Transaction

Transaction

The Transaction type is the decoded version of a PackedTransaction, which developers will use to perform smart contract actions or use directly for access to transaction data in their applications. Once a signature is generated for a given Transaction, it can also be cast into a SignedTransaction type, which will then include signature information.

The core structure of an Antelope Transaction contains the following:

1. Transaction as Proof of Stake (TaPoS) values are embedded in every transaction as part of the consensus algorithm, using the ref_block_num and ref_block_prefix fields.
2. Limitations about the execution of the transaction are also included in fields such as expiration, max_net_usage_words, max_cpu_usage_mx, and delay_sec.
3. An array of encoded smart contract actions to perform are placed within the actions field, along with advanced events like context_free_actions and transaction_extensions.

All combined, the representation of this data structure in a JSON format is as follows:

{
  expiration: "1970-01-01T00:00:00",
  ref_block_num: 0,
  ref_block_prefix: 0,
  max_net_usage_words: 0,
  max_cpu_usage_ms: 0,
  delay_sec: 0,
  context_free_actions: [],
  actions: [],
  transaction_extensions: [],
}

Each Action passed to a transaction must be encoded as either raw hex data or passed in as a Struct.

SignedTransaction

The SignedTransaction type extends a Transaction and contains additional fields for information such as signatures and context_free_data. This format retains the Transaction format itself in its decoded state, and can now be encoded into a PackedTransaction for submission to the blockchain.

The new JSON representation with these two additional fields is as follows:

{
  expiration: "1970-01-01T00:00:00",
  ref_block_num: 0,
  ref_block_prefix: 0,
  max_net_usage_words: 0,
  max_cpu_usage_ms: 0,
  delay_sec: 0,
  context_free_actions: [],
  actions: [],
  transaction_extensions: [],
  signatures: [], // New
  context_free_data: [] // New
}

PackedTransaction

The PackedTransaction type is the encoded version of either a Transaction or a SignedTransaction, where the transaction is encoded using the Serializer as the packed_trx field and the signatures appended to the signatures array. The payload format also includes additional information about the transaction such as the compression flag to control compression on the encoded payload and the packed_context_free_data field for data outside of the transaction to include.

A simplistic look at the JSON representation of this data is as follows:

{
    compression: 0,
    packed_context_free_data: '',
    packed_trx: '',
    signatures: []
}

Creating a Transaction

In most cases while creating a transaction, the application can automatically generate current TaPoS headers using the APIClient and the get_info endpoint. The resulting response from this call contains a getTransactionHeader method, which will automatically create all the appropriate fields based on the API call. The only remaining data that must be included are the actions containing an array of smart contract actions to perform.

import { Action, APIClient, Transaction } from "@wharfkit/antelope"

const client = new APIClient({ url: "https://jungle4.greymass.com" })

const info = await client.v1.chain.get_info()
const header = info.getTransactionHeader()

const transaction = Transaction.from({
  ...header,
  actions: [
    {
      account: "eosio.token",
      name: "transfer",
      authorization: [
        { actor: "corecorecore", permission: "active" },
      ],
      data: "a02e45ea52a42e4580b1915e5d268dcaba0100000000000004454f530000000019656f73696f2d636f7265206973207468652062657374203c33",
    },
  ],
})

Initializing a Transaction

Given completely formed transaction data with already encoded actions, the Transaction class works like all Antelope core types and can be loaded using the .from() static method.

import { Transaction } from "@wharfkit/antelope"

const transaction = Transaction.from({
  expiration: "1970-01-01T00:00:00",
  ref_block_num: 0,
  ref_block_prefix: 0,
  max_net_usage_words: 0,
  max_cpu_usage_ms: 0,
  delay_sec: 0,
  context_free_actions: [],
  actions: [
    {
      account: "eosio.token",
      name: "transfer",
      authorization: [
        { actor: "corecorecore", permission: "active" },
      ],
      data: "a02e45ea52a42e4580b1915e5d268dcaba0100000000000004454f530000000019656f73696f2d636f7265206973207468652062657374203c33",
    },
  ],
  transaction_extensions: [],
})

The result stored as the transaction property will be an instance of Transaction and be ready to sign.

Using ABIs

If the actions array contains unserialized data when assembling a Transaction, an ABI is required as the second parameter to facilitate the encoding.

