Author: gonwan

Coroutines in Python

January 11, 2016 by gonwan·0 Comments

Python 3.5 added native support for coroutines. Actually, there were several steps towards the current implementation. See Wikipedia, and it seems a bit messy to me:

Python 2.5 implements better support for coroutine-like functionality, based on extended generators (PEP 342).
Python 3.3 improves this ability, by supporting delegating to a subgenerator (PEP 380).
Python 3.4 introduces a comprehensive asynchronous I/O framework as standardized in PEP 3156, which includes coroutines that leverage subgenerator delegation.
Python 3.5 introduces explicit support for coroutines with async/await syntax (PEP 0492).

Before Python 2.5, there were only generators.

In Python 2.5, yield was refined to be an expression rather than a statement, which gave the possibility to implement a simple coroutine. But still a lot of work left for programmers to use it. For instance, a simple conroutine scheduler was required.

In Python 3.3, yield from was added to support subgenerators. Nothing to do with coroutines.

In Python 3.4, the Father of Python (Guido van Rossum) wrote a PEP himself to add an asyncio module to simplify coroutine usage in Python. An official scheduler was added. We can use @asyncio.coroutine to decorate a function. We can use yield from expressions to yield to a specific coroutine.

In Python 3.5, async/await syntax was added, borrowed from C#. The newest PEP made coroutines a native Python language feature, and clearly separated them from generators. A native coroutine now declares with async def syntax, and yield from is replaced with await expression. This removes generator/coroutine ambiguity. So in Python 3.5, coroutines used with asyncio may be implemented using the async def statement, or by using generators. Generator-based coroutines should be decorated with @asyncio.coroutine, although this is not strictly enforced. The decorator enables compatibility with async def coroutines, and also serves as documentation. See Python documents here.

The implementation can be found in this commit.

I wrote a echo server/client sample to try corutines. Server code first:

#!/usr/bin/python3
import asyncio

@asyncio.coroutine
def start_server():
    yield from asyncio.start_server(client_connected_handler, '127.0.0.1', 2222)

@asyncio.coroutine
def client_connected_handler(client_reader, client_writer):
    peer = client_writer.get_extra_info('peername')
    print('Connected..%s:%s' % (peer[0], peer[1]))
    while True:
        data = yield from client_reader.read(1024)
        if not data:
            print('Disconnected..%s:%s\n' % (peer[0], peer[1]))
            break
        print(data.decode(), end='')
        client_writer.write(data)

loop = asyncio.get_event_loop()
server = loop.run_until_complete(start_server())
try:
    loop.run_forever()
except KeyboardInterrupt:
    pass

server.close()
loop.run_until_complete(server.wait_closed())
loop.close()

#!/usr/bin/python3

import asyncio

@asyncio.coroutine

def start_server():

yield from asyncio.start_server(client_connected_handler, '127.0.0.1', 2222)

@asyncio.coroutine

def client_connected_handler(client_reader, client_writer):

peer = client_writer.get_extra_info('peername')

print('Connected..%s:%s' % (peer[0], peer[1]))

while True:

data = yield from client_reader.read(1024)

if not data:

print('Disconnected..%s:%s\n' % (peer[0], peer[1]))

break

print(data.decode(), end='')

client_writer.write(data)

loop = asyncio.get_event_loop()

server = loop.run_until_complete(start_server())

try:

loop.run_forever()

except KeyboardInterrupt:

pass

server.close()

loop.run_until_complete(server.wait_closed())

loop.close()

Client code here, or you can simply use telnet command:

#!/usr/bin/python3
import asyncio

@asyncio.coroutine
def tcp_echo_client():
    reader, writer = yield from asyncio.open_connection('127.0.0.1', 2222)
    writer.write(b'first line\n')
    writer.write(b'second line\n')
    writer.write(b'third line\n')
    writer.write(b'EOF\n')
    print("Lines received..")
    while True:
        line = yield from reader.readline()
        if not line:
            break
        line = line.decode()
        print(line, end='')
        if line == 'EOF\n':
            break
    writer.close()

loop = asyncio.get_event_loop()
loop.run_until_complete(tcp_echo_client())
loop.close()

#!/usr/bin/python3

import asyncio

@asyncio.coroutine

def tcp_echo_client():

reader, writer = yield from asyncio.open_connection('127.0.0.1', 2222)

writer.write(b'first line\n')

writer.write(b'second line\n')

writer.write(b'third line\n')

writer.write(b'EOF\n')

print("Lines received..")

