Type Alias LibraryLookup 

pub type LibraryLookup = Arc<HashMap<String, Arc<str>>>;

A lookup table mapping read group IDs to library names.

This is built from the SAM header’s @RG lines and used to resolve the library name (LB field) from a record’s RG tag. This matches fgbio’s behavior where grouping uses the library name, not the read group ID.

Uses Arc<str> for library names to avoid cloning strings for every read.

Note: LibraryLookup vs LibraryIndex

Both LibraryLookup and LibraryIndex exist for different use cases:

• LibraryLookup: String-based lookup returning library names. Used by ReadInfo::from where the actual library name string is needed.
• LibraryIndex: Hash-based lookup returning numeric indices. Used by compute_group_key in the hot path where only equality comparison matters, avoiding string allocations.

Aliased Type

pub struct LibraryLookup { /* private fields */ }