Module codec 

Small, strict hex and base64 codecs (the kernel carries no hex/base64 crates, and these inputs are all short, bounded key material).

Functions

base64_decode

Decode base64 in either the standard or the URL-safe alphabet, with or without = padding. Whitespace is refused. Non-canonical trailing bits are refused so an encoding cannot be malleated.

hex_decode_exact

Decode lower-case hex of exactly N bytes. Upper-case is refused so each value has one spelling.

hex_encode

Lower-case hex encoding.

is_lower_hex

True when s is exactly len lower-case hex characters.