abi

Documentation

Overview

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.

Index

• Constants
• func S256(n *big.Int) []byte
• func S2S256(n int64) []byte
• func U256(n *big.Int) []byte
• func U2U256(n uint64) []byte
• type ABI
  • func JSON(reader io.Reader) (ABI, error)
  • func (abi ABI) Pack(name string, args ...interface{}) ([]byte, error)
  • func (abi *ABI) UnmarshalJSON(data []byte) error
• type Argument
  • func (a *Argument) UnmarshalJSON(data []byte) error
• type Method
  • func (m Method) Id() []byte
  • func (m Method) String() (out string)
• type Type
  • func NewType(t string) (typ Type, err error)
  • func (t Type) String() (out string)

Examples

• JSON

Constants

const (
	IntTy byte = iota
	UintTy
	BoolTy
	SliceTy
	AddressTy
	RealTy
)

Functions

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

Types

type ABI

type ABI struct {
	Methods map[string]Method
}

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)

Example

const definition = `[{"constant":true,"inputs":[{"name":"","type":"address"}],"name":"isBar","outputs":[{"name":"","type":"bool"}],"type":"function"}]`

abi, err := JSON(strings.NewReader(definition))
if err != nil {
	log.Fatalln(err)
}
out, err := abi.Pack("isBar", common.HexToAddress("01"))
if err != nil {
	log.Fatalln(err)
}

fmt.Printf("%x\n", out)

Output:

1f2c40920000000000000000000000000000000000000000000000000000000000000001

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
}

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 Method

type Method struct {
	Name   string
	Const  bool
	Inputs []Argument
	Return Type // not yet implemented
}

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) String

func (m Method) String() (out string)

Returns the methods string signature according to the ABI spec.

Example

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

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

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 ] .

Examples:

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

func (Type) String

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