math

package
v1.9.5 Latest Latest
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Published: Sep 20, 2019 License: GPL-3.0 Imports: 3 Imported by: 0

Documentation

Overview

Package math provides integer math utilities.

Index

Constants

View Source
const (
	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
)

Integer limit values.

Variables

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

Various big integer limit values.

Functions

func BigMax added in v1.6.0

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

BigMax returns the larger of x or y.

func BigMin added in v1.6.0

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

BigMin returns the smaller of x or y.

func BigPow added in v1.6.0

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

BigPow returns a ** b as a big integer.

func Byte added in v1.6.6

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 added in v1.5.0

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 added in v1.6.0

func FirstBitSet(v *big.Int) int

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

func MustParseBig256 added in v1.6.0

func MustParseBig256(s string) *big.Int

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

func MustParseUint64 added in v1.6.0

func MustParseUint64(s string) uint64

MustParseUint64 parses s as an integer and panics if the string is invalid.

func PaddedBigBytes added in v1.6.0

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 added in v1.6.0

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 added in v1.6.0

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 added in v1.6.0

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 added in v1.6.0

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 added in v1.6.0

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

SafeAdd returns the result and whether overflow occurred.

func SafeMul added in v1.6.0

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

SafeMul returns multiplication result and whether overflow occurred.

func SafeSub added in v1.6.0

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

SafeSub returns subtraction result and whether overflow occurred.

func U256 added in v1.6.0

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

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

Types

type HexOrDecimal256 added in v1.6.0

type HexOrDecimal256 big.Int

HexOrDecimal256 marshals big.Int as hex or decimal.

func NewHexOrDecimal256 added in v1.9.0

func NewHexOrDecimal256(x int64) *HexOrDecimal256

NewHexOrDecimal256 creates a new HexOrDecimal256

func (*HexOrDecimal256) MarshalText added in v1.6.0

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

MarshalText implements encoding.TextMarshaler.

func (*HexOrDecimal256) UnmarshalText added in v1.6.0

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

UnmarshalText implements encoding.TextUnmarshaler.

type HexOrDecimal64 added in v1.6.0

type HexOrDecimal64 uint64

HexOrDecimal64 marshals uint64 as hex or decimal.

func (HexOrDecimal64) MarshalText added in v1.6.0

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

MarshalText implements encoding.TextMarshaler.

func (*HexOrDecimal64) UnmarshalText added in v1.6.0

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

UnmarshalText implements encoding.TextUnmarshaler.

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