Category: C/C++

Using vcpkg for C++ Package Management

September 28, 2022 by gonwan·0 Comments

Verified on CentOS7 and Windows 10.

1. Install v2ray and run proxy

nohup ./v2ray run config.json &
export http_proxy="socks5://localhost:xxxxx"
export https_proxy="socks5://localhost:xxxxx"

nohup ./v2ray run config.json &

export http_proxy="socks5://localhost:xxxxx"

export https_proxy="socks5://localhost:xxxxx"

v2ray unblocks github access from mainland China. Install v2ray clients and set IE proxy _only_ on Windows, bootstrap.bat & vcpkg.exe picks it automatically.

2. Download vcpkg from github and bootstrap

Download from: https://github.com/microsoft/vcpkg/releases

cd vcpkg-2022.08.15
./bootstrap-vcpkg.sh

1 2	cd vcpkg-2022.08.15 ./bootstrap-vcpkg.sh

Export vcpkg-2022.08.15 directory as ${VCPKG_ROOT}.

3. Install drogon framework for demo

The drogon framework is a high performance application framework, including client & server supports. vcpkg builds static(*.a) library by default, use x64-linux-dynamic for dynamic(*.so) library. The repo version requires g++-8 to build, install from CentOS SCL:

yum install centos-release-scl
yum install devtoolset-8
echo '. /opt/rh/devtoolset-8/enable' | tee -a /etc/profile
. /etc/profile
# export CC=/opt/rh/devtoolset-8/root/usr/bin/gcc
# export CXX=/opt/rh/devtoolset-8/root/usr/bin/g++

yum install centos-release-scl

yum install devtoolset-8

echo '. /opt/rh/devtoolset-8/enable' | tee -a /etc/profile

. /etc/profile

# export CC=/opt/rh/devtoolset-8/root/usr/bin/gcc

# export CXX=/opt/rh/devtoolset-8/root/usr/bin/g++

To build with g++-7, manually install boost-filesystem package, and edit ${VCPKG_ROOT}/ports/drogon/portfile.cmake and comment out:

...
    #-DCMAKE_DISABLE_FIND_PACKAGE_Boost=ON
...

...

#-DCMAKE_DISABLE_FIND_PACKAGE_Boost=ON

...

On Windows, open the command line for Visual Studio develop environment.

./vcpkg search drogon
# linux, drogon[postgres] dynamic build is not well supported on linux
./vcpkg install drogon[ctl,mysql,orm,redis] --triplet=x64-linux-dynamic
# windows
vcpkg install drogon[ctl,mysql,orm,redis] --triplet=x64-windows

./vcpkg search drogon

# linux, drogon[postgres] dynamic build is not well supported on linux

./vcpkg install drogon[ctl,mysql,orm,redis] --triplet=x64-linux-dynamic

# windows

vcpkg install drogon[ctl,mysql,orm,redis] --triplet=x64-windows

If openssl build fails, run:

yum install perl-IPC-Cmd perl-Data-Dumper

1	yum install perl-IPC-Cmd perl-Data-Dumper

If other errors, try to update to recent github ports. In my case, libmariadb build failed, that have been fixed in master.

4. Export drogon framework

./vcpkg export drogon:x64-linux-dynamic --zip
# Zip archive exported at: ${VCPKG_ROOT}/vcpkg-export-20220928-102415.zip
# To use the exported libraries in CMake projects use:
#    -DCMAKE_TOOLCHAIN_FILE=[...]/scripts/buildsystems/vcpkg.cmake

./vcpkg export drogon:x64-linux-dynamic --zip

# Zip archive exported at: ${VCPKG_ROOT}/vcpkg-export-20220928-102415.zip

# To use the exported libraries in CMake projects use:

# -DCMAKE_TOOLCHAIN_FILE=[...]/scripts/buildsystems/vcpkg.cmake

5. Add a demo program

// drogon_server.cpp
#include <drogon/drogon.h>
using namespace drogon;

int main()
{
    app().registerHandler(
        "/text",
        [](const HttpRequestPtr &,
           std::function<void(const HttpResponsePtr &)> &&callback) {
            auto resp = HttpResponse::newHttpResponse();
            resp->setBody("Hello World!");
            callback(resp);
        },
        {Get});
    app().registerHandler(
        "/json",
        [](const HttpRequestPtr &,
           std::function<void(const HttpResponsePtr &)> &&callback) {
            Json::Value json;
            json["Message"] = "Hello World!";
            auto resp = HttpResponse::newHttpJsonResponse(json);
            callback(resp);
        },
        {Get});
    LOG_INFO << "Server running on 0.0.0.0:8099";
    app().addListener("0.0.0.0", 8099)
         .setThreadNum(24)
         .enableServerHeader(false)
         .enableDateHeader(false)
         //.enableRunAsDaemon()
         .run();
}

// drogon_server.cpp

#include <drogon/drogon.h>

using namespace drogon;

int main()

