math

Documentation

Overview

Package math provides convenience functions to use big.Int and to parse a string into an integer.

`big.go` provides Max, Min, Pow, and Parse functions for big.Int type and it also implements encoding.TextMarshaler and encoding.TextUnmarshaler.

`integer.go` provides functions to parse string into unsigned int and to calculate safely by detecting overflow. It also provides implementation of encoding.TextMarshaler and encoding.TextUnmarshaler.

encoding.TextMarshaler is the interface implemented by an object that can marshal itself into a textual form. Its MarshalText encodes the receiver into UTF-8-encoded text and returns the result.

encoding.TextUnmarshaler is the interface implemented by an object that can unmarshal a textual representation of itself. Its UnmarshalText must be able to decode the form generated by MarshalText.

Index

• Constants
• 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 MustParseUint64(s string) uint64
• func PaddedBigBytes(bigint *big.Int, n int) []byte
• func ParseBig256(s string) (*big.Int, bool)
• func ParseUint64(s string) (uint64, bool)
• func ReadBits(bigint *big.Int, buf []byte)
• func S256(x *big.Int) *big.Int
• func SafeAdd(x, y uint64) (uint64, bool)
• func SafeMul(x, y uint64) (uint64, bool)
• func SafeSub(x, y uint64) (uint64, bool)
• func U256(x *big.Int) *big.Int
• type HexOrDecimal256
  • func (i *HexOrDecimal256) MarshalText() ([]byte, error)
  • func (i *HexOrDecimal256) UnmarshalText(input []byte) error
• type HexOrDecimal64
  • func (i HexOrDecimal64) MarshalText() ([]byte, error)
  • func (i *HexOrDecimal64) UnmarshalText(input []byte) error

Constants

const (
	// Integer limit values.
	MaxInt8   = 1<<7 - 1
	MinInt8   = -1 << 7
	MaxInt16  = 1<<15 - 1
	MinInt16  = -1 << 15
	MaxInt32  = 1<<31 - 1
	MinInt32  = -1 << 31
	MaxInt64  = 1<<63 - 1
	MinInt64  = -1 << 63
	MaxUint8  = 1<<8 - 1
	MaxUint16 = 1<<16 - 1
	MaxUint32 = 1<<32 - 1
	MaxUint64 = 1<<64 - 1
)

Variables

var (
	MaxBig256 = new(big.Int).Set(tt256m1)

	MaxBig63 = new(big.Int).Sub(tt63, common.Big1)
)

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 MustParseUint64

func MustParseUint64(s string) uint64

MustParseUint64 parses s as an 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 ParseUint64

func ParseUint64(s string) (uint64, bool)

ParseUint64 parses s as an 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 SafeAdd

func SafeAdd(x, y uint64) (uint64, bool)

SafeAdd returns the result and whether overflow occurred.

func SafeMul

func SafeMul(x, y uint64) (uint64, bool)

SafeMul returns multiplication result and whether overflow occurred.

func SafeSub

func SafeSub(x, y uint64) (uint64, bool)

SafeSub returns subtraction result and whether overflow occurred.

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 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.

type HexOrDecimal64

type HexOrDecimal64 uint64

HexOrDecimal64 marshals uint64 as hex or decimal.

func (HexOrDecimal64) MarshalText

func (i HexOrDecimal64) MarshalText() ([]byte, error)

MarshalText implements encoding.TextMarshaler.

func (*HexOrDecimal64) UnmarshalText

func (i *HexOrDecimal64) UnmarshalText(input []byte) error

UnmarshalText implements encoding.TextUnmarshaler.