The example below shows the actions[0].data field as an unserialized version of an eosio.token::transfer action, alongside an ABI that defines the structure of that data. Both of these values are then passed in during the formation of the Transaction object.

import { Transaction } from "@wharfkit/antelope"

const tx = {
  delay_sec: 0,
  expiration: "2020-07-01T17:32:13",
  max_cpu_usage_ms: 0,
  max_net_usage_words: 0,
  ref_block_num: 55253,
  ref_block_prefix: 3306698594,
  actions: [
    {
      account: "eosio.token",
      name: "transfer",
      authorization: [{ actor: "foo", permission: "active" }],
      data: {
        from: "foo",
        to: "bar",
        memo: "",
        quantity: "0.0001 EOS",
      },
    },
  ],
}

const abi = {
  structs: [
    {
      base: "",
      name: "transfer",
      fields: [
        { name: "from", type: "name" },
        { name: "to", type: "name" },
        { name: "quantity", type: "asset" },
        { name: "memo", type: "string" },
      ],
    },
  ],
  actions: [
    { name: "transfer", type: "transfer", ricardian_contract: "" },
  ],
}

const transaction = Transaction.from(tx, abi)

Loading ABIs

To encode untyped data during the creation of a Transaction, an ABI may be loaded from the blockchain using an APIClient and passed in.

import { Transaction } from "@wharfkit/antelope"

const tx = {
  delay_sec: 0,
  expiration: "2020-07-01T17:32:13",
  max_cpu_usage_ms: 0,
  max_net_usage_words: 0,
  ref_block_num: 55253,
  ref_block_prefix: 3306698594,
  actions: [
    {
      account: "eosio.token",
      name: "transfer",
      authorization: [{ actor: "foo", permission: "active" }],
      data: {
        from: "foo",
        to: "bar",
        memo: "",
        quantity: "0.0001 EOS",
      },
    },
  ],
}

const client = new APIClient({ url: "https://jungle4.greymass.com " })
const { abi } = await client.v1.chain.get_abi("eosio.token")

const transaction = Transaction.from(tx, abi)

Transaction IDs

Every transaction on an Antelope blockchain has an associated Transaction ID, which is a Checksum256 hash of the contents of the transaction. Each Transaction typed object can automatically access this ID by accessing the .id property of the transaction. This property is a getter that automatically calculates and returns the value based on its state.

const transaction = Transaction.from({
  expiration: "1970-01-01T00:00:00",
  ref_block_num: 0,
  ref_block_prefix: 0,
  max_net_usage_words: 0,
  max_cpu_usage_ms: 0,
  delay_sec: 0,
  context_free_actions: [],
  actions: [
    {
      account: "eosio.token",
      name: "transfer",
      authorization: [
        { actor: "corecorecore", permission: "active" },
      ],
      data: "a02e45ea52a42e4580b1915e5d268dcaba0100000000000004454f530000000019656f73696f2d636f7265206973207468652062657374203c33",
    },
  ],
  transaction_extensions: [],
})

console.log(transaction.id)
/*
Checksum256 {
    array: Uint8Array(32) [
        59,  68,  60, 217,  74, 207,  83, 157,
        104, 140, 205,  12, 253, 201,  33, 203,
        250, 249, 153,  25, 144,  65, 202, 131,
        170, 179,  37, 171, 250,  36, 105, 220
    ]
}
*/

console.log(String(transaction.id))
// 3b443cd94acf539d688ccd0cfdc921cbfaf999199041ca83aab325abfa2469dc

Adding a Signature

After a Transaction has been signed, a SignedTransaction type can then be created. The example below shows the simplest path to create the new signed instance, by passing in all the fields from the original transaction and then appending the signature.

import { Transaction, SignedTransaction } from "@wharfkit/antelope"

const transaction = Transaction.from({
  expiration: "1970-01-01T00:00:00",
  ref_block_num: 0,
  ref_block_prefix: 0,
  max_net_usage_words: 0,
  max_cpu_usage_ms: 0,
  delay_sec: 0,
  context_free_actions: [],
  actions: [
    {
      account: "eosio.token",
      name: "transfer",
      authorization: [
        { actor: "corecorecore", permission: "active" },
      ],
      data: "a02e45ea52a42e4580b1915e5d268dcaba0100000000000004454f530000000019656f73696f2d636f7265206973207468652062657374203c33",
    },
  ],
  transaction_extensions: [],
})

const signedTransaction = SignedTransaction.from({
  ...transaction,
  signatures: [
    "SIG_K1_KeQEThQJEk7fuQC1zLuFyXZBnVmeRJXq9SrmDJGcerq1RZbgCoH5tvt28xpM7xA1bp7tStVPw17gNMG6hFyYXuNHCU4Wpd",
  ],
})

This new SignedTransaction typed object now contains all the original data alongside the signature.