while True:

line = yield from reader.readline()

if not line:

break

line = line.decode()

print(line, end='')

if line == 'EOF\n':

break

writer.close()

loop = asyncio.get_event_loop()

loop.run_until_complete(tcp_echo_client())

loop.close()

Server output:

Connected..127.0.0.1:27643
first line
second line
third line
EOF
Disconnected..127.0.0.1:27643

Connected..127.0.0.1:27643

first line

second line

third line

EOF

Disconnected..127.0.0.1:27643

Client output:

Lines received..
first line
second line
third line
EOF

Lines received..

first line

second line

third line

EOF

With Python 3.5 on Ubuntu 16.04, we can also use async/await:

#!/usr/bin/python3
import asyncio

async def start_server():
    await asyncio.start_server(client_connected_handler, '127.0.0.1', 2222)

async def client_connected_handler(client_reader, client_writer):
    peer = client_writer.get_extra_info('peername')
    print('Connected..%s:%s' % (peer[0], peer[1]))
    while True:
        data = await client_reader.read(1024)
        if not data:
            print('Disconnected..%s:%s\n' % (peer[0], peer[1]))
            break
        print(data.decode(), end='')
        client_writer.write(data)

loop = asyncio.get_event_loop()
server = loop.run_until_complete(start_server())
try:
    loop.run_forever()
except KeyboardInterrupt:
    pass

server.close()
loop.run_until_complete(server.wait_closed())
loop.close()

#!/usr/bin/python3

import asyncio

async def start_server():

await asyncio.start_server(client_connected_handler, '127.0.0.1', 2222)

async def client_connected_handler(client_reader, client_writer):

peer = client_writer.get_extra_info('peername')

print('Connected..%s:%s' % (peer[0], peer[1]))

while True:

data = await client_reader.read(1024)

if not data:

print('Disconnected..%s:%s\n' % (peer[0], peer[1]))

break

print(data.decode(), end='')

client_writer.write(data)

loop = asyncio.get_event_loop()

server = loop.run_until_complete(start_server())

try:

loop.run_forever()

except KeyboardInterrupt:

pass

server.close()

loop.run_until_complete(server.wait_closed())

loop.close()

Basic Usage of Boost MultiIndex Containers

December 28, 2015 by gonwan·0 Comments

Just take a simple note here.
The Boost Multi-index Containers Library provides a class template named multi_index_container which enables the construction of containers maintaining one or more indices with different sorting and access semantics.

#include <string>
#include <ostream>
#include <boost/multi_index_container.hpp>
#include <boost/multi_index/ordered_index.hpp>
#include <boost/multi_index/identity.hpp>
#include <boost/multi_index/member.hpp>
#include <boost/multi_index/tag.hpp>
#include <boost/lambda/lambda.hpp>
using namespace std;
using namespace boost::multi_index;


struct auth
{
    string m_name;
    string m_pass;
    auth(const string &name, const string &pass)
        : m_name(name), m_pass(pass) { }
    bool operator<(const auth &o) const { return m_name < o.m_name; }
    friend ostream &operator<<(ostream &os, const auth &a) { os << "(" << a.m_name << ", " << a.m_pass << ")"; return os; }
};

struct employee
{
    int m_id;
    auth m_auth;
    int m_hire;
    int m_resign;
    employee(int id, const string &name, const string &pass, int hire, int resign)
        : m_id(id), m_auth(name, pass), m_hire(hire), m_resign(resign) { }
    bool operator<(const employee &o) const { return m_id < o.m_id; }
    friend ostream &operator<<(ostream &os, const employee &e) { os << "(" << e.m_id << ", " << e.m_auth << ", " << e.m_hire << ", " << e.m_resign << ")"; return os; }
};


struct auth_t { };

struct change_resign {
    int m_resign;
    change_resign(int r) : m_resign(r) { }
    void operator()(employee &e) { e.m_resign = m_resign; }
};

typedef multi_index_container<
    employee,
    indexed_by<
        /* sort by employee::operator< */
        ordered_unique<identity<employee> >,
        /* sort by less<int> on m_hire */
        ordered_non_unique<member<employee, int, &employee::m_hire> >,
        /* sort by less<auth> on m_auth */
        ordered_non_unique<tag<auth_t>, member<employee, auth, &employee::m_auth> >
    >
> employee_set;

