BOOL memoryMap = entry.completeImageContext.isAnimated;
            NSData *data = [NSData dataWithContentsOfURL:[NSURL fileURLWithPath:filePath]
                                                 options:(memoryMap) ? NSDataReadingMappedIfSafe : 0
                                                   error:NULL];
            entry.completeImage = [TIPImageContainer imageContainerWithData:data
                                                           targetDimensions:targetDimensions
                                                          targetContentMode:targetContentMode
                                                           decoderConfigMap:decoderConfigMap
                                                             codecCatalogue:nil];
            entry.completeImageData = data;
        }
    }
}

- (void)_diskCache_populateEntryWithPartialImage:(TIPImageDiskCacheEntry *)entry
                                decoderConfigMap:(nullable NSDictionary<NSString *, id> *)decoderConfigMap
{
    if (entry.partialImageContext) {
        NSString *filePath = [self filePathForSafeIdentifier:entry.safeIdentifier];
        filePath = [filePath stringByAppendingPathExtension:kPartialImageExtension];
        TIPAssertMessage(filePath != nil, @"entry.identifier = %@", entry.identifier);
        if (filePath) {
            NSData *data = [NSData dataWithContentsOfFile:filePath];
            if (data.length > 0) {
                TIPPartialImage *partialImage;
                partialImage = [[TIPPartialImage alloc] initWithExpectedContentLength:entry.partialImageContext.expectedContentLength];
                [partialImage updateDecoderConfigMap:decoderConfigMap];
                [partialImage appendData:data final:NO];
                entry.partialImage = partialImage;
            }
        }
    }
}

- (void)_diskCache_populateEntryWithTemporaryFile:(TIPImageDiskCacheEntry *)entry
{
    if (entry.partialImageContext) {
        NSString *finalPath = [self filePathForSafeIdentifier:entry.safeIdentifier];
        NSString *partialPath = [finalPath stringByAppendingPathExtension:kPartialImageExtension];
        NSString *tempPath = _CreateTempFilePath();
        TIPAssertMessage(tempPath != nil, @"entry.identifier = %@", entry.identifier);
        TIPAssertMessage(partialPath != nil, @"entry.identifier = %@", entry.identifier);
        if (tempPath && partialPath && [[NSFileManager defaultManager] copyItemAtPath:partialPath toPath:tempPath error:NULL]) {
            entry.tempFile = [[TIPImageDiskCacheTemporaryFile alloc] initWithIdentifier:entry.identifier
                                                                          temporaryPath:tempPath
                                                                              finalPath:finalPath
                                                                              diskCache:self];
        }
    }
}

- (void)_diskCache_updateImageEntry:(TIPImageCacheEntry *)entry
            forciblyReplaceExisting:(BOOL)forciblyReplaceExisting
                     safeIdentifier:(NSString *)safeIdentifier
{
    // Validate entry first
    if (!entry.identifier) {
        return;
    }
    if (!entry.partialImageContext ^ !entry.partialImage) {
        return;
    }
    if (!entry.completeImageContext ^ (!entry.completeImage && !entry.completeImageData && !entry.completeImageFilePath)) {
        return;
    }

    [self _diskCache_ensureCacheDirectoryExists];

    // Get the "existing" entry
    TIPLRUCache *manifest = [self diskCache_syncAccessManifest];
    TIPImageDiskCacheEntry *existingEntry = (TIPImageDiskCacheEntry *)[manifest entryWithIdentifier:safeIdentifier];
    const BOOL hasPreviousEntry = (existingEntry != nil);
    if (!existingEntry) {
        if (forciblyReplaceExisting || entry.completeImageContext || entry.partialImageContext) {
            existingEntry = [[TIPImageDiskCacheEntry alloc] init];
            existingEntry.identifier = entry.identifier;
        }
    } else { // existingEntry
        if (![existingEntry.identifier isEqualToString:entry.identifier]) {
            // Entries read from disk can have hashed identifiers.
            // If the safe identifiers match but the unsafe ones don't,
            // we can safely update the existing entry's identifier.
            existingEntry.identifier = entry.identifier;
        }
    }

    // Set up variables
    BOOL didChangePartial = NO, didChangeComplete = NO;
    NSFileManager *fm = [NSFileManager defaultManager];
    NSString *filePath = [self filePathForSafeIdentifier:safeIdentifier];
    NSString *partialFilePath = [filePath stringByAppendingPathExtension:kPartialImageExtension];

    // Check file path was generated
    if (!filePath) {
        NSMutableDictionary *userInfo = [[NSMutableDictionary alloc] init];
        if (entry.identifier) {
            userInfo[TIPProblemInfoKeyImageIdentifier] = entry.identifier;
        }
        if (safeIdentifier) {
            userInfo[TIPProblemInfoKeySafeImageIdentifier] = safeIdentifier;
        }
        NSURL *contextURL = entry.completeImageContext.URL ?: entry.partialImageContext.URL;
        if (contextURL) {
            userInfo[TIPProblemInfoKeyImageURL] = contextURL;
        }
        if (_cachePath) {
            // Context is helpful, but needn't expose it with a constant.
            userInfo[@"cachePath"] = _cachePath;
        }
        [_globalConfig postProblem:TIPProblemDiskCacheUpdateImageEntryCouldNotGenerateFileName
                          userInfo:userInfo];
    }

    const NSUInteger oldCost = existingEntry.partialFileSize + existingEntry.completeFileSize;
    CGSize oldDimensions;
    CGSize newDimensions;
    BOOL oldWasPlaceholder;
    BOOL newIsPlaceholder;
    BOOL conditionMetToUpdate;