{

app().registerHandler(

"/text",

[](const HttpRequestPtr &,

std::function<void(const HttpResponsePtr &)> &&callback) {

auto resp = HttpResponse::newHttpResponse();

resp->setBody("Hello World!");

callback(resp);

{Get});

app().registerHandler(

"/json",

[](const HttpRequestPtr &,

std::function<void(const HttpResponsePtr &)> &&callback) {

Json::Value json;

json["Message"] = "Hello World!";

auto resp = HttpResponse::newHttpJsonResponse(json);

callback(resp);

{Get});

LOG_INFO << "Server running on 0.0.0.0:8099";

app().addListener("0.0.0.0", 8099)

.setThreadNum(24)

.enableServerHeader(false)

.enableDateHeader(false)

//.enableRunAsDaemon()

.run();

}

# CMakeLists.txt
cmake_minimum_required(VERSION 3.15)
project(drogon_server CXX)
set(CMAKE_CXX_STANDARD 17)
message("Got CMAKE_PREFIX_PATH: ${CMAKE_PREFIX_PATH}")
find_package(Drogon CONFIG REQUIRED)
add_executable(drogon_server drogon_server.cpp)
target_link_libraries(drogon_server PRIVATE Drogon::Drogon)

# CMakeLists.txt

cmake_minimum_required(VERSION 3.15)

project(drogon_server CXX)

set(CMAKE_CXX_STANDARD 17)

message("Got CMAKE_PREFIX_PATH: ${CMAKE_PREFIX_PATH}")

find_package(Drogon CONFIG REQUIRED)

add_executable(drogon_server drogon_server.cpp)

target_link_libraries(drogon_server PRIVATE Drogon::Drogon)

Linux dynamic build is community supported, invoke cmake with:

# linux
cmake -B build -S . -DCMAKE_TOOLCHAIN_FILE=${VCPKG_ROOT}/scripts/buildsystems/vcpkg.cmake -DVCPKG_TARGET_TRIPLET=x64-linux-dynamic
# windows
cmake -B build -S . -DCMAKE_TOOLCHAIN_FILE=${VCPKG_ROOT}/scripts/buildsystems/vcpkg.cmake -DVCPKG_TARGET_TRIPLET=x64-windows

# linux

cmake -B build -S . -DCMAKE_TOOLCHAIN_FILE=${VCPKG_ROOT}/scripts/buildsystems/vcpkg.cmake -DVCPKG_TARGET_TRIPLET=x64-linux-dynamic

# windows

cmake -B build -S . -DCMAKE_TOOLCHAIN_FILE=${VCPKG_ROOT}/scripts/buildsystems/vcpkg.cmake -DVCPKG_TARGET_TRIPLET=x64-windows

Now build with make or Visual Studio.

6. Stick to a specific version

add a vcpkg.json file:

{
  "name": "drogon-server",
  "version-string": "0.1.0",
  "dependencies": [
    { "name": "drogon", "version>=": "1.7.5", "features": [ "ctl", "mysql", "orm", "redis" ] },
    "openssl"
  ],
  "overrides": [
    { "name": "drogon", "version": "1.8.0" },
    { "name": "openssl", "version-string": "1.1.1n#1" }
  ],
  "builtin-baseline": "4e73d1b47a7e5428e2ea9dbec43b136a6632a7cb"
}

{

"name": "drogon-server",

"version-string": "0.1.0",

"dependencies": [

{ "name": "drogon", "version>=": "1.7.5", "features": [ "ctl", "mysql", "orm", "redis" ] },

"openssl"

"overrides": [

{ "name": "drogon", "version": "1.8.0" },

{ "name": "openssl", "version-string": "1.1.1n#1" }

"builtin-baseline": "4e73d1b47a7e5428e2ea9dbec43b136a6632a7cb"

}

It sticks to drogon 1.8.0 and openssl 1.1.1n. ${VCPKG_ROOT} now required to be a git repository. In your project directory, install specific versions of libraries by running:

# linux
./vcpkg --feature-flags="versions" install --triplet=x64-linux-dynamic
# windows
vcpkg --feature-flags="versions" install --triplet=x64-windows

# linux

./vcpkg --feature-flags="versions" install --triplet=x64-linux-dynamic

# windows

vcpkg --feature-flags="versions" install --triplet=x64-windows

Run cmake:

# linux
cmake -B build -S . -DCMAKE_TOOLCHAIN_FILE=${VCPKG_ROOT}/scripts/buildsystems/vcpkg.cmake -DVCPKG_TARGET_TRIPLET=x64-linux-dynamic
# windows
cmake -B build -S . -DCMAKE_TOOLCHAIN_FILE=${VCPKG_ROOT}/scripts/buildsystems/vcpkg.cmake -DVCPKG_TARGET_TRIPLET=x64-windows
cd build
make

# linux

cmake -B build -S . -DCMAKE_TOOLCHAIN_FILE=${VCPKG_ROOT}/scripts/buildsystems/vcpkg.cmake -DVCPKG_TARGET_TRIPLET=x64-linux-dynamic

