SFML - Simple and Fast Multimedia Library

SFML

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sf
Packet

Utility class to build blocks of data to transfer over the network. More...

#include <Packet.hpp>

Public Member Functions
	Packet ()
	Default constructor. More...

virtual	~Packet ()
	Virtual destructor. More...

void	append (const void *data, std::size_t sizeInBytes)
	Append data to the end of the packet. More...

void	clear ()
	Clear the packet. More...

const void *	getData () const
	Get a pointer to the data contained in the packet. More...

std::size_t	getDataSize () const
	Get the size of the data contained in the packet. More...

bool	endOfPacket () const
	Tell if the reading position has reached the end of the packet. More...

	operator BoolType () const
	Test the validity of the packet, for reading. More...

Packet &	operator>> (bool &data)
	Overloads of operator >> to read data from the packet. More...

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>> (Int64 &data)

Packet &	operator>> (Uint64 &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. More...

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<< (Int64 data)

Packet &	operator<< (Uint64 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)

Protected Member Functions
virtual const void *	onSend (std::size_t &size)
	Called before the packet is sent over the network. More...

virtual void	onReceive (const void *data, std::size_t size)
	Called after the packet is received over the network. More...

Friends
class	TcpSocket

class	UdpSocket

Detailed Description

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 transferring data over the network:

data is interpreted correctly according to the endianness
the bounds of the packet are preserved (one send == one receive)

The sf::Packet class provides both input and output modes. It is designed to follow the behavior 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:

bool
fixed-size integer types (sf::Int8/16/32, sf::Uint8/16/32)
floating point numbers (float, double)
string types (char*, wchar_t*, std::string, std::wstring, sf::String)

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 void* onSend(std::size_t& size)
    {
 const void* srcData = getData();
        std::size_t srcSize = getDataSize();
 return MySuperZipFunction(srcData, srcSize, &size);
    }
 virtual void onReceive(const void* data, std::size_t size)
    {
        std::size_t dstSize;
 const void* dstData = MySuperUnzipFunction(data, size, &dstSize);
 append(dstData, dstSize);
    }
};
// Use like regular packets:
ZipPacket packet;
packet << x << s << d;
...

See also: sf::TcpSocket, sf::UdpSocket

Definition at line 47 of file Packet.hpp.

Constructor & Destructor Documentation

sf::Packet::Packet ( )

Default constructor.

Creates an empty packet.

virtual sf::Packet::~Packet ( )

virtual

Virtual destructor.

Member Function Documentation

void sf::Packet::append	(	const void *	data,
		std::size_t	sizeInBytes
	)

Append data to the end of the packet.

Parameters

data	Pointer to the sequence of bytes to append
sizeInBytes	Number of bytes to append

See also: clear

void sf::Packet::clear ( )

Clear the packet.

After calling Clear, the packet is empty.

See also: append

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.

Returns: True if all data was read, false otherwise

See also: operator bool

const void* 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.

Returns: Pointer to the data

See also: getDataSize

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.

Returns: Data size, in bytes

See also: getData

virtual void sf::Packet::onReceive	(	const void *	data,
		std::size_t	size
	)

protectedvirtual

Called after the packet is received over the network.

This function can be defined by derived classes to transform the data after it is received; this can be used for decompression, decryption, etc. The function receives a pointer to the received data, and must fill the packet with the transformed bytes. The default implementation fills the packet directly without transforming the data.

Parameters

data	Pointer to the received bytes
size	Number of bytes

See also: onSend

virtual const void* sf::Packet::onSend ( std::size_t & size )

protectedvirtual

Called before the packet is sent over the network.

This function can be defined by derived classes to transform the data before it is sent; this can be used for compression, encryption, etc. The function must return a pointer to the modified data, as well as the number of bytes pointed. The default implementation provides the packet's data without transforming it.

Parameters

size	Variable to fill with the size of data to send

Returns: Pointer to the array of bytes to send

See also: onReceive

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 behavior 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.

Returns: True if last data extraction from packet was successful

See also: endOfPacket

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.

The documentation for this class was generated from the following file:

Packet.hpp

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SFML - Simple and Fast Multimedia Library

SFML

Public Member Functions

Protected Member Functions

Friends

Detailed Description

Constructor & Destructor Documentation

Member Function Documentation