    // Update complete image
    oldDimensions = existingEntry.completeImageContext.dimensions;
    newDimensions = entry.completeImageContext.dimensions;
    oldWasPlaceholder = existingEntry.completeImageContext.treatAsPlaceholder;
    newIsPlaceholder = entry.completeImageContext.treatAsPlaceholder;

    conditionMetToUpdate = _UpdateImageConditionCheck(forciblyReplaceExisting,
                                                      oldWasPlaceholder,
                                                      newIsPlaceholder,
                                                      NO /*extra*/,
                                                      newDimensions,
                                                      oldDimensions,
                                                      existingEntry.completeImageContext.URL,
                                                      entry.completeImageContext.URL);

    if (conditionMetToUpdate) {
        existingEntry.completeImageContext = nil;
        existingEntry.completeFileSize = 0;
        if (filePath) {
            [fm removeItemAtPath:filePath error:NULL];
        }
        if (entry.completeImage || entry.completeImageData || entry.completeImageFilePath) {
            BOOL success = NO;
            NSError *error = nil;
            if (filePath) {
                if (entry.completeImage) {
                    success = [entry.completeImage saveToFilePath:filePath
                                                             type:entry.completeImageContext.imageType
                                                   codecCatalogue:nil
                                                          options:TIPImageEncodingNoOptions
                                                          quality:kTIPAppleQualityValueRepresentingJFIFQuality85
                                                           atomic:YES
                                                            error:&error];
                } else if (entry.completeImageData) {
                    success = [entry.completeImageData writeToFile:filePath
                                                           options:NSDataWritingAtomic
                                                             error:&error];
                } else {
                    success = [fm copyItemAtPath:entry.completeImageFilePath
                                          toPath:filePath
                                           error:&error];
                }
            }

            if (success) {
                existingEntry.completeImageContext = [entry.completeImageContext copy];
                existingEntry.completeFileSize = (NSUInteger)TIPFileSizeAtPath(filePath, NULL);

                // Clear partial on new entry since we set the complete image
                entry.partialImage = nil;
                entry.partialImageContext = nil;
            } else {
                NSString *key = nil;
                id value = nil;
                if (entry.completeImage) {
                    key = @"image";
                    value = entry.completeImage;
                } else if (entry.completeImageData) {
                    key = @"imageData";
                    value = [NSString stringWithFormat:@"<Data: length=%tu>", entry.completeImageData.length];
                } else {
                    key = @"imageFilePath";
                    value = entry.completeImageFilePath;
                }
                TIPLogWarning(@"Failed to update disk cache entry! %@", @{
                                                                          @"filePath" : (filePath) ?: @"<null>",
                                                                          key : value,
                                                                          @"URL" : entry.completeImageContext.URL,
                                                                          @"id" : entry.identifier,
                                                                          @"error" : (error) ?: @"???"
                                                                          });
            }
        }
        didChangeComplete = YES;
    }

    // Update partial image
    oldDimensions = existingEntry.partialImageContext.dimensions;
    oldWasPlaceholder = existingEntry.partialImageContext.treatAsPlaceholder;
    newIsPlaceholder = entry.partialImageContext.treatAsPlaceholder;
    if (!didChangeComplete) {
        newDimensions = entry.partialImageContext.dimensions;
    }

    conditionMetToUpdate = NO;
    if (existingEntry.partialImageContext != nil || entry.partialImageContext != nil) {
        // only both if there is a partial image to care about
        conditionMetToUpdate = _UpdateImageConditionCheck(forciblyReplaceExisting,
                                                          oldWasPlaceholder,
                                                          newIsPlaceholder,
                                                          (oldWasPlaceholder && didChangeComplete) /*extra*/,
                                                          newDimensions,
                                                          oldDimensions,
                                                          existingEntry.partialImageContext.URL,
                                                          entry.partialImageContext.URL);
    }

    if (conditionMetToUpdate) {
        existingEntry.partialImageContext = nil;
        existingEntry.partialFileSize = 0;
        if (partialFilePath) {
            [fm removeItemAtPath:partialFilePath error:NULL];

            if (entry.partialImage && !newIsPlaceholder) {
                NSError *error = nil;
                if ([entry.partialImage.data writeToFile:partialFilePath options:NSDataWritingAtomic error:&error]) {
                    existingEntry.partialImageContext = [entry.partialImageContext copy];
                    existingEntry.partialFileSize = entry.partialImage.byteCount;
                } else {
                    TIPLogError(@"Failed to write partial image! %@", @{ @"data.length" : @(entry.partialImage.data.length), @"filePath" : partialFilePath, @"error" : (error) ?: @"???" });
                }
            }
        }
        didChangePartial = YES;
    }

    // Nothing changed
    if (!didChangePartial && !didChangeComplete) {
        return;
    }

    // Cap our entry size
    const SInt64 max = [_globalConfig internalMaxBytesForCacheEntryOfType:self.cacheType];
    if (existingEntry && (SInt64)existingEntry.partialFileSize > max) {

        NSDictionary *userInfo = @{
                                   TIPProblemInfoKeyImageIdentifier : existingEntry.identifier,
                                   TIPProblemInfoKeySafeImageIdentifier : existingEntry.safeIdentifier,
                                   TIPProblemInfoKeyImageURL : existingEntry.partialImageContext.URL,
                                   TIPProblemInfoKeyImageDimensions : [NSValue valueWithCGSize:existingEntry.partialImageContext.dimensions],
                                   @"expectedSize" : @(existingEntry.partialImageContext.expectedContentLength),
                                   @"partialSize" : @(existingEntry.partialFileSize),
                                   };
        [_globalConfig postProblem:TIPProblemImageTooLargeToStoreInDiskCache userInfo:userInfo];

        if (partialFilePath) {
            [fm removeItemAtPath:partialFilePath error:NULL];
        }
        existingEntry.partialImage = nil;
        existingEntry.partialImageContext = nil;
        existingEntry.partialFileSize = 0;
        didChangePartial = YES;
    }
    if (existingEntry && (SInt64)existingEntry.completeFileSize > max) {

        NSValue *dimensionsValue = [NSValue valueWithCGSize:existingEntry.completeImageContext.dimensions];
        NSDictionary *userInfo = @{
                                   TIPProblemInfoKeyImageIdentifier : existingEntry.identifier,
                                   TIPProblemInfoKeySafeImageIdentifier : existingEntry.safeIdentifier,
                                   TIPProblemInfoKeyImageURL : existingEntry.completeImageContext.URL,
                                   TIPProblemInfoKeyImageDimensions : dimensionsValue,
                                   @"size" : @(existingEntry.completeFileSize),
                                   };
        [_globalConfig postProblem:TIPProblemImageTooLargeToStoreInDiskCache userInfo:userInfo];

