Vcodex is a software package for data transformation.
Examples of data transformation include compression,
delta compression, encryption, portable encodings of binary data, etc.
The software architecture of Vcodex is layered as follows:

• Libvcodex: This base library implements the methods for
  transforming data. The library assumes that there is sufficient
  main memory to process given data.
  Different transforms can be composed to perform particular tasks.
  For example, a Burrows-Wheeler compressor can be built by
  composing together the Burrows-Wheeler transform,
  a move-to-front transform, a run-length encoder, and some entropy encoder.
  
• Vcsfio(): This single function is a part of Libvcodex. It
  provides an interface to the Sfio library to deal with file data.
  Vcsfio() constructs an Sfio discipline for the particular data transformation
  task and inserts it to a given Sfio stream. After that, for encoding,
  raw data can be simply written to the stream and the Sfio discipline
  will take care of calling the Vcodex functions to encode.
  Likewise, for decoding, the Sfio discipline will automatically call
  Vcodex functions to decode data so that the application will see
  the data in plaintext.
  
• Vczip: This single executable command can be used to
  run the data transforms for both encoding and decoding.
  With the right combination of transforms, Vczip can perform
  compression tasks with performance similar to or better
  than other well-known compressors such as Gzip or Bzip2.
  Vczip is, in fact, a simple driver to collect command line arguments
  and make the appropriate invocation to vcsfio() to condition the standard
  output or input stream as the case required.
  

Libvcodex is based on a Discipline and Method architecture (see the references below)
enabling simple data processing as well as extensibility when new transforms are invented.
Data are transformed via handles created with particular transformation methods.
Below are the methods distributed in this package:

• Vcdelta: This performs delta compression and outputs results
  in the Vcdiff data encoding format. Since this method
  is a generalization of the 1977 Lempel-Ziv compression strategy,
  it can also be used to compress single data sets.
  
• Vchuffman: This performs static Huffman coding. It implements fast
  algorithms to compute the Huffman code table and to decode encoded data.
  
• Vchuffpart: This partitions data into contiguous segments with
  consistent statistics so that they compress better with different
  Huffman code tables than if a single table is used for all data.
  
• Vchuffgroup: This is similar to the above. However, it first
  partitions data into small chunks with the same size, then groups
  chunks with consistent statistics for compression.
  
• Vcbwt: This performs the famed Burrows-Wheeler transform.
  
• Vcmtf: This performs the move-to-front transform. The method can
  be parameterized to select between two different move-to-front
  strategies. The default strategy uses a simple prediction method
  to aggressively move data to the front of the queue. This works
  well with data produced by Vcbwt. The alternate strategy is the
  plain move-to-front where a data byte is moved to the front of the
  queue after it is accessed.
  
• Vcrle: This performs run-length encoding. The method can be
  parameterized to select between two different strategies. The default
  strategy finds runs and encodes the lengths and the data separately.
  The alternate strategy only encodes runs of zeros using a special
  binary encoding. This works well with data produced by the move-to-front
  transform after a Burrows-Wheeler transform.