text: """Routines to help recognizing sound files.
  
  Function whathdr() recognizes various types of sound file headers.
  It understands almost all headers that SOX can decode.
  
  The return tuple contains the following items, in this order:
  - file type (as SOX understands it)
  - sampling rate (0 if unknown or hard to decode)
  - number of channels (0 if unknown or hard to decode)
  - number of frames in the file (-1 if unknown or hard to decode)
  - number of bits/sample, or 'U' for U-LAW, or 'A' for A-LAW
  
  If the file doesn't have a recognizable type, it returns None.
  If the file can't be opened, IOError is raised.
  
  To compute the total time, divide the number of frames by the
  sampling rate (a frame contains a sample for each channel).
  
  Function what() calls whathdr().  (It used to also use some
  heuristics for raw data, but this doesn't work very well.)
  
  Finally, the function test() is a simple main program that calls
  what() for all files mentioned on the argument list.  For directory
  arguments it calls what() for all files in that directory.  Default
  argument is "." (testing all files in the current directory).  The
  option -r tells it to recurse down directories found inside
  explicitly given directories.
  """
  
  # The file structure is top-down except that the test program and its
  # subroutine come last.
  
  __all__ = ["what","whathdr"]
  
  def what(filename):
      """Guess the type of a sound file"""
      res = whathdr(filename)
      return res
  
  
  def whathdr(filename):
      """Recognize sound headers"""
      f = open(filename, 'rb')
      h = f.read(512)
      for tf in tests:
          res = tf(h, f)
          if res:
              return res
      return None
  
  
  #-----------------------------------#
  # Subroutines per sound header type #
  #-----------------------------------#
  
  tests = []
  
  def test_aifc(h, f):
      import aifc
      if h[:4] != 'FORM':
          return None
      if h[8:12] == 'AIFC':
          fmt = 'aifc'
      elif h[8:12] == 'AIFF':
          fmt = 'aiff'
      else:
          return None
      f.seek(0)
      try:
          a = aifc.openfp(f, 'r')
      except (EOFError, aifc.Error):
          return None
      return (fmt, a.getframerate(), a.getnchannels(), \
              a.getnframes(), 8*a.getsampwidth())
  
  tests.append(test_aifc)
  
  
  def test_au(h, f):
      if h[:4] == '.snd':
          f = get_long_be
      elif h[:4] in ('\0ds.', 'dns.'):
          f = get_long_le
      else:
          return None
      type = 'au'
      hdr_size = f(h[4:8])
      data_size = f(h[8:12])
      encoding = f(h[12:16])
      rate = f(h[16:20])
      nchannels = f(h[20:24])
      sample_size = 1 # default
      if encoding == 1:
          sample_bits = 'U'
      elif encoding == 2:
          sample_bits = 8
      elif encoding == 3:
          sample_bits = 16
          sample_size = 2
      else:
          sample_bits = '?'
      frame_size = sample_size * nchannels
      return type, rate, nchannels, data_size//frame_size, sample_bits
  
  tests.append(test_au)
  
  
  def test_hcom(h, f):
      if h[65:69] != 'FSSD' or h[128:132] != 'HCOM':
          return None
      divisor = get_long_be(h[128+16:128+20])
      return 'hcom', 22050//divisor, 1, -1, 8
  
  tests.append(test_hcom)
  
  
  def test_voc(h, f):
      if h[:20] != 'Creative Voice File\032':
          return None
      sbseek = get_short_le(h[20:22])
      rate = 0
      if 0 <= sbseek < 500 and h[sbseek] == '\1':
          ratecode = ord(h[sbseek+4])
          rate = int(1000000.0 / (256 - ratecode))
      return 'voc', rate, 1, -1, 8
  
  tests.append(test_voc)
  
  
  def test_wav(h, f):
      # 'RIFF' <len> 'WAVE' 'fmt ' <len>
      if h[:4] != 'RIFF' or h[8:12] != 'WAVE' or h[12:16] != 'fmt ':
          return None
      style = get_short_le(h[20:22])
      nchannels = get_short_le(h[22:24])
      rate = get_long_le(h[24:28])
      sample_bits = get_short_le(h[34:36])
      return 'wav', rate, nchannels, -1, sample_bits
  
  tests.append(test_wav)
  
  
  def test_8svx(h, f):
      if h[:4] != 'FORM' or h[8:12] != '8SVX':
          return None
      # Should decode it to get #channels -- assume always 1
      return '8svx', 0, 1, 0, 8
  
  tests.append(test_8svx)
  
  
  def test_sndt(h, f):
      if h[:5] == 'SOUND':
          nsamples = get_long_le(h[8:12])
          rate = get_short_le(h[20:22])
          return 'sndt', rate, 1, nsamples, 8
  
  tests.append(test_sndt)
  
  
  def test_sndr(h, f):
      if h[:2] == '\0\0':
          rate = get_short_le(h[2:4])
          if 4000 <= rate <= 25000:
              return 'sndr', rate, 1, -1, 8
  
  tests.append(test_sndr)
  
  
  #---------------------------------------------#
  # Subroutines to extract numbers from strings #
  #---------------------------------------------#
  
  def get_long_be(s):
      return (ord(s[0])<<24) | (ord(s[1])<<16) | (ord(s[2])<<8) | ord(s[3])
  
  def get_long_le(s):
      return (ord(s[3])<<24) | (ord(s[2])<<16) | (ord(s[1])<<8) | ord(s[0])
  
  def get_short_be(s):
      return (ord(s[0])<<8) | ord(s[1])
  
  def get_short_le(s):
      return (ord(s[1])<<8) | ord(s[0])
  
  
  #--------------------#
  # Small test program #
  #--------------------#
  
  def test():
      import sys
      recursive = 0
      if sys.argv[1:] and sys.argv[1] == '-r':
          del sys.argv[1:2]
          recursive = 1
      try:
          if sys.argv[1:]:
              testall(sys.argv[1:], recursive, 1)
          else:
              testall(['.'], recursive, 1)
      except KeyboardInterrupt:
          sys.stderr.write('\n[Interrupted]\n')
          sys.exit(1)
  
  def testall(list, recursive, toplevel):
      import sys
      import os
      for filename in list:
          if os.path.isdir(filename):
              print filename + '/:',
              if recursive or toplevel:
                  print 'recursing down:'
                  import glob
                  names = glob.glob(os.path.join(filename, '*'))
                  testall(names, recursive, 0)
              else:
                  print '*** directory (use -r) ***'
          else:
              print filename + ':',
              sys.stdout.flush()
              try:
                  print what(filename)
              except IOError:
                  print '*** not found ***'
  
  if __name__ == '__main__':
      test()
  