        [fm removeItemAtPath:filePath error:NULL];
        existingEntry.completeImage = nil;
        existingEntry.completeImageContext = nil;
        existingEntry.completeFileSize = 0;
        didChangeComplete = YES;
    }

    if (!existingEntry.partialImageContext && !existingEntry.completeImageContext) {
        // shoot... the save cannot complete -- purge the entry
        if (hasPreviousEntry) {
            [manifest removeEntry:existingEntry];
        }
    } else {

        // Update xattrs and LRU
        const NSUInteger newCost = existingEntry.partialFileSize + existingEntry.completeFileSize;
        [self _diskCache_updateByteCountsAdded:newCost removed:oldCost];
        if (!hasPreviousEntry && existingEntry) {
            _globalConfig.internalTotalCountForAllDiskCaches += 1;
        }

        [manifest addEntry:existingEntry];
        if (didChangePartial) {
            [self _diskCache_touchEntry:existingEntry
                                 forced:forciblyReplaceExisting
                                partial:YES];
        }
        if (didChangeComplete) {
            [self _diskCache_touchEntry:existingEntry
                                 forced:forciblyReplaceExisting
                                partial:NO];
        }

        if (gTwitterImagePipelineAssertEnabled) {
            if (existingEntry.partialImageContext && 0 == existingEntry.partialFileSize) {
                NSDictionary *info = @{
                                       @"dimension" : NSStringFromCGSize(existingEntry.partialImageContext.dimensions),
                                       @"URL" : existingEntry.partialImageContext.URL,
                                       @"id" : existingEntry.identifier,
                                       };
                TIPLogError(@"Cached zero cost partial image to disk cache %@", info);
            }
            if (existingEntry.completeImageContext && 0 == existingEntry.completeFileSize) {
                NSDictionary *info = @{
                                       @"dimension" : NSStringFromCGSize(existingEntry.completeImageContext.dimensions),
                                       @"URL" : existingEntry.completeImageContext.URL,
                                       @"id" : existingEntry.identifier,
                                       };
                TIPLogError(@"Cached zero cost complete image to disk cache %@", info);
            }
        }
    }

    [_globalConfig pruneAllCachesOfType:self.cacheType withPriorityCache:self];
}

- (BOOL)_diskCache_touchImage:(NSString *)safeIdentifier
                       forced:(BOOL)forced
{
    TIPLRUCache *manifest = [self diskCache_syncAccessManifest];
    TIPImageDiskCacheEntry *entry = (TIPImageDiskCacheEntry *)[manifest entryWithIdentifier:safeIdentifier];
    if (entry) {
        [self _diskCache_touchEntry:entry
                             forced:forced
                            partial:YES];
        [self _diskCache_touchEntry:entry
                             forced:forced
                            partial:NO];
    }
    return entry != nil;
}

- (void)_diskCache_touchEntry:(nullable TIPImageDiskCacheEntry *)entry
                       forced:(BOOL)forced
                      partial:(BOOL)partial
{
    TIPImageCacheEntryContext *context = (partial) ? entry.partialImageContext : entry.completeImageContext;
    if (!context) {
        return;
    }

    if (context.updateExpiryOnAccess || !context.lastAccess) {
        context.lastAccess = [NSDate date];
    } else if (!forced) {
        return;
    }

    NSDictionary *xattrs = _XAttributesFromContext(context);
    NSString *filePath = [self filePathForSafeIdentifier:entry.safeIdentifier];
    if (partial) {
        filePath = [filePath stringByAppendingPathExtension:kPartialImageExtension];
    }

    TIPAssertMessage(filePath != nil, @"entry.identifier = %@", entry.identifier);
    if (!filePath) {
        return;
    }

    const NSUInteger numberOfSetXAttributes = TIPSetXAttributesForFile(xattrs, filePath);
    if (numberOfSetXAttributes != xattrs.count) {
        NSDictionary *info = @{
                               @"filePath" : filePath,
                               @"id" : entry.identifier,
                               @"safeId" : entry.safeIdentifier,
                               @"xattrs" : xattrs
                               };
        TIPLogError(@"Error writing xattrs! (wrote %tu of %tu)\n%@", numberOfSetXAttributes, xattrs.count, info);
    }

#if DEBUG
    NSDictionary *xattrsRoundTrip = TIPGetXAttributesForFile(filePath, _XAttributesKeysToKindsMap());
    TIPAssertMessage([xattrs isEqualToDictionary:xattrsRoundTrip], @"xattrs differ!\nSet: %@\nGet: %@", xattrs, xattrsRoundTrip);
#endif
}

- (void)_diskCache_clearAllImages
{
    TIPStartMethodScopedBackgroundTask(ClearAllImages);
    TIPLRUCache *manifest = [self diskCache_syncAccessManifest];
    const SInt16 totalCount = (SInt16)manifest.numberOfEntries;
    [manifest clearAllEntries];
    [self _diskCache_updateByteCountsAdded:0 removed:(UInt64)self.atomicTotalSize];
    _globalConfig.internalTotalCountForAllDiskCaches -= totalCount;
    [[NSFileManager defaultManager] removeItemAtPath:_cachePath error:NULL];
    TIPLogInformation(@"Cleared all images in %@", self);
}

- (void)_diskCache_finalizeTemporaryFile:(TIPImageDiskCacheTemporaryFile *)tempFile
                                 context:(TIPImageCacheEntryContext *)context
{
    NSString * const finalPath = tempFile.finalPath;
    if (!finalPath) {
        NSString *message = [NSString stringWithFormat:@"%@ has a nil finalPath.  identifier: %@", NSStringFromClass([tempFile class]), tempFile.imageIdentifier];
        TIPAssertMessage(finalPath != nil, @"%@", message);
        TIPLogError(@"%@", message);
        return;
    }

