abi

package
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Published: Mar 3, 2016 License: GPL-3.0 Imports: 10 Imported by: 0

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

Examples

Constants

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

Variables

This section is empty.

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)

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