encode a data stream with a 7bit encoded variant

gistfile1.py

def decode7bit(bytes):
    """Decode the first variant integer in bytes.

    This function assumes that bytes begins with an encoded variant of an
    integer. It will read one byte at a time until the high order bit is 0 and
    the combined value of 7bit integers values will be returned along with how
    many bytes have been read.
    """
    pos = 0
    value = 0
    shift = 0
    bytes_read = 1
    while True:
        byteval = ord(bytes[pos])
        if(byteval & 128) == 0: break
        bytes_read += 1
        pos += 1
        value |= ((byteval & 0x7F) << shift)
        shift += 7
    return (value | (byteval << shift)), bytes_read


def encode7bit(value):
    """Return a variant of value in bytes.

    Each byte is encoded with a 7 bit integer and the high order bit used
    for continuation to the next byte as needed. The last byte will not have
    The continuation bit set.
    """
    temp = value
    bytes = ""
    while temp >= 128:
        bytes += chr(0x000000FF & (temp | 0x80))
        temp >>= 7
    return bytes + chr(temp)


header = "header"
data = "And this is some data..."
# first byte(s) are a version of the data
ver = encode7bit(199)
# next encode the size of the header
ds = encode7bit(len(header))
# put them together with the data
x = ver + ds + header + data
# read it back
ver, ver_br = decode7bit(x)
hs, hs_br = decode7bit(x[ver_br:])
header = x[ver_br+hs_br:ver_br+hs_br+hs]
data = x[ver_br+hs_br+hs:]
print "Version:%r" % ver
print "Header:%r" % header
print "Data:%r" % data