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rocksdb/thrift/lib/cpp/transport/TTransport.h

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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_TTRANSPORT_H
#define THRIFT_TRANSPORT_TTRANSPORT_H 1
#include "thrift/lib/cpp/Thrift.h"
#include <boost/shared_ptr.hpp>
#include "thrift/lib/cpp/transport/TTransportException.h"
#include <string>
namespace apache { namespace thrift { namespace transport {
/**
* Helper template to hoist readAll implementation out of TTransport
*/
template <class Transport_>
uint32_t readAll(Transport_ &trans, uint8_t* buf, uint32_t len) {
uint32_t have = 0;
uint32_t get = 0;
while (have < len) {
get = trans.read(buf+have, len-have);
if (get <= 0) {
throw TTransportException(TTransportException::END_OF_FILE,
"No more data to read.");
}
have += get;
}
return have;
}
/**
* Generic interface for a method of transporting data. A TTransport may be
* capable of either reading or writing, but not necessarily both.
*
*/
class TTransport {
public:
/**
* Virtual deconstructor.
*/
virtual ~TTransport() {}
/**
* Whether this transport is open.
*/
virtual bool isOpen() {
return false;
}
/**
* Tests whether there is more data to read or if the remote side is
* still open. By default this is true whenever the transport is open,
* but implementations should add logic to test for this condition where
* possible (i.e. on a socket).
* This is used by a server to check if it should listen for another
* request.
*/
virtual bool peek() {
return isOpen();
}
/**
* Opens the transport for communications.
*
* @return bool Whether the transport was successfully opened
* @throws TTransportException if opening failed
*/
virtual void open() {
throw TTransportException(TTransportException::NOT_OPEN, "Cannot open base TTransport.");
}
/**
* Closes the transport.
*/
virtual void close() {
throw TTransportException(TTransportException::NOT_OPEN, "Cannot close base TTransport.");
}
/**
* Attempt to read up to the specified number of bytes into the string.
*
* @param buf Reference to the location to write the data
* @param len How many bytes to read
* @return How many bytes were actually read
* @throws TTransportException If an error occurs
*/
uint32_t read(uint8_t* buf, uint32_t len) {
T_VIRTUAL_CALL();
return read_virt(buf, len);
}
virtual uint32_t read_virt(uint8_t* /* buf */, uint32_t /* len */) {
throw TTransportException(TTransportException::NOT_OPEN,
"Base TTransport cannot read.");
}
/**
* Reads the given amount of data in its entirety no matter what.
*
* @param s Reference to location for read data
* @param len How many bytes to read
* @return How many bytes read, which must be equal to size
* @throws TTransportException If insufficient data was read
*/
uint32_t readAll(uint8_t* buf, uint32_t len) {
T_VIRTUAL_CALL();
return readAll_virt(buf, len);
}
virtual uint32_t readAll_virt(uint8_t* buf, uint32_t len) {
return apache::thrift::transport::readAll(*this, buf, len);
}
/**
* Called when read is completed.
* This can be over-ridden to perform a transport-specific action
* e.g. logging the request to a file
*
* @return number of bytes read if available, 0 otherwise.
*/
virtual uint32_t readEnd() {
// default behavior is to do nothing
return 0;
}
/**
* Writes the string in its entirety to the buffer.
*
* Note: You must call flush() to ensure the data is actually written,
* and available to be read back in the future. Destroying a TTransport
* object does not automatically flush pending data--if you destroy a
* TTransport object with written but unflushed data, that data may be
* discarded.
*
* @param buf The data to write out
* @throws TTransportException if an error occurs
*/
void write(const uint8_t* buf, uint32_t len) {
T_VIRTUAL_CALL();
write_virt(buf, len);
}
virtual void write_virt(const uint8_t* /* buf */, uint32_t /* len */) {
throw TTransportException(TTransportException::NOT_OPEN,
"Base TTransport cannot write.");
}
/**
* Called when write is completed.
* This can be over-ridden to perform a transport-specific action
* at the end of a request.
*
* @return number of bytes written if available, 0 otherwise
*/
virtual uint32_t writeEnd() {
// default behaviour is to do nothing
return 0;
}
/**
* Flushes any pending data to be written. Typically used with buffered
* transport mechanisms.
*
* @throws TTransportException if an error occurs
*/
virtual void flush() {
// default behaviour is to do nothing
}
/**
* Attempts to return a pointer to \c len bytes, possibly copied into \c buf.
* Does not consume the bytes read (i.e.: a later read will return the same
* data). This method is meant to support protocols that need to read
* variable-length fields. They can attempt to borrow the maximum amount of
* data that they will need, then consume (see next method) what they
* actually use. Some transports will not support this method and others
* will fail occasionally, so protocols must be prepared to use read if
* borrow fails.
