Portable Components, cross-platform library for C ++

"The system must be designed so that
to stay as simple as possible
after a series of changes to it
Bjarne Stroustrup - programmer, author of C ++

Preamble

In this article I would like to tell you about the Portable Components library (abbr. POCO), which is quite popular but so rarely covered in Habré. It will be useful both to developers of business logic of a software product, and in solving most applied problems. With all the abundant cross-platform libraries for C ++, more and more people are confronted with POCO face to face and do not know where to start. In this article I will try to describe the technologies incorporated in the library and give the simplest examples of solving some problems. I would also like to note that the library has many successful open source and commercial projects.

Description

POCO is a collection of classes that simplify the process of developing, debugging and testing a software product. The library is based on the principle of a modular system with a small degree of connectivity. Like its colleague, Boost, POCO is divided into modules, each of which performs its role in the system, but does not use the paradigm of generalized programming as Boost, so carefully using patterned magic , thus avoiding some of the problems associated with searching for errors. Another significant advantage is the size of the final distribution - the POCO core size (Poco Foundation) takes about one and a half megabytes of memory (version 1.4.3.0, MSVC v100), the remaining modules range from 50 to 800 KB, which in the modern world is not much even for embedded systems . Applied Informatics Software Engineering GmbH - the developer of POCO even declares support for such tiny devices as Digi Connect ME 9210 , made in the form factor of an RJ-45 connector, having only 2 or 4 MB of flash and 8 MB of RAM on board.

POCO is mainly focused on network development and is ported to popular operating systems: Windows, Unix, Linux, eLinux, Mac OS X, Solaris, QNX Neutrino, Vxworks, Openvms, Tru64, HP-UX, Android . This list is expanding rather quickly, since all platform-dependent modules are separated from logic. In fact, on any operating system for which there is a modern compiler for the C ++ language, you can port POCO.
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The library can be used as a basis for any development, be it server or client software, while the application is guaranteed to run on any of the available architectures (I confess, sometimes not without special magic). Moreover, POCO has such powerful tools as the TCP Server Framework, Reactor Framework, which make it very easy to create high-performance WEB servers, allowing us to save development time. Also in the library there is a snap-in for creating console applications, Unix daemons, and Windows services. Parallel work with such libraries as Qt, wxWidget, GTK + is possible.

The concepts of some parts of the library are borrowed from the Java Class Library, MS .NET Framework and Apple Cocoa . These are mainly high-level things, such as flow control or timers.

Poco is written with strict adherence to the ANSI / ISO C ++ 2003 standard using the C ++ standard library and STL. Available under the “ Boost Software License ”, allowing both commercial and non-commercial use.

How to learn POCO

• Examine presentations describing technologies on the project website .
• Download the latest library version
• Build a library and examples for it
• Study materials in the POCO SDK Reference
• Read the community

Most of the examples can be found in source codes, in the SDK Reference and in presentations.

Basic modules and examples of use

Core library

• Means of Dynamic Data Typing Any and DynamicAny
  

  DynamicAny any("99"); int i = any; // i == 99 any = 65536; string s = any; // s == "65536" char c = any; //   ,   RangeException 

  
  
• Manipulations with time and date
  

   const char *date = "05.06.1977"; //Apple 2 birthday int Diff; DateTime time = DateTimeParser::parse("%d.%m.%Y", date, Diff); Timespan diff = DateTime() - time; cout << "Apple 2  " << diff.days() << "   " << DateTimeFormatter::format(time, "%e %B %Y, %W", Diff) << endl; // : "5 June 1977, Sunday" cout << "   " << (DateTime::isLeapYear(time.year()) ? "" : " "); 

  
  
• Means of working with events and alerts
  

   #include "Poco/BasicEvent.h" #include "Poco/Delegate.h" #include <iostream> using BasicEvent; using Delegate; class Source { public: BasicEvent<int> theEvent; void fireEvent(int n) { theEvent(this, n); } }; class Target { public: void onEvent(const void* pSender, int& arg) { cout << "onEvent: " << arg << endl; } }; int main(int argc, char** argv) { Source source; Target target; //      Event' source.theEvent += Delegate<Target, int>( &target, &Target::onEvent); //  source.fireEvent(42); // source.theEvent -= Delegate<Target, int>( &target, &Target::onEvent); return 0; } 

  
  
• Regular expression processing
  

   RegularExpression regular("([0-9]+) ([0-9]+)"); vector<string> arr; regular.split("123 456", 0, arr); //arr = {“123 456”, ”123”, ”456”} string s = "123 456"; regular.subst(s, "$2 $1"); // s == "456 123" 

  
  
• Tools for working with dynamic link libraries.
  

