How to construct a VersionedTransaction from raw bytes?

Question

For context, this question is in the context of a typescript browser client.

How can I construct a VersionedTransaction from an input of raw bytes of a transaction?

With legacy Transaction, I can just use Transaction.from(rawBytes), but for a VersionedTransaction, the only option is to create it through a VersionedMessage.

I'm guessing what I need to do is something like example below, where I extract the message component from the transaction bytes.

Example:

const txBytes: Uint8Array = getBytes();
const versionedMessage = VersionedMessage.deserialize(
   transactionBytes.slice(<message_bytes_start>, <message_bytes_end>)
);

const versionedTx = new VersionedTransaction(versionedMessage);

The issue is I can't find a definitive source of what message_bytes_start and message_bytes_end is. Interested if there's an easier way to do this. Thanks!

Answer 1

Answered my own question!

Here's what worked for me.

    // Raw transaction bytes
    const txBytes = bs58.decode(input.transaction);

    // Assuming single byte variant, the first byte will specify how 
    // many signatures are in the transaction
    const numOfSignatures = txBytes[0];

    // 1 (num_of_signatures byte) + num_of_signatures * 64 (each sig is 64 bytes)
    const txHeaderLength = 1 + numOfSignatures * 64;

    // Now slice the message portion (everything from end_of_header to the end)
    const versionedMessage = VersionedMessage.deserialize(
      txBytes.slice(txHeaderLength, txBytes.length)
    );
    
    // Finally, construct the versionedTx
    const versionedTx = new VersionedTransaction(versionedMessage);

Answer 2

Did you try using VersionedTransaction.deserialize? This way you don't throw away the signatures already in the transaction: https://github.com/solana-labs/solana-web3.js/blob/c7ef49cc49ee61422a4777d439a814160f6d7ce4/packages/library-legacy/src/transaction/versioned.ts#L78