Function source_line_edit_map 

pub fn source_line_edit_map(
    old: &Blob,
    new: &Blob,
    max_bytes: usize,
    max_edits: usize,
) -> Result<SourceLineMapBuild, SourceTargetError>

Build once for an old/new blob pair, regardless of how many ranges refer to that file. Limits apply before parsing and before admitting the edit map. No elapsed-time fallback changes the resulting coordinate decisions.