   SharedLibrary lib("C:\\Windows\\System32\\shell32.dll"); if (lib.isLoaded() && lib.hasSymbol("Control_RunDLL")) { auto fun = static_cast<void (*)()>(lib.getSymbol("Control_RunDLL")); fun(); //   lib.unload(); } 

  
  
• Memory management tools
  

   //  class A {}; class B : public A {} ; class C : public A {}; … SharedPtr<A> pA; SharedPtr<B> pB(new B); pA = pB; // , B  A pA = new B; //   // pB = pA; // ,  SharedPtr    pB = pA.cast<B>(); //    SharedPtr<C> pC(new C); pB = pC.cast<B>(); // pB  null //  DynamicFactory<A> factory; factory.registerClass<B>("B"); //  Instantiator<B, A> factory.registerClass<C>("C"); //  Instantiator<C, A> SharedPtr<A> pA = factory.createInstance("B"); SharedPtr<A> pB = factory.createInstance("C"); factory.unregisterClass("C"); bool isA = factory.isClass("B"), // true isB = factory.isClass("C"), // false ( ) isC = factory.isClass("habrahabr"); // false (  ?!) // Buffer<char> buffer(1024); //    1024  cin.read(buffer.begin(), buffer.size()); //   1024   stdin streamsize n = cin.gcount(); string s(buffer.begin(), n); //      cout << s << endl; //  //  MemoryPool pool(1024); //   1024   // MemoryPool pool(1024, 4, 16); //  16 ; 4   char* buffer = static_cast<char*>(pool.get()); //    cin.read(buffer, pool.blockSize()); //  stdin   streamsize n = cin.gcount(); string s(buffer, n); //  pool.release(buffer); //  cout << s << endl; // 

  
  
• Singletons
  

   class Singleton { public: int add(int i, int p) { return i+p; } static Singleton& instance() { static SingletonHolder<Singleton> single; return *single.get(); } }; … int res = Singleton::instance().add(1,2); 

  
  
• String formatters
  

   //printf-style formating string str = format("In %[0]d was %[1]s of %[2]s %[3]d", DateTime(1977,6,5).year(), // %[0]d string("b-day"), // %[1]s string("Apple"), // %[2]s 2); // %[3]d //str = “In 1977 was b-day of Apple 2” 

  
  
• Information about the system and work with environment variables
  

   cout << " : " << Environment::osName() << "\n : " << Environment::osVersion() << "\n: " << Environment::osArchitecture() << "\n. : " << Environment::nodeName() << "\nMAC-: " << Environment::nodeId(); if (Environment::has("HOME")) cout << "\n .: " << Environment::get("HOME") << endl; Environment::set("POCO", "foo"); //   POCO=foo 

  
  

Data compression

• Means for implementing streaming data compression
• Tools for creating ZIP files
  

   ofstream zipper("text.gz", ios::binary); ofstream text("text.txt", ios::binary); text << "Hello my little computer world. I can zip this string. It's wonderful."; text.close(); Zip::Compress zipc(zipper,true); zipc.addFile (Path("text.txt"), "text.txt"); zipc.close(); ifstream dezipper("text.gz", ios::binary); poco_assert (dezipper); Zip::Decompress zipd(dezipper,Path().append("\\text.dz")); zipd.decompressAllFiles(); 

  
  

Cryptography

• Pseudo Random Number Generator
  

   Random rnd; rnd.seed(); cout << ": " << rnd.next() << "\n: " << rnd.next(10) << "\n: " << rnd.nextChar() << "\n: " << rnd.nextBool() << "\n  . : " << rnd.nextDouble(); RandomInputStream ri; string rs; ri >> rs; 

  
  
• The mechanism for creating a HASH
  

   string message("      "); string passphrase("anl!sfsd9!_3g2g?f73"); //   //HMAC = Hash-based message authentication code ;) HMACEngine<SHA1Engine> encoder(passphrase); encoder.update(message); // //  encoder.digest()    string encodedstr(DigestEngine::digestToHex(encoder.digest())); // MD5  MD5Engine md5; DigestOutputStream ostr(md5); ostr << "      "; ostr.flush(); //   HEX string result = DigestEngine::digestToHex(md5.digest()); 

  
  
• X509 certificate support
• Data Encryption Mechanisms
• Stream cryptography
• OpenSSL support

Database

• Interaction with various databases (SQLite, MySQL, ODBC, etc)
  

