public async Task ReleaseAsync(DiskCacheEntry entry)
{
int refCount;
// If InCache == false this is called from FinishErase with _lock already held and cause deadlock
if (Volatile.Read(ref entry.InCache))
{
using (await _rwLock.WriteLockAsync())
{
// entry is in "_inUse" and refcount is between 1 .. N
// Call Unref inside the lock to avoid other thread incrementing concurrently
refCount = entry.Unref();
if (refCount == 1)
{
// Entry is still in cache but no longer in use.
if (_inUse.TryRemove(entry.Key, out _))
{
_lruCache.Add(entry.Key, entry);
}
}
if (refCount <= 0)
{
_inUse.TryRemove(entry.Key, out _);
entry.Delete();
return;
}
}
}
else
{
// its safe to decrment unref because Entry is not in cache anymore and refcount can only decrease now
if (entry.Refs > 0)
{
refCount = entry.Unref();
if (refCount == 0)
{
_inUse.TryRemove(entry.Key, out _);
entry.Delete();
return;
}
}
}
}
/// <summary>valueFactory
/// Get item from cache of call valueFactory if missing
/// </summary>
/// <param name="key">The key of the value that need to be filled in</param>
/// <param name="valueFactory">valueFactory should write result to the stream but not close it</param>
/// <param name="ct">Cancellation token</param>
/// <returns></returns>
public Task <ICacheEntry> GetOrAddAsync(string key, Func <string, Stream, ICacheControl, Task> valueFactory, ICacheControl cacheControl, CancellationToken ct)
{
return(createEntry.DoAsync(key, async() =>
{
ICacheEntry found = await GetAsync(key, ct).ConfigureAwait(false);
if (!(found is EmptyCacheEntry))
{
return found;
}
ArraySegment <byte> buffer;
using (var memStream = new MemoryStream())
{
await valueFactory(key, memStream, cacheControl).ConfigureAwait(false);
memStream.Position = 0;
buffer = new ArraySegment <byte>(memStream.ToArray());
}
if (!cacheControl.NoStore)
{
_cache.Add(key, buffer, (ulong)buffer.Count);
}
return new MemoryCacheEntry(buffer);
}));
}