# windows

cmake -B build -S . -DCMAKE_TOOLCHAIN_FILE=${VCPKG_ROOT}/scripts/buildsystems/vcpkg.cmake -DVCPKG_TARGET_TRIPLET=x64-windows

cd build

make

Now ldd output shows openssl 1.1 (default build is 3.0):

ldd drogon_server
        linux-vdso.so.1 =>  (0x00007ffc1bf9c000)
        libdrogon.so.1 => ./vcpkg_installed/x64-linux-dynamic/debug/lib/libdrogon.so.1 (0x00007fbbd2329000)
        libtrantor.so.1 => ./vcpkg_installed/x64-linux-dynamic/debug/lib/libtrantor.so.1 (0x00007fbbd1ea0000)
        libpthread.so.0 => /lib64/libpthread.so.0 (0x00007fbbd1c84000)
        libjsoncpp.so.25 => ./vcpkg_installed/x64-linux-dynamic/debug/lib/libjsoncpp.so.25 (0x00007fbbd19ed000)
        libstdc++.so.6 => /lib64/libstdc++.so.6 (0x00007fbbd16e5000)
        libm.so.6 => /lib64/libm.so.6 (0x00007fbbd13e3000)
        libgcc_s.so.1 => /lib64/libgcc_s.so.1 (0x00007fbbd11cd000)
        libc.so.6 => /lib64/libc.so.6 (0x00007fbbd0dff000)
        libdl.so.2 => /lib64/libdl.so.2 (0x00007fbbd0bfb000)
        libmariadb.so.3 => ./vcpkg_installed/x64-linux-dynamic/debug/lib/libmariadb.so.3 (0x00007fbbd098d000)
        libz.so.1 => ./vcpkg_installed/x64-linux-dynamic/debug/lib/libz.so.1 (0x00007fbbd0769000)
        libssl.so.1.1 => ./vcpkg_installed/x64-linux-dynamic/debug/lib/libssl.so.1.1 (0x00007fbbd04d1000)
        libcrypto.so.1.1 => ./vcpkg_installed/x64-linux-dynamic/debug/lib/libcrypto.so.1.1 (0x00007fbbcffd7000)
        libbrotlidec.so.1 => ./vcpkg_installed/x64-linux-dynamic/debug/lib/libbrotlidec.so.1 (0x00007fbbcfdb6000)
        libbrotlienc.so.1 => ./vcpkg_installed/x64-linux-dynamic/debug/lib/libbrotlienc.so.1 (0x00007fbbcf85c000)
        libbrotlicommon.so.1 => ./vcpkg_installed/x64-linux-dynamic/debug/lib/libbrotlicommon.so.1 (0x00007fbbcf63a000)
        libhiredis.so.1.0.0 => ./vcpkg_installed/x64-linux-dynamic/debug/lib/libhiredis.so.1.0.0 (0x00007fbbcf424000)
        /lib64/ld-linux-x86-64.so.2 (0x00007fbbd2ebc000)
        libcares.so.2 => ./vcpkg_installed/x64-linux-dynamic/debug/lib/libcares.so.2 (0x00007fbbcf205000)

ldd drogon_server

linux-vdso.so.1 => (0x00007ffc1bf9c000)

libdrogon.so.1 => ./vcpkg_installed/x64-linux-dynamic/debug/lib/libdrogon.so.1 (0x00007fbbd2329000)

libtrantor.so.1 => ./vcpkg_installed/x64-linux-dynamic/debug/lib/libtrantor.so.1 (0x00007fbbd1ea0000)

libpthread.so.0 => /lib64/libpthread.so.0 (0x00007fbbd1c84000)

libjsoncpp.so.25 => ./vcpkg_installed/x64-linux-dynamic/debug/lib/libjsoncpp.so.25 (0x00007fbbd19ed000)

libstdc++.so.6 => /lib64/libstdc++.so.6 (0x00007fbbd16e5000)

libm.so.6 => /lib64/libm.so.6 (0x00007fbbd13e3000)

libgcc_s.so.1 => /lib64/libgcc_s.so.1 (0x00007fbbd11cd000)

libc.so.6 => /lib64/libc.so.6 (0x00007fbbd0dff000)

libdl.so.2 => /lib64/libdl.so.2 (0x00007fbbd0bfb000)

libmariadb.so.3 => ./vcpkg_installed/x64-linux-dynamic/debug/lib/libmariadb.so.3 (0x00007fbbd098d000)

libz.so.1 => ./vcpkg_installed/x64-linux-dynamic/debug/lib/libz.so.1 (0x00007fbbd0769000)

libssl.so.1.1 => ./vcpkg_installed/x64-linux-dynamic/debug/lib/libssl.so.1.1 (0x00007fbbd04d1000)

libcrypto.so.1.1 => ./vcpkg_installed/x64-linux-dynamic/debug/lib/libcrypto.so.1.1 (0x00007fbbcffd7000)

libbrotlidec.so.1 => ./vcpkg_installed/x64-linux-dynamic/debug/lib/libbrotlidec.so.1 (0x00007fbbcfdb6000)

libbrotlienc.so.1 => ./vcpkg_installed/x64-linux-dynamic/debug/lib/libbrotlienc.so.1 (0x00007fbbcf85c000)

libbrotlicommon.so.1 => ./vcpkg_installed/x64-linux-dynamic/debug/lib/libbrotlicommon.so.1 (0x00007fbbcf63a000)

libhiredis.so.1.0.0 => ./vcpkg_installed/x64-linux-dynamic/debug/lib/libhiredis.so.1.0.0 (0x00007fbbcf424000)

