// Calling thread need to be first take writelock
private bool SetInternal(string key, DiskCacheEntry diskEntry)
{
if (_inUse.ContainsKey(key))
{
return(false);
}
if (_lruCache.ContainsKey(key))
{
return(false);
}
Volatile.Write(ref diskEntry.InCache, true);
diskEntry.Ref(); // for the LRU cache's reference.
if (diskEntry.Refs == 1)
{
_lruCache.Add(key, diskEntry);
}
else if (diskEntry.Refs > 1)
{
_inUse.TryAdd(key, diskEntry);
}
Debug.Assert(diskEntry.Refs > 0, "disk entry should have at least 1 reference");
return(true);
}
public async Task <ICacheEntry> GetOrAddAsync(string key, Func <string, Stream, ICacheControl, Task> valueFactory, ICacheControl cacheControl, CancellationToken ct)
{
using (await _rwLock.ReadLockAsync())
{
ICacheEntry found = GetInternal(key);
if (!(found is EmptyCacheEntry))
{
found.Ref(); // this entry remain valid after releasing the lock
return(found);
}
}
using (await _rwLock.WriteLockAsync())
{
ICacheEntry found = GetInternal(key);
if (!(found is EmptyCacheEntry))
{
found.Ref(); // this entry remain valid after releasing the lock
return(found);
}
var randomPath = await _fs.WriteAtomicAsync((sink, cancel) => valueFactory(key, sink, cacheControl), _cacheTmpPath, ct).ConfigureAwait(false);
var tmpEntry = new DiskCacheEntry(key, randomPath, this);
if (!cacheControl.NoStore)
{
SetInternal(key, tmpEntry);
}
var entry = GetInternal(key);
entry.Ref();
return(entry);
}
}
internal void DeleteEntry(DiskCacheEntry diskCacheEntry)
{
var refs = diskCacheEntry.Refs;
Debug.Assert(refs == 0, "disk entry should have 0 reference");
_fs.FileDelete(diskCacheEntry.EntryPath, _cacheTmpPath);
diskCacheEntry.EntryPath = "";
}
void FinishErase(string key, DiskCacheEntry entry)
{
if (entry != null)
{
Volatile.Write(ref entry.InCache, false);
entry.DisposeAsync().Wait(); // not inside LRU cache anymore
}
}
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;
}
}
}
}
internal Stream ReadEntry(DiskCacheEntry diskCacheEntry)
{
Debug.Assert(diskCacheEntry.Refs > 0, "disk entry should have at least 1 reference");
Debug.Assert(diskCacheEntry.EntryPath != "", "disk entry have been deleted");
return(_fs.FileOpenRead(diskCacheEntry.EntryPath));
}
