vlc-ios/Sources/VLCThumbnailsCache.m

/*****************************************************************************
 * VLCThumbnailsCache.m
 * VLC for iOS
 *****************************************************************************
 * Copyright (c) 2013 VideoLAN. All rights reserved.
 * $Id$
 *
 * Authors: Gleb Pinigin <gpinigin # gmail.com>
 *          Felix Paul Kühne <fkuehne # videolan.org>
 *
 * Refer to the COPYING file of the official project for license.
 *****************************************************************************/

#import "VLCThumbnailsCache.h"
#import <CommonCrypto/CommonDigest.h>

static NSInteger MaxCacheSize;
static NSCache *_thumbnailCache;

@implementation VLCThumbnailsCache

#define MAX_CACHE_SIZE_IPHONE 21  // three times the number of items shown on iPhone 5
#define MAX_CACHE_SIZE_IPAD   27  // three times the number of items shown on iPad

+(void)initialize
{
    MaxCacheSize = (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad)?
                                MAX_CACHE_SIZE_IPAD: MAX_CACHE_SIZE_IPHONE;

    _thumbnailCache = [[NSCache alloc] init];
    [_thumbnailCache setCountLimit: MaxCacheSize];
}

+ (NSString *)_md5FromString:(NSString *)string
{
    const char *ptr = [string UTF8String];
    unsigned char md5Buffer[CC_MD5_DIGEST_LENGTH];
    CC_MD5(ptr, strlen(ptr), md5Buffer);
    NSMutableString *output = [NSMutableString stringWithCapacity:CC_MD5_DIGEST_LENGTH * 2];
    for(int i = 0; i < CC_MD5_DIGEST_LENGTH; i++)
        [output appendFormat:@"%02x",md5Buffer[i]];

    return [NSString stringWithString:output];
}

+ (NSString *)_getArtworkPathFromMedia:(MLFile *)file
{
    NSString *artworkURL, *artist, *album, *title;

    if (file.isAlbumTrack) {
        artist = file.albumTrack.artist;
        album = file.albumTrack.album.name;
    }
    title = file.title;

    NSArray *searchPaths = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES);
    NSString *cacheDir = searchPaths[0];
    cacheDir = [cacheDir stringByAppendingFormat:@"/%@", [[NSBundle mainBundle] bundleIdentifier]];

    if (artist.length == 0 || album.length == 0) {
        /* Use generated hash to find art */
        artworkURL = [cacheDir stringByAppendingFormat:@"/art/arturl/%@/art.jpg", [self _md5FromString:title]];
    } else {
        /* Otherwise, it was cached by artist and album */
        artworkURL = [cacheDir stringByAppendingFormat:@"/art/artistalbum/%@/%@/art.jpg", artist, album];
    }

    return artworkURL;
}

+ (UIImage *)thumbnailForMediaFile:(MLFile *)mediaFile
{
    if (mediaFile == nil || mediaFile.objectID == nil)
        return nil;

    NSManagedObjectID *objID = mediaFile.objectID;
    UIImage *displayedImage = [_thumbnailCache objectForKey:objID];

    if (displayedImage)
        return displayedImage;

    if (mediaFile.isAlbumTrack || mediaFile.isShowEpisode)
        displayedImage = [UIImage imageWithContentsOfFile:[self _getArtworkPathFromMedia:mediaFile]];

    if (!displayedImage)
        displayedImage = mediaFile.computedThumbnail;

    if (displayedImage)
        [_thumbnailCache setObject:displayedImage forKey:objID];

    return displayedImage;
}

@end