Packing a Transaction

To encode the transaction data and prepare it for use on-chain, a SignedTransaction object must be converted to a PackedTransaction. This encodes all of the data and formats the object as a payload that the API endpoints for the blockchain will understand.

import { Transaction, SignedTransaction } from "@wharfkit/antelope"

const transaction = Transaction.from({
  expiration: "1970-01-01T00:00:00",
  ref_block_num: 0,
  ref_block_prefix: 0,
  max_net_usage_words: 0,
  max_cpu_usage_ms: 0,
  delay_sec: 0,
  context_free_actions: [],
  actions: [
    {
      account: "eosio.token",
      name: "transfer",
      authorization: [
        { actor: "corecorecore", permission: "active" },
      ],
      data: "a02e45ea52a42e4580b1915e5d268dcaba0100000000000004454f530000000019656f73696f2d636f7265206973207468652062657374203c33",
    },
  ],
  transaction_extensions: [],
})

const signedTransaction = SignedTransaction.from({
  ...transaction,
  signatures: [
    "SIG_K1_KeQEThQJEk7fuQC1zLuFyXZBnVmeRJXq9SrmDJGcerq1RZbgCoH5tvt28xpM7xA1bp7tStVPw17gNMG6hFyYXuNHCU4Wpd",
  ],
})

const packedTransaction =
  PackedTransaction.fromSigned(signedTransaction)

console.log(packedTransaction)
/*
PackedTransaction {
  signatures: [ Signature { type: 'K1', data: [Bytes] } ],
  compression: UInt8 {
    value: BN { negative: 0, words: [Array], length: 1, red: null }
  },
  packed_context_free_data: Bytes {
    array: Uint8Array(9) [
      120, 156, 99, 0, 0,
        0,   1,  0, 1
    ]
  },
  packed_trx: Bytes {
    array: Uint8Array(91) [
      120, 156,  99,  96,  64,   6, 140,  12, 203, 154,  76, 152,
       95,  25, 132,   2, 217, 225, 186,  54, 103, 207,  50,  46,
      208, 115, 125,  21, 180,  68, 207,  21,  36, 187, 226, 173,
      145, 145,  21,  76, 160,  97, 227, 196, 184,  88, 181, 222,
       83, 187,  24,  33,  90,  89,  92, 253, 131,  65, 180, 100,
      106, 126, 113, 102, 190, 110, 114, 126,  81, 170,  66, 102,
      177,  66,  73,  70, 170,  66,  82, 106, 113, 137, 130, 141,
       49,   3,   0, 115,  52,  28, 146
    ]
  }
}
*/

console.log(Serializer.objectify(packedTransaction))
/*
{
  signatures: [
    'SIG_K1_KeQEThQJEk7fuQC1zLuFyXZBnVmeRJXq9SrmDJGcerq1RZbgCoH5tvt28xpM7xA1bp7tStVPw17gNMG6hFyYXuNHCU4Wpd'
  ],
  compression: 1,
  packed_context_free_data: '789c63000000010001',
  packed_trx: '789c636040068c0ccb9a4c985f198402d9e1ba3667cf322ed0737d15b444cf1524bbe2ad9191154ca061e3c4b858b5de53bb18215a595cfd8341b4646a7e7166be6e727e51aa4266b1424946aa42526a7189828d31030073341c92'
}
*/

Unpacking a Transaction

Any instance of a PackedTransaction can be used to decode its own data and return either a Transaction using the .getTransaction method or a SignedTransaction using the .getSignedTransaction method.

const data = {
  signatures: [
    "SIG_K1_KeQEThQJEk7fuQC1zLuFyXZBnVmeRJXq9SrmDJGcerq1RZbgCoH5tvt28xpM7xA1bp7tStVPw17gNMG6hFyYXuNHCU4Wpd",
  ],
  compression: 1,
  packed_context_free_data: "789c63000000010001",
  packed_trx:
    "789c636040068c0ccb9a4c985f198402d9e1ba3667cf322ed0737d15b444cf1524bbe2ad9191154ca061e3c4b858b5de53bb18215a595cfd8341b4646a7e7166be6e727e51aa4266b1424946aa42526a7189828d31030073341c92",
}

const packedTransaction = PackedTransaction.from(data)

const signedTransaction = packedTransaction.getSignedTransaction()

const transaction = packedTransaction.getTransaction()