/lib64/ld-linux-x86-64.so.2 (0x00007fbbd2ebc000)

libcares.so.2 => ./vcpkg_installed/x64-linux-dynamic/debug/lib/libcares.so.2 (0x00007fbbcf205000)

The only difference is the existence of vcpkg.json file, when using versioning.

7. Binary caching

If you change the root path of vcpkg, better clean up the cache, or build may fail. It’s $HOME/.cache/vcpkg/archives under Linux, and %LOCALAPPDATA%\vcpkg\archives under Windows.

Coroutines in C++/Boost

January 19, 2016 by gonwan·0 Comments

Starting with 1.56, boost/asio provides asio::spawn() to work with coroutines. Just paste the sample code here, with minor modifications:

#include <boost/asio.hpp>
#include <boost/asio/spawn.hpp>
#include <boost/bind.hpp>
#include <boost/shared_ptr.hpp>
#include <boost/enable_shared_from_this.hpp>
#include <iostream>
using namespace std;
using boost::asio::ip::tcp;


class session: public boost::enable_shared_from_this<session>
{
public:
    explicit session(boost::asio::io_service &io_service)
        : socket_(io_service), timer_(io_service), strand_(io_service)
    {
    }
    tcp::socket &socket()
    {
        return socket_;
    }
    void go()
    {
        boost::asio::spawn(strand_, boost::bind(&session::echo, shared_from_this(), _1));
        boost::asio::spawn(strand_, boost::bind(&session::timeout, shared_from_this(), _1));
    }
private:
    void echo(boost::asio::yield_context yield)
    {
        try {
            char data[128];
            while (true) {
                timer_.expires_from_now(boost::posix_time::seconds(10));
                size_t n = socket_.async_read_some(boost::asio::buffer(data), yield);
                boost::asio::async_write(socket_, boost::asio::buffer(data, n), yield);
            }
        } catch (exception &) {
            socket_.close();
            timer_.cancel();
        }
    }
    void timeout(boost::asio::yield_context yield)
    {
        while (socket_.is_open()) {
            boost::system::error_code ignored_ec;
            timer_.async_wait(yield[ignored_ec]);
            if (timer_.expires_from_now() <= boost::posix_time::seconds(0)) {
                socket_.close();
            }
        }
    }
    tcp::socket socket_;
    boost::asio::deadline_timer timer_;
    boost::asio::io_service::strand strand_;
};

void do_accept(boost::asio::io_service &io_service, unsigned short port, boost::asio::yield_context yield)
{
    tcp::acceptor acceptor(io_service, tcp::endpoint(tcp::v4(), port));
    while (true) {
        boost::system::error_code ec;
        boost::shared_ptr<session> new_session(new session(io_service));
        acceptor.async_accept(new_session->socket(), yield[ec]);
        if (!ec) {
            new_session->go();
        }
    }
}

int main()
{
    try {
        boost::asio::io_service io_service;
        boost::asio::spawn(io_service, boost::bind(do_accept, boost::ref(io_service), 2222, _1));
        io_service.run();
    } catch (exception &e) {
        cerr << "Exception: " << e.what() << endl;
    }
    return 0;
}

#include <boost/asio.hpp>

#include <boost/asio/spawn.hpp>

#include <boost/bind.hpp>

#include <boost/shared_ptr.hpp>

#include <boost/enable_shared_from_this.hpp>

#include <iostream>

using namespace std;

using boost::asio::ip::tcp;

class session: public boost::enable_shared_from_this<session>

{

public:

explicit session(boost::asio::io_service &io_service)

: socket_(io_service), timer_(io_service), strand_(io_service)

{

}

tcp::socket &socket()

{

return socket_;

}

void go()

{

boost::asio::spawn(strand_, boost::bind(&session::echo, shared_from_this(), _1));

boost::asio::spawn(strand_, boost::bind(&session::timeout, shared_from_this(), _1));

}

private:

void echo(boost::asio::yield_context yield)

{

try {

char data[128];

while (true) {

timer_.expires_from_now(boost::posix_time::seconds(10));

size_t n = socket_.async_read_some(boost::asio::buffer(data), yield);

boost::asio::async_write(socket_, boost::asio::buffer(data, n), yield);

}

} catch (exception &) {

socket_.close();

timer_.cancel();

}

void timeout(boost::asio::yield_context yield)

{

while (socket_.is_open()) {

boost::system::error_code ignored_ec;

timer_.async_wait(yield[ignored_ec]);

if (timer_.expires_from_now() <= boost::posix_time::seconds(0)) {

socket_.close();

