uint256 Class Reference

256-bit unsigned big integer. More...

#include <uint256.h>

Inheritance diagram for uint256:

Collaboration diagram for uint256:

Public Member Functions
	uint256 ()
	uint256 (const base_uint< 256 > &b)
	uint256 (uint64_t b)
	uint256 (const std::string &str)
	uint256 (const std::vector< unsigned char > &vch)
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. More...
uint32_t	GetCompact (bool fNegative=false) const
uint64_t	GetHash (const uint256 &salt) 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 (const std::vector< unsigned char > &vch)
base_uint &	operator= (const base_uint &b)
base_uint &	operator= (uint64_t b)
bool	operator! () const
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
std::string	ToStringReverseEndian () const
unsigned char *	begin ()
const unsigned char *	begin () const
unsigned char *	end ()
const unsigned char *	end () const
unsigned int	size () const
uint64_t	Get64 (int n=0) const
uint32_t	Get32 (int n=0) const
unsigned int	bits () const
	Returns the position of the highest bit set plus one, or zero if the value is zero. More...
uint64_t	GetLow64 () const
unsigned int	GetSerializeSize (int nType, int nVersion) const
void	Serialize (Stream &s, int nType, int nVersion) const
void	Unserialize (Stream &s, int nType, int nVersion)
uint64_t	GetCheapHash () const
void	SetNull ()
bool	IsNull () const

Additional Inherited Members
Public Types inherited from base_uint< 256 >
enum
Public Attributes inherited from base_uint< 256 >
uint32_t	pn [WIDTH]

Detailed Description

256-bit unsigned big integer.

Definition at line 38 of file uint256.h.

Constructor & Destructor Documentation

uint256() [1/5]

uint256::uint256 ( )

inline

Definition at line 41 of file uint256.h.

uint256() [2/5]

uint256::uint256 ( const base_uint< 256 > &  b )

inline

Definition at line 42 of file uint256.h.

uint256() [3/5]

uint256::uint256 ( uint64_t  b )

inline

Definition at line 43 of file uint256.h.

uint256() [4/5]

uint256::uint256 ( const std::string &  str )

inlineexplicit

Definition at line 44 of file uint256.h.

uint256() [5/5]

uint256::uint256 ( const std::vector< unsigned char > &  vch )

inlineexplicit

Definition at line 45 of file uint256.h.

Member Function Documentation

GetCompact()

uint32_t uint256::GetCompact

(

bool

fNegative = false

)

const

Definition at line 34 of file uint256.cpp.

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GetHash()

uint64_t uint256::GetHash

(

const uint256 &

salt

)

const

Definition at line 99 of file uint256.cpp.

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SetCompact()

uint256 & 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.

Old classes definitions.

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.

Definition at line 14 of file uint256.cpp.

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

• src/uint256.h
• src/uint256.cpp