int main()
{
    employee_set es;
    es.insert(employee(1, "555", "555pass", 2012, 0));
    es.insert(employee(2, "444", "444pass", 2011, 0));
    es.insert(employee(3, "333", "333pass", 2013, 0));
    es.insert(employee(4, "222", "222pass", 2015, 0));
    es.insert(employee(5, "555", "555pass", 2014, 0)); /* dup */
    typedef employee_set::nth_index<1>::type hire_index_t;
    typedef employee_set::index<auth_t>::type auth_index_t;
    cout << "Get a view to index #1 (m_hire).." << endl;
    hire_index_t &hire_index = es.get<1>();
    std::copy(hire_index.begin(), hire_index.end(), ostream_iterator<employee>(cout, "\n"));
    cout << "Get a view to index tag auth_t (m_auth).." << endl;
    const auth_index_t &auth_index = es.get<auth_t>();
    std::copy(auth_index.begin(), auth_index.end(), ostream_iterator<employee>(cout, "\n"));
    cout << "Find.." << endl;
    hire_index_t::iterator it = hire_index.find(2015);
#if 0
    employee t = *it;
    t.m_resign = 2048;
    hire_index.replace(it, t);
#else
    hire_index.modify_key(it, boost::lambda::_1=1111);
    int old_resign = it->m_resign;
    hire_index.modify(it, change_resign(2048), change_resign(old_resign));
#endif
    cout << (*it) << endl;
    cout << "Find all.." << endl;
    pair<auth_index_t::const_iterator, auth_index_t::const_iterator> pr = auth_index.equal_range(auth("555", ""));
    std::copy(pr.first, pr.second, ostream_iterator<employee>(cout, "\n"));
    return 0;
}

#include <string>

#include <ostream>

#include <boost/multi_index_container.hpp>

#include <boost/multi_index/ordered_index.hpp>

#include <boost/multi_index/identity.hpp>

#include <boost/multi_index/member.hpp>

#include <boost/multi_index/tag.hpp>

#include <boost/lambda/lambda.hpp>

using namespace std;

using namespace boost::multi_index;

struct auth

{

string m_name;

string m_pass;

auth(const string &name, const string &pass)

: m_name(name), m_pass(pass) { }

bool operator<(const auth &o) const { return m_name < o.m_name; }

friend ostream &operator<<(ostream &os, const auth &a) { os << "(" << a.m_name << ", " << a.m_pass << ")"; return os; }

};

struct employee

{

int m_id;

auth m_auth;

int m_hire;

int m_resign;

employee(int id, const string &name, const string &pass, int hire, int resign)

: m_id(id), m_auth(name, pass), m_hire(hire), m_resign(resign) { }

bool operator<(const employee &o) const { return m_id < o.m_id; }

friend ostream &operator<<(ostream &os, const employee &e) { os << "(" << e.m_id << ", " << e.m_auth << ", " << e.m_hire << ", " << e.m_resign << ")"; return os; }

};

struct auth_t { };

struct change_resign {

int m_resign;

change_resign(int r) : m_resign(r) { }

void operator()(employee &e) { e.m_resign = m_resign; }

};

typedef multi_index_container<

employee,

indexed_by<

/* sort by employee::operator< */

ordered_unique<identity<employee> >,

/* sort by less<int> on m_hire */

ordered_non_unique<member<employee, int, &employee::m_hire> >,

/* sort by less<auth> on m_auth */

ordered_non_unique<tag<auth_t>, member<employee, auth, &employee::m_auth> >

> employee_set;

int main()

{

employee_set es;

es.insert(employee(1, "555", "555pass", 2012, 0));

es.insert(employee(2, "444", "444pass", 2011, 0));

es.insert(employee(3, "333", "333pass", 2013, 0));

es.insert(employee(4, "222", "222pass", 2015, 0));

es.insert(employee(5, "555", "555pass", 2014, 0)); /* dup */

typedef employee_set::nth_index<1>::type hire_index_t;

typedef employee_set::index<auth_t>::type auth_index_t;

cout << "Get a view to index #1 (m_hire).." << endl;

hire_index_t &hire_index = es.get<1>();

std::copy(hire_index.begin(), hire_index.end(), ostream_iterator<employee>(cout, "\n"));

cout << "Get a view to index tag auth_t (m_auth).." << endl;

const auth_index_t &auth_index = es.get<auth_t>();

std::copy(auth_index.begin(), auth_index.end(), ostream_iterator<employee>(cout, "\n"));

cout << "Find.." << endl;

hire_index_t::iterator it = hire_index.find(2015);

