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@scott-griffiths scott-griffiths released this 23 Jun 10:05
· 885 commits to main since this release
bitstring-2.1.0
2abe26f

January 23rd 2011: version 2.1.0 released

New class hierarchy introduced with simpler classes

Previously there were just two classes, the immutable Bits which was the base
class for the mutable BitString class. Both of these classes have the concept
of a bit position, from which reads etc. take place so that the bitstring could
be treated as if it were a file or stream.

Two simpler classes have now been added which are purely bit containers and
don't have a bit position. These are called ConstBitArray and BitArray. As you
can guess the former is an immutable version of the latter.

The other classes have also been renamed to better reflect their capabilities.
Instead of BitString you can use BitStream, and instead of Bits you can use
ConstBitStream. The old names are kept as aliases for backward compatibility.

The classes hierarchy is:

    ConstBitArray
       /    \
      /      \
BitArray   ConstBitStream (formerly Bits)
      \      /
       \    /
      BitStream (formerly BitString)

Other changes

A lot of internal reorganisation has taken place since the previous version,
most of which won't be noticed by the end user. Some things you might see are:

  • New package structure. Previous versions have been a single file for the
    module and another for the unit tests. The module is now split into many
    more files so it can't be used just by copying bitstring.py any more.
  • To run the unit tests there is now a script called runtests.py in the test
    directory.
  • File based bitstring are now implemented in terms of an mmap. This should
    be just an implementation detail, but unfortunately for 32-bit versions of
    Python this creates a limit of 4GB on the files that can be used. The work
    around is either to get a 64-bit Python, or just stick with version 2.0.
  • The ConstBitArray and ConstBitStream classes no longer copy byte data when
    a slice or a read takes place, they just take a reference. This is mostly
    a very nice optimisation, but there are occassions where it could have an
    adverse effect. For example if a very large bitstring is created, a small
    slice taken and the original deleted. The byte data from the large
    bitstring would still be retained in memory.
  • Optimisations. Once again this version should be faster than the last.
    The module is still pure Python but some of the reorganisation was to make
    it more feasible to put some of the code into Cython or similar, so
    hopefully more speed will be on the way.
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