pub trait Filter {
    fn register_tx(&self, txid: &Txid, script_pubkey: &Script);
    fn register_output(
        output: WatchedOutput
    ) -> Option<(usize, Transaction)>; }
Expand description

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 TemporaryFailure.

Required Methods

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

Registers interest in spends of a transaction output.

Optionally, when output.block_hash is set, should return any transaction spending the output that is found in the corresponding block along with its index.

This return value is useful for Electrum clients in order to supply in-block descendant transactions which otherwise were not included. This is not necessary for other clients if such descendant transactions were already included (e.g., when a BIP 157 client provides the full block).