Re: Enum binary access - Mailing list pgsql-hackers

On Mon, Sep 10, 2012 at 8:42 AM, Petr Chmelar <chmelarp@fit.vutbr.cz> wrote:
> Hi there,
>
> we tried to create the libpqtypes enum binary send but it doesn't work:
>
> // register types
> PGregisterType user_def[] = { {"seqtype", enum_put, enum_get} };
> PQregisterTypes(connector->getConn(), PQT_USERDEFINED, user_def, 1, 0);
>
> // enum_put throws format error
> int enum_put (PGtypeArgs *args ) {
>
>     char *val = va_arg(args->ap, char *);
>     char *out = NULL;
>     int vallen = 0, len = 0, oid = 0;
>     float sortorder = 0.0;
>
>     if (!args || !val) return 0;
>
>     /* expand buffer enough */
>     vallen = strlen(val);
>     len = sizeof(int) + sizeof(float) + (vallen * sizeof(char));
>     if (args->put.expandBuffer(args, len) == -1) return -1;
>
>     /* put header (oid, sortorder) and value */
>     out = args->put.out;
>     memcpy(out, &oid, sizeof(int));
>     out += sizeof(int);
>     memcpy(out, &sortorder, sizeof(float));
>     out += sizeof(float);
>     memcpy(out, val, vallen);
>
>     return len;
> }
>
> // enum_get (FYI, get works OK)
> int enum_get (PGtypeArgs *args) {
>     char *val = PQgetvalue(args->get.result, args->get.tup_num,
> args->get.field_num);
>     int len = PQgetlength(args->get.result, args->get.tup_num,
> args->get.field_num);
>         char **result = va_arg(args->ap, char **);
>     *result = (char *) PQresultAlloc((PGresult *) args->get.result, len *
> sizeof(char));
>     memcpy(*result, val, len * sizeof(char));
>         return 0;
> }
>
> Postgres doesn't accept enum sent like this and throws format error. This
> should be used as a prototype for derived types. There is no real "enum"
> named type. Libpqypes doesn't seem to provide simplified binary manipulation
> for enum types.
>
> What should we do, please? Can you fix it? I think there is more people that
> need access enum types in binary mode.

I was able to get it to work what I did:

*) your 'get' routine should probably be allocating a terminating
byte.  In binary situations, PQgetlength does not return the length of
the null terminator.

*) backend binary format for enums is just the label text string both
on get and put side.  So your putting the oid and sort order was
breaking the put side.  Removed that and everything worked.

*) see (very messy quickly written) code below:


#include "libpq-fe.h"
#include "libpqtypes.h"
#include "string.h"


// enum_put throws format error
int enum_put (PGtypeArgs *args ) {
   char *val = va_arg(args->ap, char *);   char *out = NULL;   int vallen = 0, len = 0, oid = 0;   float sortorder =
0.0;
   if (!args || !val) return 0;
   /* expand buffer enough */   vallen = strlen(val);   if (args->put.expandBuffer(args, len) == -1) return -1;
   out = args->put.out;   memcpy(out, val, vallen);
   return len;
}

// enum_get (FYI, get works OK)
int enum_get (PGtypeArgs *args) {   char *val = PQgetvalue(args->get.result, args->get.tup_num,
args->get.field_num);   int len = PQgetlength(args->get.result, args->get.tup_num,
args->get.field_num) + 1;       char **result = va_arg(args->ap, char **);   *result = (char *) PQresultAlloc((PGresult
*)args->get.result,
 
len * sizeof(char));   memcpy(*result, val, len * sizeof(char));   result[len] = 0;       return 0;
}


int main()
{ PGtext t = "b";
 PGconn *conn = PQconnectdb("port=5492 host=localhost"); PQinitTypes(conn);
 PGregisterType user_def[] = { {"e", enum_put, enum_get} };
 if(!PQregisterTypes(conn, PQT_USERDEFINED, user_def, 1, 0))   fprintf(stderr, "*ERROR: %s\n", PQgeterror());

 PGresult *res = PQexecf(conn, "select %e", t);
 if(!res)   fprintf(stderr, "*ERROR: %s\n", PQgeterror());
 if (!PQgetf(res, 0, "%e", 0, &t)) {   fprintf(stderr, "*ERROR: %s\n", PQgeterror()); }
 printf("%s\n", t);
 PQclear(res);
}