"""Interpret sun audio headers."""

MAGIC = '.snd'

class error(Exception):
    pass


def get_long_be(s):
    """Convert a 4-char value to integer."""
    return (ord(s[0])<<24) | (ord(s[1])<<16) | (ord(s[2])<<8) | ord(s[3])


def gethdr(fp):
    """Read a sound header from an open file."""
    if fp.read(4) != MAGIC:
        raise error, 'gethdr: bad magic word'
    hdr_size = get_long_be(fp.read(4))
    data_size = get_long_be(fp.read(4))
    encoding = get_long_be(fp.read(4))
    sample_rate = get_long_be(fp.read(4))
    channels = get_long_be(fp.read(4))
    excess = hdr_size - 24
    if excess < 0:
        raise error, 'gethdr: bad hdr_size'
    if excess > 0:
        info = fp.read(excess)
    else:
        info = ''
    return (data_size, encoding, sample_rate, channels, info)


def printhdr(file):
    """Read and print the sound header of a named file."""
    hdr = gethdr(open(file, 'r'))
    data_size, encoding, sample_rate, channels, info = hdr
    while info[-1:] == '\0':
        info = info[:-1]
    print 'File name:  ', file
    print 'Data size:  ', data_size
    print 'Encoding:   ', encoding
    print 'Sample rate:', sample_rate
    print 'Channels:   ', channels
    print 'Info:       ', repr(info)
