.. Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements. See the NOTICE file distributed with this work for additional information regarding copyright ownership. The ASF licenses this file to you under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. .. include:: ../../../common.defs .. _developer-plugins-io-vios: VIOs **** A **VIO**, or **virtual IO**, is a description of an IO operation that's currently in progress. The VIO data structure is used by vconnection users to determine how much progress has been made on a particular IO operation and to re-enable an IO operation when it stalls due to buffer space issues. VIOs are used by vconnection implementors to determine the buffer for an IO operation, how much work to do on the IO operation, and which continuation to call back when progress on the IO operation is made. The ``TSVIO`` data structure itself is opaque, but it could be defined as follows: .. code-block:: c typedef struct { TSCont continuation; TSVConn vconnection; TSIOBufferReader reader; TSMutex mutex; int nbytes; int ndone; } *TSVIO; The VIO functions below access and modify various parts of the data structure. - :c:func:`TSVIOBufferGet` - :c:func:`TSVIOVConnGet` - :c:func:`TSVIOContGet` - :c:func:`TSVIOMutexGet` - :c:func:`TSVIONBytesGet` - :c:func:`TSVIONBytesSet` - :c:func:`TSVIONDoneGet` - :c:func:`TSVIONDoneSet` - :c:func:`TSVIONTodoGet` - :c:func:`TSVIOReaderGet` - :c:func:`TSVIOReenable`