#if 0

employee t = *it;

t.m_resign = 2048;

hire_index.replace(it, t);

#else

hire_index.modify_key(it, boost::lambda::_1=1111);

int old_resign = it->m_resign;

hire_index.modify(it, change_resign(2048), change_resign(old_resign));

#endif

cout << (*it) << endl;

cout << "Find all.." << endl;

pair<auth_index_t::const_iterator, auth_index_t::const_iterator> pr = auth_index.equal_range(auth("555", ""));

std::copy(pr.first, pr.second, ostream_iterator<employee>(cout, "\n"));

return 0;

}

Output:

Get a view to index #1 (m_hire)..
(2, (444, 444pass), 2011, 0)
(1, (555, 555pass), 2012, 0)
(3, (333, 333pass), 2013, 0)
(5, (555, 555pass), 2014, 0)
(4, (222, 222pass), 2015, 0)
Get a view to index tag auth_t (m_auth)..
(4, (222, 222pass), 2015, 0)
(3, (333, 333pass), 2013, 0)
(2, (444, 444pass), 2011, 0)
(1, (555, 555pass), 2012, 0)
(5, (555, 555pass), 2014, 0)
Find..
(4, (222, 222pass), 1111, 2048)
Find all..
(1, (555, 555pass), 2012, 0)
(5, (555, 555pass), 2014, 0)

Get a view to index #1 (m_hire)..

(2, (444, 444pass), 2011, 0)

(1, (555, 555pass), 2012, 0)

(3, (333, 333pass), 2013, 0)

(5, (555, 555pass), 2014, 0)

(4, (222, 222pass), 2015, 0)

Get a view to index tag auth_t (m_auth)..

(4, (222, 222pass), 2015, 0)

(3, (333, 333pass), 2013, 0)

(2, (444, 444pass), 2011, 0)

(1, (555, 555pass), 2012, 0)

(5, (555, 555pass), 2014, 0)

Find..

(4, (222, 222pass), 1111, 2048)

Find all..

(1, (555, 555pass), 2012, 0)

(5, (555, 555pass), 2014, 0)

To use with pointer values, only limited change needed as highlighted:

#include <string>
#include <ostream>
#include <boost/multi_index_container.hpp>
#include <boost/multi_index/ordered_index.hpp>
#include <boost/multi_index/identity.hpp>
#include <boost/multi_index/member.hpp>
#include <boost/multi_index/tag.hpp>
#include <boost/lambda/lambda.hpp>
using namespace std;
using namespace boost::multi_index;


struct auth
{
    string m_name;
    string m_pass;
    auth(const string &name, const string &pass)
        : m_name(name), m_pass(pass) { }
    bool operator<(const auth &o) const { return m_name < o.m_name; }
    friend ostream &operator<<(ostream &os, const auth &a) { os << "(" << a.m_name << ", " << a.m_pass << ")"; return os; }
};

struct employee
{
    int m_id;
    auth m_auth;
    int m_hire;
    int m_resign;
    employee(int id, const string &name, const string &pass, int hire, int resign)
        : m_id(id), m_auth(name, pass), m_hire(hire), m_resign(resign) { }
    bool operator<(const employee &o) const { return m_id < o.m_id; }
    friend ostream &operator<<(ostream &os, const employee *e) { os << "(" << e->m_id << ", " << e->m_auth << ", " << e->m_hire << ", " << e->m_resign << ")"; return os; }
};


struct auth_t { };

struct change_resign {
    int m_resign;
    change_resign(int r) : m_resign(r) { }
    void operator()(employee *e) { e->m_resign = m_resign; }
};

typedef multi_index_container<
    employee *,
    indexed_by<
        /* sort by employee::operator< */
        ordered_unique<identity<employee> >,
        /* sort by less<int> on m_hire */
        ordered_non_unique<member<employee, int, &employee::m_hire> >,
        /* sort by less<auth> on m_auth */
        ordered_non_unique<tag<auth_t>, member<employee, auth, &employee::m_auth> >
    >
> employee_set;

