math

Documentation

Overview

Package math provides integer math utilities.

Index

• Variables
• func BigMax(x, y *big.Int) *big.Int
• func BigMin(x, y *big.Int) *big.Int
• func BigPow(a, b int64) *big.Int
• func Byte(bigint *big.Int, padlength, n int) byte
• func Exp(base, exponent *big.Int) *big.Int
• func FirstBitSet(v *big.Int) int
• func MustParseBig256(s string) *big.Int
• func PaddedBigBytes(bigint *big.Int, n int) []byte
• func ParseBig256(s string) (*big.Int, bool)
• func ReadBits(bigint *big.Int, buf []byte)
• func S256(x *big.Int) *big.Int
• func U256(x *big.Int) *big.Int
• type DirRange
  • func (a DirRange) Len() int
  • func (a DirRange) Less(i, j int) bool
  • func (a DirRange) Swap(i, j int)
• type HexOrDecimal256
  • func (i *HexOrDecimal256) MarshalText() ([]byte, error)
  • func (i *HexOrDecimal256) UnmarshalText(input []byte) error

Variables

var (
	MaxBig256 = new(big.Int).Set(tt256m1)
	MaxBig63  = new(big.Int).Sub(tt63, big.NewInt(1))
)

Various big integer limit values.

Functions

func BigMax

func BigMax(x, y *big.Int) *big.Int

BigMax returns the larger of x or y.

func BigMin

func BigMin(x, y *big.Int) *big.Int

BigMin returns the smaller of x or y.

func BigPow

func BigPow(a, b int64) *big.Int

BigPow returns a ** b as a big integer.

func Byte

func Byte(bigint *big.Int, padlength, n int) byte

Byte returns the byte at position n, with the supplied padlength in Little-Endian encoding. n==0 returns the MSB Example: bigint '5', padlength 32, n=31 => 5

func Exp

func Exp(base, exponent *big.Int) *big.Int

Exp implements exponentiation by squaring. Exp returns a newly-allocated big integer and does not change base or exponent. The result is truncated to 256 bits.

Courtesy @karalabe and @chfast

func FirstBitSet

func FirstBitSet(v *big.Int) int

FirstBitSet returns the index of the first 1 bit in v, counting from LSB.

func MustParseBig256

func MustParseBig256(s string) *big.Int

MustParseBig256 parses s as a 256 bit big integer and panics if the string is invalid.

func PaddedBigBytes

func PaddedBigBytes(bigint *big.Int, n int) []byte

PaddedBigBytes encodes a big integer as a big-endian byte slice. The length of the slice is at least n bytes.

func ParseBig256

func ParseBig256(s string) (*big.Int, bool)

ParseBig256 parses s as a 256 bit integer in decimal or hexadecimal syntax. Leading zeros are accepted. The empty string parses as zero.

func ReadBits

func ReadBits(bigint *big.Int, buf []byte)

ReadBits encodes the absolute value of bigint as big-endian bytes. Callers must ensure that buf has enough space. If buf is too short the result will be incomplete.

func S256

func S256(x *big.Int) *big.Int

S256 interprets x as a two's complement number. x must not exceed 256 bits (the result is undefined if it does) and is not modified.

S256(0)        = 0
S256(1)        = 1
S256(2**255)   = -2**255
S256(2**256-1) = -1

func U256

func U256(x *big.Int) *big.Int

U256 encodes as a 256 bit two's complement number. This operation is destructive.

Types

type DirRange

type DirRange []uint64

func (DirRange) Len

func (a DirRange) Len() int

func (DirRange) Less

func (a DirRange) Less(i, j int) bool

func (DirRange) Swap

func (a DirRange) Swap(i, j int)

type HexOrDecimal256

type HexOrDecimal256 big.Int

HexOrDecimal256 marshals big.Int as hex or decimal.

func (*HexOrDecimal256) MarshalText

func (i *HexOrDecimal256) MarshalText() ([]byte, error)

MarshalText implements encoding.TextMarshaler.

func (*HexOrDecimal256) UnmarshalText

func (i *HexOrDecimal256) UnmarshalText(input []byte) error

UnmarshalText implements encoding.TextUnmarshaler.