About
-----

Text compression format that can be decompressed starting at any point.
Little-endian byte ordering is used.


Header
------

TCR files always start with:

!!8-Bit!!


Layout
------

Header
256 key dictionary
compressed text


Dictionary
----------

A dictionary of key and replacement string. There are a total of 256 keys,
0 - 255. Each string is preceded with one byte that represents the length of
the string.


Compressed text
---------------

The compressed text is a series of values 0-255 which correspond to a key and
thus a string. Reassembling is replacing each key in the compressed text with
its corresponding string.


Compressor
-----------------

From Andrew Giddings TCR.c (http://www.cix.co.uk/~gidds/Software/TCR.html):

The TCR compression format is easy to describe: after the fixed header is a
dictionary of 256 strings, each preceded by a length byte.  The rest of the
file is a list of codes from this dictionary.

The compressor works by starting with each code defined as itself.  While
there's an unused code, it finds the most common two-code combination, and
creates a new code for it, replacing all occurrences in the text with the
new code.

It also searches for codes that are always followed by another, which it can
merge, possibly freeing up some.