OTL 4.0, Example 758 (otl_read_from_stream() / otl_write_to_stream() and STL containers).

This example demonstrates how otl_read_from_stream() / otl_write_to_stream() template functions can be used with STL containers (vectors, sets, maps, etc.).

Source Code

#include <iostream>
#include <vector>
#include <set>
#include <map>
#include <iterator>
#include <string>

// #define OTL_ODBC_UNIX // uncomment this line if UnixODBC is used
#define OTL_ODBC_ALTERNATE_RPC
#if !defined(_WIN32) && !defined(_WIN64)
#define OTL_ODBC
#else
#define OTL_ODBC_POSTGRESQL // required with PG ODBC on Windows
#endif
#define OTL_STL // Turn on STL features
#ifndef OTL_ANSI_CPP
#define OTL_ANSI_CPP // Turn on ANSI C++ typecasts
#endif
#include <otlv4.h> // include the OTL 4 header file

using namespace std;

otl_connect db; // connect object
// my row class
class my_row_class{
public:
int f1;
string f2;

// default constructor
my_row_class():f1(0),f2(){}

// general purpose constructor
my_row_class(const int af1, const string& af2):f1(af1),f2(af2){}

// destructor
~my_row_class(){}

// copy constructor
my_row_class(const my_row_class& row):f1(row.f1),f2(row.f2){}

// copy assignment operator
my_row_class& operator=(const my_row_class& row)
{
f1=row.f1;
f2=row.f2;
return *this;
}

#if defined(OTL_CPP_11_ON) || defined(_MSC_VER) && (_MSC_VER >= 1600)
// when move constructors / assignment operators are supported

my_row_class(my_row_class&& r):f1(r.f1),f2(move(r.f2)){}

my_row_class& operator=(my_row_class&& r)
{
f1=r.f1;
f2=move(r.f2);
return *this;
}

#endif

};

// "less-than" functor for "my set"
class my_set_less_than{
public:

bool operator()(const my_row_class& row1, const my_row_class& row2) const
{
if(row1.f1<row2.f1)
return true;
else
return false;
}
};

// various STL containers
typedef vector<my_row_class> my_vector_type;
typedef map<int,string,less<int> > my_map_type;
typedef set<my_row_class,my_set_less_than> my_set_type;

// redefined operator>> for reading my_row_class& from otl_stream
otl_stream& operator>>(otl_stream& s, my_row_class& row)
{
s>>row.f1>>row.f2;
return s;
}

// redefined operator<< for writing const my_row_class& into
// otl_stream
otl_stream& operator<<(otl_stream& s, const my_row_class& row)
{
s<<row.f1<<row.f2;
return s;
}

// redefined operator>> for reading my_map_type::value_type& from
// otl_stream
otl_stream& operator>>(otl_stream& s, my_map_type::value_type& row)
{
// std::map's key is const, which needs to be cast away
s>>const_cast<int&>(row.first);
s>>row.second;
return s;
}

// redefined operator<< for writing const my_map_type::value_type&
// into otl_stream
otl_stream& operator<<(otl_stream& s, const my_map_type::value_type& row)
{
s<<row.first<<row.second;
return s;
}
void insert() // insert rows into table { otl_stream o(50, // buffer size
"insert into test_tab values(:f1<int>,:f2<char[31]>)",
// SQL statement
db // connect object
);

my_vector_type vo; // vector of rows
my_set_type so; // set of rows
my_map_type mo; // map of pairs<int,string>

// populate the vector
for(int i=1;i<=3;++i)
vo.push_back(my_row_class(i,"NameXXX"));

// insert the vector into the table
otl_write_to_stream(vo.begin(),vo.end(),o);

// populate the set
for(int i=4;i<=6;++i)
so.insert(my_row_class(i,"NameXXX"));

// insert the set into the table
otl_write_to_stream(so.begin(),so.end(),o);

// populate the set
for(int i=7;i<=10;++i)
mo[i]="NameXXX";

// insert the map into the table
otl_write_to_stream(mo.begin(),mo.end(),o);
} void select() { otl_stream i(50, // buffer size
"select * from test_tab where f1>=:f1<int> and f1<=:f11<int>*2",
// SELECT statement
db // connect object
);
// create select stream

my_vector_type v; // vector of rows
my_set_type s; // set of rows
my_map_type m;

// assigning :f1 = 4, :f11 = 4, and triggering an execution of the
// SELECT statement
i<<4<<4;

// read all rows to be fetched into the vector
otl_read_from_stream(i,back_inserter(v));

// print out the content of the vector
for(my_vector_type::const_iterator x=v.begin(); x!=v.end(); ++x)
cout<<"F1="<<(*x).f1<<", F2="<<(*x).f2<<endl;
cout<<"==========================="<<endl;

// assigning :f1 = 4, :f11 = 4, and triggering an execution of the
// SELECT statement
i<<4<<4;

// read all rows to be fetched into the set
otl_read_from_stream(i,inserter(s,s.end()));

// print out the content of the set
for(my_set_type::const_iterator x=s.begin(); x!=s.end(); ++x)
cout<<"F1="<<(*x).f1<<", F2="<<(*x).f2<<endl;
cout<<"==========================="<<endl;

// assigning :f1 = 4, :f11 = 4, and triggering an execution of the
// SELECT statement
i<<4<<4;

// read all rows to be fetched into the set
otl_read_from_stream(i,inserter(m,m.end()));

// print out the content of the set
for(my_map_type::const_iterator x=m.begin(); x!=m.end(); ++x)
cout<<"FIRST="<<(*x).first<<", SECOND="<<(*x).second<<endl;
cout<<"==========================="<<endl;
} int main() { otl_connect::otl_initialize(); // initialize the database API environment try{ db.rlogon("scott/tiger@postgresql"); // connect to the database otl_cursor::direct_exec ( db, "drop table test_tab", otl_exception::disabled // disable OTL exceptions ); // drop table otl_cursor::direct_exec ( db, "create table test_tab(f1 int, f2 varchar(30))" ); // create table insert(); // insert records into table select(); // select records from table } catch(otl_exception& p){ // intercept OTL exceptions cerr<<p.msg<<endl; // print out error message cerr<<p.stm_text<<endl; // print out SQL that caused the error cerr<<p.var_info<<endl; // print out the variable that caused the error } db.logoff(); // disconnect from the database return 0; }

Output

F1=4, F2=NameXXX
F1=5, F2=NameXXX
F1=6, F2=NameXXX
F1=7, F2=NameXXX
F1=8, F2=NameXXX
===========================
F1=4, F2=NameXXX
F1=5, F2=NameXXX
F1=6, F2=NameXXX
F1=7, F2=NameXXX
F1=8, F2=NameXXX
===========================
FIRST=4, SECOND=NameXXX
FIRST=5, SECOND=NameXXX
FIRST=6, SECOND=NameXXX
FIRST=7, SECOND=NameXXX
FIRST=8, SECOND=NameXXX
===========================

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Copyright 1996-2017, Sergei Kuchin, email: skuchin@gmail.com.

Permission to use, copy, modify and redistribute this document for any purpose is hereby granted without fee, provided that the above copyright notice appear in all copies. THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.