static public async Task <Tuple <BitmapImage, bool> > TryRetrieveOnlineCacheAsync(string cacheName)
{
try
{
var cachePath = Path.Combine(localCache.Path, cacheName);
if (_bitmapDiskCache.TryGetValue(cachePath, out BitmapImage img))
{
// Memory cache hit
return(new Tuple <BitmapImage, bool>(img, true));
}
else
{
var file = await localCache.TryGetItemAsync(cacheName) as StorageFile;
if (file == null)
{
return(CacheMiss);
}
using (var fs = await file.OpenReadAsync())
{
if (fs.Size == 0)
{
_bitmapDiskCache.TryAdd(cachePath, null);
return(CacheDisabled); // Empty file stub
}
img = await CreateBitmapFromStreamAsync(fs);
if (img != null)
{
_bitmapDiskCache.AddOrUpdate(cachePath, img);
return(new Tuple <BitmapImage, bool>(img, true)); // Cache found
}
}
}
}
catch { }
return(CacheDisabled); // Decode error
}
public static async Task <(BitmapImage, bool)> InternalGetAsync(string cacheName, int requiredSize)
{
using (await _sync.LockAsync())
{
if (_bitmapDiskCache.TryGetValue(cacheName, out var cachedValue))
{
if (cachedValue == null || cachedValue.DecodePixelWidth == 0 || cachedValue.DecodePixelWidth >= requiredSize)
{
return(cachedValue, true);
}
else
{
_bitmapDiskCache.TryRemove(cacheName);
}
}
var folder = await EnsureThumbnailFolderCreatedAsync();
var item = await folder.TryGetItemAsync(cacheName);
if (item == null || !(item is StorageFile))
{
return(null, false);
}
var file = (StorageFile)item;
using (var stream = await file.OpenReadAsync())
{
if (stream.Size == 0)
{
_bitmapDiskCache.Add(cacheName, null);
return(null, true);
}
var img = await TryDecodeAsync(stream, requiredSize);
_bitmapDiskCache.Add(cacheName, img);
return(img, true);
}
}
}