fastq_to_fastq.py 文件源码

def get_compression_type(filename):
    """
    Attempts to guess the compression (if any) on a file using the first few bytes.
    http://stackoverflow.com/questions/13044562
    """
    magic_dict = {'gz': (b'\x1f', b'\x8b', b'\x08'),
                  'bz2': (b'\x42', b'\x5a', b'\x68'),
                  'zip': (b'\x50', b'\x4b', b'\x03', b'\x04')}
    max_len = max(len(x) for x in magic_dict)

    unknown_file = open(filename, 'rb')
    file_start = unknown_file.read(max_len)
    unknown_file.close()
    compression_type = 'plain'
    for file_type, magic_bytes in magic_dict.items():
        if file_start.startswith(magic_bytes):
            compression_type = file_type
    if compression_type == 'bz2':
        sys.exit('Error: cannot use bzip2 format - use gzip instead')
    if compression_type == 'zip':
        sys.exit('Error: cannot use zip format - use gzip instead')
    return compression_type