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From Jean Rodier <Jean.Rod...@tatacommunications.com>
Subject Is the Thrift serialization compatible both directions?
Date Thu, 18 Jan 2018 15:56:03 GMT
Hi,

Is this statement true, especially the last part?  (from: https://diwakergupta.github.io/thrift-missing-guide/)

Any new fields that you add should be optional. This means that any messages serialized by
code using your "old" message format can be parsed by your new generated code, as they won’t
be missing any required elements. Similarly, messages created by your new code can be parsed
by your old code: old binaries simply ignore the new field when parsing. However, the unknown
fields are not discarded, and if the message is later serialized, the unknown fields are serialized
along with it — so if the message is passed on to new code, the new fields are still
available.

I tested is using the following files in C++ and apparently it is not…

File msg1.thrift
--------------------
namespace cpp msg1
struct msgStruct {
    1:                        i32 version,
    2:                        i64 time
}

File msg2.thrift
--------------------
namespace cpp msg2
struct msgStruct {
    1:                        i32 version,
    2:                        i64 time,
    3: optional i32 flag
}

File main.cpp
------------------
/*
Build commands:
   thrift --gen cpp msg1.thrift
   thrift --gen cpp msg2.thrift

   g++ main.cpp -o test -lthrift -lthriftz */

#include <vector>
using namespace std;

#include <thrift/Thrift.h>
#include <thrift/protocol/TProtocol.h>
#include <thrift/protocol/TCompactProtocol.h>
#include <thrift/protocol/TJSONProtocol.h> #include <thrift/transport/TTransport.h>

#include "gen-cpp/msg1_types.h"      // Thrift generated
#include "gen-cpp/msg2_types.h"      // Thrift generated

template<typename T>
void serialize(const T & obj, vector<uint8_t> & s) {
   ::boost::shared_ptr<apache::thrift::transport::TMemoryBuffer> buffer(new apache::thrift::transport::TMemoryBuffer());
   //::boost::shared_ptr<apache::thrift::protocol::TCompactProtocol> protocol(new apache::thrift::protocol::TCompactProtocol(buffer));
   ::boost::shared_ptr<apache::thrift::protocol::TJSONProtocol> protocol(new apache::thrift::protocol::TJSONProtocol(buffer));

   obj.write(protocol.get());

   uint8_t * buf;
   uint32_t sz;

   buffer.get()->getBuffer(&buf, &sz);
   s.resize(sz);
   s.assign(buf, buf + sz);
}

template<typename T>
void deserialize(const vector<uint8_t> & s, T & obj) {
   ::boost::shared_ptr<apache::thrift::transport::TMemoryBuffer> buffer(new apache::thrift::transport::TMemoryBuffer((uint8_t*)s.data(),
s.size()));
   //::boost::shared_ptr<apache::thrift::protocol::TCompactProtocol> protocol(new apache::thrift::protocol::TCompactProtocol(buffer));
   ::boost::shared_ptr<apache::thrift::protocol::TJSONProtocol> protocol(new apache::thrift::protocol::TJSONProtocol(buffer));

   obj.read(protocol.get());
}

int main(int argc, char** argv) {
   msg2::msgStruct m2;
   m2.__set_version(123);
  m2.__set_time(456);
   m2.__set_flag(789);

   vector<uint8_t> buf;
   serialize<msg2::msgStruct>(m2, buf);

   string output(buf.begin(), buf.end());
   cout << output << endl;
   // {"1":{"i32":123},"2":{"i64":456},"3":{"i32":789}}

   msg1::msgStruct m1;
   deserialize<msg1::msgStruct>(buf, m1);

   vector<uint8_t> buf2;
   serialize<msg1::msgStruct>(m1, buf2);

   string output2(buf2.begin(), buf2.end());
   cout << output2 << endl;
   // {"1":{"i32":123},"2":{"i64":456}} expecting {"1":{"i32":123},"2":{"i64":456},"3":{"i32":789}}

   msg2::msgStruct m2_2;
   deserialize<msg2::msgStruct>(buf2, m2_2);

   vector<uint8_t> buf3;
   serialize<msg2::msgStruct>(m2_2, buf3);

   string output3(buf3.begin(), buf3.end());
   cout << output3 << endl;
   // {"1":{"i32":123},"2":{"i64":456}} expecting {"1":{"i32":123},"2":{"i64":456},"3":{"i32":789}}
}

#include "gen-cpp/msg1_types.cpp"      // Thrift generated
#include "gen-cpp/msg1_constants.cpp"  // Thrift generated
#include "gen-cpp/msg2_types.cpp"      // Thrift generated
#include "gen-cpp/msg2_constants.cpp"  // Thrift generated
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