Web3.Abi.Decode

Helpers to decode contract return values from JSON received through ports from the JS Web3 layer.

address : Decoder Address

Decode an Address return value.

uint256 : Decoder BigInt

Decode a uint256 return value as a BigInt. Accepts both decimal strings ("100") and 0x-prefixed hex strings ("0x64").

int256 : Decoder BigInt

Decode an int256 return value as a BigInt.

bool : Decoder Bool

Decode a bool return value.

string : Decoder String

Decode a string return value.

bytes32 : Decoder String

Decode a bytes32 hex string (e.g. an event topic). Expects a 0x-prefixed 66-character hex string and returns it as-is.

uint8 : Decoder Int

Decode a uint8 return value as an Elm Int (validated 0–255).

uint16 : Decoder Int

Decode a uint16 return value as an Elm Int (validated 0–65535).

uint32 : Decoder Int

Decode a uint32 return value as an Elm Int (validated 0–4294967295).

uint64 : Decoder BigInt

Decode a uint64 return value as a BigInt (exceeds JS/Elm safe Int range).

uint128 : Decoder BigInt

Decode a uint128 return value as a BigInt.

hexSlot : Int -> String -> String

Extract the 64-character hex of the 32-byte word at slot index n (0-indexed) from a 0x-prefixed ABI-encoded hex string.

hexSlot 0 "0x0000...0064" == "0000...0064"

uint256Slot : Int -> String -> Maybe BigInt

Decode a uint256 from slot n of a raw 0x-hex ABI response.

addressSlot : Int -> String -> Maybe Address

Decode an Address from slot n of a raw 0x-hex ABI response. Addresses are right-aligned in the 32-byte slot.

boolSlot : Int -> String -> Maybe Bool

Decode a bool from slot n of a raw 0x-hex ABI response.

stringSlot : Int -> String -> Maybe String

Decode a dynamic UTF-8 string from slot n of a raw 0x-hex ABI response. Slot n contains an offset pointer; the string length and data follow at that offset.

listSlot : Int -> (Int -> String -> Maybe a) -> String -> Maybe (List a)

Decode a dynamic array from slot n. Each element is decoded by calling elemDecoder slotIndex fullHex. Works for static-element arrays (uint256[], address[], etc.) where elements are stored consecutively.

tuple2Hex :

(Int -> String -> Maybe a)

-> (Int -> String -> Maybe b)

-> String

-> Maybe ( a, b )

Decode a static 2-tuple from the head of a 0x-hex ABI response. Each decoder is called with its slot index (0, 1).

tuple3Hex :

(Int -> String -> Maybe a)

-> (Int -> String -> Maybe b)

-> (Int -> String -> Maybe c)

-> String

-> Maybe ( a, b, c )

Decode a static 3-tuple from the head of a 0x-hex ABI response.

decodeRevertReason : String -> Maybe String

Attempt to decode an EVM revert reason from raw revert data.

Checks for the Error(string) selector 0x08c379a2 and decodes the ABI-encoded string that follows. Returns Nothing if the data is not a standard Error(string) revert.

decodeRevertReason "0x08c379a200000000000000000000000000000000000000000000000000000000000000200000000000000000000000000000000000000000000000000000000000000011496e73756666696369656e742066756e647300000000000000000000000000"
--> Just "Insufficient funds"

quietgarden/elm-web3/2.0.0

Web3.Abi.Decode

Modules