}

tcp::socket socket_;

boost::asio::deadline_timer timer_;

boost::asio::io_service::strand strand_;

};

void do_accept(boost::asio::io_service &io_service, unsigned short port, boost::asio::yield_context yield)

{

tcp::acceptor acceptor(io_service, tcp::endpoint(tcp::v4(), port));

while (true) {

boost::system::error_code ec;

boost::shared_ptr<session> new_session(new session(io_service));

acceptor.async_accept(new_session->socket(), yield[ec]);

if (!ec) {

new_session->go();

}

int main()

{

try {

boost::asio::io_service io_service;

boost::asio::spawn(io_service, boost::bind(do_accept, boost::ref(io_service), 2222, _1));

io_service.run();

} catch (exception &e) {

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

}

return 0;

}

The Python in my previous article can be used to work with the code above. I also tried to write a TCP server with only boost::coroutines classes. select() is used, since I want the code to be platform independent. NOTE: with coroutines, we have only _one_ thread.

#ifdef _WIN32
#include <winsock2.h>
#include <ws2tcpip.h>
#include <windows.h>
#pragma comment(lib, "ws2_32.lib")
#pragma warning(disable: 4996)
#define sock_send(s, str, len)      send(s, str, len, 0)
#define sock_close(s)               closesocket(s)
#else
#include <arpa/inet.h>
#include <sys/types.h>
#include <sys/socket.h>
#define sock_send(s, str, len)      send(s, str, len, MSG_NOSIGNAL)
#define sock_close(s)               close(s)
#endif
#include <cerrno>
#include <cstdio>
#include <cstring>
#include <iostream>
#include <list>
#include <boost/bind.hpp>
#include <boost/coroutine/all.hpp>
#include <boost/shared_ptr.hpp>
using namespace std;


#ifdef _WIN32
struct Win32SocketWrapper
{
    Win32SocketWrapper()
    {
        WSADATA wsaData;
        WSAStartup(0x0202, &wsaData);
    }
    ~Win32SocketWrapper()
    {
        WSACleanup();
    }
} g_win32_socket_wrapper;
#endif


class session
{
    typedef boost::coroutines::symmetric_coroutine<void> coro_t;
public:
    explicit session(int sock)
        : socket_(sock)
    {
        echo_coro_ = coro_t::call_type(boost::bind(&session::echo, this, _1));
    }
    int socket()
    {
        return socket_;
    }
    void go()
    {
        echo_coro_();
    }
    void echo(coro_t::yield_type &yield)
    {
        int rc;
        char buffer[128];
        while (true) {
            memset(buffer, 0, sizeof(buffer));
            yield(); rc = recv(socket_, buffer, sizeof(buffer), 0);
            if (rc == 0 || rc == -1) { /* close or error */
                printf("socket[%d] closed, rc=%d..\n", socket_, rc);
                sock_close(socket_);
                socket_ = -1;
                /* do not release here, or the whole coroutine context will be invalid.. */
                break;
            } else {
                sock_send(socket_, buffer, rc);
            }
        }
    }
private:
    int socket_;
    coro_t::call_type echo_coro_;
};

void event_loop(int server_sock)
{
    list<boost::shared_ptr<session> > session_list;
    int rc, maxfd, client_sock;
    fd_set rdset;
    struct sockaddr_in client_addr;
    size_t addr_size = sizeof(struct sockaddr_in);

    while (true) {
        FD_ZERO(&rdset);
        FD_SET(server_sock, &rdset);
        maxfd = server_sock;
        list<boost::shared_ptr<session> >::iterator it = session_list.begin();
        while (it != session_list.end()) {
            if ((*it)->socket() == -1) {
                session_list.erase(it++);
            } else {
                FD_SET((*it)->socket(), &rdset);
                if (maxfd < (*it)->socket()) {
                    maxfd = (*it)->socket();
                }
                ++it;
            }
        }
        /* max fd value plus 1 */
        rc = select(maxfd+1, &rdset, 0, 0, NULL);
        if (rc == -1) {
            continue;
        } else {
            if (FD_ISSET(server_sock, &rdset)) {
                client_sock = (int)accept(server_sock, (struct sockaddr *)&client_addr, (socklen_t *)&addr_size);
                printf("socket[%d] accepted: %s:%d..\n", client_sock, inet_ntoa(client_addr.sin_addr), ntohs(client_addr.sin_port));
                boost::shared_ptr<session> new_session(new session(client_sock));
                new_session->go(); /* go first */
                session_list.push_back(new_session);
            }
            for (list<boost::shared_ptr<session> >::iterator it = session_list.begin(); it != session_list.end(); ++it) {
                if (FD_ISSET((*it)->socket(), &rdset)) {
                    (*it)->go();
                }
            }
        }
    }
}

int main() 
{
    int rc, server_sock;
    struct sockaddr_in server_addr;

    server_sock = (int)socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    server_addr.sin_family = AF_INET;
    server_addr.sin_addr.s_addr = htonl(INADDR_ANY);
    server_addr.sin_port = htons(2222);
    rc = bind(server_sock, (struct sockaddr *)&server_addr, sizeof(struct sockaddr_in));
    if (rc < 0) {
        fprintf(stderr, "bind: %s.\n", strerror(errno));
        return -1;
    }
    listen(server_sock, 5);
    /* loop */
    event_loop(server_sock);
    sock_close(server_sock);
    return 0;
}

