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Published: Jan 25, 2016 License: GPL-3.0 Imports: 18 Imported by: 105



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The common package contains the ethereum utility library.


As a subdirectory the main go-ethereum repository, you get it with go get


RLP (Recursive Linear Prefix) Encoding

RLP Encoding is an encoding scheme used by the Ethereum project. It encodes any native value or list to a string.

More in depth information about the encoding scheme see the Wiki article.

rlp := common.Encode("doge")
fmt.Printf("%q\n", rlp) // => "\0x83dog"

rlp = common.Encode([]interface{}{"dog", "cat"})
fmt.Printf("%q\n", rlp) // => "\0xc8\0x83dog\0x83cat"
decoded := common.Decode(rlp)
fmt.Println(decoded) // => ["dog" "cat"]

Patricia Trie

Patricie Tree is a merkle trie used by the Ethereum project.

More in depth information about the (modified) Patricia Trie can be found on the Wiki.

The patricia trie uses a db as backend and could be anything as long as it satisfies the Database interface found in common/db.go.

db := NewDatabase()

// db, root
trie := common.NewTrie(db, "")

trie.Put("puppy", "dog")
trie.Put("horse", "stallion")
trie.Put("do", "verb")
trie.Put("doge", "coin")

// Look up the key "do" in the trie
out := trie.Get("do")
fmt.Println(out) // => verb


The patricia trie, in combination with RLP, provides a robust, cryptographically authenticated data structure that can be used to store all (key, value) bindings.

// ... Create db/trie

// Note that RLP uses interface slices as list
value := common.Encode([]interface{}{"one", 2, "three", []interface{}{42}})
// Store the RLP encoded value of the list
trie.Put("mykey", value)


Value is a Generic Value which is used in combination with RLP data or ([])interface{} structures. It may serve as a bridge between RLP data and actual real values and takes care of all the type checking and casting. Unlike Go's reflect.Value it does not panic if it's unable to cast to the requested value. It simple returns the base value of that type (e.g. Slice() returns []interface{}, Uint() return 0, etc).

Creating a new Value

NewEmptyValue() returns a new *Value with it's initial value set to a []interface{}

AppendList() appends a list to the current value.

Append(v) appends the value (v) to the current value/list.

val := common.NewEmptyValue().Append(1).Append("2")
Retrieving values

Get(i) returns the i item in the list.

Uint() returns the value as an unsigned int64.

Slice() returns the value as a interface slice.

Str() returns the value as a string.

Bytes() returns the value as a byte slice.

Len() assumes current to be a slice and returns its length.

Byte() returns the value as a single byte.

val := common.NewValue([]interface{}{1,"2",[]interface{}{3}})
val.Get(0).Uint() // => 1
val.Get(1).Str()  // => "2"
s := val.Get(2)   // => Value([]interface{}{3})
s.Get(0).Uint()   // => 3


Decoding streams of RLP data is simplified

val := common.NewValueFromBytes(rlpData)


Encoding from Value to RLP is done with the Encode method. The underlying value can be anything RLP can encode (int, str, lists, bytes)

val := common.NewValue([]interface{}{1,"2",[]interface{}{3}})
rlp := val.Encode()
// Store the rlp data



Package common contains various helper functions.



View Source
const (
	HashLength    = 32
	AddressLength = 20


View Source
var (
	Big1     = big.NewInt(1)
	Big2     = big.NewInt(2)
	Big3     = big.NewInt(3)
	Big0     = big.NewInt(0)
	BigTrue  = Big1
	BigFalse = Big0
	Big32    = big.NewInt(32)
	Big36    = big.NewInt(36)
	Big97    = big.NewInt(97)
	Big98    = big.NewInt(98)
	Big256   = big.NewInt(0xff)
	Big257   = big.NewInt(257)
	MaxBig   = String2Big("0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff")