    NSString * const tempPath = tempFile.temporaryPath;
    if (!tempPath) {
        NSString *message = [NSString stringWithFormat:@"%@ has a nil temporaryPath.  identifier: %@", NSStringFromClass([tempFile class]), tempFile.imageIdentifier];
        TIPAssertMessage(tempPath != nil, @"%@", message);
        TIPLogError(@"%@", message);
        return;
    }

    NSString * const partialPath = [finalPath stringByAppendingPathExtension:kPartialImageExtension];
    NSString * const safeIdentifier = [finalPath lastPathComponent];
    TIPAssert([safeIdentifier isEqualToString:TIPSafeFromRaw(tempFile.imageIdentifier)]);

    [self _diskCache_ensureCacheDirectoryExists];

    BOOL const isPartial = [context isKindOfClass:[TIPPartialImageEntryContext class]];
    if (!isPartial) {
        if (![context isKindOfClass:[TIPCompleteImageEntryContext class]]) {
            TIPAssertMessage(NO, @"Invalid or nil context provided!");
            return;
        }
    }

    if (isPartial && context.treatAsPlaceholder) {
        // don't cache incomplete placeholders
        [self clearTemporaryFilePath:tempFile.temporaryPath];
        return;
    }

    NSUInteger const size = (NSUInteger)TIPFileSizeAtPath(tempFile.temporaryPath, NULL);
    if (!size) {
        [self clearTemporaryFilePath:tempFile.temporaryPath];
        return;
    }

    NSFileManager * const fm = [NSFileManager defaultManager];
    TIPLRUCache * const manifest = [self diskCache_syncAccessManifest];
    TIPImageDiskCacheEntry *entry = (TIPImageDiskCacheEntry *)[manifest entryWithIdentifier:safeIdentifier];
    TIPImageCacheEntryContext * const oldPartialContext = entry.partialImageContext;
    TIPImageCacheEntryContext * const oldCompleteContext = entry.completeImageContext;
    CGSize const newDimensions = context.dimensions;
    CGSize const oldPartialDimensions = oldPartialContext.dimensions;
    CGSize const oldCompleteDimensions = oldCompleteContext.dimensions;

    // 1) Remove lowest fidelity entries where appropriate

    if (entry) {
        if (!isPartial) {
            // This is a complete entry...

            if (oldPartialContext) {
                if ((oldPartialDimensions.width * oldPartialDimensions.height) <= (newDimensions.width * newDimensions.height)) {
                    // if the old partial image is smaller (or equal), remove it
                    [self _diskCache_updateByteCountsAdded:0
                                                   removed:entry.partialFileSize];
                    entry.partialFileSize = 0;
                    entry.partialImageContext = nil;
                    [fm removeItemAtPath:partialPath error:NULL];
                }
            }

            if (oldCompleteContext) {
                const BOOL oldSizeTooSmall = (oldCompleteDimensions.width * oldCompleteDimensions.height) < (newDimensions.width * newDimensions.height);
                if (oldSizeTooSmall || oldCompleteContext.treatAsPlaceholder) {
                    // if the old complete image is smaller, remove it
                    [self _diskCache_updateByteCountsAdded:0
                                                   removed:entry.completeFileSize];
                    entry.completeFileSize = 0;
                    entry.completeImageContext = nil;
                    [fm removeItemAtPath:finalPath error:NULL];
                } else {
                    // otherwise, clear ourself
                    [self clearTemporaryFilePath:tempFile.temporaryPath];
                    return;
                }
            }
        } else {
            // This is a partial entry...

            if (oldPartialContext) {
                if ((oldPartialDimensions.width * oldPartialDimensions.height) <= (newDimensions.width * newDimensions.height)) {
                    // if the old partial image is smaller (or equal), remove it
                    [self _diskCache_updateByteCountsAdded:0
                                                   removed:entry.partialFileSize];
                    entry.partialFileSize = 0;
                    entry.partialImageContext = nil;
                    [fm removeItemAtPath:partialPath error:NULL];
                }
            }

            if (oldCompleteContext) {
                if ((oldCompleteDimensions.width * oldCompleteDimensions.height) >= (newDimensions.width * newDimensions.height)) {
                    // if the old complete image is larger (or equal), clear ourselves
                    [self clearTemporaryFilePath:tempFile.temporaryPath];
                    return;
                }
            }
        }
    }

    // 2) Move our new bytes into the disk cache

    NSError *error;
    if ([fm moveItemAtPath:tempFile.temporaryPath toPath:(isPartial) ? partialPath : finalPath error:&error]) {
        context = [context copy];

        const BOOL newEntry = !entry;
        if (!entry) {
            entry = [[TIPImageDiskCacheEntry alloc] init];
            entry.identifier = tempFile.imageIdentifier;
        }

        if (isPartial) {
            entry.partialFileSize = size;
            entry.partialImageContext = (id)context;
        } else {
            entry.completeFileSize = size;
            entry.completeImageContext = (id)context;
        }

        [self _diskCache_updateByteCountsAdded:size removed:0];
        if (newEntry) {
            _globalConfig.internalTotalCountForAllDiskCaches += 1;
        }

        if (gTwitterImagePipelineAssertEnabled) {
            if (entry.partialImageContext && 0 == entry.partialFileSize) {
                TIPLogError(@"Cached zero cost partial image to disk cache %@", @{
                                                                                  @"dimension" : NSStringFromCGSize(entry.partialImageContext.dimensions),
                                                                                  @"URL" : entry.partialImageContext.URL,
                                                                                  @"id" : entry.identifier,
                                                                                  });
            }
            if (entry.completeImageContext && 0 == entry.completeFileSize) {
                TIPLogError(@"Cached zero cost complete image to disk cache %@", @{
                                                                                   @"dimension" : NSStringFromCGSize(entry.completeImageContext.dimensions),
                                                                                   @"URL" : entry.completeImageContext.URL,
                                                                                   @"id" : entry.identifier,
                                                                                   });
            }
        }

        [manifest addEntry:entry];
        [self _diskCache_touchEntry:entry
                             forced:YES
                            partial:isPartial];
        [_globalConfig pruneAllCachesOfType:self.cacheType withPriorityCache:self];
    } else {
        TIPLogWarning(@"%@", error);
    }
}

