Blocks and Transactions

You can use the BlockData and TransactionData data structures to index important information about the Fuel network for your dApp.

BlockData

pub struct BlockData {
    pub height: u64,
    pub id: Bytes32,
    pub producer: Option<Bytes32>,
    pub time: i64,
    pub transactions: Vec<TransactionData>,
}

The BlockData struct is how blocks are represented in the Fuel indexer. It contains metadata such as the ID, height, and time, as well as a list of the transactions it contains (represented by TransactionData). It also contains the public key hash of the block producer, if present.

TransactionData

pub struct TransactionData {
    pub transaction: Transaction,
    pub status: TransactionStatus,
    pub receipts: Vec<Receipt>,
    pub id: TxId,
}

The TransactionData struct contains important information about a transaction in the Fuel network. The id field is the transaction hash, which is a 32-byte string. The receipts field contains a list of Receipts, which are generated by a Fuel node during the execution of a Sway smart contract; you can find more information in the Receipts section.

Transaction

pub enum Transaction {
    Script(Script),
    Create(Create),
    Mint(Mint),
}

Transaction refers to the Fuel transaction entity and can be one of three distinct types: Script, Create, or Mint. Explaining the differences between each of the types is out of scope for the Fuel indexer; however, you can find information about the Transaction type in the Fuel specifications.

enum TransactionType : uint8 {
    Script = 0,
    Create = 1,
    Mint = 2,
}

Transaction is invalid if:

• type > TransactionType.Create
• gasLimit > MAX_GAS_PER_TX
• blockheight() < maturity
• inputsCount > MAX_INPUTS
• outputsCount > MAX_OUTPUTS
• witnessesCount > MAX_WITNESSES
• No inputs are of type InputType.Coin or InputType.Message
• More than one output is of type OutputType.Change for any asset ID in the input set
• Any output is of type OutputType.Change for any asset ID not in the input set
• More than one input of type InputType.Coin for any Coin ID in the input set
• More than one input of type InputType.Contract for any Contract ID in the input set
• More than one input of type InputType.Message for any Message ID in the input set

When serializing a transaction, fields are serialized as follows (with inner structs serialized recursively):

1. uint8, uint16, uint32, uint64: big-endian right-aligned to 8 bytes.
2. byte[32]: as-is.
3. byte[]: as-is, with padding zeroes aligned to 8 bytes.

When deserializing a transaction, the reverse is done. If there are insufficient bytes or too many bytes, the transaction is invalid.

TransactionScript

enum ReceiptType : uint8 {
    Call = 0,
    Return = 1,
    ReturnData = 2,
    Panic = 3,
    Revert = 4,
    Log = 5,
    LogData = 6,
    Transfer = 7,
    TransferOut = 8,
    ScriptResult = 9,
    MessageOut = 10,
}

Given helper len() that returns the number of bytes of a field.

Transaction is invalid if:

• Any output is of type OutputType.ContractCreated
• scriptLength > MAX_SCRIPT_LENGTH
• scriptDataLength > MAX_SCRIPT_DATA_LENGTH
• scriptLength * 4 != len(script)
• scriptDataLength != len(scriptData)

IMPORTANT:

When signing a transaction, receiptsRoot is set to zero.

When verifying a predicate, receiptsRoot is initialized to zero.

When executing a script, receiptsRoot is initialized to zero.

The receipts root receiptsRoot is the root of the binary Merkle tree of receipts. If there are no receipts, its value is set to the root of the empty tree, i.e. 0xe3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855.

TransactionCreate

Transaction is invalid if:

• Any input is of type InputType.Contract
• Any output is of type OutputType.Contract or OutputType.Variable
• More than one output is of type OutputType.Change with asset_id of zero
• Any output is of type OutputType.Change with non-zero asset_id
• It does not have exactly one output of type OutputType.ContractCreated
• bytecodeLength * 4 > CONTRACT_MAX_SIZE
• tx.data.witnesses[bytecodeWitnessIndex].dataLength != bytecodeLength * 4
• bytecodeWitnessIndex >= tx.witnessesCount
• The keys of storageSlots are not in ascending lexicographic order
• The computed contract ID (see below) is not equal to the contractID of the one OutputType.ContractCreated output
• storageSlotsCount > MAX_STORAGE_SLOTS
• The Sparse Merkle tree root of storageSlots is not equal to the stateRoot of the one OutputType.ContractCreated output

Creates a contract with contract ID as computed here.

TransactionMint

The transaction is created by the block producer and is not signed. Since it is not usable outside of block creation or execution, all fields must be fully set upon creation without any zeroing.

Transaction is invalid if:

• Any output is not of type OutputType.Coin
• Any two outputs have the same asset_id
• txPointer is zero or doesn't match the block.

TransactionStatus

pub enum TransactionStatus {
    Failure {
        block_id: String,
        time: DateTime<Utc>,
        reason: String,
    },
    SqueezedOut {
        reason: String,
    },
    Submitted {
        submitted_at: DateTime<Utc>,
    },
    Success {
        block_id: String,
        time: DateTime<Utc>,
    },
}

TransactionStatus refers to the status of a Transaction in the Fuel network.