public CacheEntry CreateView(long offset, uint size, MemoryMappedFileAccess access)
{
if (_IsDisposed)
throw new ObjectDisposedException("Cache");
if (access == MemoryMappedFileAccess.Write)
access = MemoryMappedFileAccess.ReadWrite;
int? freeSlot = null;
int? oldestUsedSlot = null;
long oldestUsedTimestamp = long.MaxValue;
for (int i = 0; i < Capacity; i++) {
var item = Cache[i];
if (item == null || item.IsDisposed) {
freeSlot = i;
continue;
}
if (item.CreatedWhen < oldestUsedTimestamp)
oldestUsedSlot = i;
if (offset < item.Offset)
continue;
if (offset + size > item.Offset + item.Size)
continue;
if (item.AddRef())
return item;
else {
freeSlot = i;
break;
}
}
if (!freeSlot.HasValue && !oldestUsedSlot.HasValue)
throw new InvalidDataException();
long actualOffset;
uint actualSize;
var view = CreateViewUncached(offset, size, MemoryMappedFileAccess.ReadWrite, out actualOffset, out actualSize);
var newEntry = new CacheEntry(view, actualOffset, actualSize);
newEntry.AddRef();
long slotIndex = freeSlot.GetValueOrDefault(oldestUsedSlot.GetValueOrDefault(0));
var oldEntry = Interlocked.Exchange(ref Cache[slotIndex], newEntry);
if (oldEntry != null)
oldEntry.RemoveRef();
return newEntry;
}
public CacheEntry CreateView(long offset, uint size, MemoryMappedFileAccess access)
{
if (_IsDisposed)
{
throw new ObjectDisposedException("Cache");
}
if (access == MemoryMappedFileAccess.Write)
{
access = MemoryMappedFileAccess.ReadWrite;
}
int? freeSlot = null;
int? oldestUsedSlot = null;
long oldestUsedTimestamp = long.MaxValue;
for (int i = 0; i < Capacity; i++)
{
var item = Cache[i];
if (item == null || item.IsDisposed)
{
freeSlot = i;
continue;
}
if (item.CreatedWhen < oldestUsedTimestamp)
{
oldestUsedSlot = i;
}
if (offset < item.Offset)
{
continue;
}
if (offset + size > item.Offset + item.Size)
{
continue;
}
if (item.AddRef())
{
return(item);
}
else
{
freeSlot = i;
break;
}
}
if (!freeSlot.HasValue && !oldestUsedSlot.HasValue)
{
throw new InvalidDataException();
}
long actualOffset;
uint actualSize;
var view = CreateViewUncached(offset, size, MemoryMappedFileAccess.ReadWrite, out actualOffset, out actualSize);
var newEntry = new CacheEntry(view, actualOffset, actualSize);
newEntry.AddRef();
long slotIndex = freeSlot.GetValueOrDefault(oldestUsedSlot.GetValueOrDefault(0));
var oldEntry = Interlocked.Exchange(ref Cache[slotIndex], newEntry);
if (oldEntry != null)
{
oldEntry.RemoveRef();
}
return(newEntry);
}