- (void)_diskCache_inspect:(TIPInspectableCacheCallback)callback
{
    NSMutableArray *completedEntries = [[NSMutableArray alloc] init];
    NSMutableArray *partialEntries = [[NSMutableArray alloc] init];

    TIPLRUCache *manifest = [self diskCache_syncAccessManifest];
    for (TIPImageDiskCacheEntry *cacheEntry in manifest) {
        TIPImagePipelineInspectionResultEntry *entry;
        Class resultClass;

        resultClass = [TIPImagePipelineInspectionResultCompleteDiskEntry class];
        entry = [TIPImagePipelineInspectionResultEntry entryWithCacheEntry:cacheEntry
                                                                     class:resultClass];
        if (entry) {
            [completedEntries addObject:entry];
        }

        resultClass = [TIPImagePipelineInspectionResultPartialDiskEntry class];
        entry = [TIPImagePipelineInspectionResultEntry entryWithCacheEntry:cacheEntry
                                                                     class:resultClass];
        if (entry) {
            [partialEntries addObject:entry];
        }
    }

    callback(completedEntries, partialEntries);
}

- (BOOL)_diskCache_renameImageEntryWithOldIdentifier:(NSString *)oldIdentifier
                                       newIdentifier:(NSString *)newIdentifier
                                               error:(out NSError * __nullable * __nullable)errorOut
{
    NSString *oldSafeID = TIPSafeFromRaw(oldIdentifier);
    TIPLRUCache *manifest = [self diskCache_syncAccessManifest];
    TIPImageDiskCacheEntry *oldEntry = (TIPImageDiskCacheEntry *)[manifest entryWithIdentifier:oldSafeID
                                                                                     canMutate:NO];
    if (!oldEntry) {
        if (errorOut) {
            *errorOut = [NSError errorWithDomain:NSPOSIXErrorDomain
                                            code:ENOENT
                                        userInfo:nil];
        }
        return NO;
    }

    NSString *newSafeID = TIPSafeFromRaw(newIdentifier);
    TIPCompleteImageEntryContext *completeContext = oldEntry.completeImageContext;
    NSString *oldCompleteFilePath = (completeContext) ? [self filePathForSafeIdentifier:oldSafeID] : nil;
    TIPPartialImageEntryContext *partialContext = oldEntry.partialImageContext;
    NSString *oldPartialFilePath = (partialContext) ? [[self filePathForSafeIdentifier:oldSafeID] stringByAppendingPathExtension:kPartialImageExtension] : nil;

    NSError *error = nil;
    BOOL fail = NO;
    if (oldCompleteFilePath) {
        NSString *newCompleteFilePath = [self filePathForSafeIdentifier:newSafeID];
        fail = ![[NSFileManager defaultManager] moveItemAtPath:oldCompleteFilePath
                                                        toPath:newCompleteFilePath
                                                         error:&error];
    }

    if (!fail && oldPartialFilePath) {
        NSString *newPartialFilePath = [[self filePathForSafeIdentifier:newSafeID] stringByAppendingPathExtension:kPartialImageExtension];
        fail = ![[NSFileManager defaultManager] moveItemAtPath:oldPartialFilePath
                                                        toPath:newPartialFilePath
                                                         error:&error];
        if (fail) {
            if (oldCompleteFilePath) {
                // complete images take precedence over partial
                fail = NO;
                error = nil;
                [[NSFileManager defaultManager] removeItemAtPath:oldPartialFilePath error:NULL];
            }
        }
    }

    if (!fail) {
        TIPImageDiskCacheEntry *newEntry = [oldEntry copy];
        newEntry.identifier = newIdentifier;
        [manifest removeEntry:oldEntry];
        [manifest addEntry:newEntry];
        [self _diskCache_updateByteCountsAdded:newEntry.completeFileSize + newEntry.partialFileSize
                                       removed:0];
        _globalConfig.internalTotalCountForAllDiskCaches += 1;
    }

    TIPAssert(fail ^ !error);
    if (errorOut) {
        *errorOut = error;
    }
    return !fail;
}

@end

@implementation TIPImageDiskCache (PrivateExposed)

- (TIPLRUCache *)diskCache_syncAccessManifest
{
    if (!_diskCache_flags.manifestIsLoading) {
        // quick - unsynchronized...
        // ...safe since _diskCache_flags.manifestIsLoading is sync'd on diskCache queue
        return _manifest;
    }

    // slow - synchronized
    return [self manifest];
}

- (void)diskCache_updateImageEntry:(TIPImageCacheEntry *)entry forciblyReplaceExisting:(BOOL)force
{
    @autoreleasepool {
        [self _diskCache_updateImageEntry:entry
                  forciblyReplaceExisting:force
                           safeIdentifier:TIPSafeFromRaw(entry.identifier)];
    }
}

- (nullable NSString *)diskCache_imageEntryFilePathForIdentifier:(NSString *)identifier
                                        hitShouldMoveEntryToHead:(BOOL)hitToHead
                                                         context:(out TIPImageCacheEntryContext * __autoreleasing __nullable * __nullable)contextOut
{
    TIPCompleteImageEntryContext *context = nil;
    NSFileManager *fm = [NSFileManager defaultManager];
    NSString *safeIdentifer = TIPSafeFromRaw(identifier);
    NSString *filePath = [self filePathForSafeIdentifier:safeIdentifer];

    if (_diskCache_flags.manifestIsLoading) {
        if ([fm fileExistsAtPath:filePath]) {
            const NSUInteger size = TIPFileSizeAtPath(filePath, NULL);
            if (size) {
                NSDictionary *xattributes = TIPGetXAttributesForFile(filePath, _XAttributesKeysToKindsMapForCompleteEntry());
                context = (id)_ContextFromXAttributes(xattributes, NO);
                if (![context isKindOfClass:[TIPCompleteImageEntryContext class]]) {
                    context = nil;
                }
            }
        }
    } else {
        TIPImageCacheEntry *entry = (TIPImageCacheEntry *)[_manifest entryWithIdentifier:safeIdentifer
                                                                               canMutate:hitToHead];
        context = [entry.completeImageContext copy];
    }

    if (!context) {
        filePath = nil;
    }

    if (contextOut) {
        *contextOut = context;
    }
    return filePath;
}

- (nullable TIPImageDiskCacheEntry *)diskCache_imageEntryForIdentifier:(NSString *)identifier
                                                               options:(TIPImageDiskCacheFetchOptions)options
                                                      targetDimensions:(CGSize)targetDimensions
                                                     targetContentMode:(UIViewContentMode)targetContentMode
                                                      decoderConfigMap:(nullable NSDictionary<NSString *, id> *)decoderConfigMap
{
    return [self _diskCache_getImageEntry:identifier
                                  options:options
                         targetDimensions:targetDimensions
                        targetContentMode:targetContentMode
                         decoderConfigMap:decoderConfigMap];
}

