arith_uint256 Class Reference

#include <arith_uint256.h>

Inheritance diagram for arith_uint256:

Public Member Functions
	arith_uint256 ()
	arith_uint256 (const base_uint< 256 > &b)
	arith_uint256 (uint64_t b)
	arith_uint256 (const std::string &str)
arith_uint256 &	SetCompact (uint32_t nCompact, bool *pfNegative=nullptr, bool *pfOverflow=nullptr)
uint32_t	GetCompact (bool fNegative=false) const
Public Member Functions inherited from base_uint< 256 >
	base_uint ()
	base_uint (const base_uint &b)
	base_uint (uint64_t b)
	base_uint (const std::string &str)
base_uint &	operator= (const base_uint &b)
base_uint &	operator= (uint64_t b)
const base_uint	operator~ () const
const base_uint	operator- () const
double	getdouble () const
base_uint &	operator^= (const base_uint &b)
base_uint &	operator^= (uint64_t b)
base_uint &	operator&= (const base_uint &b)
base_uint &	operator|= (const base_uint &b)
base_uint &	operator|= (uint64_t b)
base_uint &	operator<<= (unsigned int shift)
base_uint &	operator>>= (unsigned int shift)
base_uint &	operator+= (const base_uint &b)
base_uint &	operator+= (uint64_t b64)
base_uint &	operator-= (const base_uint &b)
base_uint &	operator-= (uint64_t b64)
base_uint &	operator *= (uint32_t b32)
base_uint &	operator *= (const base_uint &b)
base_uint &	operator/= (const base_uint &b)
base_uint &	operator++ ()
const base_uint	operator++ (int)
base_uint &	operator-- ()
const base_uint	operator-- (int)
int	CompareTo (const base_uint &b) const
bool	EqualTo (uint64_t b) const
std::string	GetHex () const
void	SetHex (const char *psz)
void	SetHex (const std::string &str)
std::string	ToString () const
unsigned int	size () const
unsigned int	bits () const
uint64_t	GetLow64 () const

Friends
uint256	ArithToUint256 (const arith_uint256 &)
arith_uint256	UintToArith256 (const uint256 &)

Additional Inherited Members
Protected Attributes inherited from base_uint< 256 >
uint32_t	pn [WIDTH]
Static Protected Attributes inherited from base_uint< 256 >
static constexpr int	WIDTH

Detailed Description

256-bit unsigned big integer.

Constructor & Destructor Documentation

arith_uint256() [1/4]

arith_uint256::arith_uint256 ( )

inline

arith_uint256() [2/4]

arith_uint256::arith_uint256 ( const base_uint< 256 > &  b )

inline

arith_uint256() [3/4]

arith_uint256::arith_uint256 ( uint64_t  b )

inline

arith_uint256() [4/4]

arith_uint256::arith_uint256 ( const std::string &  str )

inlineexplicit

Member Function Documentation

GetCompact()

uint32_t arith_uint256::GetCompact

(

bool

fNegative = false

)

const

SetCompact()

arith_uint256 & arith_uint256::SetCompact	(	uint32_t	nCompact,
		bool *	pfNegative = nullptr,
		bool *	pfOverflow = nullptr
	)

The "compact" format is a representation of a whole number N using an unsigned 32bit number similar to a floating point format. The most significant 8 bits are the unsigned exponent of base 256. This exponent can be thought of as "number of bytes of N". The lower 23 bits are the mantissa. Bit number 24 (0x800000) represents the sign of N. N = (-1^sign) * mantissa * 256^(exponent-3)

Satoshi's original implementation used BN_bn2mpi() and BN_mpi2bn(). MPI uses the most significant bit of the first byte as sign. Thus 0x1234560000 is compact (0x05123456) and 0xc0de000000 is compact (0x0600c0de)

Bitcoin only uses this "compact" format for encoding difficulty targets, which are unsigned 256bit quantities. Thus, all the complexities of the sign bit and using base 256 are probably an implementation accident.

Friends And Related Function Documentation

ArithToUint256

uint256 ArithToUint256 ( const arith_uint256 &  )

friend

UintToArith256

arith_uint256 UintToArith256 ( const uint256 &  )

friend

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

• src/arith_uint256.h
• src/arith_uint256.cpp