   Data::SQLite::Connector::registerConnector(); Data::Session ses("SQLite", "mydb.db"); int count = 0; ses << "SELECT COUNT(*) FROM PERSON", into(count), now; cout << "People in DB " << count; string firstName(""; string lastName(""); int age = 0; ses << "INSERT INTO PERSON VALUES (:fn, :ln, :age)", use(firstName), use(lastName), use(age), now; ses << "SELECT (firstname, lastname, age) FROM Person", into(firstName), into(lastName), into(age, -1), now; Data::SQLite::Connector::unregisterConnector(); 

  
  
• Session pool
• RecordSet
  

   Statement select(session); select << "SELECT * FROM Person"; select.execute(); RecordSet rs(select); 

  
  
• Tuples
  

   struct Person { string fullname, city; size_t age; }; … typedef Tuple<string, string, int> Person; vector<Person> people; people.push_back(Person("Bart Simpson", "Springfield", 12)); people.push_back(Person("Lisa Simpson", "Springfield", 10)); Statement insert(session); insert << "INSERT INTO Person VALUES(:name, :address, :age)", use(people), now; 

  
  

File system

• Platform-independent work with files and directories
  

   Path p_wind("C:\\Windows\\system32\\cmd.exe"); Path p_unix("/bin/sh"); p_wind = "projects\\poco"; p_unix = "projects/poco"; p_unix.parse("/usr/include/stdio.h", Path::PATH_UNIX); bool ok = p_unix.tryParse("/usr/*/stdio.h"); ok = p_unix.tryParse("/usr/include/stdio.h", Path::PATH_UNIX); ok = p_unix.tryParse("/usr/include/stdio.h", Path::PATH_WINDOWS); ok = p_unix.tryParse("DSK$PROJ:[POCO]BUILD.COM", Path::PATH_GUESS); 

  
  

Work with logs

• Powerful Log Management Tool
• Formatting logs
• Log transfer channels
  

   //   AutoPtr<SimpleFileChannel> pChannel(new SimpleFileChannel); pChannel->setProperty("path", "log.log"); pChannel->setProperty("rotation", "2 K"); Logger::root().setChannel(pChannel); Logger& logger = Logger::get("TestLogger"); //   TestLogger for (int i = 0; i < 13; ++i) logger.information("   13 "); //   AutoPtr<FileChannel> pChannel(new FileChannel); pChannel->setProperty("path", " log.log"); pChannel->setProperty("rotation", "2 K"); pChannel->setProperty("archive", "timestamp"); Logger::root().setChannel(pChannel); Logger& logger = Logger::get("TestLogger"); //   TestLogger for (int i = 0; i < 13; ++i) logger.information("   13 "); //   AutoPtr<ConsoleChannel> pCons(new ConsoleChannel); AutoPtr<AsyncChannel> pAsync(new AsyncChannel(pCons)); Logger::root().setChannel(pAsync); Logger& logger = Logger::get("TestLogger"); //   TestLogger for (int i = 0; i < 13; ++i) logger.information("   13 "); //-  AutoPtr<ConsoleChannel> pCons(new ConsoleChannel); AutoPtr<SimpleFileChannel> pFile(new SimpleFileChannel("test.log")); AutoPtr<SplitterChannel> pSplitter(new SplitterChannel); pSplitter->addChannel(pCons); pSplitter->addChannel(pFile); Logger::root().setChannel(pSplitter); Logger::root().information("     "); Logger& logger = Logger::get("TestLogger"); LogStream lstr(logger); lstr << "        " << endl; //  AutoPtr<ConsoleChannel> pCons(new ConsoleChannel); AutoPtr<PatternFormatter> pPF(new PatternFormatter); // "-- :: : " pPF->setProperty("pattern", "%Y-%m-%d %H:%M:%S %s: %t"); AutoPtr<FormattingChannel> pFC(new FormattingChannel(pPF, pCons)); Logger::root().setChannel(pFC); Logger::get("TestChannel").information("   "); 

Multithreading

• Platform-independent support for threads and thread pools
  

   //  Runnable. Hello JAVA. class ThreadRunner: public Runnable { virtual void run() { cout << "     " << endl; } }; //     class ThreadRunnerNoRunnable { void norun() { cout << "     " << endl; } }; … ThreadRunner runnable; Thread thread; thread.start(runnable); //  thread.join(); //   ThreadRunnerNoRunnable norunnable; RunnableAdapter< ThreadRunnerNoRunnable > runnable2(norunnable, & ThreadRunnerNoRunnable::norun); Thread thread2; Thread2.start(norunnable); //  Thread2.join(); //   //  class ThreadRunner: public Runnable { virtual void run() { static int num; cout << "      " << endl; for (int i=0; i<100; ++i) ++num; } }; … ThreadRunner runnable1, runnable2, runnable3; //  ThreadPool::defaultPool().start(runnable1); ThreadPool::defaultPool().start(runnable2); ThreadPool::defaultPool().start(runnable3); //   ThreadPool::defaultPool().joinAll(); 

