algorithm
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... * Compress specialized data (e.g., raster graphics) as well
as the best currently available specialized algorithms.
A simple counting argument shows that no lossless compression
algorithm ...
... algorithms.
A simple counting argument shows that no lossless compression
algorithm can compress every possible input data set. For the
format defined here, the worst case expansion is 5 bytes per 32K-
byte block, i.e., a size increase of 0.015% for large data sets.
...
...
Each block is compressed using a combination of the LZ77 algorithm
and Huffman coding. The Huffman trees for each block are independent
...
... trees for each block are independent
of those for previous or subsequent blocks; the LZ77 algorithm may
use a reference to a duplicated string occurring in a previous block,
up to 32K input bytes before.
...
...
Given an alphabet with known symbol frequencies, the Huffman
algorithm allows the construction of an optimal prefix code
(one which represents strings with those symbol frequencies
...
... various alphabets must not exceed certain maximum code lengths.
This constraint complicates the algorithm for computing code
lengths from symbol frequencies. Again, see Chapter 5,
references for details.
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... by the sequence of bit lengths (2, 1, 3, 3). The following
algorithm generates the codes as integers, intended to be read
from most- to least-significant bit. The code lengths are
...
... defined.
In all cases, the decoding algorithm for the actual data is as
follows:
...
... literal/length or distance alphabet will not occur in the
block, and should not participate in the Huffman code
construction algorithm given earlier. If only one distance
code is used, it is encoded using one bit, not zero bits ...
... Compression algorithm details ...
... compressed data format without reference to any particular
compression algorithm, the format is related to the compressed
formats produced by LZ77 (Lempel-Ziv 1977, see reference [2 ...
... implementor of a compressor follow the general
algorithm presented here, which is known not to be patented per se.
The material in this section is not part of the definition of the
specification per se, and a compressor ...
... hash chains are singly linked. There are no
deletions from the hash chains; the algorithm simply discards matches
that are too old. To avoid a worst-case situation, very long hash
chains are arbitrarily truncated at a certain length, determined by a
...
... Ziv J., Lempel A., "A Universal Algorithm for Sequential Data Compression", IEEE Transactions ...