ABI (ex_abi v0.5.7)

Documentation for ABI, the function interface language for Solidity. Generally, the ABI describes how to take binary Ethereum and transform it to or from types that Solidity understands.

Link to this section Summary

Functions

Decodes the given data based on the function or tuple signature.

Encodes the given data into the function signature or tuple signature.

Finds and decodes the correct function from a list of ABI.FunctionSelectors

Parses the given ABI specification document into an array of ABI.FunctionSelectors.

Link to this section Functions

Link to this function

decode(function_signature, data, data_type \\ :input)

Decodes the given data based on the function or tuple signature.

In place of a signature, you can also pass one of the ABI.FunctionSelector structs returned from parse_specification/1.

Examples

iex> ABI.decode("baz(uint,address)", "00000000000000000000000000000000000000000000000000000000000000320000000000000000000000000000000000000000000000000000000000000001" |> Base.decode16!(case: :lower))
[50, <<1::160>>]

iex> ABI.decode("(address[])", "00000000000000000000000000000000000000000000000000000000000000200000000000000000000000000000000000000000000000000000000000000000" |> Base.decode16!(case: :lower))
[{[]}]

iex> ABI.decode("(string)", "00000000000000000000000000000000000000000000000000000000000000200000000000000000000000000000000000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000000b457468657220546f6b656e000000000000000000000000000000000000000000" |> Base.decode16!(case: :lower))
[{"Ether Token"}]

iex> File.read!("priv/dog.abi.json")
...> |> Jason.decode!
...> |> ABI.parse_specification
...> |> Enum.find(&(&1.function == "bark")) # bark(address,bool)
...> |> ABI.decode("b85d0bd200000000000000000000000000000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000000000001" |> Base.decode16!(case: :lower))
[<<1::160>>, true]
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encode(function_signature, data, data_type \\ :input)

Encodes the given data into the function signature or tuple signature.

In place of a signature, you can also pass one of the ABI.FunctionSelector structs returned from parse_specification/1.

Examples

iex> ABI.encode("baz(uint,address)", [50, <<1::160>> |> :binary.decode_unsigned])
...> |> Base.encode16(case: :lower)
"a291add600000000000000000000000000000000000000000000000000000000000000320000000000000000000000000000000000000000000000000000000000000001"

iex> ABI.encode("(address[])", [{[]}] ) |> Base.encode16(case: :lower)
"000000000000000000000000000000000000000000000000000000000000002000000000000000000000000000000000000000000000000000000000000000200000000000000000000000000000000000000000000000000000000000000000"

iex> ABI.encode("baz(uint8)", [9999])
** (RuntimeError) Data overflow encoding uint, data `9999` cannot fit in 8 bits

iex> ABI.encode("(uint,address)", [{50, <<1::160>> |> :binary.decode_unsigned}])
...> |> Base.encode16(case: :lower)
"00000000000000000000000000000000000000000000000000000000000000320000000000000000000000000000000000000000000000000000000000000001"

iex> ABI.encode("(string)", [{"Ether Token"}])
...> |> Base.encode16(case: :lower)
"00000000000000000000000000000000000000000000000000000000000000200000000000000000000000000000000000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000000b457468657220546f6b656e000000000000000000000000000000000000000000"

iex> ABI.encode("test(uint[], uint[])", [[1], [2]])
...> |> Base.encode16(case: :lower)
"f0d7f6eb000000000000000000000000000000000000000000000000000000000000004000000000000000000000000000000000000000000000000000000000000000800000000000000000000000000000000000000000000000000000000000000001000000000000000000000000000000000000000000000000000000000000000100000000000000000000000000000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000000000002"

iex> File.read!("priv/dog.abi.json")
...> |> Jason.decode!
...> |> ABI.parse_specification
...> |> Enum.find(&(&1.function == "bark")) # bark(address,bool)
...> |> ABI.encode([<<1::160>> |> :binary.decode_unsigned, true])
...> |> Base.encode16(case: :lower)
"b85d0bd200000000000000000000000000000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000000000001"
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find_and_decode(function_selectors, data, data_type \\ :input)

Finds and decodes the correct function from a list of ABI.FunctionSelectors

The function is found based on the method_id, which is generated from the keccak hash of the function head. More information can be found here:

https://solidity.readthedocs.io/en/develop/abi-spec.html

Keep in mind, you must include the method identifier in the passed in data otherwise this won't work as expected. If you are decoding transaction input data the identifier is the first four bytes and should already be there.

