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246 lines
6.3 KiB
Python
246 lines
6.3 KiB
Python
"""Routines to help recognizing sound files.
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Function whathdr() recognizes various types of sound file headers.
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It understands almost all headers that SOX can decode.
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The return tuple contains the following items, in this order:
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- file type (as SOX understands it)
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- sampling rate (0 if unknown or hard to decode)
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- number of channels (0 if unknown or hard to decode)
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- number of frames in the file (-1 if unknown or hard to decode)
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- number of bits/sample, or 'U' for U-LAW, or 'A' for A-LAW
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If the file doesn't have a recognizable type, it returns None.
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If the file can't be opened, OSError is raised.
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To compute the total time, divide the number of frames by the
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sampling rate (a frame contains a sample for each channel).
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Function what() calls whathdr(). (It used to also use some
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heuristics for raw data, but this doesn't work very well.)
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Finally, the function test() is a simple main program that calls
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what() for all files mentioned on the argument list. For directory
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arguments it calls what() for all files in that directory. Default
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argument is "." (testing all files in the current directory). The
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option -r tells it to recurse down directories found inside
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explicitly given directories.
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"""
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# The file structure is top-down except that the test program and its
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# subroutine come last.
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__all__ = ['what', 'whathdr']
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from collections import namedtuple
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SndHeaders = namedtuple('SndHeaders',
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'filetype framerate nchannels nframes sampwidth')
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def what(filename):
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"""Guess the type of a sound file."""
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res = whathdr(filename)
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return res
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def whathdr(filename):
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"""Recognize sound headers."""
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with open(filename, 'rb') as f:
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h = f.read(512)
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for tf in tests:
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res = tf(h, f)
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if res:
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return SndHeaders(*res)
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return None
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#-----------------------------------#
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# Subroutines per sound header type #
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#-----------------------------------#
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tests = []
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def test_aifc(h, f):
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import aifc
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if not h.startswith(b'FORM'):
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return None
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if h[8:12] == b'AIFC':
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fmt = 'aifc'
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elif h[8:12] == b'AIFF':
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fmt = 'aiff'
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else:
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return None
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f.seek(0)
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try:
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a = aifc.open(f, 'r')
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except (EOFError, aifc.Error):
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return None
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return (fmt, a.getframerate(), a.getnchannels(),
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a.getnframes(), 8 * a.getsampwidth())
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tests.append(test_aifc)
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def test_au(h, f):
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if h.startswith(b'.snd'):
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func = get_long_be
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elif h[:4] in (b'\0ds.', b'dns.'):
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func = get_long_le
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else:
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return None
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filetype = 'au'
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hdr_size = func(h[4:8])
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data_size = func(h[8:12])
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encoding = func(h[12:16])
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rate = func(h[16:20])
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nchannels = func(h[20:24])
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sample_size = 1 # default
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if encoding == 1:
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sample_bits = 'U'
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elif encoding == 2:
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sample_bits = 8
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elif encoding == 3:
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sample_bits = 16
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sample_size = 2
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else:
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sample_bits = '?'
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frame_size = sample_size * nchannels
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if frame_size:
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nframe = data_size / frame_size
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else:
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nframe = -1
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return filetype, rate, nchannels, nframe, sample_bits
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tests.append(test_au)
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def test_hcom(h, f):
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if h[65:69] != b'FSSD' or h[128:132] != b'HCOM':
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return None
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divisor = get_long_be(h[144:148])
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if divisor:
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rate = 22050 / divisor
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else:
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rate = 0
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return 'hcom', rate, 1, -1, 8
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tests.append(test_hcom)
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def test_voc(h, f):
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if not h.startswith(b'Creative Voice File\032'):
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return None
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sbseek = get_short_le(h[20:22])
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rate = 0
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if 0 <= sbseek < 500 and h[sbseek] == 1:
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ratecode = 256 - h[sbseek+4]
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if ratecode:
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rate = int(1000000.0 / ratecode)
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return 'voc', rate, 1, -1, 8
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tests.append(test_voc)
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def test_wav(h, f):
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import wave
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# 'RIFF' <len> 'WAVE' 'fmt ' <len>
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if not h.startswith(b'RIFF') or h[8:12] != b'WAVE' or h[12:16] != b'fmt ':
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return None
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f.seek(0)
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try:
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w = wave.openfp(f, 'r')
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except (EOFError, wave.Error):
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return None
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return ('wav', w.getframerate(), w.getnchannels(),
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w.getnframes(), 8*w.getsampwidth())
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tests.append(test_wav)
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def test_8svx(h, f):
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if not h.startswith(b'FORM') or h[8:12] != b'8SVX':
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return None
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# Should decode it to get #channels -- assume always 1
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return '8svx', 0, 1, 0, 8
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tests.append(test_8svx)
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def test_sndt(h, f):
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if h.startswith(b'SOUND'):
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nsamples = get_long_le(h[8:12])
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rate = get_short_le(h[20:22])
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return 'sndt', rate, 1, nsamples, 8
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tests.append(test_sndt)
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def test_sndr(h, f):
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if h.startswith(b'\0\0'):
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rate = get_short_le(h[2:4])
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if 4000 <= rate <= 25000:
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return 'sndr', rate, 1, -1, 8
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tests.append(test_sndr)
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#-------------------------------------------#
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# Subroutines to extract numbers from bytes #
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#-------------------------------------------#
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def get_long_be(b):
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return (b[0] << 24) | (b[1] << 16) | (b[2] << 8) | b[3]
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def get_long_le(b):
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return (b[3] << 24) | (b[2] << 16) | (b[1] << 8) | b[0]
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def get_short_be(b):
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return (b[0] << 8) | b[1]
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def get_short_le(b):
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return (b[1] << 8) | b[0]
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#--------------------#
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# Small test program #
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#--------------------#
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def test():
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import sys
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recursive = 0
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if sys.argv[1:] and sys.argv[1] == '-r':
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del sys.argv[1:2]
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recursive = 1
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try:
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if sys.argv[1:]:
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testall(sys.argv[1:], recursive, 1)
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else:
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testall(['.'], recursive, 1)
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except KeyboardInterrupt:
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sys.stderr.write('\n[Interrupted]\n')
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sys.exit(1)
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def testall(list, recursive, toplevel):
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import sys
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import os
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for filename in list:
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if os.path.isdir(filename):
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print(filename + '/:', end=' ')
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if recursive or toplevel:
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print('recursing down:')
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import glob
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names = glob.glob(os.path.join(filename, '*'))
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testall(names, recursive, 0)
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else:
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print('*** directory (use -r) ***')
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else:
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print(filename + ':', end=' ')
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sys.stdout.flush()
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try:
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print(what(filename))
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except OSError:
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print('*** not found ***')
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if __name__ == '__main__':
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test()
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