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#ifdef _WIN32

#include <winsock2.h>

#include <ws2tcpip.h>

#include <windows.h>

#pragma comment(lib, "ws2_32.lib")

#pragma warning(disable: 4996)

#define sock_send(s, str, len) send(s, str, len, 0)

#define sock_close(s) closesocket(s)

#else

#include <arpa/inet.h>

#include <sys/types.h>

#include <sys/socket.h>

#define sock_send(s, str, len) send(s, str, len, MSG_NOSIGNAL)

#define sock_close(s) close(s)

#endif

#include <cerrno>

#include <cstdio>

#include <cstring>

#include <iostream>

#include <list>

#include <boost/bind.hpp>

#include <boost/coroutine/all.hpp>

#include <boost/shared_ptr.hpp>

using namespace std;

#ifdef _WIN32

struct Win32SocketWrapper

{

Win32SocketWrapper()

{

WSADATA wsaData;

WSAStartup(0x0202, &wsaData);

}

~Win32SocketWrapper()

{

WSACleanup();

}

} g_win32_socket_wrapper;

#endif

class session

{

typedef boost::coroutines::symmetric_coroutine<void> coro_t;

public:

explicit session(int sock)

: socket_(sock)

{

echo_coro_ = coro_t::call_type(boost::bind(&session::echo, this, _1));

}

int socket()

{

return socket_;

}

void go()

{

echo_coro_();

}

void echo(coro_t::yield_type &yield)

{

int rc;

char buffer[128];

while (true) {

memset(buffer, 0, sizeof(buffer));

yield(); rc = recv(socket_, buffer, sizeof(buffer), 0);

if (rc == 0 || rc == -1) { /* close or error */

printf("socket[%d] closed, rc=%d..\n", socket_, rc);

sock_close(socket_);

socket_ = -1;

/* do not release here, or the whole coroutine context will be invalid.. */

break;

} else {

sock_send(socket_, buffer, rc);

}

private:

int socket_;

coro_t::call_type echo_coro_;

};

void event_loop(int server_sock)

{

list<boost::shared_ptr<session> > session_list;

int rc, maxfd, client_sock;

fd_set rdset;

struct sockaddr_in client_addr;

size_t addr_size = sizeof(struct sockaddr_in);

while (true) {

FD_ZERO(&rdset);

FD_SET(server_sock, &rdset);

maxfd = server_sock;

list<boost::shared_ptr<session> >::iterator it = session_list.begin();

while (it != session_list.end()) {

if ((*it)->socket() == -1) {

session_list.erase(it++);

} else {

FD_SET((*it)->socket(), &rdset);

if (maxfd < (*it)->socket()) {

maxfd = (*it)->socket();

}

++it;

}

/* max fd value plus 1 */

rc = select(maxfd+1, &rdset, 0, 0, NULL);

if (rc == -1) {

continue;

} else {

if (FD_ISSET(server_sock, &rdset)) {

client_sock = (int)accept(server_sock, (struct sockaddr *)&client_addr, (socklen_t *)&addr_size);

printf("socket[%d] accepted: %s:%d..\n", client_sock, inet_ntoa(client_addr.sin_addr), ntohs(client_addr.sin_port));

boost::shared_ptr<session> new_session(new session(client_sock));

new_session->go(); /* go first */

session_list.push_back(new_session);

}

for (list<boost::shared_ptr<session> >::iterator it = session_list.begin(); it != session_list.end(); ++it) {

if (FD_ISSET((*it)->socket(), &rdset)) {

(*it)->go();

}

int main()

{

int rc, server_sock;

struct sockaddr_in server_addr;

server_sock = (int)socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);

server_addr.sin_family = AF_INET;

server_addr.sin_addr.s_addr = htonl(INADDR_ANY);

server_addr.sin_port = htons(2222);

rc = bind(server_sock, (struct sockaddr *)&server_addr, sizeof(struct sockaddr_in));

if (rc < 0) {

fprintf(stderr, "bind: %s.\n", strerror(errno));

return -1;

}

listen(server_sock, 5);

/* loop */

event_loop(server_sock);

sock_close(server_sock);

return 0;

}

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;

}

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.

Qt4学习笔记 (7)

January 22, 2015 by gonwan·0 Comments

This is a repost from my previous Qt learning series, based on Qt 4.3.

本篇说一下Qt对于脚本的支持, 即QtScript模块.

