helper

Documentation

Index

• Constants
• Variables
• func AllZero(b []byte) bool
• func BigMax(x, y *big.Int) *big.Int
• func BigMin(x, y *big.Int) *big.Int
• func BigPow(a, b int64) *big.Int
• func BigUint64(v *big.Int) (uint64, bool)
• func Byte(bigint *big.Int, padlength, n int) byte
• func BytesToString(data []byte) string
• func Exp(base, exponent *big.Int) *big.Int
• func GetDataBig(data []byte, start *big.Int, size *big.Int) []byte
• func HexToBytes(str string) []byte
• func JoinBytes(data ...[]byte) []byte
• func LeftPadBytes(slice []byte, l int) []byte
• func Max(x, y uint64) uint64
• func Min(x, y uint64) uint64
• func PaddedBigBytes(bigint *big.Int, n int) []byte
• func ReadBits(bigint *big.Int, buf []byte)
• func ReverseSlice(s interface{})
• func RightPadBytes(slice []byte, l int) []byte
• func S256(x *big.Int) *big.Int
• func SafeAdd(x, y uint64) (uint64, bool)
• func SafeMul(x, y uint64) (uint64, bool)
• func ToWordSize(size uint64) uint64
• func U256(x *big.Int) *big.Int

Constants

const (
	MaxUint64 = uint64(1<<64 - 1)

	// number of bits in a big.Word
	WordBits = 32 << (uint64(^big.Word(0)) >> 63)
	// number of bytes in a big.Word
	WordBytes = WordBits / 8
	// number of bytes in a vm word
	WordSize = 32
)

Variables

var (
	Big0   = big.NewInt(0)
	Big1   = big.NewInt(1)
	Big2   = big.NewInt(2)
	Big10  = big.NewInt(10)
	Big31  = big.NewInt(31)
	Big32  = big.NewInt(32)
	Big256 = big.NewInt(256)
	Big257 = big.NewInt(257)

	Tt255   = BigPow(2, 255)
	Tt256   = BigPow(2, 256)
	Tt256m1 = new(big.Int).Sub(Tt256, big.NewInt(1))
)

Functions

func AllZero

func AllZero(b []byte) bool

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 BigUint64

func BigUint64(v *big.Int) (uint64, bool)

BigUint64 returns the integer casted to a uint64 and returns whether it overflowed in the process.

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 BytesToString

func BytesToString(data []byte) string

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.

func GetDataBig

func GetDataBig(data []byte, start *big.Int, size *big.Int) []byte

GetDataBig returns a slice from the data based on the start and size and pads up to size with zero's. This function is overflow safe.

func HexToBytes

func HexToBytes(str string) []byte

func JoinBytes

func JoinBytes(data ...[]byte) []byte

func LeftPadBytes

func LeftPadBytes(slice []byte, l int) []byte

leftPadBytes zero-pads slice to the left up to length l.

func Max

func Max(x, y uint64) uint64

func Min

func Min(x, y uint64) uint64

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 ReadBits

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

ReadBits encodes the absolute amount 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 ReverseSlice

func ReverseSlice(s interface{})

func RightPadBytes

func RightPadBytes(slice []byte, l int) []byte

rightPadBytes zero-pads slice to the right up to length l.

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 ToWordSize

func ToWordSize(size uint64) uint64

ToWordSize returns the ceiled word size required for memory expansion.

func U256

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

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