fur::download::bitfield::Bitfield Class Reference

#include <bitfield.hpp>

Public Member Functions
	Bitfield (int64_t len)
	Create a new Bitfield with the provided length (in bits). More...
	Bitfield (std::vector< uint8_t > storage, int64_t len)
void	set (int64_t index, bool value)
	Set the bit to the provided index to either 1 or 0, depending on value. More...
void	set (int64_t index)
	Set the bit to the provided index to 1. More...
void	unset (int64_t index)
	Set the bit to the provided index to 0. More...
bool	get (int64_t index) const
	Get the value of the bit at the provided index. More...
std::vector< uint8_t >	get_bytes () const
	Get the bitfield as an array of bytes. More...

Public Attributes
const int64_t	len

Friends
std::ostream &	operator<< (std::ostream &os, const Bitfield &bitfield)

Detailed Description

Bitfield is basically just a bit array that is used to keep track of what pieces a peer has to offer. A 1-bit indicates a piece that we can ask for while a 0-bit is a piece that the peer doesn't have.

Attention

A Bitfield cannot be resized once created.

Note that we could've used a type from the standard library instead but they had a couple of disadvantages:

• bitset only works with a number of bits known at compile time but we don't know the number of bits, which matches the number of pieces, until we read a torrent file.
• std::vector<bool> is a specialized template which shouldn't actually result in entire bytes being allocated. Because it is not, then, a standard STL container, its usage is discouraged. See https://en.wikipedia.org/wiki/Bit_array.

Constructor & Destructor Documentation

Bitfield() [1/2]

fur::download::bitfield::Bitfield::Bitfield ( int64_t  len )

explicit

Create a new Bitfield with the provided length (in bits).

Bitfield() [2/2]

fur::download::bitfield::Bitfield::Bitfield ( std::vector< uint8_t >  storage, int64_t  len  )

inline

Create a new Bitfield from an existing backing storage. The length in bits must be provided because the last byte is not necessarily used till the last bit.

Member Function Documentation

get()

bool fur::download::bitfield::Bitfield::get

(

int64_t

index

)

const

Get the value of the bit at the provided index.

get_bytes()

std::vector<uint8_t> fur::download::bitfield::Bitfield::get_bytes ( ) const

inline

Get the bitfield as an array of bytes.

set() [1/2]

void fur::download::bitfield::Bitfield::set ( int64_t  index )

inline

Set the bit to the provided index to 1.

set() [2/2]

void fur::download::bitfield::Bitfield::set	(	int64_t	index,
		bool	value
	)

Set the bit to the provided index to either 1 or 0, depending on value.

unset()

void fur::download::bitfield::Bitfield::unset ( int64_t  index )

inline

Set the bit to the provided index to 0.

Friends And Related Function Documentation

operator<<

std::ostream& operator<< ( std::ostream &  os, const Bitfield &  bitfield  )

friend

Display the Bitfield as a 8-column grid. Each row is a byte. Bit 0 is in the topmost left corner.

Member Data Documentation

len

const int64_t fur::download::bitfield::Bitfield::len

Store the length for checking that no out-of-bounds read or write is performed. The actual length in bits cannot be computed from the number of bytes in storage because the last byte might not be used in its entirety if the number of bits is not a multiple of 8.

Attention

A Bitfield cannot be resized once created.

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

• /home/runner/work/furrent/furrent/src/download/bitfield.hpp
• /home/runner/work/furrent/furrent/src/download/bitfield.cpp