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/*
* 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.
*/
#ifndef _THRIFT_TRANSPORT_TVIRTUALTRANSPORT_H_
#define _THRIFT_TRANSPORT_TVIRTUALTRANSPORT_H_ 1
#include <thrift/transport/TTransport.h>
namespace apache {
namespace thrift {
namespace transport {
/**
* Helper class that provides default implementations of TTransport methods.
*
* This class provides default implementations of read(), readAll(), write(),
* borrow() and consume().
*
* In the TTransport base class, each of these methods simply invokes its
* virtual counterpart. This class overrides them to always perform the
* default behavior, without a virtual function call.
*
* The primary purpose of this class is to serve as a base class for
* TVirtualTransport, and prevent infinite recursion if one of its subclasses
* does not override the TTransport implementation of these methods. (Since
* TVirtualTransport::read_virt() calls read(), and TTransport::read() calls
* read_virt().)
*/
class TTransportDefaults : public TTransport {
public:
/*
* TTransport *_virt() methods provide reasonable default implementations.
* Invoke them non-virtually.
*/
uint32_t read(uint8_t* buf, uint32_t len) { return this->TTransport::read_virt(buf, len); }
uint32_t readAll(uint8_t* buf, uint32_t len) { return this->TTransport::readAll_virt(buf, len); }
void write(const uint8_t* buf, uint32_t len) { this->TTransport::write_virt(buf, len); }
const uint8_t* borrow(uint8_t* buf, uint32_t* len) {
return this->TTransport::borrow_virt(buf, len);
}
void consume(uint32_t len) { this->TTransport::consume_virt(len); }
protected:
TTransportDefaults() {}
};
/**
* Helper class to provide polymorphism for subclasses of TTransport.
*
* This class implements *_virt() methods of TTransport, to call the
* non-virtual versions of these functions in the proper subclass.
*
* To define your own transport class using TVirtualTransport:
* 1) Derive your subclass from TVirtualTransport<your class>
* e.g: class MyTransport : public TVirtualTransport<MyTransport> {
* 2) Provide your own implementations of read(), readAll(), etc.
* These methods should be non-virtual.
*
* Transport implementations that need to use virtual inheritance when
* inheriting from TTransport cannot use TVirtualTransport.
*
* @author Chad Walters <chad@powerset.com>
*/
template <class Transport_, class Super_ = TTransportDefaults>
class TVirtualTransport : public Super_ {
public:
/*
* Implementations of the *_virt() functions, to call the subclass's
* non-virtual implementation function.
*/
virtual uint32_t read_virt(uint8_t* buf, uint32_t len) {
return static_cast<Transport_*>(this)->read(buf, len);
}
virtual uint32_t readAll_virt(uint8_t* buf, uint32_t len) {
return static_cast<Transport_*>(this)->readAll(buf, len);
}
virtual void write_virt(const uint8_t* buf, uint32_t len) {
static_cast<Transport_*>(this)->write(buf, len);
}
virtual const uint8_t* borrow_virt(uint8_t* buf, uint32_t* len) {
return static_cast<Transport_*>(this)->borrow(buf, len);
}
virtual void consume_virt(uint32_t len) { static_cast<Transport_*>(this)->consume(len); }
/*
* Provide a default readAll() implementation that invokes
* read() non-virtually.
*
* Note: subclasses that use TVirtualTransport to derive from another
* transport implementation (i.e., not TTransportDefaults) should beware that
* this may override any non-default readAll() implementation provided by
* the parent transport class. They may need to redefine readAll() to call
* the correct parent implementation, if desired.
*/
uint32_t readAll(uint8_t* buf, uint32_t len) {
Transport_* trans = static_cast<Transport_*>(this);
return ::apache::thrift::transport::readAll(*trans, buf, len);
}
protected:
TVirtualTransport() {}
/*
* Templatized constructors, to allow arguments to be passed to the Super_
* constructor. Currently we only support 0, 1, or 2 arguments, but
* additional versions can be added as needed.
*/
template <typename Arg_>
TVirtualTransport(Arg_ const& arg)
: Super_(arg) {}
template <typename Arg1_, typename Arg2_>
TVirtualTransport(Arg1_ const& a1, Arg2_ const& a2)
: Super_(a1, a2) {}
};
}
}
} // apache::thrift::transport
#endif // #ifndef _THRIFT_TRANSPORT_TVIRTUALTRANSPORT_H_
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