mirror of
https://github.com/facebook/rocksdb.git
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446 lines
17 KiB
C++
446 lines
17 KiB
C++
/*
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* Licensed to the Apache Software Foundation (ASF) under one
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* or more contributor license agreements. See the NOTICE file
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* distributed with this work for additional information
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* regarding copyright ownership. The ASF licenses this file
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* to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance
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* with the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing,
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* software distributed under the License is distributed on an
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* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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* KIND, either express or implied. See the License for the
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* specific language governing permissions and limitations
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* under the License.
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*/
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#ifndef THRIFT_ASYNC_TASYNCTRANSPORT_H_
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#define THRIFT_ASYNC_TASYNCTRANSPORT_H_ 1
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#include "thrift/lib/cpp/thrift_config.h"
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#include <sys/uio.h>
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#include <inttypes.h>
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#include <memory>
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namespace folly {
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class IOBuf;
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}
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namespace apache { namespace thrift {
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namespace transport {
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class TSocketAddress;
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class TTransportException;
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}
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namespace async {
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class TEventBase;
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/**
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* TAsyncTransport defines an asynchronous API for streaming I/O.
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*
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* This class provides an API to for asynchronously waiting for data
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* on a streaming transport, and for asynchronously sending data.
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*
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* The APIs for reading and writing are intentionally asymmetric. Waiting for
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* data to read is a persistent API: a callback is installed, and is notified
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* whenever new data is available. It continues to be notified of new events
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* until it is uninstalled.
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*
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* TAsyncTransport does not provide read timeout functionality, because it
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* typically cannot determine when the timeout should be active. Generally, a
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* timeout should only be enabled when processing is blocked waiting on data
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* from the remote endpoint. For server-side applications, the timeout should
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* not be active if the server is currently processing one or more outstanding
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* requests on this transport. For client-side applications, the timeout
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* should not be active if there are no requests pending on the transport.
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* Additionally, if a client has multiple pending requests, it will ususally
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* want a separate timeout for each request, rather than a single read timeout.
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*
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* The write API is fairly intuitive: a user can request to send a block of
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* data, and a callback will be informed once the entire block has been
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* transferred to the kernel, or on error. TAsyncTransport does provide a send
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* timeout, since most callers want to give up if the remote end stops
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* responding and no further progress can be made sending the data.
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*/
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class TAsyncTransport {
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public:
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class ReadCallback {
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public:
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virtual ~ReadCallback() {}
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/**
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* When data becomes available, getReadBuffer() will be invoked to get the
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* buffer into which data should be read.
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*
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* This method allows the ReadCallback to delay buffer allocation until
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* data becomes available. This allows applications to manage large
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* numbers of idle connections, without having to maintain a separate read
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* buffer for each idle connection.
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*
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* It is possible that in some cases, getReadBuffer() may be called
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* multiple times before readDataAvailable() is invoked. In this case, the
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* data will be written to the buffer returned from the most recent call to
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* readDataAvailable(). If the previous calls to readDataAvailable()
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* returned different buffers, the ReadCallback is responsible for ensuring
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* that they are not leaked.
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*
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* If getReadBuffer() throws an exception, returns a NULL buffer, or
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* returns a 0 length, the ReadCallback will be uninstalled and its
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* readError() method will be invoked.
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*
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* getReadBuffer() is not allowed to change the transport state before it
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* returns. (For example, it should never uninstall the read callback, or
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* set a different read callback.)
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*
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* @param bufReturn getReadBuffer() should update *bufReturn to contain the
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* address of the read buffer. This parameter will never
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* be NULL.
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* @param lenReturn getReadBuffer() should update *lenReturn to contain the
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* maximum number of bytes that may be written to the read
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* buffer. This parameter will never be NULL.
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*/
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virtual void getReadBuffer(void** bufReturn, size_t* lenReturn) = 0;
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/**
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* readDataAvailable() will be invoked when data has been successfully read
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* into the buffer returned by the last call to getReadBuffer().
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*
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* The read callback remains installed after readDataAvailable() returns.
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* It must be explicitly uninstalled to stop receiving read events.
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* getReadBuffer() will be called at least once before each call to
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* readDataAvailable(). getReadBuffer() will also be called before any
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* call to readEOF().
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*
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* @param len The number of bytes placed in the buffer.
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*/
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virtual void readDataAvailable(size_t len) THRIFT_NOEXCEPT = 0;
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/**
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* readEOF() will be invoked when the transport is closed.
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*
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* The read callback will be automatically uninstalled immediately before
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* readEOF() is invoked.
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*/
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virtual void readEOF() THRIFT_NOEXCEPT = 0;
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/**
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* readError() will be invoked if an error occurs reading from the
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* transport.
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*
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* The read callback will be automatically uninstalled immediately before
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* readError() is invoked.
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*
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* @param ex An exception describing the error that occurred.