@end

@implementation TIPImageDiskCache (Manifest)

- (void)_manifest_populateManifestWithCachePath:(NSString *)cachePath
{
    const uint64_t machStart = mach_absolute_time();
    [self _manifest_populateEntriesWithCachePath:cachePath
                                      completion:^(unsigned long long totalSize,
                                                   NSArray<TIPImageDiskCacheEntry *> *entries,
                                                   NSArray<NSString *> *falseEntryPaths) {

        // remove files on background queue BEFORE updating the manifest
        // to avoid race condition with earily read path
        NSFileManager *fm = [NSFileManager defaultManager];
        tip_dispatch_async_autoreleasing(self->_globalConfig.queueForDiskCaches, ^{
            for (NSString *falseEntryPath in falseEntryPaths) {
                [fm removeItemAtPath:falseEntryPath error:NULL];
            }
        });

        [self _manifest_finalizePopulateManifest:entries
                                       totalSize:totalSize];

        const uint64_t machEnd = mach_absolute_time();
        TIPLogInformation(@"%@('%@') took %.3fs to populate its manifest", NSStringFromClass([self class]), self.cachePath.lastPathComponent, TIPComputeDuration(machStart, machEnd));

        [self prune]; // goes to the background queue
    }];
}

- (void)_manifest_populateEntriesWithCachePath:(NSString *)cachePath
                                    completion:(TIPImageDiskCacheManifestPopulateEntriesCompletionBlock)completionBlock
{
    tip_dispatch_async_autoreleasing(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

        NSError *error;
        NSArray<NSURL *> *entryURLs = cachePath ? TIPContentsAtPath(cachePath, &error) : nil;
        if (!entryURLs) {
            TIPLogError(@"%@ could not load its cache entries from path '%@'. %@", NSStringFromClass([self class]), cachePath, error);
            tip_dispatch_async_autoreleasing(self->_manifestQueue, ^{
                completionBlock(0, nil, nil);
            });
            return;
        }

        __block unsigned long long totalSize = 0;
        NSDate *now = [NSDate date];

        NSMutableArray<TIPImageDiskCacheEntry *> *entries = [[NSMutableArray alloc] init];
        NSMutableArray<NSString *> *falseEntryPaths = [[NSMutableArray alloc] init];
        NSMutableDictionary<NSString *, TIPImageDiskCacheEntry *> *manifest = [[NSMutableDictionary alloc] initWithCapacity:entryURLs.count];
        NSOperationQueue *manifestCacheQueue = _ImageDiskCacheManifestCacheQueue();
        NSOperationQueue *manifestIOQueue = _ImageDiskCacheManifestIOQueue();
        dispatch_queue_t manifestAccessQueue = self->_manifestQueue;
        __block TIPImageDiskCacheManifestPopulateEntriesCompletionBlock clearableCompletionBlock = [completionBlock copy];

        NSOperation *finalIOOperation = [NSBlockOperation blockOperationWithBlock:^{
            // nothing, just an operation for dependency ordering
        }];
        NSOperation *finalCacheOperation = [NSBlockOperation blockOperationWithBlock:^{

            // sort entries
            _SortEntries(entries);

            // assert that we don't dupe entries
            if (gTwitterImagePipelineAssertEnabled) {
                NSSet *entrySet = [NSSet setWithArray:entries];
                TIPAssertMessage(entrySet.count == entries.count, @"Manifest load yielded the same entry (or entries) to be counted more than once!!!");
            }

            tip_dispatch_async_autoreleasing(manifestAccessQueue, ^{

                // Call the completion block
                clearableCompletionBlock(totalSize, entries, falseEntryPaths);

                // MUST clear the block since not clearing it can lead to a retain cycle
                clearableCompletionBlock = nil;

            });
        }];
        [finalCacheOperation addDependency:finalIOOperation];

        for (NSURL *entryURL in entryURLs) {
            // putting the construction of the operation to load a manifest entry
            // in a function to avoid risking capturing self which can lead to a
            // retain cycle.
            NSOperation *ioOp = _ImageDiskCacheManifestLoadOperation(manifest,
                                                                     falseEntryPaths,
                                                                     entries,
                                                                     &totalSize,
                                                                     entryURL,
                                                                     cachePath,
                                                                     now,
                                                                     manifestCacheQueue,
                                                                     finalCacheOperation);
            [finalIOOperation addDependency:ioOp];
            [manifestIOQueue addOperation:ioOp];
        }

        [manifestIOQueue addOperation:finalIOOperation];
        [manifestCacheQueue addOperation:finalCacheOperation];
    });
}

- (void)_manifest_finalizePopulateManifest:(NSArray<TIPImageDiskCacheEntry *> *)entries
                                 totalSize:(unsigned long long)totalSize
{
    const BOOL didLoadEntries = entries != nil;
    const SInt16 count = (didLoadEntries) ? (SInt16)entries.count : 0;
    _manifest = (didLoadEntries) ? [[TIPLRUCache alloc] initWithEntries:entries delegate:self] : nil;
    pthread_mutex_unlock(&_manifestMutex);
    tip_dispatch_async_autoreleasing(_globalConfig.queueForDiskCaches, ^{
        self->_diskCache_flags.manifestIsLoading = NO;
        if (didLoadEntries) {
            const UInt64 removeSize = self->_earlyRemovedBytesSize;
            self->_earlyRemovedBytesSize = 0;
            self->_globalConfig.internalTotalCountForAllDiskCaches += count;
            [self _diskCache_updateByteCountsAdded:totalSize
                                           removed:removeSize];
        }
    });
}

