Trait Filter

pub trait Filter {
    // Required methods
    fn register_tx(&self, txid: &Txid, script_pubkey: &Script);
    fn register_output(&self, output: WatchedOutput);
}

The Filter trait defines behavior for indicating chain activity of interest pertaining to channels.

This is useful in order to have a Watch implementation convey to a chain source which transactions to be notified of. Notification may take the form of pre-filtering blocks or, in the case of BIP 157/BIP 158, only fetching a block if the compact filter matches. If receiving full blocks from a chain source, any further filtering is unnecessary.

After an output has been registered, subsequent block retrievals from the chain source must not exclude any transactions matching the new criteria nor any in-block descendants of such transactions.

Note that use as part of a Watch implementation involves reentrancy. Therefore, the Filter should not block on I/O. Implementations should instead queue the newly monitored data to be processed later. Then, in order to block until the data has been processed, any Watch invocation that has called the Filter must return InProgress.

Required Methods

fn register_tx(&self, txid: &Txid, script_pubkey: &Script)

Registers interest in a transaction with txid and having an output with script_pubkey as a spending condition.

fn register_output(&self, output: WatchedOutput)

Registers interest in spends of a transaction output.

Note that this method might be called during processing of a new block. You therefore need to ensure that also dependent output spents within an already connected block are correctly handled, e.g., by re-scanning the block in question whenever new outputs have been registered mid-processing.

Implementors