Get double values from binary cursor

Hi, all.

i want to get a double values from binary cursor

in libpq < 7.4 it was simple
memcpy(&dfVal, PQgetvalue(...), sizeof(dfVal));

but now we have to convert data from MSB to LSB format
it is ok for int
but how to convert a double

i'am tried to write a simple program, but it does not work ....

#include <libpq-fe.h>
#include <netinet/in.h>
#include <stdio.h>
#include <string.h>

typedef unsigned int int4;
typedef double       float8;

int main()
{   if ( sizeof(int4) * 2  != sizeof(float8) )   {       printf("Error");       return 1;   }
   PGconn * conn = PQconnectdb("dbname=test host=localhost user=trusted");   PGresult * res;
   PQclear( PQexec(conn, "begin; declare my_cur binary cursor for 
select 123.123;") );   res = PQexec(conn,"fetch 1 from my_cur");
   float8 dfVal;   float8 dfOrig = 123.123;
   union   {       float8  f;       int4    n[2];   } swap;
   memcpy(&(swap.n), PQgetvalue( res, 0, 0 ), sizeof(int4) * 2 );
   int4 tmp  = ntohl(swap.n[0]);   swap.n[0] = ntohl(swap.n[1]);   swap.n[1] = tmp;
   dfVal = swap.f;
   printf("ret = [%f]\norig = [%f]\n", dfVal, orig);
   PQclear(res);   PQfinish(conn);   return 0;
}

Is something wrong?
Thank for any help.