bam.py 文件源码

def parse_bgzf_header(f):
    cur_pos = f.tell()
    header_fmt = "BBBBIBBH"

    d = f.read(12)

    # We are at EOF when read returns an empty string
    if d == '':
        return None

    header = struct.unpack(header_fmt, d)

    # Check for a valid gzip header
    if header[0] != 31 or header[1] != 139:
        raise Exception("Not a valid gzip header")

    xlen = header[7]
    bsize = get_bsize(f, f.tell(), xlen)

    next_pos = cur_pos + bsize + 1
    f.seek(next_pos)
    return next_pos