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*/
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virtual void readError(const transport::TTransportException& ex)
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THRIFT_NOEXCEPT = 0;
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};
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class WriteCallback {
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public:
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virtual ~WriteCallback() {}
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/**
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* writeSuccess() will be invoked when all of the data has been
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* successfully written.
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*
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* Note that this mainly signals that the buffer containing the data to
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* write is no longer needed and may be freed or re-used. It does not
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* guarantee that the data has been fully transmitted to the remote
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* endpoint. For example, on socket-based transports, writeSuccess() only
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* indicates that the data has been given to the kernel for eventual
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* transmission.
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*/
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virtual void writeSuccess() THRIFT_NOEXCEPT = 0;
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/**
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* writeError() will be invoked if an error occurs writing the data.
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*
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* @param bytesWritten The number of bytes that were successfull
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* @param ex An exception describing the error that occurred.
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*/
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virtual void writeError(size_t bytesWritten,
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const transport::TTransportException& ex)
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THRIFT_NOEXCEPT = 0;
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};
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virtual ~TAsyncTransport() {}
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/**
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* Set the read callback.
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*
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* See the documentation for ReadCallback above for a description of how the
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* callback will be invoked. Note that the callback remains installed until
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* it is explicitly uninstalled, or until an error occurs.
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*
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* If a ReadCallback is already installed, it is replaced with the new
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* callback.
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*
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* Note that setReadCallback() may invoke the ReadCallback immediately,
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* before returning.
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*
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* @param callback The callback to invoke when data is available.
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* This parameter may be NULL to uninstall the current
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* read callback.
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*/
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virtual void setReadCallback(ReadCallback* callback) = 0;
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/**
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* Get the currently installed read callback.
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*
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* @return Returns a pointer to the installed ReadCallback, or NULL if no
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* ReadCallback is installed.
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*/
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virtual ReadCallback* getReadCallback() const = 0;
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/**
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* Write data to the transport.
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*
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* write() will always return immediately. The WriteCallback will later be
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* invoked from the main TEventBase loop when the write has completed.
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*
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* Additional write attempts may be started before the first write completes.
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* The subsequent write requests will be queued, and processed in the order
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* in which they were called.
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*
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* @param callback The callback to invoke when the data has been written.
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* The callback may not be NULL.
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* @param buf The buffer containing the data to write. The caller is
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* responsible for ensuring that this buffer remains valid
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* until the callback is invoked. This parameter may not
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* be NULL.
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* @param bytes The number of bytes to write.
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*/
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virtual void write(WriteCallback* callback,
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const void* buf, size_t bytes) = 0;
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/**
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* Write non-contiguous data to the transport.
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*
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* writev() will always return immediately. The WriteCallback will later be
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* invoked from the main TEventBase loop when the write has completed.
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*
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* Additional write attempts may be started before the first write completes.
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* The subsequent write requests will be queued, and processed in the order
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* in which they were called.
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*
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* @param callback The callback to invoke when the data has been written.
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* The callback may not be NULL.
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* @param vec A pointer to an array of iovec objects. The caller is
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* responsible for ensuring that the buffers remain valid
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* until the callback is invoked. This parameter may not
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* be NULL.
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* @param count The number of iovec objects in the vec array.
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*/
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virtual void writev(WriteCallback* callback,
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const iovec* vec, size_t count) = 0;
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/**
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* Write a chain of IOBufs to the transport.
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*
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* writeChain() will always return immediately. The WriteCallback will
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* later be invoked from the main TEventBase loop when the write has
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* completed.
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*
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* Additional write attempts may be started before the first write completes.
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* The subsequent write requests will be queued, and processed in the order
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* in which they were called.
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*
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* @param callback The callback to invoke when the data has been written.
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* The callback may not be NULL.
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* @param iob The head of an IOBuf chain. The TAsyncTransport
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* will take ownership of this chain and delete it
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* after writing.
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* @param cork Whether to delay the write until the next non-corked
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* write operation. (Note: may not be supported in all
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* subclasses or on all platforms.)
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*/
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virtual void writeChain(WriteCallback* callback,
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std::unique_ptr<folly::IOBuf>&& iob,
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bool cork = false) = 0;
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/**
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* Close the transport.
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*
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* This gracefully closes the transport, waiting for all pending write
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* requests to complete before actually closing the underlying transport.
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*
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* If a read callback is set, readEOF() will be called immediately. If there
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* are outstanding write requests, the close will be delayed until all
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* remaining writes have completed. No new writes may be started after
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* close() has been called.
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*/
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virtual void close() = 0;
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/**
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* Close the transport immediately.
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*
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* This closes the transport immediately, dropping any outstanding data
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* waiting to be written.
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*
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* If a read callback is set, readEOF() will be called immediately.
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* If there are outstanding write requests, these requests will be aborted
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* and writeError() will be invoked immediately on all outstanding write
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* callbacks.
