validate_prefix_length can avoid creating new Strings

[rnbguy]

Bug Summary

validate_prefix_length unnecessarily creates a new String using u64::MIN and u64::MAX which can be avoided.

Details

The current implementation looks as follows.

ibc-rs/crates/ibc/src/core/ics24_host/identifier/validate.rs

Lines 59 to 79 in ccca3ff

	pub fn validate_prefix_length(
	prefix: &str,
	min_id_length: u64,
	max_id_length: u64,
	) -> Result<(), Error> {
	// Checks if the prefix forms a valid identifier length when constructed with `u64::MIN`
	validate_identifier_length(
	&format!("{prefix}-{}", u64::MIN),
	min_id_length,
	max_id_length,
	)?;
	// Checks if the prefix forms a valid identifier length when constructed with `u64::MAX`
	validate_identifier_length(
	&format!("{prefix}-{}", u64::MAX),
	min_id_length,
	max_id_length,
	)?;
	Ok(())
	}

Instead of doing

validate_identifier_length( 
         &format!("{prefix}-{}", u64::MIN), 
         min_id_length, 
         max_id_length, 
     )

we can directly pass prefix with {min,max}_id_length with negative offset for format!("-{}", u64::MIN).

validate_identifier_length( 
         prefix,
         min_id_length - 2,
         max_id_length - 2,
     )

And, similar for u64::MAX with offset 21. But we need to be careful that these subtractions don't underflow.

Version

v0.47.0