C library for high-throughput sequencing data formats

 HTSlib is an implementation of a unified C library for accessing common file
 formats, such as SAM (Sequence Alignment/Map), CRAM and VCF (Variant Call
 Format), used for high-throughput sequencing data, and is the core library
 used by samtools and bcftools. HTSlib only depends on zlib. It is known to be
 compatible with gcc, g++ and clang.
 .
 HTSlib implements a generalized BAM (binary SAM) index, with file extension
 ‘csi’ (coordinate-sorted index). The HTSlib file reader first looks for the
 new index and then for the old if the new index is absent.