Reading same BAM file twice with htslib

Question

I would like to read iteratively the same BAM file twice using htslib.

My option is to use hts_open, sam_hdr_read, then sam_read1 as much as needed to read the file until EOF.

Is there a possibility to "rewind", and use sam_read1 again from the beginning of the file, without closing the file, destroying the object, and opening it again?

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EDIT

My aim is group the reads by the barcode. The first pass would allocate the specific sizes first (the number of reads by barcode), then store the reads.

I know I could sort the reads first (using samtools sort -t BX), but I would like to skip this step using pre-allocation.

Answer 1

The best solution is to reopen the file. For a coordinate sorted file you have the option to jump back to the start of the first chromosome with index but that is more complex, less flexible and won't be faster.