Fixed read conditions in IOperationDocumentStorage implementations

src/HotChocolate/PersistedOperations/src/PersistedOperations.AzureBlobStorage/AzureBlobOperationDocumentStorage.cs

@@ -71,10 +71,10 @@ public AzureBlobOperationDocumentStorage(BlobContainerClient client)
                     buffer = newBuffer;
                 }
 
-                var read = await blobStream.ReadAsync(buffer, position, 256, ct);
+                var read = await blobStream.ReadAsync(buffer.AsMemory(position, 256), ct);
                 position += read;
 
-                if (read < 256)
+                if (read == 0)
                 {
                     break;
                 }

src/HotChocolate/PersistedOperations/src/PersistedOperations.FileSystem/FileSystemOperationDocumentStorage.cs

@@ -49,14 +49,14 @@ public FileSystemOperationDocumentStorage(IOperationDocumentFileMap documentMap)
         const int chunkSize = 4096;
         await using var stream = new FileStream(filePath, FileMode.Open, FileAccess.Read);
         using var writer = new PooledArrayWriter();
-        var read = 0;
+        int read;
 
         do
         {
             var memory = writer.GetMemory(chunkSize);
             read = await stream.ReadAsync(memory, cancellationToken).ConfigureAwait(false);
             writer.Advance(read);
-        } while (read == chunkSize);
+        } while (read != 0);
 
         var document = Utf8GraphQLParser.Parse(writer.WrittenSpan);
         return new OperationDocument(document);