[GENERAL] Extracting data from BYTEA column to binary file using libpq

[Julia Jacobson]

Hello everybody out there using PostgreSQL,

What is the problem with the following C++ code for the extraction of 
data from a BYTEA column to a binary file?

#include <stdlib.h>
#include <stdio.h>
#include <iostream>
#include <fstream>
#include "libpq-fe.h"
using namespace std;

main ()
{
  PGconn *conn;
  conn = PQconnectdb("hostaddr='databaseserver.com' port='5432' 
dbname='test_db' user='test_user' password='secret'");
  int size;
  const char* contents;
  PGresult* res;
  res = PQexecParams(conn,
  "SELECT filecontent FROM pictures WHERE picture_id='3'",
  0, NULL,NULL,NULL,NULL,
  1);

  if (res && PQresultStatus(res)==PGRES_TUPLES_OK)
  {
    size = PQgetlength(res, 0, 0);
    contents = PQgetvalue(res, 0, 0);
  }
  ofstream myFile ("picture.jpg", ios::out | ios::binary);
  myFile.write (contents);
  myFile.close();
}

Thanks in advance,
Julia

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