linux - Is preset dictionary is only useful for first 32 K bytes of data ? -

i wanted use preset dictionary compressor , de-compressor. read here preset dictionary helpful first 32k bytes of data , after recent 32k data used dictionary. true? missing here ?

that's correct, preset dictionary used virtual input decompressor processed before actual compressed input, can use compressed codes replicate parts of it.

the deflate algorithm of zlib uses window of 32 kb size refer bytes decompressed before - parts of window , byte literals can use decompression. preset dictionary initialises window, data there "shifted out" real decompressed data, first 32k bytes of data can use decreasing part of preset dictionary.