std::string incompressible; for (int step = 1; step <= 128; ++step) { for (int inc = 0; inc < step; ++inc) { for (int i = inc; i < 256; i += step) { incompressible.push_back(i); } } }This generates a 32,768-byte string incompressible, with byte values:
0, 1, 2, 3, 4, 5, ..., 255, // step = 1, inc = 0
0, 2, 4, 6, 8, 10, ..., 254, // step = 2, inc = 0
1, 3, 5, 7, 9, 11, ..., 255, // step = 2, inc = 1
0, 3, 6, 9, 12, 15, ..., // step = 3, inc = 0
1, 4, 7, 10, 13, 16, ..., // step = 3, inc = 1
2, 5, 8, 11, 14, 17, ..., // step = 3, inc = 2
...
...
incompressible is not compressible with zlib/deflate, because:
- frequency of every symbols (characters) are the same, so Huffman coding is helpless.
- minimum match length of LZ77 chosen by deflate is 3, and incompressible contains no 3-tuple that duplicates. (Technically, there will be only literals in encoded deflate stream, no length-distance pairs.)