@param fn BCF file name @return The index, or NULL if an error occurred. @note This only works for BCF files. Consider synced_bcf_reader instead which works for both BCF and VCF.
See Implementation
@param fn BCF file name @return The index, or NULL if an error occurred. @note This only works for BCF files. Consider synced_bcf_reader instead which works for both BCF and VCF.