*
* @oaram buf A buffer where the data can be stored if needed.
* If borrow doesn't return buf, then the contents of
* buf after the call are undefined. This parameter may be
* NULL to indicate that the caller is not supplying storage,
* but would like a pointer into an internal buffer, if
* available.
* @param len *len should initially contain the number of bytes to borrow.
* If borrow succeeds, *len will contain the number of bytes
* available in the returned pointer. This will be at least
* what was requested, but may be more if borrow returns
* a pointer to an internal buffer, rather than buf.
* If borrow fails, the contents of *len are undefined.
* @return If the borrow succeeds, return a pointer to the borrowed data.
* This might be equal to \c buf, or it might be a pointer into
* the transport's internal buffers.
* @throws TTransportException if an error occurs
*/
const uint8_t* borrow(uint8_t* buf, uint32_t* len) {
T_VIRTUAL_CALL();
return borrow_virt(buf, len);
}
virtual const uint8_t* borrow_virt(uint8_t* /* buf */, uint32_t* /* len */) {
return NULL;
}
/**
* Remove len bytes from the transport. This should always follow a borrow
* of at least len bytes, and should always succeed.
* TODO(dreiss): Is there any transport that could borrow but fail to
* consume, or that would require a buffer to dump the consumed data?
*
* @param len How many bytes to consume
* @throws TTransportException If an error occurs
*/
void consume(uint32_t len) {
T_VIRTUAL_CALL();
consume_virt(len);
}
virtual void consume_virt(uint32_t /* len */) {
throw TTransportException(TTransportException::NOT_OPEN,
"Base TTransport cannot consume.");
}
protected:
/**
* Simple constructor.
*/
TTransport() {}
};
/**
* Generic factory class to make an input and output transport out of a
* source transport. Commonly used inside servers to make input and output
* streams out of raw clients.
*
*/
class TTransportFactory {
public:
TTransportFactory() {}
virtual ~TTransportFactory() {}
/**
* Default implementation does nothing, just returns the transport given.
*/
virtual boost::shared_ptr<TTransport> getTransport(boost::shared_ptr<TTransport> trans) {
return trans;
}
};
/**
* A duplex transport factory used to make input and output transports in a
* single call. This can be used to ensure the input and output transports
* are the pointers to the same object, for example.
*
* TTransportPair.first = Input Transport
* TTransportPair.second = Output Transport
*/
typedef std::pair<boost::shared_ptr<TTransport>,
boost::shared_ptr<TTransport> > TTransportPair;
class TDuplexTransportFactory {
public:
TDuplexTransportFactory() {}
virtual ~TDuplexTransportFactory() {}
virtual TTransportPair getTransport(boost::shared_ptr<TTransport> trans) {
return std::make_pair(trans, trans);
}
virtual TTransportPair getTransport(TTransportPair transports) {
return std::make_pair(transports.first, transports.second);
}
};
/**
* Adapts a TTransportFactory to a TDuplexTransportFactory that returns
* a new transport object for both input and output
*/
template <class Factory_>
class TSingleTransportFactory : public TDuplexTransportFactory {
public:
TSingleTransportFactory() {
factory_.reset(new Factory_());
}
explicit TSingleTransportFactory(
boost::shared_ptr<Factory_> factory) :
factory_(factory) {}
virtual TTransportPair getTransport(boost::shared_ptr<TTransport> trans) {
return std::make_pair(factory_->getTransport(trans),
factory_->getTransport(trans));
}
virtual TTransportPair getTransport(TTransportPair transports) {
return std::make_pair(factory_->getTransport(transports.first),
factory_->getTransport(transports.second));
}
private:
boost::shared_ptr<Factory_> factory_;
};
/**
* Use TDualTransportFactory to construct input and output transports from
* different factories.
*/
class TDualTransportFactory : public TDuplexTransportFactory {
public:
TDualTransportFactory(
boost::shared_ptr<TTransportFactory> inputFactory,
boost::shared_ptr<TTransportFactory> outputFactory) :
inputFactory_(inputFactory),
outputFactory_(outputFactory) {}
virtual TTransportPair getTransport(boost::shared_ptr<TTransport> trans) {
return std::make_pair(inputFactory_->getTransport(trans),
outputFactory_->getTransport(trans));
}
virtual TTransportPair getTransport(TTransportPair transports) {
return std::make_pair(inputFactory_->getTransport(transports.first),
outputFactory_->getTransport(transports.second));
}
private:
boost::shared_ptr<TTransportFactory> inputFactory_;
boost::shared_ptr<TTransportFactory> outputFactory_;
};
}}} // apache::thrift::transport
#endif // #ifndef THRIFT_TRANSPORT_TTRANSPORT_H