int main()
{
    employee_set es;
    es.insert(new employee(1, "555", "555pass", 2012, 0));
    es.insert(new employee(2, "444", "444pass", 2011, 0));
    es.insert(new employee(3, "333", "333pass", 2013, 0));
    es.insert(new employee(4, "222", "222pass", 2015, 0));
    es.insert(new employee(5, "555", "555pass", 2014, 0)); /* dup */
    typedef employee_set::nth_index<1>::type hire_index_t;
    typedef employee_set::index<auth_t>::type auth_index_t;
    cout << "Get a view to index #1 (m_hire).." << endl;
    hire_index_t &hire_index = es.get<1>();
    std::copy(hire_index.begin(), hire_index.end(), ostream_iterator<employee *>(cout, "\n"));
    cout << "Get a view to index tag auth_t (m_auth).." << endl;
    const auth_index_t &auth_index = es.get<auth_t>();
    std::copy(auth_index.begin(), auth_index.end(), ostream_iterator<employee *>(cout, "\n"));
    cout << "Find.." << endl;
    hire_index_t::iterator it = hire_index.find(2015);
#if 0
    employee *t = *it;
    t->m_auth.m_name = "888";
    /* must use replace() to notify changes in indexed fields */
    hire_index.replace(it, t);
#else
    hire_index.modify_key(it, boost::lambda::_1=1111);
    int old_resign = (*it)->m_resign;
    hire_index.modify(it, change_resign(2048), change_resign(old_resign));
#endif
    cout << (*it) << endl;
    cout << "Find all.." << endl;
    pair<auth_index_t::const_iterator, auth_index_t::const_iterator> pr = auth_index.equal_range(auth("555", ""));
    std::copy(pr.first, pr.second, ostream_iterator<employee *>(cout, "\n"));
    /* clear */
    for (employee_set::const_iterator it = es.begin(); it != es.end(); ++it) {
        delete *it;
    }
    employee_set().swap(es);
    return 0;
}

#include <string>

#include <ostream>

#include <boost/multi_index_container.hpp>

#include <boost/multi_index/ordered_index.hpp>

#include <boost/multi_index/identity.hpp>

#include <boost/multi_index/member.hpp>

#include <boost/multi_index/tag.hpp>

#include <boost/lambda/lambda.hpp>

using namespace std;

using namespace boost::multi_index;

struct auth

{

string m_name;

string m_pass;

auth(const string &name, const string &pass)

: m_name(name), m_pass(pass) { }

bool operator<(const auth &o) const { return m_name < o.m_name; }

friend ostream &operator<<(ostream &os, const auth &a) { os << "(" << a.m_name << ", " << a.m_pass << ")"; return os; }

};

struct employee

{

int m_id;

auth m_auth;

int m_hire;

int m_resign;

employee(int id, const string &name, const string &pass, int hire, int resign)

: m_id(id), m_auth(name, pass), m_hire(hire), m_resign(resign) { }

bool operator<(const employee &o) const { return m_id < o.m_id; }

friend ostream &operator<<(ostream &os, const employee *e) { os << "(" << e->m_id << ", " << e->m_auth << ", " << e->m_hire << ", " << e->m_resign << ")"; return os; }

};

struct auth_t { };

struct change_resign {

int m_resign;

change_resign(int r) : m_resign(r) { }

void operator()(employee *e) { e->m_resign = m_resign; }

};

typedef multi_index_container<

employee *,

indexed_by<

/* sort by employee::operator< */

ordered_unique<identity<employee> >,

/* sort by less<int> on m_hire */

ordered_non_unique<member<employee, int, &employee::m_hire> >,

/* sort by less<auth> on m_auth */

ordered_non_unique<tag<auth_t>, member<employee, auth, &employee::m_auth> >

> employee_set;

int main()

{

employee_set es;

es.insert(new employee(1, "555", "555pass", 2012, 0));

es.insert(new employee(2, "444", "444pass", 2011, 0));

es.insert(new employee(3, "333", "333pass", 2013, 0));

es.insert(new employee(4, "222", "222pass", 2015, 0));

es.insert(new employee(5, "555", "555pass", 2014, 0)); /* dup */

typedef employee_set::nth_index<1>::type hire_index_t;

typedef employee_set::index<auth_t>::type auth_index_t;

cout << "Get a view to index #1 (m_hire).." << endl;

hire_index_t &hire_index = es.get<1>();

std::copy(hire_index.begin(), hire_index.end(), ostream_iterator<employee *>(cout, "\n"));

cout << "Get a view to index tag auth_t (m_auth).." << endl;

const auth_index_t &auth_index = es.get<auth_t>();

std::copy(auth_index.begin(), auth_index.end(), ostream_iterator<employee *>(cout, "\n"));

cout << "Find.." << endl;

hire_index_t::iterator it = hire_index.find(2015);

