3877 

  3878 def uvarintencode(value):

  3879     """Encode an unsigned integer value to a varint.

  3880 

  3881     A varint is a variable length integer of 1 or more bytes. Each byte

  3882     except the last has the most significant bit set. The lower 7 bits of

  3883     each byte store the 2's complement representation, least significant group

  3884     first.

  3885 

  3886     >>> uvarintencode(0)

  3887     '\\x00'

  3888     >>> uvarintencode(1)

  3889     '\\x01'

  3890     >>> uvarintencode(127)

  3891     '\\x7f'

  3892     >>> uvarintencode(1337)

  3893     '\\xb9\\n'

  3894     >>> uvarintencode(65536)

  3895     '\\x80\\x80\\x04'

  3896     >>> uvarintencode(-1)

  3897     Traceback (most recent call last):

  3898         ...

  3899     ProgrammingError: negative value for uvarint: -1

  3900     """

  3901     if value < 0:

  3902         raise error.ProgrammingError('negative value for uvarint: %d'

  3903                                      % value)

  3904     bits = value & 0x7f

  3905     value >>= 7

  3906     bytes = []

  3907     while value:

  3908         bytes.append(pycompat.bytechr(0x80 | bits))

  3909         bits = value & 0x7f

  3910         value >>= 7

  3911     bytes.append(pycompat.bytechr(bits))

  3912 

  3913     return ''.join(bytes)

  3914 

  3915 def uvarintdecodestream(fh):

  3916     """Decode an unsigned variable length integer from a stream.

  3917 

  3918     The passed argument is anything that has a ``.read(N)`` method.

  3919 

  3920     >>> try:

  3921     ...     from StringIO import StringIO as BytesIO

  3922     ... except ImportError:

  3923     ...     from io import BytesIO

  3924     >>> uvarintdecodestream(BytesIO(b'\\x00'))

  3925     0

  3926     >>> uvarintdecodestream(BytesIO(b'\\x01'))

  3927     1

  3928     >>> uvarintdecodestream(BytesIO(b'\\x7f'))

  3929     127

  3930     >>> uvarintdecodestream(BytesIO(b'\\xb9\\n'))

  3931     1337

  3932     >>> uvarintdecodestream(BytesIO(b'\\x80\\x80\\x04'))

  3933     65536

  3934     >>> uvarintdecodestream(BytesIO(b'\\x80'))

  3935     Traceback (most recent call last):

  3936         ...

  3937     Abort: stream ended unexpectedly (got 0 bytes, expected 1)

  3938     """

  3939     result = 0

  3940     shift = 0

  3941     while True:

  3942         byte = ord(readexactly(fh, 1))

  3943         result |= ((byte & 0x7f) << shift)

  3944         if not (byte & 0x80):

  3945             return result

  3946         shift += 7