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Intro

Zlib/Make-dht is a slightly modified version of the Zlib library. You supply the literal/length and distance symbol frequencies. Make-dht produces a Huffman table that deflate() would have inserted in the Deflate block. We introduced a new zlib function, deflate_make_dht(). Also provided sample code in examples/makedht.c

Why and who needs this function?

• If you are studying Zlib.
• If you are debugging your own inflate implementation, implemented in software or hardware, and you want to test it with various huffman tables that zlib would have produced.
• If your hardware cannot produce its own huffman table and needs zlib's help.

How to use it?

Clone abalib/zlib and checkout make-dht or develop:

git clone https://github.com/abalib/zlib
git checkout make-dht

Follow the zlib README instructions.

cd to zlib root directory
./configure
make
cd examples
cc -O -I.. -o makedht  makedht.c ../libz.a

Usage example:

./makedht jabber1.lzcount jabber1.dht

bytes: 19  invalid bits: 4
00000000000000000000000000000094
203826000000220058c5a6900244f0c3
d7770700000000000000000000000000


Hex dump of the same:

xxd jabber1.dht
0000000: 2038 2600 0000 2200 58c5 a690 0244 f0c3   8&...".X....D..
0000010: d777 07                                  .w.

Contents of jabber1.lzcount. Symbol 32 occurs 2 times, 39 occurs 1 times, ... , distance symbols 0 and 29 occur 0 times. Missing symbols occur 0 times by default:

32  :          2
39  :          1
84  :          1
97  :          1
98  :          1
114 :          1
115 :          1
119 :          1
256 :          1
0   :          0
29  :          0

More details on usage are found in the makedht.c comments.