  
  
• Thread Synchronization Tools
  

   class ThreadRunner: public Runnable { public: ThreadRunner(int &num, Mutex& mutex) : num(num), mutex(mutex) {} virtual void run() { while (num < 100) { ScopedLock<Mutex> lock(mutex); // ,    for (int i=0; i<5; ++i) cout << "TID:" << Thread::currentTid() << " NUM:" << ++num << endl; Thread::sleep(100); } } private: int& num; Mutex& mutex; }; ... int num = 0; Mutex mutex; Thread th1; ThreadRunner tr1(num,mutex); th1.start(tr1); while (num < 100) { ScopedLock<Mutex> lock(mutex); // ,    for (int i=0; i<5; ++i) cout << "TID:" << Thread::currentTid() << " NUM:" << ++num << endl; Thread::sleep(100); } th1.join(); 

  
  
• Work Queues
• Timers
• Task manager
• Active Objects: Activities and Active Methods

Network technologies

• Sockets
  

   Net::SocketAddress sa("www.habrahabr.ru", 80); Net::StreamSocket socket(sa); Net::SocketStream str(socket); str << "GET / HTTP/1.1\r\n" "Host: habrahabr.ru\r\n" "\r\n"; str.flush(); StreamCopier::copyStream(str, cout); //  Net::ServerSocket srv(8080); //     while(true) { Net::StreamSocket ss = srv.acceptConnection(); { Net::SocketStream str(ss); str << "HTTP/1.0 200 OK\r\n" "Content-Type: text/html\r\n" "\r\n" "<html><head><title>  </title></head>" "<body><h1><a href=\"http://habrahabr.ru\">   .</a></h1></body></html>" << flush; } } 

  
  
• Multithreaded servers
• DNS
  

   const HostEntry& entry = DNS::hostByName("www.habrahabr.ru"); cout << " : " << entry.name() << endl; const HostEntry::AliasList& aliases = entry.aliases(); for (HostEntry::AliasList::const_iterator it1 = aliases.begin(); it1 != aliases.end(); ++it1) cout << ": " << *it1 << endl; const HostEntry::AddressList& addrs = entry.addresses(); for (HostEntry::AddressList::const_iterator it2 = addrs.begin(); it2 != addrs.end(); ++it2) cout << "IP: " << it2->toString() << endl; 

  
  
• Clients for some application layer protocols (FTP, SMTP, etc.)
• HTTP (S) server, HTTP authentication
• C ++ code compiler - HTML inserts, HTML form processing, MIME
• URI support, UUID
• RFC 6455 support
• SSL / TLS support

Processes

• Manipulations with processes (start, stop)
  

   cout << " PID: " << Process::id() << endl; vector<string> args; args.push_back("shell32"); args.push_back("ShellAboutA"); Process::launch("rundll32", args); 

  
  
• Process synchronization
• Shared memory mechanism
  

   File file("Shared.dat"); SharedMemory mem(file, SharedMemory::AM_READ); cout << &*mem.begin() << endl; 

  
  

Streaming operations

• Stream encoding / decoding BASE-64, HexBinary
  

   Base64Encoder encoder(cout); encoder << "    Base64    stdout"; 

  
  
• Memory I / O Streams
• URI stream support
  

   Net::HTTPStreamFactory::registerFactory(); auto_ptr<istream> input( URIStreamOpener::defaultOpener().open("http://habrahabr.ru") ); cout << input->rdbuf(); 

  
  

Text encoding

• Support encoding to / from UTF-8 and Unicode
  

   string utf8(" UTF-8 ."); UTF8Encoding decoder; TextIterator end(utf8); for (TextIterator iter(utf8, decoder); iter != end; ++iter) int unicode = *iter; 

  
  
• Encoding Conversion Support
  

   string latin(" Latin1 ."); Latin1Encoding decoder; UTF8Encoding encoder; OutputStreamConverter converter(cout, decoder, encoder); converter << latin << endl; // latin - UTF-8  

  
  

Utility

• A framework for creating console and server applications.
• Support command line arguments

Configuration

• Creating Unix-daemons and Windows Services

XML

• DOM, SAX2 support
• Support both read mode and write mode

Conclusion

In conclusion, I would like to note that the description of some modules was omitted because these modules deserve special attention and require separate articles. I sincerely believe that this library has a bright future. I would also like to see in POCO some of the buns from the new standard C ++ 11 .
The next article I would like to talk about specific things in the POCO. I will be glad to objective comments and objections.
Thanks for reading.