XDR serializing variable lenght array of string - c++

Question

I am serializing a packet over XDR but i do not understand how to provide vector of string. I have here a small fully working serialization / deserialization for a std::vector of uint64_t. Here my code:
Serializer:
#include <stdio.h>
#include <iostream>
#include <rpc/rpc.h>
#include <vector>
#define MAX_LENGTH_ 100
int main(void)
{
XDR xdr;
xdrstdio_create(&xdr, stdout, XDR_ENCODE);
std::vector<uint64_t> ids; // vector i want to send
ids.push_back(1);
ids.push_back(2);
ids.push_back(3);
// serializing the vector
uint64_t *_ids = &ids[0];
uint32_t size = ids.size();
xdr_array(&xdr,(char**)(&_ids), &size, MAX_LENGTH_,sizeof(uint64_t),(xdrproc_t)xdr_u_long);
return 1;
}
Deserializer:
#include <stdio.h>
#include <iostream>
#include <rpc/rpc.h>
#include <vector>
#define MAX_LENGTH_ 100
int main(void)
{
XDR xdrs;
xdrstdio_create(&xdrs, stdin, XDR_DECODE);
uint64_t *ids_ = new uint64_t[MAX_LENGTH_];
uint32_t size;
bool status = xdr_array(&xdrs,(char**)(&ids_), &size, MAX_LENGTH_,
sizeof(uint64_t), (xdrproc_t)xdr_u_long);
std::vector<uint64_t> ids(ids_,ids_+size);
for(std::vector<uint64_t>::iterator it = ids.begin(); it != ids.end(); ++it)
{
std::cout << *it <<std::endl;
}
return 1;
}
The following code works... running ./serializer | ./deserializer i obtain 1 2 3. Now I do not know how to handle having to serialize std::vector<std::string>. A single string works well using xdr_string.
http://linux.die.net/man/3/xdr_array
Any help would be very much appreciated!
EDIT:
I have tried the following:
Serializer:
#include <stdio.h>
#include <iostream>
#include <rpc/rpc.h>
#include <vector>
#include <algorithm>
#include <cstring>
#define MAX_VECTOR_LENGTH_ 100
#define MAX_STRING_LENGTH_ 50
char *convert(const std::string & s)
{
char *pc = new char[s.size()+1];
std::strcpy(pc, s.c_str());
return pc;
}
int main(void)
{
XDR xdr;
xdrstdio_create(&xdr, stdout, XDR_ENCODE);
std::vector<std::string> messages; // vector i want to send
messages.push_back("this is");
messages.push_back("my string");
messages.push_back("vector test");
// transform the vector to c style
std::vector<char*> messagesCStyle;
std::transform(messages.begin(), messages.end(), std::back_inserter(messagesCStyle), convert);
// serializing the vector
char **_messages = &messagesCStyle[0];
uint32_t size = messages.size();
xdr_array(&xdr,(char**)(&_messages), &size, MAX_VECTOR_LENGTH_ * MAX_STRING_LENGTH_,sizeof(char),(xdrproc_t)xdr_string);
return 1;
}
Deserializer:
#include <stdio.h>
#include <iostream>
#include <rpc/rpc.h>
#include <vector>
#define MAX_VECTOR_LENGTH_ 100
#define MAX_STRING_LENGTH_ 50
int main(void)
{
XDR xdrs;
xdrstdio_create(&xdrs, stdin, XDR_DECODE);
std::vector<char*> messagesCStyle_;
uint32_t size;
bool status = xdr_array(&xdrs,(char**)(&messagesCStyle_), &size, MAX_VECTOR_LENGTH_,
MAX_STRING_LENGTH_, (xdrproc_t)xdr_string);
for(std::vector<char*>::iterator it = messagesCStyle_.begin(); it != messagesCStyle_.end(); ++it)
{
std::cout << *it <<std::endl;
}
return 1;
}
I am pretty sure the code for the Serializer is not best but at least it seams to work. However the deserializer does not!! I think the problem is related to the fact that i do not know how much memory to allocate before calling the xdr_array. Any help?

Answer 1

I made it work:
Encoder:
#include <stdio.h>
#include <iostream>
#include <rpc/rpc.h>
#include <vector>
#include <algorithm>
#include <cstring>
#define MAX_VECTOR_LENGTH_ 100
#define MAX_STRING_LENGTH_ 50
char *convert(const std::string & s)
{
char *pc = new char[s.size()+1];
std::strcpy(pc, s.c_str());
return pc;
}
int main(void)
{
XDR xdr;
xdrstdio_create(&xdr, stdout, XDR_ENCODE);
std::vector<std::string> messages; // vector i want to send
messages.push_back("this is");
messages.push_back("my string");
messages.push_back("vector test");
messages.push_back("this is a relatively long string!!!");
// transform the vector to c style
std::vector<char*> messagesCStyle;
std::transform(messages.begin(), messages.end(),
std::back_inserter(messagesCStyle),
[](const std::string & s){
char *pc = new char[s.size()+1];
std::strcpy(pc, s.c_str());
return pc;
});
// serializing the vector
char **_messages = &messagesCStyle[0];
uint32_t size = messages.size();
xdr_array(&xdr,(char**)(&_messages), &size, MAX_VECTOR_LENGTH_ * MAX_STRING_LENGTH_,sizeof(char*),(xdrproc_t)xdr_string);
return 1;
}
Decoder:
#include <stdio.h>
#include <iostream>
#include <rpc/rpc.h>
#include <vector>
#define MAX_VECTOR_LENGTH_ 100
#define MAX_STRING_LENGTH_ 50
int main(void)
{
XDR xdrs;
uint32_t size;
char** buffer = NULL;
xdrstdio_create(&xdrs, stdin, XDR_DECODE);
bool status = xdr_array(&xdrs, (char**) &buffer, &size, MAX_VECTOR_LENGTH_,
sizeof(char*), (xdrproc_t)xdr_string);
std::cout << "status: " << status << std::endl;
std::cout << "size: " << size << std::endl;
std::vector<std::string> stringMessages_(buffer, buffer + size);
for(std::vector<std::string>::iterator it = stringMessages_.begin(); it != stringMessages_.end(); ++it)
{
std::cout << *it <<std::endl;
}
for (int i = 0; i < size; i++) {
free(buffer[i]);
}
free(buffer);
return 1;
}