@end

static NSDictionary * __nullable _XAttributesFromContext(TIPImageCacheEntryContext * __nullable context)
{
    if (!context || !context.URL) {
        return nil;
    }

    if (!context.lastAccess) {
        context.lastAccess = [NSDate date];
    }

    NSMutableDictionary *d = [[NSMutableDictionary alloc] initWithCapacity:_XAttributesKeysToKindsMap().count];

    TIPAssert(context.TTL > 0.0);

    // Alwasy set ALL values
    d[kXAttributeContextURLKey] = context.URL;
    d[kXAttributeContextLastAccessKey] = context.lastAccess;
    d[kXAttributeContextTTLKey] =  @(context.TTL);
    d[kXAttributeContextUpdateTLLOnAccessKey] = @(context.updateExpiryOnAccess);
    d[kXAttributeContextDimensionXKey] = @(context.dimensions.width);
    d[kXAttributeContextDimensionYKey] = @(context.dimensions.height);
    d[kXAttributeContextAnimated] = @(context.isAnimated);

    if ([context isKindOfClass:[TIPPartialImageEntryContext class]]) {
        TIPPartialImageEntryContext *partialContext = (id)context;
        d[kXAttributeContextLastModifiedKey] = partialContext.lastModified ?: @"!";
        d[kXAttributeContextExpectedSizeKey] = @(partialContext.expectedContentLength);
    } else {
        d[kXAttributeContextLastModifiedKey] = @"!";
        d[kXAttributeContextExpectedSizeKey] = @0;
    }

    if (context.treatAsPlaceholder) {
        d[kXAttributeContextTreatAsPlaceholderKey] = @YES;
    }

    return d;
}

static TIPImageCacheEntryContext * __nullable _ContextFromXAttributes(NSDictionary *xattrs, BOOL notYetComplete)
{
    id val;
    TIPImageCacheEntryContext *context = nil;
    if (!notYetComplete) {
        context = [[TIPCompleteImageEntryContext alloc] init];
    } else {
        context = [[TIPPartialImageEntryContext alloc] init];
        TIPPartialImageEntryContext *partialContext = (id)context;
        val = xattrs[kXAttributeContextLastModifiedKey];
        partialContext.lastModified = [(NSString *)val length] < 4 ? nil : val;
        val = xattrs[kXAttributeContextExpectedSizeKey];
        partialContext.expectedContentLength = [(NSNumber *)val unsignedIntegerValue];
    }

    val = xattrs[kXAttributeContextURLKey];
    if (!val) {
        return nil;
    }
    context.URL = val;

    val = xattrs[kXAttributeContextLastAccessKey];
    if (!val) {
        return nil;
    }
    context.lastAccess = val;

    val = xattrs[kXAttributeContextTTLKey];
    if (!val) {
        return nil;
    }
    context.TTL = [(NSNumber *)val doubleValue];

    val = xattrs[kXAttributeContextAnimated];
    if (!val) {
        // Don't fail on missing "animated" property
        val = @NO;
    }
    context.animated = [(NSNumber *)val boolValue];

    CGSize dimensions = CGSizeZero;
    dimensions.width = (CGFloat)[xattrs[kXAttributeContextDimensionXKey] doubleValue];
    dimensions.height = (CGFloat)[xattrs[kXAttributeContextDimensionYKey] doubleValue];
    if (dimensions.width < 1.0 || dimensions.height < 1.0) {
        return nil;
    }
    context.dimensions = dimensions;

    val = xattrs[kXAttributeContextUpdateTLLOnAccessKey];
    context.updateExpiryOnAccess = [val boolValue];

    val = xattrs[kXAttributeContextTreatAsPlaceholderKey];
    context.treatAsPlaceholder = [val boolValue];

    return context;
}

static NSOperation *
_ImageDiskCacheManifestLoadOperation(NSMutableDictionary<NSString *, TIPImageDiskCacheEntry *> *manifest,
                                     NSMutableArray<NSString *> *falseEntryPaths,
                                     NSMutableArray<TIPImageDiskCacheEntry *> *entries,
                                     unsigned long long *totalSizeInOut,
                                     NSURL *entryURL,
                                     NSString *cachePath,
                                     NSDate *timestamp,
                                     NSOperationQueue *manifestCacheQueue,
                                     NSOperation *finalCacheOperation)
{
    __weak typeof(finalCacheOperation) weakFinalCacheOperation = finalCacheOperation;
    return [NSBlockOperation blockOperationWithBlock:^{
        NSString *path = entryURL.lastPathComponent;
        TIPImageCacheEntryContext *context = nil;
        NSString *rawIdentifier = nil;
        NSError *error = nil;
        const BOOL isTmp = [[path pathExtension] isEqualToString:kPartialImageExtension];
        NSString * const safeIdentifier = isTmp ? [path stringByDeletingPathExtension] : path;
        NSString *entryPath = [entryURL path];

        const NSUInteger size = [[entryURL resourceValuesForKeys:@[NSURLFileSizeKey] error:&error][NSURLFileSizeKey] unsignedIntegerValue];
        if (!size) {
            TIPLogError(@"Could not get filesize of '%@': %@", entryURL, error);
        } else {
            rawIdentifier = TIPRawFromSafe(safeIdentifier);

            NSDictionary *xattrMap = isTmp ? _XAttributesKeysToKindsMap() : _XAttributesKeysToKindsMapForCompleteEntry();
            context = (rawIdentifier) ? _ContextFromXAttributes(TIPGetXAttributesForFile(entryPath, xattrMap), isTmp) : nil;
            if (isTmp && ![context isKindOfClass:[TIPPartialImageEntryContext class]]) {
                context = nil;
            } else if (!isTmp && [context isKindOfClass:[TIPPartialImageEntryContext class]]) {
                context = nil;
            }
        }