#if 0

employee *t = *it;

t->m_auth.m_name = "888";

/* must use replace() to notify changes in indexed fields */

hire_index.replace(it, t);

#else

hire_index.modify_key(it, boost::lambda::_1=1111);

int old_resign = (*it)->m_resign;

hire_index.modify(it, change_resign(2048), change_resign(old_resign));

#endif

cout << (*it) << endl;

cout << "Find all.." << endl;

pair<auth_index_t::const_iterator, auth_index_t::const_iterator> pr = auth_index.equal_range(auth("555", ""));

std::copy(pr.first, pr.second, ostream_iterator<employee *>(cout, "\n"));

/* clear */

for (employee_set::const_iterator it = es.begin(); it != es.end(); ++it) {

delete *it;

}

employee_set().swap(es);

return 0;

}

Enabing Pretty Permalinks

December 28, 2015 by gonwan·0 Comments

Well.. long time no see. Just have some time to optimize the site for better analysis.

According to the official tutorial:
1. Enable mod_rewrite in apache2.

# sudo a2enmod rewrite

1	# sudo a2enmod rewrite

2. Enable FollowSymLinks option, which is default.
3. Enable FileInfo directives. Edit /etc/apache2/sites-available/yoursite.com.conf, add:

  <Directory /home/yourname/yoursite/>
    Require all granted
    AllowOverride FileInfo
  </Directory>

Require all granted

AllowOverride FileInfo

</Directory>

4. Restart apache:

# sudo service apache2 restart

1	# sudo service apache2 restart

Updated Dec 31, 2015:
Enabling mod_rewrite rewrites all requests including the one used by mod_status. To disable this, add a rule to the .htaccess file.

RewriteCond %{REQUEST_URI} !=/server-status

1	RewriteCond %{REQUEST_URI} !=/server-status

Then, change its user & group attributes to prevent overwriting from apache.

3 New Plugins Installed

July 8, 2015 by gonwan·0 Comments

Just added another personal site for one of my friends. So another chance to speed up loading for my own site, from mainland china >.<

1. Disable google fonts: Remove Google Fonts References

2. Use local avatar: WP User Avatar

3. Use local emoji: WP Local Emoji (installed, but not activated.)

Database Access Layer in C++

April 15, 2015 by gonwan·0 Comments

We have JDBC in Java… and SOCI in C++… Well, it’s not so easy as it should be. To build with cmake:

# mkdir ../build
# cd ../build
# set ORACLE_HOME=C:\oraclexe\app\oracle\product\10.2.0\server
# cmake -G "Visual Studio 9 2008" -DMYSQL_INCLUDE_DIR="C:\Program Files\MySQL\MySQL Server 5.5\include" -DMYSQL_LIBRARIES="C:\Program Files\MySQL\MySQL Server 5.5\lib\libmysql.lib" ../soci-3.2.3

# mkdir ../build

# cd ../build

# set ORACLE_HOME=C:\oraclexe\app\oracle\product\10.2.0\server

# cmake -G "Visual Studio 9 2008" -DMYSQL_INCLUDE_DIR="C:\Program Files\MySQL\MySQL Server 5.5\include" -DMYSQL_LIBRARIES="C:\Program Files\MySQL\MySQL Server 5.5\lib\libmysql.lib" ../soci-3.2.3

The documents seem outdated, many options do not work. Just managed to figure out from the *.cmake source files. You can also download the oracle instant client SDK, and re-arrange the directory structure for build.

Code snippet I extracted from its unit tests:

#include "soci.h"
#include "soci-mysql.h"
//#include "soci-oracle.h"
#include <ctime>
#include <string>
#include <iostream>
#include <sstream>
using namespace std;