    Qt支持的脚本基于ECMAScript脚本语言, 这个东西又是javascript, jscript的基础. 所以, 一般只要学过javascript就基本会写Qt脚本了. 自此开始, Qt脚本现在就叫javascript.
    不过作为土人, javascript中有一个prototype的概念, 现在才知道. javascript本没有类的概念, 跟不用说是继承之类的了. 但是凭借prototype的特性, 我们可以实现类似C++中类, 以及类继承等一些特性.
    prototype是个什么概念? 因为这个单词实在表意不清, 导致我花了很多时间来理解这个. 每个javascript对象都有一个指向另一个对象的引用, 这就是它的prototype. 一个对象的prototype定义了这个对象可以进行的操作集. 用C++来类比的话, 这些操作集是一定是成员函数. 看下面的javascript代码:

function Shape(x, y) {
    this.x = x;
    this.y = y;
}
Shape.prototype.area = function() { return 0; }

function Circle(x, y, radius) {
    Shape.call(this, x, y);
    this.radius = radius;
}
Circle.prototype = new Shape;
Circle.prototype.area = function() {
    return Math.PI * this.radius * this.radius;
}

function Shape(x, y) {

this.x = x;

this.y = y;

}

Shape.prototype.area = function() { return 0; }

function Circle(x, y, radius) {

Shape.call(this, x, y);

this.radius = radius;

}

Circle.prototype = new Shape;

Circle.prototype.area = function() {

return Math.PI * this.radius * this.radius;

}

我们把Circle对象的prototype设置成Shape对象, 实际上就是把Shape对象的prototype赋给了Circle对象, 让Circle对象的初始操作集跟Circle对象是一样的. 之后我们又重载了area()函数, 当然我们还可以加入新的函数. 它对应的C++代码如下:

class Shape
{
public:
    Shape(double x, double y) {
        this->x = x;
        this->y = y;
    }
    virtual double area() const { return 0; }
    double x;
    double y;
};

class Circle : public Shape
{
public:
    Circle(double x, double y, double radius) : Shape(x, y)
    {
        this->radius = radius;
    }
    double area() const { return M_PI * radius * radius; }
    double radius;
};

class Shape

{

public:

Shape(double x, double y) {

this->x = x;

this->y = y;

}

virtual double area() const { return 0; }

double x;

double y;

};

class Circle : public Shape

{

public:

Circle(double x, double y, double radius) : Shape(x, y)

{

this->radius = radius;

}

double area() const { return M_PI * radius * radius; }

double radius;

};

所以, 我们看到了, 对于一个javascript对象来说, 它还包括了一个内部的prototype对象. 对于Qt要用C++来实现类似prototype的功能的话, 除了要写一个javascript中的对应类, 还要写这个类对应的prototype类. 这个东西很高级, 也很麻烦, 所以建议看官方文档: http://doc.trolltech.com/4.3/qtscript.html#making-use-of-prototype-based-inheritance

下面我们来说一下一般怎样从Qt的C++代码中调用Qt的script代码. 假设我们要写一个dialog, 上面有一个QPushButton, 一个QLineEdit. 点击QPushButton的时候, 会弹出一个QMessageBox来显示消息.

a) 直接写Qt的C++代码的话, 只要用signal/slot就行了:

void HelloDialog::helloClicked()
{
    QString text = textEdit->text();
    text = "Hello " + text;
    QMessageBox::information(this, "info", text);
}

void HelloDialog::helloClicked()

{

QString text = textEdit->text();

text = "Hello " + text;

QMessageBox::information(this, "info", text);

}

b) 现在我们要加入javascript 的支持. 要解决的大概有这么一些问题: javascript中怎么拿到QLineEdit里的字符串? javascript中怎么调用QMessage这个Qt的类? 我们还是先来看代码:

QScriptValue constructQMessageBox(QScriptContext *, QScriptEngine *engine) {
    return engine->newQObject(new QMessageBox());
}

void HelloDialog::helloClicked()
{
    QString helloScript = scriptsDir.filePath("xxx.js");
    QFile file(helloScript);
    if (!file.open(QIODevice::ReadOnly)) {
        return;
    }
    QTextStream in(&file);
    in.setCodec("UTF-8");
    QString script = in.readAll();
    file.close();
    // section 1
    QScriptEngine engine;
    QScriptValue helloDialog = engine.newQObject(this);
    engine.globalObject().setProperty("helloDialog", helloDialog);
    // section 2
    QScriptValue constructor = engine.newFunction(constructQMessageBox);
    QScriptValue qsMetaObject = engine.newQMetaObject(&(QMessageBox::staticMetaObject), constructor);
    engine.globalObject().setProperty("QMessageBox", qsMetaObject);

    QScriptValue result = engine.evaluate(script);
}

QScriptValue constructQMessageBox(QScriptContext *, QScriptEngine *engine) {

return engine->newQObject(new QMessageBox());

}

void HelloDialog::helloClicked()

{

QString helloScript = scriptsDir.filePath("xxx.js");

QFile file(helloScript);

if (!file.open(QIODevice::ReadOnly)) {

return;

}

QTextStream in(&file);

in.setCodec("UTF-8");

QString script = in.readAll();

file.close();

// section 1

QScriptEngine engine;

