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C++ and portability issues Is C++ portable? Yes, theoretically...
Standard library is too tiny:
No filesystem access No network No multiprocessing/multithreading No serious unicode support ... and it's not going to change in C++0x!
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C++ and portability issues Real-world C++ programmers have to use libraries for
everything
Some libraries are good, some are bad Some are portable, some are not Some become unmaintained after a while ... big mess!
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C++ and portability issues Windows programmers use Win32 API
But Microsoft only improves .NET framework! Naked Win32 API is a pain to use!
Linux programmers use POSIX POSIX is mostly C-oriented It's totally useless for Windows
Mac C++ programmers are doomed Either POSIX or Carbon... Cocoa is for Objective-C only!
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Qt to the rescue! Qt is not only a GUI toolkit: it's also a complete
portability layer!
Even for command line applications Lots of carefully designed and very mature classes for
everyday C++ programming
Prefer quick everyday usability over “abstract perfection”
Fast to learn, fast to use, compact code
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Qt Portability Layer QtCore
Data structures, rich types, system information, reactor (event loop), multi-threading
QtNetwork
Sockets, IP, TCP, UDP, HTTP, FTP, SSL QtXml
Full DOM implementation SAX2 parser
QtWebKit
Web browser engine, used by Safari/Chrome
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QtCore: quick overview QtCore is very “wide” but not “deep”
Many simple classes But lots of them!
Exploring all it would require a full training on its own!
We will just see some random examples, that will show the typical design of QtCore classes
Easy to use, and very powerful
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QtCore: Implicit sharing Many Qt classes use “implicit sharing”
Each instance is actually a pointer to shared data, with a reference counter
Net result: fast pass-by-value, easier code, less performance bugs.
Fully multithreaded safe
No mutex/locks, use CPU-specific atomic increments/decrements.
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QtCore: Implicit sharing
Returning by value offer more readable API:
QList<QObject> c = obj->children(); Chainability: obj->children().count(); Can also nest containers with no overhead
With STL containers, it would have been:
list<QObject> c; obj->children(c); Using an argument as return value is bad for
readability!
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Text processing Qt offers many good primitives for text processing. QFile: line-by-line processing QRegExp: Perl regular expressions (many methods
accept it, even findChildren()!) QString: many powerful methods (inspired by Perl)
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QtCore: strings (1/3) QString: unicode strings representation
Implicit sharing policy: pass by value!
Well-suited for text, don't use for binary data
QByteArray is better for 8-bit binary data
Contains loads of functionality for any kind of text processing
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QtCore: strings (2/3) Basic: constructor, resize(), [] / .at(), .size(), .resize(),
.fill()
Modification: .append(), .prepend(), .insert(), .replace() (RX), .remove() (RX)
Whitespaces: .trimmed(), simplified()
Grouping: .split() (RX), .join()
Searching: .indexOf(), .lastIndexOf(), .find() (RX), .{starts|ends}With(), .contains() (RX), .count() (RX)
Comparison: <, <=, ==, >=, >, ::localeAwareCompare()
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QtCore: strings (3/3) Conversion to: .toUpper(), .toLower(), toInt(),
.toDouble(), .toAscii(), .toLatin1(), .toUtf8(),
.toLocal8Bit(), toUcs4()
Conversion from: like above, ::number(n,base)
Formatting: .sprintf() (bad), .arg() (good)
Use %number formatting instead of %type (like printf)
Fully type-safe More translator-friendly (can safely-reorder)
... and much more!
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QtCore: date/time support (1/3)
QDate: one instance is one specific calendar day
Formatting: .{to|from}String() (ISO or locale) Weeks: .weekNumber(), .dayOfWeek() Jumping: .addDays/Months/Years() Texts: ::{long|short}{Day|Month}Name() Validation: ::isLeapYear(), ::isValid() Ordering: <, <=, ==, >=, >, .daysTo() Factory: ::currentDate()
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QtCore: date/time support (2/3)
QTime: one instance is one specific time (instant)
Formatting: .{to|from}String() (ISO or locale) Jumping: .addSecs(), .addMSecs() Validation: ::isValid() Measuring: .start(), .restart(), .elapsed() Ordering: <, <=, >=, >, .secsTo(), .msecsTo() Factory: ::currentTime()
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QtCore: date/time support (3/3)
QDateTime: an instance is one specific calendar time at a specific time (instant)
Combination of the previous two, merging all the functionalities!
Time formats: Localtime/UTC
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STL containers STL containers are good because:
They are standard C++ They are ready-to-use and very efficient The generic iterator concept is powerful
STL containers are bad because:
They are verbose to use (eg: iterating) They are incomplete
Hash table anyone? They bloat the executable code due to template
expansion
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Qt Containers Designed “the Qt way”
Easy to use, no complex stuff Implicitly shared
You can pass by value without impacting performance (more readable code!)
Minimal inline expansion
Generate light executables for embedded code
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Qt Containers QList<>, QLinkedList<>, QVector<>
QList<> is an array of pointers Random access Best for most purpose (very fast operations)
QLinkedList<> is a true linked list of pointers O(1) insertion in the middle, no random access
QVector<> is an array of objects Occupy contiguous space in memory Slow insertions, but cache friendly
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Qt Containers QVector<> is an array of objects
Occupy contiguous space in memory Slow insertions, but cache friendly
QList<> is an array of pointers
Random access Best for most purpose (very fast operations)
QSet<>
Fast set of objects (no repetition) Implemented through hash-table (much faster
than std::set!) not ordered→
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Qt Containers QHash<>, QMap<>
Associative arrays (map values to keys) QHash<> relies on qHash() and operator==(), QMap
on operator<() Hashtables are O(1) for lookups, maps are O(logn) Iteration: hashtables have random order, maps have
fixed order
Qt / XML parsers
Stream based
QXmlReader
SAX2 QXmlStreamReader
Qt specific
DOM
QtDom*
W3C
QXmlReader
SAX2 only http://www.saxproject.org
not validating, namespace support
SAX2 parsing is callback based
for each sax-event a different function is called the parser has no state
QDom*
in memory representation of the XML document
follow the W3C recommendations
useful to manipulate the XML document
not validating, namespace support
QtNetwork
Qt module to make networking programs
QtGui not required high-level classes
for http/ftp clients low-level classes
direct access to the underling socket event driven (= high performance)
SSL support
QtNetwork
high level classes
QNetworkAccessManager
QFtp
low level classes
QTcpServer
QTcpSocket
QUdpServer
QUdpSocket
QSsl*
QtNetwork
QMetworkAccessManager
event driven the event loop must be running → QNetworkRequest
full support for setting http headers QNetworkReply
access to the reply headers signals to track the downloading process
QtNetwork
QNetworkDiskCache
simple, disk based, cache QAbstractNetworkCache for a custom cache
QnetworkProxy
route network connections through a proxy SOCK5, HTTP, HTTP Caching, FTP Caching
transparent to the networking code application wide / per socket
anonymous or username/password
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