def compute_fasta_offset(sequence_location, header_size, line_size,
    cr_lf_size=1):
    """
    Given a location on a FASTA sequence (assuming one sequence per file),
    the length of the header line and a line length (including CR/LF),
    (assumes the line size is constant throughout the file),
    returns the file location of the specified sequence location
    """
    num_lines = int(sequence_location / (line_size - cr_lf_size))
    line_offset = sequence_location % (line_size - cr_lf_size)
    return num_lines * line_size + line_offset + header_size