Common big integers often used

View Source
var (
	Base36Chars          = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"
	ICAPLengthError      = errors.New("Invalid ICAP length")
	ICAPEncodingError    = errors.New("Invalid ICAP encoding")
	ICAPChecksumError    = errors.New("Invalid ICAP checksum")
	ICAPCountryCodeError = errors.New("Invalid ICAP country code")
	ICAPAssetIdentError  = errors.New("Invalid ICAP asset identifier")
	ICAPInstCodeError    = errors.New("Invalid ICAP institution code")
	ICAPClientIdentError = errors.New("Invalid ICAP client identifier")
View Source
var (
	Douglas  = BigPow(10, 42)
	Einstein = BigPow(10, 21)
	Ether    = BigPow(10, 18)
	Finney   = BigPow(10, 15)
	Szabo    = BigPow(10, 12)
	Shannon  = BigPow(10, 9)
	Babbage  = BigPow(10, 6)
	Ada      = BigPow(10, 3)
	Wei      = big.NewInt(1)

The different number of units


func AbsolutePath

func AbsolutePath(Datadir string, filename string) string

func AddressToICAP

func AddressToICAP(a Address) (string, error)

func AddressToIndirectICAP

func AddressToIndirectICAP(a Address, instCode string) (string, error)

TODO: integrate with ICAP namereg when it's available

func Big

func Big(num string) *big.Int


Shortcut for new(big.Int).SetString(..., 0)

func BigCopy

func BigCopy(src *big.Int) *big.Int

Big copy

Creates a copy of the given big integer

func BigD

func BigD(data []byte) *big.Int

func BigMax

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

Big max

Returns the maximum size big integer

func BigMin

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

Big min

Returns the minimum size big integer

func BigPow

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

Big pow

Returns the power of two big integers

func BigToBytes

func BigToBytes(num *big.Int, base int) []byte

Big to bytes

Returns the bytes of a big integer with the size specified by **base** Attempts to pad the byte array with zeros.

func BitTest

func BitTest(num *big.Int, i int) bool

func ByteSliceToInterface

func ByteSliceToInterface(slice [][]byte) (ret []interface{})

func Bytes2Big

func Bytes2Big(data []byte) *big.Int

func Bytes2Hex

func Bytes2Hex(d []byte) string

func BytesToBig

func BytesToBig(data []byte) *big.Int


func BytesToNumber

func BytesToNumber(b []byte) uint64

Bytes to number

Attempts to cast a byte slice to a unsigned integer

func CopyBytes

func CopyBytes(b []byte) (copiedBytes []byte)

Copy bytes

Returns an exact copy of the provided bytes

func CurrencyToString

func CurrencyToString(num *big.Int) string

Currency to string Returns a string representing a human readable format

func DefaultDataDir

func DefaultDataDir() string

func DefaultIpcPath

func DefaultIpcPath() string

func DeleteFromByteSlice

func DeleteFromByteSlice(s [][]byte, hash []byte) [][]byte

func EmptyHash

func EmptyHash(h Hash) bool

func ExpandHomePath

func ExpandHomePath(p string) (path string)

func FileExist

func FileExist(filePath string) bool

func FirstBitSet

func FirstBitSet(v *big.Int) int

func FormatData

func FormatData(data string) []byte

func FromHex

func FromHex(s string) []byte

func HasHexPrefix

func HasHexPrefix(str string) bool

func Hex2Bytes

func Hex2Bytes(str string) []byte

func Hex2BytesFixed

func Hex2BytesFixed(str string, flen int) []byte

func HomeDir

func HomeDir() string

func IsHex

func IsHex(str string) bool

func IsHexAddress

func IsHexAddress(s string) bool

IsHexAddress verifies whether a string can represent a valid hex-encoded Ethereum address or not.

func LeftPadBytes

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

func LeftPadString

func LeftPadString(str string, l int) string

func LoadJSON

func LoadJSON(file string, val interface{}) error

LoadJSON reads the given file and unmarshals its content.

func MakeName

func MakeName(name, version string) string

MakeName creates a node name that follows the ethereum convention for such names. It adds the operation system name and Go runtime version the name.

func NumberToBytes

func NumberToBytes(num interface{}, bits int) []byte

Number to bytes

Returns the number in bytes with the specified base

func PP

func PP(value []byte) string

PP Pretty Prints a byte slice in the following format:


func ParseData

func ParseData(data ...interface{}) (ret []byte)

func ReadVarInt

func ReadVarInt(buff []byte) (ret uint64)