        NSBlockOperation *cacheOp = [NSBlockOperation blockOperationWithBlock:^{
            if (!context || ([timestamp timeIntervalSinceDate:context.lastAccess] > context.TTL)) {
                [falseEntryPaths addObject:entryPath];
                return;
            }

            BOOL manifestCacheHit = NO;
            TIPImageDiskCacheEntry *entry = nil;

            entry = manifest[safeIdentifier];
            if (!entry) {
                entry = [[TIPImageDiskCacheEntry alloc] init];
                entry.identifier = rawIdentifier;
                manifest[safeIdentifier] = entry;
                [entries addObject:entry];
            } else {
                manifestCacheHit = YES;
            }

            if (manifestCacheHit) {
                TIPAssertMessage([entry.identifier isEqualToString:rawIdentifier], @"\n\tentry.identifier = %@\n\trawIdentifier = %@", entry.identifier, rawIdentifier);
            }

            if (isTmp) {
                TIPAssertMessage(!entry.partialImageContext, @"\n\tentry.identifier = %@\n\trawIdentifier = %@", entry.identifier, rawIdentifier);
                entry.partialImageContext = (id)context;
                entry.partialFileSize = size;
            } else {
                TIPAssertMessage(!entry.completeImageContext, @"\n\tentry.identifier = %@\n\trawIdentifier = %@", entry.identifier, rawIdentifier);
                entry.completeImageContext = (id)context;
                entry.completeFileSize = size;
            }
            *totalSizeInOut = *totalSizeInOut + size;

            if (entry.partialImageContext && entry.completeImageContext) {
                const CGSize partialDimensions = entry.partialImageContext.dimensions;
                const CGSize completeDimensions = entry.completeImageContext.dimensions;

                if ((partialDimensions.width * partialDimensions.height) <= (completeDimensions.width * completeDimensions.height)) {
                    // We have a partial image that is lower fidelity than a completed image...
                    // remove the partial image from our disk cache

                    NSString * const partialEntryPath = [entryPath stringByAppendingPathExtension:kPartialImageExtension];

                    *totalSizeInOut = *totalSizeInOut - entry.partialFileSize;
                    entry.partialFileSize = 0;
                    entry.partialImageContext = nil;

                    TIPLogWarning(@"Partial image in disk cache is lower fidelity than complete image counterpart, removing: %@", partialEntryPath);

                    [falseEntryPaths addObject:partialEntryPath];
                }
            }
        }];

        [weakFinalCacheOperation addDependency:cacheOp];
        [manifestCacheQueue addOperation:cacheOp];
    }];
}

static BOOL _UpdateImageConditionCheck(const BOOL force,
                                       const BOOL oldWasPlaceholder,
                                       const BOOL newIsPlaceholder,
                                       const BOOL extraCondition,
                                       const CGSize newDimensions,
                                       const CGSize oldDimensions,
                                       NSURL * __nullable oldURL,
                                       NSURL * __nullable newURL)
{
    if (force) {
        // forced
        return YES;
    }
    if (oldWasPlaceholder && !newIsPlaceholder) {
        // are we replacing a placeholder w/ a non-placeholder?
        return YES;
    }
    if (extraCondition) {
        // extra condition
        return YES;
    }
    if (oldWasPlaceholder != newIsPlaceholder) {
        // placeholderness missmatch
        return NO;
    }

    // IMPORTANT: We use "last in wins" logic.
    // It is easier for clients to detect larger varients matching smaller varients
    // than smaller variants matching larger variants.
    // This way, clients can load the smaller variant first, load the larger variant second and
    // (next time they access smaller or larger variant) the larger variant is cached.

    if ((newDimensions.width * newDimensions.height) >= (oldDimensions.width * oldDimensions.height)) {
        // we're replacing based on size, is the image identical?
        // Be sure we aren't replacing the identical image (by URL)
        const BOOL isIdenticalImage = CGSizeEqualToSize(oldDimensions, newDimensions) && [oldURL isEqual:newURL];
        if (!isIdenticalImage) {
            return YES;
        }
    }

    return NO;
}

static NSOperationQueue *_ImageDiskCacheManifestCacheQueue()
{
    static NSOperationQueue *sQueue;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        sQueue = [[NSOperationQueue alloc] init];
        sQueue.name = @"com.twitter.tip.disk.manifest.cache.queue";
        sQueue.maxConcurrentOperationCount = 1;
        sQueue.qualityOfService = NSQualityOfServiceUtility;
    });
    return sQueue;
}

static NSOperationQueue *_ImageDiskCacheManifestIOQueue()
{
    static NSOperationQueue *sQueue;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        sQueue = [[NSOperationQueue alloc] init];
        sQueue.name = @"com.twitter.tip.disk.manifest.io.queue";
        sQueue.maxConcurrentOperationCount = 4; // parallelized
        sQueue.qualityOfService = NSQualityOfServiceUtility;
    });
    return sQueue;
}

static dispatch_queue_t _ImageDiskCacheManifestAccessQueue()
{
    static dispatch_queue_t sQueue;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        sQueue = dispatch_queue_create("com.twitter.tip.disk.manifest.access.queue", DISPATCH_QUEUE_SERIAL);
    });
    return sQueue;
}

static void _SortEntries(NSMutableArray<TIPImageDiskCacheEntry *> *entries)
{
    [entries sortUsingComparator:^NSComparisonResult(TIPImageDiskCacheEntry *entry1, TIPImageDiskCacheEntry *entry2) {
        NSDate *lastAccess1 = entry1.mostRecentAccess;
        NSDate *lastAccess2 = entry2.mostRecentAccess;

        // Simple check if both are nil (or identical)
        if (lastAccess1 == lastAccess2) {
            return NSOrderedSame;
        }

        // Put the missing access at the end
        if (!lastAccess1) {
            return NSOrderedDescending;
        } else if (!lastAccess2) {
            return NSOrderedAscending;
        }

        // Full compare
        return [lastAccess2 compare:lastAccess1];
    }];
}

NS_ASSUME_NONNULL_END