int main()
{
    try {
        soci::session sql(soci::mysql, "host=192.168.1.101 db=mysql user=root password=111111");
        //soci::session sql(soci::oracle, "service=192.168.1.102/ORCL user=sys password=111111");
        soci::row v;
        /* comma operator is overloaded here.. */
        soci::statement st = (sql.prepare << "SELECT * FROM user", into(v));
        //soci::statement st = (sql.prepare << "SELECT * FROM SYS.USER$", into(v));
        st.execute(true);  /* with data exchange */
        unsigned int num_fields = v.size();
        cout << "fields: " << num_fields << endl;
        num_fields = (num_fields <= 9) ? num_fields : 9;
        unsigned long num_rows = (unsigned long)st.get_affected_rows();
        cout << "rows: " << num_rows << endl;
        for (size_t i = 0; i < num_fields; ++i) {
            const soci::column_properties &props = v.get_properties(i);
            cout << props.get_name() << '\t';
        }
        cout << endl;
        do {
            stringstream ss;
            for (size_t i = 0; i < num_fields; ++i) {
                if (v.get_indicator(i) == soci::i_null) {
                    ss << "NULL";
                    break;
                }
                const soci::column_properties &props = v.get_properties(i);
                switch (props.get_data_type()) {
                case soci::dt_string:
                    ss << v.get<string>(i);
                    break;
                case soci::dt_double:
                    ss << v.get<double>(i);
                    break;
                case soci::dt_integer:
                    ss << v.get<int>(i);
                    break;
                case soci::dt_long_long:
                    ss << v.get<long long>(i);
                    break;
                case soci::dt_unsigned_long_long:
                    ss << v.get<unsigned long long>(i);
                    break;
                case soci::dt_date:
                    tm dt = v.get<tm>(i);
                    ss << asctime(&dt);
                    break;
                }
                ss << '\t';
            }
            cout << ss.str() << endl;
        } while (st.fetch());
    } catch (soci::soci_error &e) {
        cerr << "Error: " << e.what() << endl;
    }
    return 0;
}

#include "soci.h"

#include "soci-mysql.h"

//#include "soci-oracle.h"

#include <ctime>

#include <string>

#include <iostream>

#include <sstream>

using namespace std;

int main()

{

try {

soci::session sql(soci::mysql, "host=192.168.1.101 db=mysql user=root password=111111");

//soci::session sql(soci::oracle, "service=192.168.1.102/ORCL user=sys password=111111");

soci::row v;

/* comma operator is overloaded here.. */

soci::statement st = (sql.prepare << "SELECT * FROM user", into(v));

//soci::statement st = (sql.prepare << "SELECT * FROM SYS.USER$", into(v));

st.execute(true); /* with data exchange */

unsigned int num_fields = v.size();

cout << "fields: " << num_fields << endl;

num_fields = (num_fields <= 9) ? num_fields : 9;

unsigned long num_rows = (unsigned long)st.get_affected_rows();

cout << "rows: " << num_rows << endl;

for (size_t i = 0; i < num_fields; ++i) {

const soci::column_properties &props = v.get_properties(i);

cout << props.get_name() << '\t';

}

cout << endl;

do {

stringstream ss;

for (size_t i = 0; i < num_fields; ++i) {

if (v.get_indicator(i) == soci::i_null) {

ss << "NULL";

break;

}

const soci::column_properties &props = v.get_properties(i);

switch (props.get_data_type()) {

case soci::dt_string:

ss << v.get<string>(i);

break;

case soci::dt_double:

ss << v.get<double>(i);

break;

case soci::dt_integer:

ss << v.get<int>(i);

break;

case soci::dt_long_long:

ss << v.get<long long>(i);

break;

case soci::dt_unsigned_long_long:

ss << v.get<unsigned long long>(i);

break;

case soci::dt_date:

tm dt = v.get<tm>(i);

ss << asctime(&dt);

break;

}

ss << '\t';

}

cout << ss.str() << endl;

} while (st.fetch());

} catch (soci::soci_error &e) {

cerr << "Error: " << e.what() << endl;

}

return 0;

}

Updated Apr 20, 2015:

1. Under RHEL5/CentOS5, I got errors like:

./test_oracle: error while loading shared libraries: /home/gonwan/oracle11_64/lib/libnnz11.so: cannot restore segment prot after reloc: Permission denied

1	./test_oracle: error while loading shared libraries: /home/gonwan/oracle11_64/lib/libnnz11.so: cannot restore segment prot after reloc: Permission denied

It’s due to SELinux security feature. Simply workaround it with:

# chcon -t texrel_shlib_t *.so*

1	# chcon -t texrel_shlib_t .so

2. Oracle uses oraociei11.dll or libociei.so for client data. They are both large files(110+MB), since they support multiple languages. Instead, you can use oraociicus11.dll(30+MB) or libociicus.so(10-MB). These files contain only English support.

0x2B|~0x2B

My broken wings still strong enough to cross the ocean with.

Author: gonwan

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Database Access Layer in C++