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*/
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virtual void closeNow() = 0;
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/**
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* Reset the transport immediately.
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*
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* This closes the transport immediately, sending a reset to the remote peer
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* if possible to indicate abnormal shutdown.
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*
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* Note that not all subclasses implement this reset functionality: some
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* subclasses may treat reset() the same as closeNow(). Subclasses that use
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* TCP transports should terminate the connection with a TCP reset.
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*/
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virtual void closeWithReset() {
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closeNow();
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}
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/**
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* Perform a half-shutdown of the write side of the transport.
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*
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* The caller should not make any more calls to write() or writev() after
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* shutdownWrite() is called. Any future write attempts will fail
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* immediately.
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*
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* Not all transport types support half-shutdown. If the underlying
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* transport does not support half-shutdown, it will fully shutdown both the
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* read and write sides of the transport. (Fully shutting down the socket is
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* better than doing nothing at all, since the caller may rely on the
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* shutdownWrite() call to notify the other end of the connection that no
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* more data can be read.)
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*
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* If there is pending data still waiting to be written on the transport,
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* the actual shutdown will be delayed until the pending data has been
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* written.
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*
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* Note: There is no corresponding shutdownRead() equivalent. Simply
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* uninstall the read callback if you wish to stop reading. (On TCP sockets
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* at least, shutting down the read side of the socket is a no-op anyway.)
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*/
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virtual void shutdownWrite() = 0;
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/**
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* Perform a half-shutdown of the write side of the transport.
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*
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* shutdownWriteNow() is identical to shutdownWrite(), except that it
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* immediately performs the shutdown, rather than waiting for pending writes
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* to complete. Any pending write requests will be immediately failed when
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* shutdownWriteNow() is called.
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*/
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virtual void shutdownWriteNow() = 0;
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/**
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* Determine if transport is open and ready to read or write.
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*
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* Note that this function returns false on EOF; you must also call error()
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* to distinguish between an EOF and an error.
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*
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* @return true iff the transport is open and ready, false otherwise.
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*/
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virtual bool good() const = 0;
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/**
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* Determine if the transport is readable or not.
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*
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* @return true iff the transport is readable, false otherwise.
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*/
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virtual bool readable() const = 0;
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/**
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* Determine if transport is connected to the endpoint
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*
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* @return false iff the transport is connected, otherwise true
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*/
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virtual bool connecting() const = 0;
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/**
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* Determine if an error has occurred with this transport.
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*
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* @return true iff an error has occurred (not EOF).
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*/
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virtual bool error() const = 0;
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/**
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* Attach the transport to a TEventBase.
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*
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* This may only be called if the transport is not currently attached to a
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* TEventBase (by an earlier call to detachEventBase()).
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*
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* This method must be invoked in the TEventBase's thread.
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*/
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virtual void attachEventBase(TEventBase* eventBase) = 0;
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/**
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* Detach the transport from its TEventBase.
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*
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* This may only be called when the transport is idle and has no reads or
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* writes pending. Once detached, the transport may not be used again until
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* it is re-attached to a TEventBase by calling attachEventBase().
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*
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* This method must be called from the current TEventBase's thread.
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*/
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virtual void detachEventBase() = 0;
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/**
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* Get the TEventBase used by this transport.
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*
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* Returns NULL if this transport is not currently attached to a TEventBase.
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*/
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virtual TEventBase* getEventBase() const = 0;
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/**
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* Set the send timeout.
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*
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* If write requests do not make any progress for more than the specified
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* number of milliseconds, fail all pending writes and close the transport.
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*
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* If write requests are currently pending when setSendTimeout() is called,
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* the timeout interval is immediately restarted using the new value.
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*
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* @param milliseconds The timeout duration, in milliseconds. If 0, no
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* timeout will be used.
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*/
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virtual void setSendTimeout(uint32_t milliseconds) = 0;
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/**
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* Get the send timeout.
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*
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* @return Returns the current send timeout, in milliseconds. A return value
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* of 0 indicates that no timeout is set.
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*/
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virtual uint32_t getSendTimeout() const = 0;
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/**
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* Get the address of the local endpoint of this transport.
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*
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* This function may throw TTransportException on error.
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*
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* @param address The local address will be stored in the specified
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* TSocketAddress.
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*/
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virtual void getLocalAddress(transport::TSocketAddress* address) const = 0;
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/**
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* Get the address of the remote endpoint to which this transport is
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* connected.
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*
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* This function may throw TTransportException on error.
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*
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* @param address The remote endpoint's address will be stored in the
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* specified TSocketAddress.
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*/
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virtual void getPeerAddress(transport::TSocketAddress* address) const = 0;
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};
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}}} // apache::thrift::async
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#endif // #ifndef THRIFT_ASYNC_TASYNCTRANSPORT_H_
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