Utility class to build blocks of data to transfer over the network. More...
#include <Packet.hpp>
Public Member Functions | |
Packet () | |
Default constructor. | |
virtual | ~Packet () |
Virtual destructor. | |
void | Append (const void *data, std::size_t sizeInBytes) |
Append data to the end of the packet. | |
void | Clear () |
Clear the packet. | |
const char * | GetData () const |
Get a pointer to the data contained in the packet. | |
std::size_t | GetDataSize () const |
Get the size of the data contained in the packet. | |
bool | EndOfPacket () const |
Tell if the reading position has reached the end of the packet. | |
operator BoolType () const | |
Test the validity of the packet, for reading. | |
Packet & | operator>> (bool &data) |
Overloads of operator >> to read data from the packet. | |
Packet & | operator>> (Int8 &data) |
Packet & | operator>> (Uint8 &data) |
Packet & | operator>> (Int16 &data) |
Packet & | operator>> (Uint16 &data) |
Packet & | operator>> (Int32 &data) |
Packet & | operator>> (Uint32 &data) |
Packet & | operator>> (float &data) |
Packet & | operator>> (double &data) |
Packet & | operator>> (char *data) |
Packet & | operator>> (std::string &data) |
Packet & | operator>> (wchar_t *data) |
Packet & | operator>> (std::wstring &data) |
Packet & | operator>> (String &data) |
Packet & | operator<< (bool data) |
Overloads of operator << to write data into the packet. | |
Packet & | operator<< (Int8 data) |
Packet & | operator<< (Uint8 data) |
Packet & | operator<< (Int16 data) |
Packet & | operator<< (Uint16 data) |
Packet & | operator<< (Int32 data) |
Packet & | operator<< (Uint32 data) |
Packet & | operator<< (float data) |
Packet & | operator<< (double data) |
Packet & | operator<< (const char *data) |
Packet & | operator<< (const std::string &data) |
Packet & | operator<< (const wchar_t *data) |
Packet & | operator<< (const std::wstring &data) |
Packet & | operator<< (const String &data) |
Friends | |
class | TcpSocket |
class | UdpSocket |
Utility class to build blocks of data to transfer over the network.
Packets provide a safe and easy way to serialize data, in order to send it over the network using sockets (sf::TcpSocket, sf::UdpSocket).
Packets solve 2 fundamental problems that arise when transfering data over the network:
The sf::Packet class provides both input and output modes. It is designed to follow the behaviour of standard C++ streams, using operators >> and << to extract and insert data.
It is recommended to use only fixed-size types (like sf::Int32, etc.), to avoid possible differences between the sender and the receiver. Indeed, the native C++ types may have different sizes on two platforms and your data may be corrupted if that happens.
Usage example:
sf::Uint32 x = 24; std::string s = "hello"; double d = 5.89; // Group the variables to send into a packet sf::Packet packet; packet << x << s << d; // Send it over the network (socket is a valid sf::TcpSocket) socket.Send(packet); ----------------------------------------------------------------- // Receive the packet at the other end sf::Packet packet; socket.Receive(packet); // Extract the variables contained in the packet sf::Uint32 x; std::string s; double d; if (packet >> x >> s >> d) { // Data extracted successfully... }
Packets have built-in operator >> and << overloads for standard types:
Like standard streams, it is also possible to define your own overloads of operators >> and << in order to handle your custom types.
struct MyStruct { float number; sf::Int8 integer; std::string str; }; sf::Packet& operator <<(sf::Packet& packet, const MyStruct& m) { return packet << m.number << m.integer << m.str; } sf::Packet& operator >>(sf::Packet& packet, MyStruct& m) { return packet >> m.number >> m.integer >> m.str; }
Packets also provide an extra feature that allows to apply custom transformations to the data before it is sent, and after it is received. This is typically used to handle automatic compression or encryption of the data. This is achieved by inheriting from sf::Packet, and overriding the OnSend and OnReceive functions.
Here is an example:
class ZipPacket : public sf::Packet { virtual const char* OnSend(std::size_t& size) { const char* srcData = GetData(); std::size_t srcSize = GetDataSize(); return MySuperZipFunction(srcData, srcSize, &size); } virtual void OnReceive(const char* data, std::size_t size) { std::size_t dstSize; const char* dstData = MySuperUnzipFunction(data, size, &dstSize); Append(dstData, dstSize); } }; // Use like regular packets: ZipPacket packet; packet << x << s << d; ...
Definition at line 47 of file Packet.hpp.
sf::Packet::Packet | ( | ) |
Default constructor.
Creates an empty packet.
virtual sf::Packet::~Packet | ( | ) | [virtual] |
Virtual destructor.
void sf::Packet::Append | ( | const void * | data, | |
std::size_t | sizeInBytes | |||
) |
Append data to the end of the packet.
data | Pointer to the sequence of bytes to append | |
sizeInBytes | Number of bytes to append |
void sf::Packet::Clear | ( | ) |
bool sf::Packet::EndOfPacket | ( | ) | const |
Tell if the reading position has reached the end of the packet.
This function is useful to know if there is some data left to be read, without actually reading it.
const char* sf::Packet::GetData | ( | ) | const |
Get a pointer to the data contained in the packet.
Warning: the returned pointer may become invalid after you append data to the packet, therefore it should never be stored. The return pointer is NULL if the packet is empty.
std::size_t sf::Packet::GetDataSize | ( | ) | const |
Get the size of the data contained in the packet.
This function returns the number of bytes pointed to by what GetData returns.
sf::Packet::operator BoolType | ( | ) | const |
Test the validity of the packet, for reading.
This operator allows to test the packet as a boolean variable, to check if a reading operation was successful.
A packet will be in an invalid state if it has no more data to read.
This behaviour is the same as standard C++ streams.
Usage example:
float x; packet >> x; if (packet) { // ok, x was extracted successfully } // -- or -- float x; if (packet >> x) { // ok, x was extracted successfully }
Don't focus on the return type, it's equivalent to bool but it disallows unwanted implicit conversions to integer or pointer types.
Packet& sf::Packet::operator<< | ( | bool | data | ) |
Overloads of operator << to write data into the packet.
Packet& sf::Packet::operator>> | ( | bool & | data | ) |
Overloads of operator >> to read data from the packet.