Trait ConvertBlockNumber 

pub trait ConvertBlockNumber<L, N> {
    // Required methods
    fn equivalent_moment_in_time(local_moment: L) -> N;
    fn equivalent_block_duration(local_duration: L) -> N;
}

Converts previous (local) block number into the new one. May just be identity functions if sticking with the local block number.

Required Methods

fn equivalent_moment_in_time(local_moment: L) -> N

Converts to the new type and finds the equivalent moment in time as from the view of the new block provider

Example usage

// Let's say you are a parachain and switching block providers to the relay chain.
// This will return what the relay block number was at the moment the previous provider's
// number was `local_moment`.
fn equivalent_moment_in_time(local_moment: u32) -> u32 {
	// How long it's been since 'local_moment' from the parachains pov.
	let local_block_number = System::block_number();
	let local_duration = u32::abs_diff(local_block_number, local_moment);
	// How many blocks that is from the relay's pov.
	let relay_duration = Self::equivalent_block_duration(local_duration);
	// What the relay block number must have been at 'local_moment'.
	let relay_block_number = ParachainSystem::last_relay_block_number();
	if local_block_number >= local_moment {
		// Moment was in past.
		relay_block_number.saturating_sub(relay_duration)
	} else {
		// Moment is in future.
		relay_block_number.saturating_add(relay_duration)
	}
}

fn equivalent_block_duration(local_duration: L) -> N

Returns the equivalent number of new blocks it would take to fulfill the same amount of time in seconds as the old blocks.

For instance - If you previously had 12s blocks and are now following the relay chain’s 6, one local block is equivalent to 2 relay blocks in duration.

Visualized

 
    6s         6s
|---------||---------|

         12s
|--------------------|

^ Two 6s relay blocks passed per one 12s local block.

Example Usage

// Following the scenerio above.
fn equivalent_block_duration(local_duration: u32) -> u32 {
	local_duration.saturating_mul(2)
}

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementors