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Published: Jan 25, 2016 License: GPL-3.0 Imports: 13 Imported by: 3



Package abi implements the Ethereum ABI (Application Binary Interface).

The Ethereum ABI is strongly typed, known at compile time and static. This ABI will handle basic type casting; unsigned to signed and visa versa. It does not handle slice casting such as unsigned slice to signed slice. Bit size type casting is also handled. ints with a bit size of 32 will be properly cast to int256, etc.



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const (
	IntTy byte = iota


This section is empty.


func S256

func S256(n *big.Int) []byte

func S2S256

func S2S256(n int64) []byte

func U256

func U256(n *big.Int) []byte

U256 will ensure unsigned 256bit on big nums

func U2U256

func U2U256(n uint64) []byte

S256 will ensure signed 256bit on big nums


type ABI

type ABI struct {
	Methods map[string]Method
	Events  map[string]Event

The ABI holds information about a contract's context and available invokable methods. It will allow you to type check function calls and packs data accordingly.

func JSON

func JSON(reader io.Reader) (ABI, error)

JSON returns a parsed ABI interface and error if it failed.

func (ABI) Call

func (abi ABI) Call(executer Executer, name string, args ...interface{}) interface{}

Call executes a call and attemps to parse the return values and returns it as an interface. It uses the executer method to perform the actual call since the abi knows nothing of the lower level calling mechanism.

Call supports all abi types and includes multiple return values. When only one item is returned a single interface{} will be returned, if a contract method returns multiple values an []interface{} slice is returned.

func (ABI) Pack

func (abi ABI) Pack(name string, args ...interface{}) ([]byte, error)

Pack the given method name to conform the ABI. Method call's data will consist of method_id, args0, arg1, ... argN. Method id consists of 4 bytes and arguments are all 32 bytes. Method ids are created from the first 4 bytes of the hash of the methods string signature. (signature = baz(uint32,string32))

func (*ABI) UnmarshalJSON

func (abi *ABI) UnmarshalJSON(data []byte) error

type Argument

type Argument struct {
	Name    string
	Type    Type
	Indexed bool // indexed is only used for Event

Argument holds the name of the argument and the corresponding type. Types are used when packing and testing arguments.

func (*Argument) UnmarshalJSON

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

type Event

type Event struct {
	Name   string
	Inputs []Argument

Event is an event potentially triggered by the EVM's LOG mechanism. The Event holds type information (inputs) about the yielded output

func (Event) Id

func (e Event) Id() common.Hash

type Executer

type Executer func(datain []byte) []byte

Executer is an executer method for performing state executions. It takes one argument which is the input data and expects output data to be returned as multiple 32 byte word length concatenated slice

type Method

type Method struct {
	Name    string
	Const   bool
	Inputs  []Argument
	Outputs []Argument

Callable method given a `Name` and whether the method is a constant. If the method is `Const` no transaction needs to be created for this particular Method call. It can easily be simulated using a local VM. For example a `Balance()` method only needs to retrieve something from the storage and therefor requires no Tx to be send to the network. A method such as `Transact` does require a Tx and thus will be flagged `true`. Input specifies the required input parameters for this gives method.

func (Method) Id

func (m Method) Id() []byte

func (Method) Sig

func (m Method) Sig() string

Sig returns the methods string signature according to the ABI spec.


function foo(uint32 a, int b)    =    "foo(uint32,int256)"

Please note that "int" is substitute for its canonical representation "int256"

func (Method) String

func (m Method) String() string

type Type

type Type struct {
	Kind reflect.Kind
	Type reflect.Type
	Size int
	T    byte // Our own type checking
	// contains filtered or unexported fields

Type is the reflection of the supported argument type

func NewType

func NewType(t string) (typ Type, err error)

NewType returns a fully parsed Type given by the input string or an error if it can't be parsed.

Strings can be in the format of:

Input  = Type [ "[" [ Number ] "]" ] Name .
Type   = [ "u" ] "int" [ Number ] .


string     int       uint       real
string32   int8      uint8      uint[]
address    int256    uint256    real[2]

func (Type) String

func (t Type) String() (out string)

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