To find and decode events instead of functions, see find_and_decode_event/6

Examples

iex> File.read!("priv/dog.abi.json")
...> |> Jason.decode!
...> |> ABI.parse_specification
...> |> ABI.find_and_decode("b85d0bd200000000000000000000000000000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000000000001" |> Base.decode16!(case: :lower))
{%ABI.FunctionSelector{type: :function, function: "bark", input_names: ["at", "loudly"], method_id: <<184, 93, 11, 210>>, returns: [], types: [:address, :bool]}, [<<0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1>>, true]}
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parse_specification(doc, opts \\ [])

Parses the given ABI specification document into an array of ABI.FunctionSelectors.

Non-function entries (e.g. constructors) in the ABI specification are skipped. Fallback function entries are accepted.

This function can be used in combination with a JSON parser, e.g. Jason, to parse ABI specification JSON files.

Opts:

  • :include_events? - Include events in the output list (as %FunctionSelector{} with a type of :event). Defaults to false
                     for backwards compatibility reasons.

Examples

iex> File.read!("priv/dog.abi.json")
...> |> Jason.decode!
...> |> ABI.parse_specification
[%ABI.FunctionSelector{type: :function, function: "bark", input_names: ["at", "loudly"], method_id: <<184, 93, 11, 210>>, returns: [], types: [:address, :bool]},
 %ABI.FunctionSelector{type: :function, function: "rollover", method_id: <<176, 86, 180, 154>>, returns: [:bool], types: []}]

iex> [%{
...>   "constant" => true,
...>   "inputs" => [
...>     %{"name" => "at", "type" => "address"},
...>     %{"name" => "loudly", "type" => "bool"}
...>   ],
...>   "name" => "bark",
...>   "outputs" => [],
...>   "payable" => false,
...>   "stateMutability" => "nonpayable",
...>   "type" => "function"
...> }]
...> |> ABI.parse_specification
[%ABI.FunctionSelector{type: :function, function: "bark", method_id: <<184, 93, 11, 210>>, input_names: ["at", "loudly"], returns: [], types: [:address, :bool]}]

iex> [%{
...>   "inputs" => [
...>      %{"name" => "_numProposals", "type" => "uint8"}
...>   ],
...>   "payable" => false,
...>   "stateMutability" => "nonpayable",
...>   "type" => "constructor"
...> }]
...> |> ABI.parse_specification
[%ABI.FunctionSelector{function: nil, input_names: ["_numProposals"], inputs_indexed: nil, method_id: <<99, 53, 230, 34>>, returns: [], type: :constructor, types: [uint: 8]}]

iex> [%{
...>   "payable" => false,
...>   "stateMutability" => "nonpayable",
...>   "type" => "fallback"
...> }]
...> |> ABI.parse_specification
[%ABI.FunctionSelector{type: :function, function: nil, returns: [], types: [], method_id: nil}]

iex> File.read!("priv/dog.abi.json")
...> |> Jason.decode!
...> |> ABI.parse_specification(include_events?: true)
...> |> Enum.filter(&(&1.type == :event))
[%ABI.FunctionSelector{type: :event, function: "WantsPets", input_names: ["_from_human", "_number", "_belly"], inputs_indexed: [true, false, true], method_id: <<235, 155, 60, 76>>, types: [:string, {:uint, 256}, :bool]}]

iex> File.read!("priv/example1.abi.json")
...> |> Jason.decode!
...> |> ABI.parse_specification(include_events?: true)