QScriptValue helloDialog = engine.newQObject(this);

engine.globalObject().setProperty("helloDialog", helloDialog);

// section 2

QScriptValue constructor = engine.newFunction(constructQMessageBox);

QScriptValue qsMetaObject = engine.newQMetaObject(&(QMessageBox::staticMetaObject), constructor);

engine.globalObject().setProperty("QMessageBox", qsMetaObject);

QScriptValue result = engine.evaluate(script);

}

    我们先把整个javascript文件读进来, 加入一堆设置, 最后调用QScriptEngine::evaluate()函数来执行这段javascript. QScriptEngine这个类就相当于javascript的解释器.
    javascript里没有类这个概念, 所有的变量都是var类型. 如果要让Qt的C++类在javascript里运行, 那么先要将它包装(wrap)成一个javascript的类型. 代码的section 1部分把this(即当前的dialog)先做了包装, 然后把包装后的对象加入到javascript的运行环境的全局变量中.
    接着来解决QMessageBox的问题. 由于javascript中没有类, 继而也就是没构造函数这个概念, 但是当我们在javascript中new一个Qt C++对象的时候, 还是需要调用它的构造函数. 代码的section 2部分先把一个C++回调函数(之所以称为回调函数, 是因为要作为QScriptEngine::newFunction()的参数, signature是固定的)包装成一个QScriptValue, 然后把它和QMessageBox的meta-object信息一起包装成一个QScriptValue, 最后依样画葫芦地加入到javascript的运行环境的全局变量中. 这样我们就能在javascript中new出一个QMessageBox了.
    有一个很重要问题. 就是Qt的meta-object系统和javascript的调用系统是有对应关系的. 在javascript中, 一个var如果是QObject包装而来, 那么这个QObject的所有property(Q_PROPERTY声明), signal/slot都是可以在javascript中调用的. 还有就是这个QObject的所有child (指的是包含而不是继承关系), 也是可以直接访问的.
    看一下javascript代码. 其中greeting和text都是属性:

function showMessage(parent, title, text)
{
    var messageBox = new QMessageBox;
    messageBox.windowTitle = title;
    messageBox.text = text;
    messageBox.icon = QMessageBox.Information;
    return messageBox.exec();
}

return showMessage(helloDialog, "info", helloDialog.greeting + " " + helloDialog.text);

function showMessage(parent, title, text)

{

var messageBox = new QMessageBox;

messageBox.windowTitle = title;

messageBox.text = text;

messageBox.icon = QMessageBox.Information;

return messageBox.exec();

}

return showMessage(helloDialog, "info", helloDialog.greeting + " " + helloDialog.text);

c) 我们实现了用javascript来控制逻辑. GUI的话, Qt也提供了一种可以直接读取*.ui的方法: QUiLoader::load()函数. 于是我们连GUI也可以不用直接编译到binary里去了. 我们要做的就是用Qt的C++代码搭一个大概的框架, 加载需要的*.ui, *.js文件, 在适当的时候调用适当的javascript函数就行了. 而且*.ui文件对于每个控件都会有一个objectName的属性, 用uic生成代码的话, 这个值就是变量名, 如果用QUiLoader::load()的话, 这个就被赋给了QObject的objectName这个property. 当我们要在一个QWidget的javascript对象里引用它的子控件的时候, 便能直接用这个objectName来引用. 于是*.ui 和*.js文件可以说简直配合的天衣无缝那.
还是来看代码, Qt的C++代码没什么好说的, 就看javascript代码:

function showMessage(parent, title, text)
{
    var messageBox = new QMessageBox;
    messageBox.windowTitle = title;
    messageBox.text = text;
    messageBox.icon = QMessageBox.Information;
    return messageBox.exec();
}

function doClick()
{
    var text = dialog.textEdit.text;
    showMessage(dialog, "info", "Hello " + text);
}

dialog.show();
dialog.helloButton.clicked.connect(doClick);
return 0;

function showMessage(parent, title, text)

{

var messageBox = new QMessageBox;

messageBox.windowTitle = title;

messageBox.text = text;

messageBox.icon = QMessageBox.Information;

return messageBox.exec();

}

function doClick()

{

var text = dialog.textEdit.text;

showMessage(dialog, "info", "Hello " + text);

}

dialog.show();

dialog.helloButton.clicked.connect(doClick);

return 0;

直接访问子控件是不是清爽多了? 呵呵. 代码见这里. 其它请参考官方文档:
*) http://doc.trolltech.com/4.3/ecmascript.html
*) http://doc.trolltech.com/4.3/qtscript.html

0x2B|~0x2B

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

Category: C/C++

Using vcpkg for C++ Package Management

1. Install v2ray and run proxy

2. Download vcpkg from github and bootstrap

3. Install drogon framework for demo

4. Export drogon framework

5. Add a demo program

6. Stick to a specific version

7. Binary caching

Coroutines in C++/Boost

Basic Usage of Boost MultiIndex Containers

Database Access Layer in C++

Qt4学习笔记 (7)