Read variable int

Read a variable length number in big endian byte order

func Report

func Report(extra ...interface{})

func RightPadBytes

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

func RightPadString

func RightPadString(str string, l int) string

func S256

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

func String2Big

func String2Big(num string) *big.Int

func StringToByteFunc

func StringToByteFunc(str string, cb func(str string) []byte) (ret []byte)

func ToAddress

func ToAddress(slice []byte) (addr []byte)

func ToHex

func ToHex(b []byte) string

func U256

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


type Address

type Address [AddressLength]byte

func BigToAddress

func BigToAddress(b *big.Int) Address

func BytesToAddress

func BytesToAddress(b []byte) Address

///////// Address

func HexToAddress

func HexToAddress(s string) Address

func ICAPToAddress

func ICAPToAddress(s string) (Address, error)

func StringToAddress

func StringToAddress(s string) Address

func (Address) Big

func (a Address) Big() *big.Int

func (Address) Bytes

func (a Address) Bytes() []byte

func (Address) Hash

func (a Address) Hash() Hash

func (Address) Hex

func (a Address) Hex() string

func (Address) MarshalJSON

func (a Address) MarshalJSON() ([]byte, error)

Serialize given address to JSON

func (*Address) Set

func (a *Address) Set(other Address)

Sets a to other

func (*Address) SetBytes

func (a *Address) SetBytes(b []byte)

Sets the address to the value of b. If b is larger than len(a) it will panic

func (*Address) SetString

func (a *Address) SetString(s string)

Set string `s` to a. If s is larger than len(a) it will panic

func (Address) Str

func (a Address) Str() string

Get the string representation of the underlying address

func (*Address) UnmarshalJSON

func (a *Address) UnmarshalJSON(data []byte) error

Parse address from raw json data

type Bytes

type Bytes []byte

func (Bytes) String

func (self Bytes) String() string

type Hash

type Hash [HashLength]byte

func BigToHash

func BigToHash(b *big.Int) Hash

func BytesToHash

func BytesToHash(b []byte) Hash

func HexToHash

func HexToHash(s string) Hash

func StringToHash

func StringToHash(s string) Hash

func (Hash) Big

func (h Hash) Big() *big.Int

func (Hash) Bytes

func (h Hash) Bytes() []byte

func (Hash) Generate

func (h Hash) Generate(rand *rand.Rand, size int) reflect.Value

Generate implements testing/quick.Generator.

func (Hash) Hex

func (h Hash) Hex() string

func (Hash) MarshalJSON

func (h Hash) MarshalJSON() ([]byte, error)

Serialize given hash to JSON

func (*Hash) Set

func (h *Hash) Set(other Hash)

Sets h to other

func (*Hash) SetBytes

func (h *Hash) SetBytes(b []byte)

Sets the hash to the value of b. If b is larger than len(h) it will panic

func (*Hash) SetString

func (h *Hash) SetString(s string)

Set string `s` to h. If s is larger than len(h) it will panic

func (Hash) Str

func (h Hash) Str() string

Get the string representation of the underlying hash

func (*Hash) UnmarshalJSON

func (h *Hash) UnmarshalJSON(input []byte) error

UnmarshalJSON parses a hash in its hex from to a hash.

type List

type List struct {
	Length int
	// contains filtered or unexported fields

The list type is an anonymous slice handler which can be used for containing any slice type to use in an environment which does not support slice types (e.g., JavaScript, QML)

func EmptyList

func EmptyList() *List

func NewList

func NewList(t interface{}) *List

Initialise a new list. Panics if non-slice type is given.

func (*List) Append

func (self *List) Append(v interface{})

Appends value at the end of the slice. Panics when incompatible value is given.

func (*List) Get

func (self *List) Get(i int) interface{}

Get N element from the embedded slice. Returns nil if OOB.

func (*List) GetAsJson

func (self *List) GetAsJson(i int) interface{}

func (*List) Interface

func (self *List) Interface() interface{}

Returns the underlying slice as interface.

func (*List) ToJSON

func (self *List) ToJSON() string

For JavaScript <3

type StorageSize

type StorageSize float64

func (StorageSize) Int64

func (self StorageSize) Int64() int64

func (StorageSize) String

func (self StorageSize) String() string


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